Uzoma Nwabara,
Kunran Yang
,
Akshay Talekar,
Varinia Bernales
,
Jorge González,
Stuart Miller
* and
Jinfeng Wu
*
Materials Discovery Research Institute, UL Research Institutes, Skokie, Illinois 60077, USA. E-mail: stuart.miller@ul.org; jeff.wu@ul.org
First published on 15th July 2025
The full integration of sustainable technologies to combat climate change heavily depends on the discovery of cost-competitive, safe, and durable performative materials, specifically for electrochemical systems that can generate energy, store energy, and produce chemicals. Due to the vast exploration space, scientists have adapted high throughput methods, both computational and experimental, for screening, synthesis, and testing to accelerate material discovery. In this review, we analyze such high throughput methodologies reported in the literature that have been applied to electrochemical material discovery. We find that most reported studies utilize computational methods, including density functional theory and machine learning, over experimental methods. Some labs have combined computational and experimental methods to create powerful tools for a closed loop material discovery process through automated setups and machine learning. Either way, over 80% of the publications we reviewed focus on catalytic materials, revealing a shortage in high throughput ionomer, membrane, electrolyte, and substrate material research. Moreover, we find that most material screening criteria do not consider cost, availability, and safety, all of which are crucial properties when assessing the economic feasibility of proposed materials. In addition, we discover that high throughput electrochemical material discovery research is only being conducted in a handful of countries, revealing the global opportunity to collaborate and share resources and data for further acceleration of material discovery. Finally, we acknowledge the development of autonomous labs and other initiatives as the future of high throughput research methodologies.
The accelerating climate crisis and rising energy demands require sustainable electrochemical technologies for energy storage, generation, and chemical production. Over the past two decades, electrochemical technologies have gained much attention due to improved material and reactor performance and new material discovery, propelling commercialization and scale-up. However, key performance benchmarks (e.g., activity, selectivity, and energy efficiency) still need to be achieved before such emerging technologies can compete economically with existing fossil fuel-based processes.9–13 Material bottlenecks—such as cost, durability, and scalability, continue to limit progress. For example, precious metal catalysts such as platinum, gold, and iridium are still state of the art for many electrochemical reactions. At the same time, the substrates, ionomers, membranes, and electrolytes used in the reactors degrade over long-term operation, posing significant challenges. Additionally, safety concerns must be considered when scaling up the production and handling of such materials. Overcoming these barriers requires discovering and introducing new materials and methods that are more cost-effective, stable, and safer to drive feasibility.
In recent decades, many researchers have successfully identified, synthesized, and characterized promising materials through standard benchtop chemistries and instruments. Yet, the conventional approach in these studies involves proposing, synthesizing, and testing one material, meaning that the research and discovery timescale for each material can take months or even years. Despite the multitude of groups across the globe committed to developing electrochemical technologies, this rate of material discovery is simply not sufficient, as we have yet to reach the needed benchmarks for feasibility. High-throughput (HT) computational and experimental methods offer a transformative solution by significantly accelerating material discovery to meet these global challenges.14–17 Here, HT methods involve setups or techniques designed for fully synthesizing, characterizing, screening, or analyzing multiple materials samples in a shorter time than traditional benchtop chemistry and engineering.
Unsurprisingly, the advancement and availability of theoretical prediction methods and supercomputing in the last 20–30 years have encouraged the use of simulated chemistry experiments. These simulations not only predict and explain material performance but also suggest new materials for synthesis and testing. Reported computational chemistry studies in the literature depict the ability to explore and screen materials in the order of 106 in a single project using methods such as first-principles density functional theory (DFT) and advanced machine learning (ML) techniques, including deep learning and active learning (AL). Moreover, HT experimentation has expanded with new setups created to test or characterize tens or hundreds of samples in days instead of months or years. As shown in Fig. 1, the integration between computational and experimental HT approaches is also promising and imperative for fast-tracking material discovery, which will help progress sustainable electrochemical technologies. Other researchers have stressed the need for experimental validation in HT computational screening workflows as well.18
By screening millions of material candidates computationally and validating the most promising experimentally, high-throughput workflows drastically reduce discovery timelines. This acceleration is critical for achieving key performance benchmarks required for the commercialization of renewable technologies, such as green hydrogen production, carbon capture, and advanced energy storage. Here, we review high-throughput methods—both computational and experimental—from the literature dedicated to discovering materials (catalysts, electrolytes, ionomers, etc.) for electrochemical energy applications. The objective of this review is to provide an overview of the popular HT techniques, state-of-the-art materials, and novel setups to serve as a reference point for scientists currently incorporating or initiating HT approaches into their research. We first highlight notable efforts with exceptional performance or unique setups, as well as common focuses and approaches. Finally, we provide an overview and a perspective of gaps that are worth further exploration.
To further minimize the computational cost associated with these calculations and facilitate large-scale material screening, DFT has been extensively used to compute descriptors—quantifiable representations of specific properties that connect complex electronic structure calculations and macroscopic properties. An effective descriptor can serve as a valuable metric for identifying promising candidates.34,35 A relevant example is the study of electrocatalysts, which are typically evaluated based on their reactivity toward a particular reaction. The reactivity descriptor that can quantify the catalyst's activity is often represented by the Gibbs free energy (ΔG) associated with the rate-limiting step (RLS) of the reaction. In many cases, the RLS is determined by the adsorption of one or one set of given reactants or intermediates. With this and the development of the computational hydrogen electrode model by Nørskov et al.,36 adsorption energy has become a well-studied descriptor for predicting catalytic activity. While activity and selectivity are crucial metrics for a successful catalyst, other essential factors, including chemical and electrochemical stability, must be considered. A comprehensive list of commonly used descriptors is provided in Section 2.1.2 and Table 1, and a detailed description of the most common methodologies in computational HT is given in ESI Table S1.† While convergence thresholds are system-dependent and therefore not directly comparable across studies, readers are directed to the original literature for application-specific optimization details.
Material | Rxn(s) | Method(s) | Descriptor(s) | ML algorithm | Suggested material(s) | Year | Ref. | |||
---|---|---|---|---|---|---|---|---|---|---|
DFT | ML | |||||||||
a ETR: extra-trees regressor, SVM: support vector machine, KRR: kernel ridge regressor, XGB: extreme GBR, ANN: feedforward artificial NN, LSR: least squares regression, RNN: recurrent NN, CBC: CatBoost classifier, RNC: radius neighbors classifier, LR: logistic regression, HGB: histogram-based GBR, LGBM: light gradient boosting machine, XRT: extremely randomized trees, DTs: decision trees, KNN: k-nearest neighbors, LAS: lasso regression, GBDT: gradient boosting decision tree, AB: AdaBoost, PLS: partial least squares, RDG: ridge regression, MLP: multilayer perceptron, ENR: elastic net regressor, GNN: graph NN, NORR: NO reduction reaction, BRT: boosted-regression-tree, MOR: methanol oxidation reaction, MD: molecular dynamics, minGPT: minimal generative pretraining transformer, 1Ddiffusion: 1D denoising diffusion probabilistic model, Diffusion-LM: diffusion language model, and BO: Bayesian optimization. | ||||||||||
Catalyst | eCO2RR | ✓ | ✓ | ΔGCO | ETR | GPR | CrN | 2023 | 37 | |
ΔGCHO | SVM | KRR | TiN | |||||||
ΔGOH | GBR | XGB | Cr3N2 | |||||||
Limiting potential differences | Cr2N | |||||||||
CoN | ||||||||||
Catalyst | eCO2RR | ✓ | ✓ | ΔGCO | ANN | None stated | 2015 | 38 | ||
Catalyst | eCO2RR | ✓ | ΔGCO | N/A | N6V4–AgCr | 2021 | 39 | |||
ΔGOOH/CHO | ||||||||||
Catalyst | eCO2RR | ✓ | ΔGCO | N/A | None stated | 2020 | 40 | |||
ΔGOH | ||||||||||
Catalyst | HER | ✓ | ΔGH | N/A | NbS2 | IrTe2 | 2020 | 41 | ||
Ba2Cu2 | NbSe2 | |||||||||
C8 | Ti2Se2 | |||||||||
Pr4C2Cl5 | TaSe2 | |||||||||
Ce4C2Br5 | ||||||||||
Catalyst | HER | ✓ | ✓ | Zero band gap | LSR | VS2 | MnS2 | 2021 | 42 | |
Thermodynamic stability | GBR | NiS2 | CrSe2 | |||||||
Low vacancy formation energy | RFR | ZrTe2 | TiTe2 | |||||||
ΔGH | ANN | PdTe | VSe2 | |||||||
Catalyst | HER | ✓ | ✓ | RNN | SVM | OsB2 | 2020 | 43 | ||
KRR | RF | Sc–N | ||||||||
Catalyst | HER | ✓ | ✓ | Thermodynamic stability energy | AB | GBR | Pd@B4 | Fe@P3 | 2022 | 44 |
Dissolution potential | CBC | XRT | Ru@N2C2 | Mn@P4 | ||||||
ΔGH | RNC | RF | Pt@B2N2 | Fe@P4 | ||||||
LR | DT | Fe@N3 | ||||||||
HGB | SVM | |||||||||
Bagging | KNN | |||||||||
LGBM | XGB | |||||||||
Catalyst | HER | ✓ | ΔGH | N/A | Zn@MoSvaSe | 2021 | 45 | |||
Cd@MoSvaSe | ||||||||||
Co@MovaSSe | ||||||||||
Catalyst | HER | ✓ | ✓ | Rotation angle of heterojunctions | LAS | MoTe2/WTe2 | 2020 | 46 | ||
Catalyst | HER | ✓ | Number of valence e− × electronegativity of dopants | N/A | None stated | 2022 | 47 | |||
ΔGH | ||||||||||
Catalyst | HER | ✓ | Strain energy (includes ΔGH, exchange current, overpotential, and TOF) | N/A | Fe–N-SWCNTs | 2023 | 48 | |||
Catalyst | HER | ✓ | ✓ | “Frozen” ΔGH | ANN | GBDT | None stated | 2020 | 49 | |
Relaxation energy | ||||||||||
Catalyst | HER | ✓ | ✓ | Distance contribution descriptor | SVM | Pt33Pd17Ni15.5Cu16P18.5 | 2023 | 50 | ||
Catalyst | HER | ✓ | ✓ | Variety (22) | RF | LSR | CN/MX2 heterostructures w/Sc and Ti intercalated | 2024 | 51 | |
AB | RDG | |||||||||
KNN | GBR | |||||||||
KRR | MLP | |||||||||
PLS | SVM | |||||||||
Catalyst | HER | ✓ | ✓ | ΔGH | AB | LAS | 28 promising materials in SI | 2023 | 52 | |
ENR | PLS | |||||||||
GBR | RF | |||||||||
KNN | RDG | |||||||||
KRR | ||||||||||
Catalyst | HER | ✓ | ✓ | ΔGH | RF | Ti3C2I2–Ir | 2022 | 53 | ||
Cohesive energy | ANN | Ti3C2Br2–Cu | ||||||||
SVM | Ti3C2Br2–Pt | |||||||||
LAS | Ti3C2Cl2–Cu | |||||||||
KNN | Ti3C2Cl2–Pt | |||||||||
Bayesian | Ti3C2Se2–Au | |||||||||
Ti3C2Te2–Nb | ||||||||||
Catalyst | HER | ✓ | Adsorption energy | N/A | Co–pyromellitic dithioanhydride (HER) | 2023 | 54 | |||
NORR | Limiting potential | Co–3,8-phenanthroline-5,6-dione (NORR) | ||||||||
Ratio of the d-band center + ratio of the work function | Co–phenan-thraquinone (NORR) | |||||||||
Catalyst | HER | ✓ | ✓ | ΔGCO | GNN | Cu3Pt | 2021 | 55 | ||
ORR | ΔGH | FeCuPt2 | ||||||||
ΔGO | ||||||||||
Catalyst | HER | ✓ | ✓ | ΔGH | ANN | None stated | 2021 | 56 | ||
OER | ΔQCu–Cu | |||||||||
Catalyst | NRR | ✓ | ✓ | Segregation energy | RF | Zr1Cr | 2024 | 57 | ||
ΔGN | Hf1Cr | |||||||||
Catalyst | NRR | ✓ | ✓ | Isolated electron number of d orbitals | BRT | Mo and W | 2021 | 58 | ||
Catalyst | NRR | ✓ | Binding energy between metal atoms | N/A | Mo@BM-β12 | 2021 | 59 | |||
Cohesive energy | Mn@BM-β12 | |||||||||
ΔGN | ||||||||||
Limiting potential | ||||||||||
Catalyst | OER | ✓ | Pourbaix (Nernst eqn) | N/A | Co–Ir | 2020 | 60 | |||
ΔGO | Fe–Ir | |||||||||
ΔGOH | Mo–Ir | |||||||||
Catalyst | OER | ✓ | ✓ | Transition metal–oxygen bond length | GBR | IrO2 | Fe(SbO3)4 | 2024 | 61 | |
First ionization energy | Fe(SbO3)2 | MoWO6 | ||||||||
Co(SbO3)2 | TiSnO4 | |||||||||
Ni(SbO3)2 | CoSbO4 | |||||||||
FeSbO4 | Ti(WO4)2 | |||||||||
Catalyst | OER | ✓ | Area-specific resistance | RF | SrZr0.125Nb0.125Co0.625Cu0.125O3 | 2024 | 62 | |||
ORR | K0.25Sm0.125Sr0.625Nb0.125Ta0.125Co0.75O3 | |||||||||
Bi0.125Sr0.875Y0.125Ni0.125Co0.75O3 | ||||||||||
Catalyst | OER | ✓ | Cohesive energy | N/A | IrN2 monolayer | 2021 | 63 | |||
ORR | ΔGx | |||||||||
Elastic constants | ||||||||||
Phonon distribution | ||||||||||
Formation energy | ||||||||||
Dissolution potential | ||||||||||
Catalyst | OER | ✓ | ✓ | ΔGOH | XGB | None stated | 2024 | 64 | ||
ORR | ΔGOOH | RF | ||||||||
ΔGO | ETR | |||||||||
ΔGOOH | GBR | |||||||||
Coordination number | ||||||||||
6 more features | ||||||||||
Catalyst | ORR | ✓ | Itinerant electrons | XGB | 15 different materials predicted | 2024 | 65 | |||
LGBM | ||||||||||
ANN | ||||||||||
Catalyst | ORR | ✓ | Surface energy | N/A | Ag3(Mn, Fe, or Co) | 2016 | 66 | |||
Segregation energy | Ag3(Zr, Mo, or Ru) | |||||||||
d-Band center | Ag3(Ta and W) | |||||||||
ΔGO | Ag–(Mn or Fe) | |||||||||
Ag–(Ta or W) | ||||||||||
Catalyst | ORR | ✓ | Formation energy | N/A | Co–ON3 | 2022 | 67 | |||
Single atom binding energy | ||||||||||
ΔGOH | ||||||||||
ΔGOOH | ||||||||||
Catalyst | ORR | ✓ | Oxygen vacancy formation energy | N/A | Dependent | 2017 | 68 | |||
MOR | Single Pt atom adsorption energy | |||||||||
Metal-induced electronic states | ||||||||||
Charge variation of deposited Pt | ||||||||||
Ionomer | ORR | ✓ | Proton conductivity | GPR | 60 new polymer candidates | 2023 | 69 | |||
Water uptake | ||||||||||
Gas permeability | ||||||||||
Band gap | ||||||||||
Thermal decomposition temperature | ||||||||||
Glass transition temperature | ||||||||||
Young's modulus | ||||||||||
Electrolyte | ✓ | Adiabatic redox energy | N/A | LiNi0.5Mn1.5O4 | 2015 | 70 | ||||
Vertical redox energy | ||||||||||
Reorganization energy | ||||||||||
Electrolyte | ✓ | Stoichiometrically valid reactions | N/A | None stated | 2023 | 71 | ||||
Electrolyte | ✓ | Redox potential | N/A | None stated | 2015 | 72 | ||||
Solubility | ||||||||||
Stability | ||||||||||
Electrolyte | ✓ | ✓ | Trajectory | GNN | None stated | 2023 | 73 | |||
Electrolyte | MD | ✓ | Ionic conductivity | minGPT | None stated | 2024 | 74 | |||
1Ddiffusion | ||||||||||
Diffusion-LM | ||||||||||
Electrolyte | MD | ✓ | Ionic conductivity | minGPT | None stated | 2024 | 75 | |||
Electrolyte | ✓ | ✓ | Diffusion coefficient | BO | Li3YBr6 | 2025 | 76 | |||
Electrolyte | ✓ | Ion conductivity | GNN | Li6PBrO5 | Li2AsF5 | 2024 | 77 | |||
GBDT | Li2Ta2O3F6 | LiZnPSe4 | ||||||||
Li10Mg7Cl24 | LiHgPSe4 | |||||||||
Li7Cl3O2 | LiBSe2 | |||||||||
Li2SbF5 | LiCuBr2 |
The second prominent descriptor type involves the electronic structure aspect and its derived properties, e.g., the d-band center, band gaps, work functions, phonon spectra, metal-induced electronic states, and charge variations. These descriptors are typically obtained from DFT-level calculations, unveiling atomic interaction and electronic features. However, due to the complex impact of electronic structures on reactivity and materials' properties, these descriptors may not indicate the same trend when conducting structure prediction for different systems. Mechanical descriptors, including elastic constants, Young's modulus, and glass transition temperature, are frequently reported in the literature, as they are used for predicting and comparing experimentally measurable properties. Geometric descriptors are similarly valuable and can vary based on material types. Examples include the rotation angle of heterojunctions, the distance contribution descriptor, the transition metal–oxygen bond length for mixed metal salts, and the coordination number in alloys, among others.46,50 These descriptors are often directly calculated through structural optimization, and no further electrochemical studies are needed. Therefore, they are efficient in predicting the structures' properties when there is a clear structure–property relationship. Finally, the intrinsic-structure descriptors gather prior knowledge from either theories or experiments, and they often do not require DFT calculations. These descriptors vary by material type and their respective properties such as the number of valence electrons, dopant electronegativity, the number of isolated d-orbital electrons, and the first ionization energy. These properties have been well studied and reported, and hence these descriptors can be easily implemented in material screening workflows where the studied materials normally have well-defined structures. For HT studies and screening, many researchers use multiple descriptors or modify common descriptors to increase scrutiny and find more applicable materials.
The integration of ML methods in HT material discovery processes has already showcased multiple advantages.29 Different algorithms allow models to be trained on various data types (graph, numeric, image, natural language, etc.) and enable many different predictive tasks (regression, classification, data generation, etc.). Thus, ML can be applied to a myriad of use cases for materials discovery. For example, ML methods can predict material synthesizability by analyzing existing experimental data such as reaction conditions and time. In addition, ML models or their key features can also accelerate DFT calculation processes and reduce calculation workloads when searching a vast compositional space. This is often done by training ML models using DFT data. Additionally, multiple data sources (experimental, computational, literature, etc.) can be integrated into ML models, making HT experiments and calculations faster, more scalable, and more suitable for complex multifactor-dependent material systems. Another advantage ML methods offer is the ability to implicitly build relationships and patterns between independent and dependent variables, such as structural features (e.g., composition) and macroscopic properties (e.g., conductivity), respectively, within a dataset. Therefore, scientists can better understand materials and then exploit these relationships to drive innovation through inverse material design where ML models predict hypothetical structures with targeted properties. The versatility of ML makes it a powerful tool for creating new solutions to computational materials discovery.
In recent years, the use of generative AI models (large language models, diffusion models, reinforcement learning-based generative models, etc.) in materials design has been on the rise. Yet, generative AI is still limited to applications in academia and research as evidence of its applications in industry or production/manufacturing environments is lacking. In research applications, scientists have applied generative AI to aid in materials discovery. For example, Song et al. and Li et al. applied inverse material design via ML to synthesize materials with specific properties for electrochemical CO2 reduction or high-capacity energy storage, respectively.82,83 Moreover, Alverson et al. utilized generative AI models such as variational auto-encoders, generative adversarial networks, and genetic algorithms as use cases for creating crystals and proposing new structures.84 Additionally, Bang, Kim, Hong et al. expanded on inverse design using generative AI models to discover materials with multiple properties, rather than optimizing a single property.85 While generative AI in materials discovery shows promise in limited applications in electrochemical materials discovery, it shares many of the pain points seen in other ML methods, such as a lack of publicly available robust training datasets and the limited ability of models to generalize outside of training dataset distributions and to real world experimentation.
While ML is a powerful tool that helps improve the quality and efficiency of the HT materials discovery process in many ways, it comes with drawbacks and challenges. First, insufficient high-quality data impede training accurate, generalizable machine learning models.86 Data-intensive ML models such as NNs and RFR require large, information-dense datasets for suitable performance. Creating datasets from experimental work, especially when traversing all possibilities of a material database, is demanding as experiments are expensive and time-consuming, require highly skilled experts, and are often proprietary. A lack of quality data can lead to poor model predictions when exploring beyond a model's training dataset distributions. Second, integrating multiple data sources (such as experimental work and DFT simulations) to train ML models lacks standardization, making collaborative efforts to solve problems in the field more challenging.87 Third, many ML algorithms behave as a “black box”, making their predictions challenging to trust and their proposed structure–property relationships impossible to explain explicitly. Nevertheless, these challenges can be addressed by building more robust and interpretive models and placing an emphasis on standardizing data handling practices.87
In contrast, the quality of ML models relies heavily on the amount and diversity of high-quality datasets, and their predictive ability often degrades when predicting beyond the distribution of the training sets. As a result, real-world applications of ML in HT discovery of materials require careful consideration when curating a training dataset and can be aided by uncertainty quantification and ongoing benchmarking against DFT calculations and real-world experiments.
A hybrid approach that combines DFT and ML leverages the complementary strengths of both methods to overcome their individual limitations. DFT calculations provide high-fidelity, physics-based training data with reliable energetics and electronic properties for well-defined material systems, serving as the foundation for accurate ML model development. Quantum chemical calculations ensure that the training dataset captures the fundamental physical relationships between structures and properties. Conversely, ML models trained on these high-quality DFT data can rapidly screen candidate materials at a larger scale with a fraction of the computational cost, enabling exploration of vast chemical spaces that would be prohibitively expensive using DFT alone. Readers are referred to Section 4 for examples of the combinatorial approaches.
Data reproducibility remains a major bottleneck in computational materials discovery. Experiments from which training datasets are derived may have similar product compositions but differ in the structure or properties due to changes in process parameters. Reproducibility can be improved by thorough capture of metadata and tracking key information such as ingredient lots, sample storage conditions, equipment calibration logs, etc. Initiatives such as the Materials Genome Initiative, Materials Acceleration Platform, and, for computational datasets, Novel Materials Discovery aim to improve reproducibility by hosting datasets that have detailed metadata, thus permitting multi-organizational validation of workflows.89–91 Reproducibility is also aided by laboratory information management systems that can assist in capturing metadata, process parameters, and equipment information, which allow more systematic and comprehensive experimentation records. Traditional lab equipment with automated data logging capabilities (e.g., ThermoFisher and HeiDolph) also helps reduce data noise and user input errors, which benefits experimental reproducibility. Automated chemistry platforms with end-to-end logging, such as Chemspeed and Unchained Labs automated platforms, are also helping to reduce human-caused variability to ensure reproducibility. Additionally, performing replicate analysis under controlled conditions will aid in improving reproducibility, allowing researchers to identify outliers. Replicate analysis must be balanced with resource limitations carefully as it is expensive and can be out of reach for many groups.
Standardized procedures enhance reproducibility as using agreed upon standards makes collaborative efforts and experimental validation simpler.92 Inconsistencies in procedures for characterization, calibration, or sample storage demand correction through standardization. Adopting community standards for experimental work can help reduce noise within experimental datasets and improve reproducibility.
In addition to improving experimental data quality via noise reduction, researchers can use data curation and filtration techniques. For example, anomaly detection using statistical thresholds and certain ML techniques (e.g., clustering or isolation forests) can reduce outliers from experimental data. Moreover, validating experimental data with computational results allows researchers to identify experiments that may have strayed from theoretical expectations. This technique could also be used to reduce the cost of replicate analysis as only samples that deviate from theoretical expectations would require such analysis.
Experiment reproducibility also affects ML, a data-driven technique. The usefulness of ML models depends on how well their predictions can generalize to physical experiments. Thus, if ML models are trained on non-reproduceable experimental datasets, their predictions may not generalize.
Limited sharing of experimental data in publications also acts as a bottleneck for the reproducibility and validation of results within the research community. Therefore, researchers practice data (i.e., datasets, methodologies, and metadata) sharing on platforms such as Zenodo, Figshare, Kaggle, or GitHub to promote reproducing experiments. When sharing information on data-driven methods such as ML, not only is it important to provide model weights, but also information such as training and testing datasets, the source of the datasets, dataset metadata, data cleaning procedures, data preprocessing steps, and training procedures (e.g., feature selection and hyperparameter optimization).
At first, Mao et al. used the aforementioned H adsorption energy (ΔGH) as the descriptor for the HER activity of Cu-based alloy nanoclusters with varying dopant concentrations.56 The DFT study depicted that changing the dopant concentration evolved the structure of the alloy, which affected the excess energy (structure stability), the number of active sites, and the ΔGH. From here, the authors figured that doping created a significant charge difference between the Cu vertex and edge sites and associated that with ΔGH. Therefore, the researchers proposed the average partial atomic charge difference between these two adjacent sites, ΔQCu–Cu, as a new descriptor that is easier to compute than ΔGH. Finding a more accessible descriptor to compute reduces the costs of computational material discovery via DFT, thus making this method more accessible to all researchers.
Yohannes et al. evaluated transition metal nitrides as eCO2RR catalysts using activity, selectivity, and stability DFT descriptors.37 Again, adsorption energies, ΔGCO and ΔGCHO, are used as descriptors to mark activity toward C1 products. Additionally, the authors uncommonly applied the adsorption energy of hydroxyl, ΔGOH, to predict the stability of the catalyst against –OH poisoning. If bound too strongly, the *OH can stay on the surface and hinder active sites for eCO2RR or reduce to water, thus stealing electrons and decreasing efficiency. Moreover, the HER is parasitic to eCO2RR, so the authors again used H adsorption energy, ΔGH, to predict eCO2RR selectivity on a catalyst surface over the HER. High selectivity (Faradaic efficiency) for eCO2RR reduces downstream separation costs, making the HER an undesired side reaction. With these descriptors, several Co-, Cr-, and Ti-based nitrides were suggested as catalysts worth further eCO2RR experimentation. This study showcases how adsorption energy can be applied in unique ways to probe properties outside of activity.
While most researchers funnel down materials with each step having a new criterion (single-objective approach), Kavalsky et al. performed a multiobjective optimization combining DFT and ML methods to discover single-atom alloy (SAA) electrocatalysts for the NRR.57 The researchers first employed sequential learning to train an ML model and build their full catalyst design space, which was then evaluated using DFT as implemented in the Autocat workflow shown in Fig. 2.98 The scores of three crucial performance metrics, stability, cost, and activity, were evaluated simultaneously to help discover electrocatalysts for nitrogen reduction. The chosen multiobjective descriptors were segregation energy (stability), the Herfindahl–Hirschman index (material cost), and ΔGN (activity), which presented Zr1Cr, Au1Re, Ag1Re, Ti1Fe, and Hf1Cr as promising performers (note that X1Y denotes a single dopant of species X into a host of species Y in the context of an SAA as shown in Table 1). The authors stated that this tactic catches suitable materials that single-objective screening would typically omit. This work indicated that considering small compromises in specific material properties when constructing such models can strengthen discovery.
![]() | ||
Fig. 2 Closed-loop workflow for discovery of SAA electrocatalysts. The workflow starts from selection of a material from the design space, followed by structure geometry optimization and the subsequent N-atom adsorption calculation. The calculated results are used to retrain the ML surrogate model, which encodes activity, cost, and stability metrics and outputs the candidate scores. The highest scoring candidate is selected for evaluation. Reproduced with permission from ref. 98. Copyright 2024 Royal Society of Chemistry. |
Unlike most materials science labs focused on HT screening catalysts, Tran et al. used ML to explore polymers for ionomers and membranes in fuel cells.69 This study aimed to find alternatives to Nafion, the state-of-the-art polymeric material for fuel cells and electrolyzers. Although proven effective in many circumstances, Nafion, a cation exchange ionomer, is expensive and not always best suited for its application. Replacing Nafion could also address safety concerns. Nafion is classified as a per- and polyfluoroalkyl substance, PFAS, which presents health effects due to its slow break down and persistence in the environment; traces of PFASs have been found in the blood of people and animals globally.99,100 In any case, the authors used eight key properties (e.g., ion conductivity, gas permeability, band gap, etc.) of Nafion as a benchmark for screening 30000 previously reported polymers using multiple ML models. The authors identified 60 new polymers as possible replacements because their predicted properties outperformed those of Nafion. Yet, this study did not include any safety-centered metrics to evaluate candidates for health effects and handling, identifying a need to improve this method. This work's strategy is enabled by polymer informatics, hoping to further leverage ML for future studies in discovering unencountered polymers.
Large-scale batteries, both solid-state and redox flow, can function as electrical grid stabilizers during periods of low demand by storing excess energy supply for later use. This application requires battery materials to be resilient against multiple charges and discharges during their lifetime. Therefore, researchers have employed HT methods to scope out new battery electrolytes with multiple oxidation states for charge storage, high ionic conductivity, wide potential ranges for stability, and high earth abundance for costs.
Researchers often use the so-called HOMO–LUMO gap, which is an electronic property calculated as the difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), to assess the stability descriptor of battery electrolytes' solvents. Generally, a larger HOMO–LUMO gap is associated with more stable materials. This approach enables rapid assessment without requiring the optimization of oxidized or reduced electrolyte molecules. However, the Knap lab indicated the impact of molecular geometry relaxation during electrolyte oxidation, providing evidence by screening the electrochemical stability of 100 carbonate and 300 phosphate molecules as solvents for Li battery electrolytes.70 Initially, the Knap lab's HT screening model focused on the oxidation and reduction potentials of isolated solvent molecules to determine their stability windows. Additionally, the model involved geometry optimization as some less stable (smaller gap) molecular formations of the electrolyte decomposed under different conditions. After presenting these results, the authors commented on their initial method and stated the importance of also including intermolecular interactions with other solvent molecules as well as Li ions. To enhance the prediction of the electrochemical stability of isolated electrolyte, the authors explicitly incorporated solvent molecules into their models. This approach allowed the authors to simulate H-abstraction and Li+ semi-fluorination scenarios more accurately. While preferred DFT models typically center on simple representations and minimal intermolecular interactions, making them a straightforward yet insightful tool, Knap et al. noted that more accurate results require more extensive and computationally intensive DFT calculations that may be beyond the reach of most researchers.
Material | Rxn(s) | HT application | Cell(s) | Deposition method | Best material(s) | Year | Ref. |
---|---|---|---|---|---|---|---|
a Scanning electrochemical microscopy cell.b Proton exchange membrane.c Membrane electrode assembly cell.d Rotating disk electrode cell. | |||||||
Catalyst | eCO2RR | Electroanalysis | 3-Electrode | Automated liquid handler deposition robot | Au6Ag2Cu2 | 2021 | 101 |
Catalyst | eCO2RR | Electroanalysis | SECMa | Polishing | Sn/SnO2 | 2020 | 102 |
Catalyst | eCO2RR | Synthesis | H-cell | Spin cast | Cu0.8In0.2 | 2017 | 103 |
Catalyst | eCO2RR | Material ID | SFC | Magnetron sputtering | Pd–Zn | 2019 | 104 |
Electroanalysis | |||||||
Catalyst | HER | Production | 3-Electrode | Dip coating | HC–MoS2/Mo2C | 2020 | 105 |
Catalyst | HER | Electroanalysis | 3-Electrode | Sputtering | Pd63Ni16Fe21 | 2023 | 106 |
Catalyst | HER | Electroanalysis | 3-Electrode | Sputtering | Ni56.5Co35Ti8.5 | 2022 | 107 |
Catalyst | HER | Synthesis | SDC | Sputtering | Co56Cr8Fe19Mo7Ni10 | 2022 | 108 |
Characterization | |||||||
Electroanalysis | |||||||
Catalyst | HER | Material ID | SDC | Co-sputtering | Co23Cu34Mo17Pd14Re12 | 2024 | 109 |
Flow cell | Spray-coating | ||||||
Catalyst | HER | Synthesis | PEMb and MEAc | Spark ablation | IrO2 | 2022 | 110 |
OER | |||||||
Catalyst | OER | Synthesis | Flow cell | Drop casted | CoO | 2022 | 111 |
Electroanalysis | 3-Electrode | Co(50%)Ni(50%) | |||||
CoNiFe (up to 12.5%) | |||||||
Catalyst | OER | Electroanalysis | SDC | Drop casted | Not stated | 2013 | 112 |
Catalyst | OER | Material ID | SDC | Ink jet printing-assisted co-op assembly | FeO.3Ni0.7Ox | 2013 | 113 |
Electroanalysis | Fe0.23C0.13Ni0.07Ti0.57Ox | ||||||
Characterization | |||||||
Catalyst | OER | Material ID | SDC | Inkjet printing | Ni30Fe7Co20Ce43Ox | 2014 | 114 |
Electroanalysis | RDEd | ||||||
Catalyst | OER | Material ID | SDC | Inkjet printing | (Ni0.1La0.1Co0.3Ce0.5)Ox | 2014 | 115 |
Electroanalysis | RDE | ||||||
Catalyst | OER | Material ID | SDC | Reactive co-sputtering | Mn0.4Sb0.22Sn0.08Ti0.3 | 2023 | 116 |
Electroanalysis | |||||||
Catalyst | OER | Synthesis | 25 compartment 3 electrode cell | Automated pipetting robot | La0.2Sr0.8Fe1−yCoyO3 | 2023 | 117 |
Electroanalysis | |||||||
Catalyst | OER | Characterization | SDC | Combinatorial reactive magnetron co-sputtering | Ni1−y−zFeyCrzOx | 2017 | 118 |
Electroanalysis | |||||||
Catalyst | OER | Synthesis | Joule heating method (synthesis) | Not stated | Fe–CoO | 2023 | 119 |
ORR | 3-Electrode cell | ||||||
Catalyst | ORR | Electroanalysis | SFC | N/A | Not stated | 2012 | 120 |
Catalyst | ORR | Synthesis | SDC | Drop cast printing | PtPdRhNi | 2020 | 121 |
Electroanalysis | RDE | PtPdFeCoNi | |||||
RRDE | |||||||
Catalyst | ORR | Electroanalysis | Scanning gas diffusion electrode half cell | Ultrasonic spray coating | Pt/C | 2024 | 122 |
Catalyst | ORR | Material ID | SDC | Co-sputtering | Ti14Ni17Cu16Zr21Pd17Hf15 (ORR) | 2022 | 123 |
HER | Electroanalysis | Ti11Ni13Cu18Zr17Pd19Hf22 (HER) | |||||
Catalyst | HER | Synthesis | Customized PEM electrolyzer | Spark ablation | NiFe | 2020 | 124 |
OER | Ni(O)OH | ||||||
IPA oxidation | |||||||
Catalyst | IPA oxidation | Electroanalysis | SDC | Combinatorial magnetron co-sputtering | Pt1Ru1Ir1.5/C | 2023 | 125 |
Drop cast | |||||||
Catalyst | MOR | Electroanalysis | Customized 25 compartment MEA | Not stated | PtRu | 2002 | 126 |
Gas diffusion electrode | eCO2RR | Electroanalysis | AutoGDE (SFC) | Evaporation | N/A | 2024 | 127 |
Multiple | eCO2RR | Electroanalysis | SFC | N/A | Cu foil | 2014 | 128 |
HER |
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Fig. 3 Examples of scanning cells for HT material screening. (a) Scanning droplet developed at the JCAP. Reproduced with permission from ref. 112. Copyright 2023 Royal Society of Chemistry. (b) Scanning droplet cell with expanded views of (top) droplet contacting the sample and (bottom) compositional library deposited on a Cu foil substrate. Reproduced with permission from ref. 121. Copyright 2020 National Academy of Sciences. Scanning flow cells with (c) an incorporated channel for inline ICP-MS and (d) an outlet for online EC-MS measurements and surrounding argon to block air diffusion. Reproduced with permission from ref. 122. Copyright 2014 AIP Publishing LLC. |
The Joint Center for Artificial Photosynthesis, JCAP, designed and built its own scanning droplet cell (SDC) to conduct HT screening and mapping mainly of OER catalysts.112–116 This setup, displayed in Fig. 3a, invokes a stationary 3-electrode cell, equipped with counter and reference electrodes, that comes in electrical contact with the working electrode via a controlled-area electrolyte droplet. Again, the working electrode sits on a motorized X–Y stage, which moves to change the sample. The cell does not press down on the working electrode substrate and thus is an open system exposed to the atmosphere, which is not a concern for studying the OER. The researchers created compositional libraries of catalysts using inkjet printing or co-sputtering and then mapped them with the SDC. The publications from this group boast automated screening of anywhere from 100 to 5400 different catalyst compositions and the creation of their corresponding activity maps (current vs. composition). Their work has led to the proposal of several different candidate materials for OER catalysis that are worth exploring further.
Unlike a SDC, a scanning flow cell (SFC), equipped with a gasket, touches down onto the working electrode surface to create a seal and thus a closed system.104,120,122,127,128 The electrolyte is ushered to and from the surface while tests are conducted instead of staying stationary in a droplet. SFCs are better for reactions where purity or oxygen reactivity may be a concern or reactions that require product quantification, like eCO2RR. Mayrhofer et al. reported a customized SFC for testing ORR catalysts.120 Their initial reported design had argon surrounding the cell tip to discourage air diffusion, and they conducted proof-of-concept experiments to determine catalyst geometric area, O2 saturation time, and any flaws in the design. This SFC was improved upon by adding online product analysis via electrochemical mass spectroscopy (EC-MS)128 and later gas flow and dissolution analysis via inductively coupled plasma-mass spectrometer (ICP-MS), as shown in Fig. 3c and d.122 Screening with SFCs typically takes longer than that with SDCs because of the extra time needed to properly make contact and to clean the surface after detaching. Even so, SFCs are an imperative tool for materials screening and discovery as many reactions, including those discussed here (e.g., the HER eCO2RR), require closed systems for proper electroanalysis.
Although not consistent with the scope of this review, we would like to highlight that many labs have developed successful electrochemical scanning cells for other studies, such as corrosion or photoelectrochemistry, which are also pertinent to material development and mitigation efforts.129–137
One example of these setups is the one developed and patented by Smotkin et al., which consists of a segmented MEA-type fuel cell capable of screening 25 catalyst samples at once.126,138–140 While the samples shared a common counter electrode and the reactant flowed to each in series, each catalyst in the array was isolated using a Teflon gasket and equipped with its own sensor to control potential and measure current. Instead of a multi-channel potentiostat, this study utilizes a voltage follower, a current follower, a programmable computer card, and LabView to set the potential output and acquire the current. The authors commented on their initial design and pointed out areas of improvement, such as the need to make sample preparation scalable. Although their reports focus mainly on bimetallic PtRu catalysts, their setup can easily be adapted to screen a library of different materials simultaneously.
Certain setups rely on optical techniques to screen samples for electrolysis. These optical methods incorporate cameras to visualize all samples simultaneously and interpret their reaction kinetics. For instance, Zou et al. designed a HT bubble screening tool to study Pd–Ni–Fe alloys for the HER.106 Co-sputtering all metals at once created a compositional library on a Cu electrode, which was later submerged in a glass 3-electrode cell for testing. The researchers positioned a camera at the bottom of the cell to record the gaseous H2 bubbles forming from the HER across the electrode. Then, the authors associated the bubble diameter (volume) with the activity at that position and composition, as shown in Fig. 4a. Hence, the larger the bubble, the better the activity, resulting in an activity map. The authors discovered Pd63Ni16Fe21 to be the optimal composition for their proposed alloy. Moreover, Hitt et al. observed eCO2RR activity of an array of 72 different catalyst compositions using a camera positioned over a customized gas-fed 3-electrode cell with an optically transparent window (Fig. 4b).101 Here, the authors added a pH indicator to the electrolyte and left it unstirred. Thus, as eCO2RR proceeded, over all catalyst samples at various applied potentials and protons were consumed, the pH increased, and the color of the electrolyte changed. The onset of the color change was related to the onset potential of eCO2RR for that catalyst. Lower values suggested a more active catalyst, and the authors created an activity map with their data. Au6Ag2Cu2 was the most active catalyst for CO production from eCO2RR. Although both examples, the bubble screening and pH sensing, demonstrate rapid catalyst screening, they cannot perform product quantification and assume uniform potential distribution across the electrode. Yet, these studies aimed to quickly identify the best material, which they succeeded in and followed up with a full electroanalysis of that material in a traditional single cell.
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Fig. 4 (a) HT bubble screening setup for measuring HER activity with an example of the camera view below. The camera below the working electrode allows for visualization of the H2 bubbles forming on the catalyst compositional library. WE: working electrode; CE: counter electrode; RE: reference electrode. Reproduced with permission from ref. 106. Copyright 2023 Elsevier B.V. (b) An exploded (top) and live (bottom) view of a custom, 72-sample HT cell for measuring eCO2RR activity based on color change with a pH indicator. The authors validated the setup by depositing the same catalyst in each location and ensuring that the pH color did not vary. Reproduced with permission from ref. 101. Copyright 2021 Springer Nature Ltd. |
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Fig. 5 Schematic of the VSParticle nanoparticle printing technology. A certain wattage is applied to metal electrodes which causes the metal to ablate and particles to detach. The particles agglomerate to form nanoparticles as they are carried by inert Ar to a vacuum chamber where they are printed via a nozzle onto a substrate of choice held by an XYZ-stage. Reproduced with permission from ref. 110. Copyright 2022 MDPI. |
The materials listed in Table 2 have potential for use in a myriad of electrochemical applications, yet most were studied at the lab scale. If a certain catalyst or electrolyte, for example, proves performative and cost-effective, then the next step would be scaling up its production. Zhang et al. took that next step by reporting HT production of two-dimensional MoS2 flakes for fabricating thermally treated MoS2/Mo2C (HC–MoS2/Mo2C) catalyst for the HER.105 The reported method involved extracting raw Mo concentrates (MoS2, MoO2, MoO3, and others) from an active open pit mine and exfoliating it with Mo2C to form two-dimensional MoS2 flakes. These MoS2 flakes were then dispersed in water to make an ink for dip-coating a high-surface area Cu foam substrate in. Lastly, the dipped substrate was heated in a CH4/H2 mixture to form the final electrode which exhibited a high activity of 1 A cm−2 at an overpotential of 347 mV. While HC–MoS2/Mo2C's performance is comparable to that of state-of-the-art Pt/C, the authors determined that the price of the Mo concentrate precursor is 5× cheaper than that of Pt. This reduction in material cost plus their HT method made HC–MoS2/Mo2C ∼30× cheaper than commercial Pt/C. Choosing to omit any purification steps helped reduce the cost of production while showing the resilience of the catalyst even with the existence of impurities originating from the mine. The authors anticipate their method being extended to other natural materials for HT electrocatalyst production.
Material | Rxn(s) | Cell(s) | Model(s) | DFT descriptor(s) | ML algorithm | Top material(s) | Year | Ref. | |||
---|---|---|---|---|---|---|---|---|---|---|---|
DFT | ML | ||||||||||
a Metal organic framework.b Rotating ring disk electrode.c LR: linear regression. | |||||||||||
Catalyst | eCO2RR | 3-Electrode | ✓ | Pore limited diameter | N/A | MOFsa | GAFRUD | 2022 | 150 | ||
Coordination of unsaturated metal sites | CAJQEL | ||||||||||
Adsorption capacity | cg400449c | ||||||||||
Catalyst | eCO2RR | Flow cell | ✓ | ✓ | ΔGCO | GNN | CuAl | 2024 | 79 | ||
ΔGH | |||||||||||
Formation energy | |||||||||||
Catalyst | HER | N/A | ✓ | ΔGH | N/A | BiPt alloy | 2006 | 151 | |||
Catalyst | HER | RDE | ✓ | A-site ionic electronegativity | N/A | (Gd0.5La0.5)BaCo2O5.5+δ | 2019 | 152 | |||
Catalyst | OER | H-cell | ✓ | N/A | BO | Co0.2Mn0.7Ni0.1Ox | 2023 | 153 | |||
Co0.6Fe0.3Ni0.1Ox | |||||||||||
Catalyst | OER | 3-Electrode | ✓ | ✓ | Bond length between metal ions & atom 2 | GBR | Ni covalent organic framework | 2021 | 154 | ||
Average charge of the active site | |||||||||||
Electron affinity for the metal center | |||||||||||
Ionic radius of the active site atom | |||||||||||
Catalyst | OER | 3-Electrode | ✓ | Decomposition energy | N/A | LaAlO3 | 2022 | 78 | |||
Pourbaix (Nernst equation) | |||||||||||
Cubic Pm3m space group | |||||||||||
Catalyst | OER | 3-Electrode | ✓ | ✓ | Electronic structure (O 2p band center, M 3d band center, and Bader charges) | RF | Co2.5Ga0.5O4 | 2024 | 155 | ||
ΔGO | BO | ||||||||||
ΔGOH | LAS | ||||||||||
ΔGOOH | |||||||||||
Catalyst | ORR | Multi-channel (4) flow double electrode cell | ✓ | N/A | SVM | Fe4.8%Zn95.2% | 2020 | 156 | |||
RDE | GBR | ||||||||||
Catalyst | ORR | RRDEb | ✓ | ΔGOOH | N/A | Cobalt porphyrin | 2022 | 157 | |||
Catalyst | ORR | SECM | ✓ | ΔGO on Fe | N/A | FeNiCuCoPt/CNFs | 2024 | 158 | |||
RRDE | |||||||||||
Catalyst | ORR | MEA | ✓ | d-Band center | N/A | Pt3Co | 2020 | 159 | |||
ΔGO | |||||||||||
ΔGOH | |||||||||||
Catalyst | ORR | Sealed glass cell | ✓ | Dissolution reaction energy | N/A | 26 OER oxide candidates | 2022 | 80 | |||
OER | Energy above the convex hull | 2 ORR oxide candidates | |||||||||
Electrolyte | HER | Button cell | ✓ | Oxygen vacancy | ΔGCO2 | N/A | BaSnxCe0.8−xYb0.2O3−δ | 2024 | 160 | ||
ORR | Hydration energy | ΔGH2O | |||||||||
OER | |||||||||||
Electrolyte | ✓ | ✓ | Li mole fraction | Li diffusivity | GNN | NaxLi3−xYCl6 | 2024 | 161 | |||
Band gap | Cost | ||||||||||
Redox potential | Shear modulus | ||||||||||
Stability | Density | ||||||||||
Electrolyte | ✓ | N/A | LRc | 1,4-Dioxane | 2022 | 162 | |||||
GPR | |||||||||||
Electrolyte | ✓ | ✓ | N/A | BO | dioxane![]() ![]() ![]() ![]() |
2024 | 163 | ||||
Electrolyte | ✓ | Energy above the convex hull | N/A | Li3OCl | 2025 | 164 | |||||
Reaction energy | |||||||||||
Band gap | |||||||||||
Ionic conductivity | |||||||||||
Electrolyte | ✓ | Li-phonon band center | N/A | Li3ErCl6 and 17 other candidates | 2019 | 165 |
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Fig. 6 (a) Material screening based on phase stability. (b) Workflow of discovering solid electrolytes with miscellaneous screening criteria. (c) Ionic conductivities of NaxLi3−xYCl6 measured at different temperatures. (d) Relationship between the crystal structure and ionic conductivity. Reproduced with permission from ref. 161. Copyright 2024 American Chemical Society. |
Sarwar et al. recently performed HT-DFT calculations to study the electrocatalytic activity and stability of over 2000 Pt3M bimetallic alloys for the ORR, where M represents a list of 21 metals.159 The researchers evaluated the effectiveness of descriptors such as the surface d-band center and ΔGO and investigated the impact of M surface segregation under vacuum and O- and OH-induced conditions. By conducting experimental studies, the authors were then able to correlate the O-induced segregation energy with the percentage of M metal loss (leaching). Moreover, the computational findings indicated that the d-band center might not be a reliable descriptor once surface segregation effects occur as the d-band center could not predict the decrease in ORR activity once the M metal migrated to the surface (leaching). This phenomenon was confirmed with the electroanalysis data as ORR activity displayed an enhanced correlation with ΔGO compared with the d-band center. Therefore, the authors concluded that ΔGO could serve as a better descriptor when considering the surface and binding energy changes post-segregation. This discovery suggests that some descriptors may be suited for certain catalyst morphologies, which could motivate more tailored DFT calculations for specific material configurations.
Coupling experimentation and computation for Karim et al. involved conducting experiments not only after but also before creating their ML model.156 At first, the researchers prepared 36 different catalyst samples using a HT automated synthesis platform and followed up by testing them all for ORR activity. The electrochemical cell for running the ORR was a customized multi-channel flow cell capable of screening four catalyst samples at a time. Out of the resulting dataset, 60–80% were used to train five ML models with the synthesis parameters (Fe atomic%, pyrolysis T, and Fe precursor) as inputs. Each ML model utilized a different algorithm to help find the minimal (optimal) RMSE and mean absolute percentage error. The best-performing algorithms were gradient boosting and support vector regressions. From here, the authors used these two optimal models to predict ORR activity as a function of the synthesis parameters, which represents outputting new catalysts. Taking it a step further, the researchers synthesized new catalysts using these predicted parameters and tested them for ORR activity to validate the model. The new material not only met but exceeded its modeled performance. Continuing this method of synthesis, testing, training, and predicting could allow the authors to iteratively improve their model and find the next best materials for the ORR before expanding it to other reactions.
To find the optimal solvent for electrolytes in redox flow batteries, researchers at PNNL and Argonne National Laboratory developed an automated workflow that linked robotic HT synthesis and analysis with ML, as shown in Fig. 7.163 In short, they built a closed-loop, ML-guided HT experimentation setup to further speed up screening. To start their study, the authors listed 22 possible solvent candidates and then created an additional 2079 candidates based on binary mixtures of various volume ratios of the original 22. Next, their automated robotic platform synthesized 58 of these candidates (both singular and binary solvents) for model training at a rate of ∼39 min per sample. Each electrolyte sample was prepped for nuclear magnetic resonance (NMR) and then manually transported to an auto-sampling NMR machine for quantitative analysis of 1H NMR spectra. The integrated peak areas were used to calculate solubility. The results from these 58 samples first trained a surrogate model to determine whether Bayesian Optimization (BO), a type of AL, would be effective with this dataset. The surrogate model training was then validated with 40 additional solvent candidates and then it was asked to identify the solvent with the highest solubility out of its 98 samples. Once the surrogate model was verified, the authors deployed BO to complete their ML-guided, closed-loop setup and then ran three cycles. Each cycle started with (1) the model suggesting 40 solvent samples, (2) synthesis and evaluation as described above, and (3) feeding the results back into the model. BO only took one cycle to identify dioxane:
dimethyl sulfoxide @ 0.8
:
0.2 vol% as the solvent with the highest solubility. Since the subsequent cycles did not detect a better solvent, the authors halted their evaluation meaning that their model only needed 218 measurements from the >2000 sample dataset to output the optimal solvents and solvent ratio. The detailed automated HTE system for solubility measurement is given in Fig. 8. This demonstration of BO underscores how active (machine) learning can drive experimentation toward minimizing the time and calculations (cost) needed to screen larger datasets and discover materials.
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Fig. 7 Schematic of the closed-loop electrolyte screening process based on an ML-guided HT experimentation platform. Reproduced with permission from ref. 163. Copyright 2024 Springer Nature Ltd. |
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Fig. 8 (a) Schematic representation of the automated HTE system for solubility measurement. The automation process consists of powder (b) and solvent (c) dispensing, (d) saturated sample monitoring, and nuclear magnetic resonance (NMR) sampling (e) and analysis (f). (g) Evaluated experimental time per sample for different solubility measurement methods. Reproduced with permission from ref. 163. Copyright 2024 Springer Nature Ltd. |
Understanding that the search space for catalyst multi-element electrocatalysts is too vast even for automated HT robotic platforms, Kodera and Sayama also incorporated ML into their robot system to explore catalysts for the OER and HClO production using seawater.153 Their fully automatic robot was able to conduct synthesis and electroanalysis of 88 catalyst samples per day. The authors started by setting their system to synthesize and analyze different combinations of four elements (Co, Mn, Fe, and Ni), chosen based on their reported performance, to obtain 286 data entries. With these data, the authors investigated composition optimization using BO by having the ML model and robot run cycles; the model suggested 10 materials which the robot system then synthesized and analyzed. The cycles were halted after four loops when the model identified the top 10 performing materials of the 286 original samples. Thus, only 40 samples were needed to validate and optimize the model. The authors stress that, as stated in the previous paragraph, BO-guided experiments reduce the time needed to evaluate datasets and optimize materials. In addition, the authors proposed choosing more elements, expanding the abilities of their robot platform, and using multi-objective optimization such as that by Kavalsky et al.57
HT method | Pros | Cons |
---|---|---|
Experimental | Physical observations & real-world results | Spatial and time limits |
High data reliability | More resource intensive | |
Accounts for synthesis conditions | Safety/environmental constraints | |
Computational | Massive screening (>103 materials) | Model accuracy limitations |
Cost-effective and rapid testing | Requires experimental validation | |
Safe exploration | Difficulty in capturing synthesizability |
The distribution of methods reviewed in this article is depicted in Fig. 9a as a bar graph. We can see that most reports conducted HT studies via computation, which we expect since it is faster, safer, and less resource-intensive than experiments. There is a significant discrepancy, however, in the material type (Fig. 9b). Of all the publications we discovered and analyzed for this review, over 80% focused on catalysts no matter the reaction. Although responsible for driving the reaction, the catalyst is not the only component of an electrochemical reactor. These percentages in Fig. 9b are only based on the thorough search we conducted in the literature space and thus not representative of the entire field; yet we still suggest that critical components such as membranes, ionomers, and substrates remain underexplored using high-throughput methods although they are necessary in such systems. These components are critical to the long-term operation, durability, and efficiency of electrochemical systems. Many degradation mechanisms that lead to failure and insufficient lifetimes in electrochemical systems are associated with not only the catalyst but also the substrate (or membrane) it is deposited on and/or the ionomer that binds them together, if applicable.167 The development of polymer informatics platforms could facilitate the discovery of next-generation ionomer and membrane materials that rival or outperform current standards such as Nafion and other PFAS polymers that also present environmental liabilities. Moreover, highly conductive electrolytes provide ion transport but may be corrosive or detrimental to all components in the system in the long term. Although ∼12% of the reports investigated electrolytes, most pertain to batteries and not those for fuel cells and electrolyzers. Therefore, this review underscores the need for broader HT efforts that investigate all materials involved in electrochemical reactors to address performance bottlenecks effectively. Nevertheless, we understand that constructing compositional libraries and datasets for materials such as polymers and substrates is more complex than for catalysts. Polymers for ionomers and membranes are not as simple to model as metal catalysts due to their larger size, intricate structures, and heterogeneous nature.168 These macrostructures generally feature complex arrangements with numerous degrees of freedom, which increases the computational demand of simulations. Like polymers, substrates–materials onto which catalysts are deposited—are also macrostructures and generally heterogeneous. Accurately capturing complex interactions and dynamic behavior of these polymers and substrates with their surroundings requires advanced computational techniques and a considerable number of resources.
Another potentially critical direction involves extending HT methodologies beyond material-level screening to capture device-level performance metrics. Current HT platforms typically evaluate properties such as onset potential, overpotential, or adsorption energy in simplified environments. However, real-world performance is governed by how materials function within integrated systems. Developing modular experimental platforms that can vary multiple components simultaneously—for instance, testing combinations of catalysts, ionomers, and membranes within the same electrochemical cell—would allow for the co-optimization of interdependent variables. Incorporating accelerated stress tests and diagnostics into HT setups could also provide early insights into material degradation pathways and lifetime expectations, enabling more predictive screening of materials for industrial relevance.
As mentioned in Section 2.1, many DFT studies successfully utilize activity descriptors, whether ΔG or partial atomic charges, and stability descriptors to screen catalyst materials. While activity and stability are imperative, many of the computational methods reviewed here do not consider the cost, availability, safety, both environmental and personal, and complexity of synthesis when proposing new materials. Some of these suggested materials are dangerous, expensive, and synthetically impractical, which makes their window for scale-up very slim and complicated. In addition, some materials may be sourced from carbon-intensive processes, which defeats the purpose of green technologies and calls for carbon neutrality analysis when discovering and proposing new materials. This issue presents opportunities to discover new descriptors that can screen for these properties, such as hazard diamond ratings or toxicity of precursors, material biodegradability, earth abundance indices, and cost indices of metals (like that used by Kavalsky et al.57). Jia et al. applied cohesive and formation energies as descriptors for ease of synthesis which more researchers can expand on.63 Integrating life cycle assessment into computational models makes it possible to evaluate the environmental impact and predict the long-term behavior of materials.186–188 There is also the opportunity to identify and explore other properties and descriptors not named here that are important for a material's feasibility. These descriptors can be extracted from databases, developed using cheminformatics tools, or derived from techno-economic proxies such as precursor cost or process energy intensity. When it comes to experimental methods, more scientists can consider comparing the cost of their suggested material(s) to the state of the art on top of comparing the performance and commenting on the safety of the material(s) they suggest.
In this review, we examined studies that benefit from combining ML and DFT approaches to make their HT screening even more powerful as a tool. However, it is worth mentioning that access to effective and significant computational resources applicable to the generation of databases required to train ML models is a challenge for many researchers around the world. The same can be said for experimentation, as fully equipped, functioning labs are expensive to build, let alone automated HT systems. In fact, Table 5 roughly estimates and compares the cost of HT experimental equipment, HT supercomputers, and supercomputing time. The price of a fully functioning HT lab can easily reach $100000 USD in equipment alone, not considering overhead, utilities, maintenance, etc., to keep it up and running. Access to well-equipped shared facilities such as those found at universities and national labs would remove the burden of procuring such equipment, making HT experiments cheaper. Yet, access to such facilities can be limited to specific users and user rates may apply, which can add to cost over time as more experiments are conducted and more materials are screened.
Experimental | Computational | |||
---|---|---|---|---|
HT equipment | Method | Average cost (USD) | HT equipment | Average cost (USD) |
Scanning flow/droplet cell169,170 | Electroanalysis | $110![]() ![]() |
1-Rack high performance computing cluster with 10 CPU nodes171–173 | $200![]() ![]() |
X-ray diffraction147 | Characterization | $300![]() |
||
X-ray fluorescence146,174 | Characterization | $100![]() |
||
Confocal microscopy175,176 | Characterization | $70![]() ![]() |
||
Nanoprinter177 | Synthesis | $350![]() |
Supercomputing time178–181 | $0.005–$0.0625 per hour |
Automated synthesis platform182,183 | Synthesis | $70![]() ![]() |
||
Robotic arm184,185 | Versatile | $25![]() ![]() |
Going off method costs, we also examined where these HT studies were being conducted. Looking at Fig. 10, we see that most of the HT studies we evaluated here were performed by researchers in only a handful of countries (19). However, the motivation for such studies stems from a global issue. We understand that our review, while thorough, is not exhaustive and can only offer a glimpse of what is occurring in this field. Either way, we in countries with access to these resources can push the envelope and collaborate with those in countries that do not. To democratize participation, future work should prioritize the development of low-cost, open-source datasets, modelling tools and cloud-based simulation platforms that reduce entry barriers. Similarly, the establishment of shared robotic facilities or “HT-as-a-service” centers, where researchers can remotely submit and analyze samples, could dramatically broaden global engagement. Capacity-building programs, research exchanges, and international consortia that foster technology transfer and technical training will be particularly important in regions where energy transitions are most urgently needed. Such collaborations can offer more unique perspectives on HT material discovery, leading to new and improved ideas.
Detailed information on data preprocessing steps and links to datasets were missing in many of the papers that we analyzed in this review. Such information is pertinent as it allows researchers to make informed decisions about comparing model performance and therefore finalize model use for their own studies. Access to datasets and preprocessing steps helps one determine model generalizability and helps improve model interpretability, especially when it comes to “black box” models such as neural networks or ensemble learning models. Furthermore, sharing preprocessing steps allows the research community to (1) validate model performance and results through independent experimentation, leading to more robust models and computational methods and (2) modify and build upon these models and datasets.
We recognize that researchers have already taken steps to make HT computational methods and experimental setups available to everyone. Published studies may include how to obtain the data and links to open-source code (e.g., GitHub). Some authors go so far as to ask readers to comment or build on their results and are open to connecting with other researchers about their work. For uses such as training ML models, finding material properties, or simply comparing results, researchers have created open datasets for people to pull from and/or augment. One example is the Open Catalyst Datasets, which are meant to aid in ML model training.189,190 This dataset is part of the larger Materials Project which allows researchers to access computed information on known and hypothetical materials.191 Researchers at the Toyota and the Massachusetts Institute of Technology collaborated to create a cloud platform for sharing polymer electrolyte data.192 Many other material databases have been designed for similar purposes that scientists continue to add to and use for their research.193–195 Equally important is the development of standardized experimental formats and reporting guidelines that support machine readability and enable cross-laboratory benchmarking. Practicing open-source research should be continued as it is an imperative tool for materials discovery and is becoming more prevalent among researchers, especially in the fields we discussed here. A coordinated community effort to develop open-access HT datasets, curated with rich metadata including synthesis conditions, characterization protocols, and failure modes, would dramatically expand the reproducibility and generalizability of future research.
Footnote |
† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d5ta00331h |
This journal is © The Royal Society of Chemistry 2025 |