Achieving a balance of rapid Zn²⁺ desolvation and hydrogen evolution reaction inertia at the interface of the Zn anode

Abstract

It is difficult to achieve fast kinetics of Zn²⁺(H₂O)₆ desolvation as well as HER inertia at the same electrolyte/Zn interface during long-term cycling of Zn plating/stripping in aqueous Zn-ion batteries. Herein, an effective interface construction strategy with hydrophilic transition metal oxides was proposed to achieve that balance using a CeO₂ layer coating. The hydrophilic CeO₂ layer can bring a balance between improving the access to the anode surface for Zn²⁺(H₂O)₆ electrolyte ions, providing uniform Zn²⁺ nucleation sites and HER inertia. What's more, Zn corrosion can be significantly inhibited benefiting from this coating layer. The efficiency of aqueous Zn-ion batteries showed a great enhancement. Ultra-long plating/stripping stability up to 1600 h and excellent recovery (returning to 0.5 from 20 mA cm⁻²) for the symmetric CeO₂@Zn system were observed. A full cell with the MnO₂ cathode (CeO₂@Zn//MnO₂) with good reversibility and stability (∼600 cycles) was fabricated for practical application. Our work provides a fundamental understanding and an essential solution to deal with the balance between rapid desolvation and inhibition of the hydrogen evolution reaction, which is important for promoting the practical application of rechargeable Zn batteries.

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1. Introduction

Among various future battery technologies beyond the lithium ion, aqueous zinc-ion batteries (ZIBs) with near-neutral electrolytes have attracted particular attention in recent years due to the following advantages: low cost, good safety, and a high abundance of Zn.^1–3 However, the great potential development of Zn metal anodes is severely hampered by the low plating/stripping coulombic efficiency (CE) and poor cycling stability caused by hydrogen evolution, corrosion and dendrite formation in slightly acidic electrolytes.^4–6 The side reactions could be expressed as follows:

H₂O + e⁻ → ½H₂↑ + OH⁻

4Zn²⁺ + 6OH⁻ + SO₄²⁻ + nH₂O → Zn₄SO₄(OH)₆·nH₂O↓

The growth of Zn dendrites originated from the inhomogenous nucleation sites during the long-term cycling process, especially under large current density conditions.^7–10 What's more, Zn dendrite growth and the HER would accelerate with each other.¹¹ With the growth of dendrites, more active sites would be exposed and accelerate the HER rate;¹² while a rough surface would be formed on the surface of Zn as Zn corrodes in the HER.¹⁰ This lowers the energy barrier of the desolvation process of Zn²⁺(H₂O)₆ at the interface of the electrolyte/electrode to enhance a fast mass transfer kinetics of Zn plating/stripping, which is important for fostering homogeneous ion distribution and uniform deposition.¹³ As reported by the research studies, hydrophilic surfaces are beneficial for driving the first trapping process of Zn²⁺(H₂O)₆, however, this always occur along with solvent molecule degradation and the HER.⁷

Though various strategies have been reported on tackling these anode issues, it is still difficult to reach a certain balance between HER inertia and fast kinetics of Zn²⁺(H₂O)₆ desolvation^4,10,14–17 to achieve continuous regulation of the deposition behavior of Zn during a long-term cycling process. Hence, suppressing the parasitic reaction and inducing homogeneous Zn plating/stripping at the fundamental level are urgently needed.^7,11,18

Analyzing the thermodynamic problems, based on the research results of the field of electrocatalysis,^19–21 the HER is a typical two-electron transfer reaction with one catalytic intermediate (H*, where * denotes a site on the electrode surface) and occurs via either the Volmer–Tafel or the Volmer–Heyrovsky mechanism:²²

Volmer step:

H⁺ + e + * → H* (1)

Heyrovsky step:

H* + H⁺ + e → H₂ + * (2)

Tafel step:

2H* → H₂ + 2* (3)

The hydrogen adsorption free energy ΔG_H above controlled the rate of the overall reaction. Based on the Sabatier's principle that the binding energy between the catalyst and the reactant should be neither too strong nor too weak, if hydrogen binds to the surface too weakly, the adsorption (Volmer) step will limit the overall reaction rate, whereas if the binding is too strong, the rate will be limited by the desorption (Heyrovsky/Tafel) step.^23,24 For 2M ZnSO₄ aqueous solution, it was weakly acidic because of the reaction Zn²⁺ + 2H₂O = Zn(OH)₂ + 2H⁺.^25,26 It is very easy for (1) the Volmer step to occur because that H⁺ owns an empty 1s orbital which could bind strongly with the surface O.²⁷ However, too much strength of the O–H bond can make the following desorption (2)/(3) (Heyrovsky/Tafel) step very difficult to occur, bringing the high energy barrier of the whole HER process. Therefore, barely transition metal oxides were used for electrocatalytic HER in acidic medium.^27,28 Here in the system of aqueous Zn-ion batteries, the HER is taken as an adverse reaction which needs to be inhibited.¹²

Based on this, CeO₂ was deliberately chosen as a coating layer to fabricate an interface bringing a balance between HER inertia and fast kinetics of Zn²⁺(H₂O)₆ desolvation. On one hand, CeO₂ is a kind of typical indirect transition N-type semiconductor which is unfavorable for HER.^17,27,29,30 On the other hand, it has a hydrophilic property.³¹ This gives the potential of CeO₂ that ensures a fast capture of Zn²⁺(H₂O)₆ leading to a uniform distribution of Zn²⁺ nucleation sites as well as inhibiting the HER adverse reaction.^4,15,24,32 What's more, the standard electrode potential of Ce⁴⁺/Ce³⁺ in aqueous solutions at 25 °C (vs. NHE) was much higher than φ_Zn²⁺/Zn as shown in the following:

Ce⁴⁺ + e ⇄ Ce³⁺ 1.72 v

H⁺ + e ⇄ 1/2 H₂ 0 v

Zn²⁺ + 2e ⇄ Zn −0.76 v

It means that during the zinc deposition/stripping process, the CeO₂ modified layer is stable and does not allow other side reactions. Furthermore, the semiconductor CeO₂ layer can prevent the dissolution of alkaline zinc sulfate by-products into the electrolyte, slowing down the rate of corrosion on the zinc surface, which furthermore prohibits the HER.^4,16,24,32 This positive role of CeO₂ is shown in Fig. 1.

Fig. 1 Schematic diagram of the protection mechanism of the CeO₂ layer for CeO₂@Zn in Zn-ion batteries.

2. Results and discussion

To fabricate the coating layer, CeO₂ powder was dispersed in 4% PVDF and then drop cast onto the surface of Zn foil, NMP was removed by drying in the oven as described in the ESI.† The X-ray diffraction pattern in Fig. S1† shows the successful cast of CeO₂ without any changes in the crystal structure. Meanwhile, a small amount of PVDF here was used to guarantee the elasticity and flexibility of the coating layer as reported by our group members before.³³

The hydrophilicity of the interface was confirmed from the contact angle measurements in 2 M ZnSO₄ electrolyte. As shown in Fig. 2f and g, the significantly improved hydrophilicity of the CeO₂@Zn foil anode was proved by the smaller contact angle of 60.69° compared to that of Zn foil (92.25°), that makes a great contribution to the easier desolvation process for Zn²⁺(H₂O)₆ at the interface of the CeO₂ layer.

Fig. 2 Voltage profiles of symmetric cells based on Zn foil and the CeO₂@Zn anode at (a) 2 mA cm⁻² with a capacity of 1 mA h cm⁻², (b) 5 mA cm⁻² with a capacity of 2.5 mA h cm⁻² and (c) 5 mA cm⁻² with a capacity of 10 mA h cm⁻², (d) CV curves of Zn//Ti and CeO₂@Zn//Ti (0.2 mA cm⁻² for 15 h), (e) LSV curves of bare Zn foil and CeO₂@Zn foil under a neutral electrolyte, (f) the contact angle measurement results for (g) bare Zn and (g) the fabricated Zn anodes.

To examine the inhibitory effect on hydrogen evolution of this coating layer, CeO₂ modified on Zn foil was examined in a three-electrode system with 1 M Na₂SO₄ aqueous electrolyte, in which CeO₂@Zn foil or Zn foil was used as the working electrode, Ag/AgCl as the reference electrode, and carbon rod as the counter electrode (for more details, see the ESI†). As depicted in Fig. 2e, the LSV curves show that the overpotential for CeO₂@Zn foil to reach a current density of 20 mA cm⁻² was ∼110 mV, much higher than that of pure Zn foil, which provides direct evidence of the inhibition of the HER by the CeO₂ coating layer.

Long-term cycling stability of the symmetric batteries under different current densities and area capacities were tested as shown in Fig. 2a, b and Fig. S9–S12.† The symmetric CeO₂@Zn cells exhibited a prolonged lifespan over 1600 h (2 mA cm⁻², 1 mA h cm⁻²), 750 h (5 mA cm⁻², 2.5 mA h cm⁻²), 150 h (5 mA cm⁻², 10 mA h cm⁻²) and 75 h (20 mA cm⁻², 20 mA h cm⁻²), respectively, compared to that of the bare Zn anode at about ∼360 h, ∼80 h, ∼20 h and ∼40 h. According to the above experimental results, this might be ascribed to the stable hydrophilicity and the formation of an HER inert solid electrolyte interface layer; all the symmetric CeO₂@Zn cells lasted longer than the symmetric bare Zn cells. The corresponding CE curves are also presented in Fig. S11–S13.†

The nucleation stage is a pivotal step for understanding the transformation course of Zn dendrite formation. The positive role played by the CeO₂ coating layer on this aspect was proven by the overpotential evolution of symmetric Zn//Zn and CeO₂@Zn//CeO₂@Zn cells at a current density of 2.0 mA cm⁻² with a total capacity of 1.0 mA h cm⁻² at the initial 3 cycles.¹¹ As can be seen from Fig. S14,† each Zn²⁺ deposition process has a typical nucleation overpotential in the Zn//Zn cell. However, there is no obvious nucleation overpotential for the CeO₂@Zn//CeO₂@Zn cell except the initial nucleation overpotential, which shows that the CeO₂ coating layer reduces the energy barrier of Zn²⁺ nucleation and changes the deposition process of Zn²⁺ compared with that of bare Zn. The positive role in inhibiting the HER played by the CeO₂ coating layer can also be proven by the phenomenon that the symmetric Zn//Zn batteries split much quickly than CeO₂@Zn//CeO₂@Zn cells because of the gas inside during long-term cycling.

Zn deposition on a foreign substrate such as bare Ti foil was investigated as shown in Fig. 2d. A crossover characteristic of nucleation processes was observed while sweeping the potential toward the positive direction and labelled as “A” in Fig. 2d, and the potential value of which is also known as the crossover potential (E_oc). The potential difference between the crossover point (A) and the point (B/B′) where Zn²⁺ starts to be reduced on the substrate is regarded as the polarization voltage difference. No excess decomposition current on the CeO₂ interphase was observed, indicating that chemically stable films did not bring about other side reactions during cycling.^11,34

To better understand the behavior of the CeO₂ coating layer during the Zn electrodeposition process, an optical microscope was used to monitor in situ the surface morphology of the dendritic growth for Zn electrodes (CeO₂@Zn and Zn). Homemade optical cells were fabricated with a transparent glass plate and 10 mA cm⁻² was applied to the cells as shown in Fig. 3 and the ESI.† It can be seen from Fig. 3a that Zn dendrites were distributed randomly on the bare Zn surface after 10 min, and formed tree-like Zn dendrites after 30 min deposition. These Zn dendrites cannot be reused and might puncture the diaphragm. The formation of these fragile dendrites (dead Zn) resulted in short circuits during the cycling stability test for Zn//Zn symmetry cells (Fig. 2a–c and Fig. S5, S9, and S10†). In contrast, it could be observed through the in situ deposition video (Fig. 3b and ESI video 1 and 2†) that CeO₂ uniformly covered the surface of Zn foil at the beginning; Zn²⁺ tended to electrodeposit above the surface of Zn but under the CeO₂ layer when the voltage was applied, which prevented Zn₄SO₄(OH)₆·nH₂O from dissolving into the electrolyte. This could also be proved from the XRD patterns of bare Zn and CeO₂@Zn after 250 cycling tests as seen from Fig. 5. The CeO₂ layer pushed slowly and evenly with no observed dendrites on the surface of CeO₂@Zn even after 30 min. Its uniform deposition could be attributed to the homogenization of the nucleation site by the CeO₂ layer alongside the inhibition of the HER as discussed earlier in Fig. 1.

Fig. 3 Optical microscope images of (a) bare Zn and (b) CeO₂@Zn in the aqueous ZnSO₄ electrolyte to characterize the dendrite growth during plating at a current density of 10 mA cm⁻².

The feasibility of CeO₂@Zn anodes in the practical application was further verified by full cells using MnO₂ as the cathode. MnO₂ was synthesized by a hydrothermal method according to a previous reports,³⁵ with its purity and phase state characterized by XRD as shown in Fig. S1.† The featured peaks of the sample corresponded to the standard α-MnO₂ (JCPDS: 44-0141) spectrogram, which indicated that the synthesized MnO₂ was in the α crystal phase. It indicated a nanorod morphology for the α-MnO₂ used in this experiment (Fig. S2†). For the full cell test, 0.1 M MnSO₄ was added to 2 M ZnSO₄ electrolyte to suppress the disproportion reaction of MnO₂.³⁵ As seen in Fig. 4a, both Zn//MnO₂ and CeO₂@Zn//MnO₂ showed the same two pairs of anodic/cathodic peaks in the CV curves derived from the two-step reverse oxidation/reduction between MOOH and MnO₂, in agreement with those reported in other literature studies.⁴

Fig. 4 Performance of Zn/MnO₂ and CeO₂@Zn//MnO₂ batteries: (a) CV curves at a scanning rate of 0.1 mV s⁻¹, (b) Nyquist plots, (c) DC curves at 0.2 C derived from (d) rate performance at various current densities, (e) cycling performance at 0.5 C and (f) DC curves derived from (e).

The similar CV curves of CeO₂@Zn//MnO₂ compared to that of the Zn//MnO₂ full cell revealed similar redox behavior and indicated that the CeO₂ coating layer did not affect the redox reactions in MnO₂. Furthermore, as shown in Fig. 4b the charge transfer resistance Rct value of CeO₂@Zn//MnO₂ was much lower than that of Zn//MnO₂, which indicates a more profound Zn²⁺ ion transfer at the electrolyte/anode interface of CeO₂@Zn//MnO₂, in consistence with the results of the previous contact angle test (Fig. 2f and g).

Of interest, while Zn//MnO₂ (∼165 mA h g⁻¹) and CeO₂@Zn//MnO₂ (∼169 mA h g⁻¹) have almost the same specific capacity for the initial discharge profile at 0.2 C (Fig. 4c and Fig. S6†), however, there is an obvious faster fading of the capacity for the uncoated Zn//MnO₂ (discharge capacity ∼120 mA h g⁻¹) at the second discharge step compared to CeO₂@Zn//MnO₂ (discharge capacity ∼159 mA h g⁻¹). The possible mechanism was controversial and has been deeply discussed by researchers in recent years.⁴

H⁺ plays a vital role for the charge storage mechanism in our rechargeable Zn//MnO₂ system, and our experimental results can be explained according to the H⁺ conversion reaction mechanism reported recently.⁴ For the first discharge step, MnO₂ reacts with a proton from water to form MnOOH (MnO₂ + H⁺ + e⁻ + MnOOH) in both cells, since the electrolyte was the same for both Zn//MnO₂ and CeO₂@Zn//MnO₂ at the beginning. Counter to the H⁺ ions reacting with MnO₂, the resulting OH⁻ ions reacted with ZnSO₄ and H₂O in the aqueous electrolyte to form large flake-like ZnSO₄[Zn(OH)₂]₃·xH₂O and reached a neutral charge in the system. As shown in Fig. 2e, the coating layer of the anticatalytic HER CeO₂, thereby alleviating H⁺ to form H₂ and promoting the formation of MnOOH. This supports the longer cycling stability and shorter decreasing of specific capacity for CeO₂@Zn//MnO₂ compared to that of Zn//MnO₂ observed in Fig. 4f.

The rate capability of full cells was evaluated at current densities from 0.2 to 2.0 C (Fig. 4d and Fig. S5†). It was observed that the modified CeO₂@Zn//MnO₂ showed better capacity than that of bare Zn//MnO₂ at various current densities, both of which exhibited excellent reversibility (returning to 2.0 from 0.2 C). This illustrates the high feasibility of this energy storage system. The long-term cycling performance of full cells (CeO₂@Zn//MnO₂ and Zn//MnO₂) was tested at 0.5 C between 1.0 and 1.8 V (Fig. 4e). For CeO₂@Zn//MnO₂, the capacity gradually increased with every activation before 500 cycles, but then gradually decreased since ∼500 laps and led to 30% capacity retention rate after 1500 cycles. However, the capacity of Zn//MnO₂ steadily lasted around 600 cycles and then cut off.

To further validate our analysis on the performances above, we disassembled the tested batteries and analyzed their structures and morphologies. Scanning electron microscopy (SEM) images revealed the surface morphology of the bare Zn and CeO₂@Zn anodes in the symmetric cells before and after cycling (Fig. 5a–d). Initially, the bare Zn anode exhibit a smooth and shiny metallic sheen surface (Fig. 5a), CeO₂@Zn was also smooth but with a thin layer of the CeO₂ solid covering the surface (Fig. 5c). After 250 cycles, a layer of coarse nanoflakes covered the surface of the bare Zn layer (Fig. 5b and Fig. S4†) which was randomly distributed. However, the SEM images show that CeO₂@Zn still maintained a relatively smooth and strong solid surface with a homogeneous Zn deposition, with no tree-like nanoflakes being observed (Fig. 5d). XRD patterns have proven that the sediment on CeO₂@Zn was Zn₄SO₄(OH)₆·4H₂O. In contrast, much less Zn₄SO₄(OH)₆·xH₂O (x = 4,5) was observed for bare Zn since it was dissolved in the electrolyte and this has been verified previously in the literature.³⁶ This intuitively proves the positive role of the CeO₂ layer in preventing zinc surface corrosion and formation of dendrites.

Fig. 5 SEM photos of : (a) Zn and (b) Zn after 250^th cycles, (c) CeO₂@Zn and (d) CeO₂@Zn electrode after 250^th cycles, respectively; (e) the XRD patterns of the corresponding electrodes in (a).

3. Conclusions

In summary, an efficient hydrophilic interface strategy that can bring a balance between the rapid desolvation kinetics of Zn²⁺(H₂O)₆ and inhibition of the HER by CeO₂ layer coating was developed. It greatly improved the easy access of electrolyte ions to the anode surface, provided uniform Zn²⁺ nucleation sites, inhibited the HER and Zn corrosion desolvation, leading to a significant enhancement of the efficiency of aqueous Zn-ion batteries (Table S1 in the ESI†). The long-term stability of symmetrical CeO₂@Zn//CeO₂@Zn batteries was observed as they lasted for ∼1600 h without obvious dendrite formation, which is almost 4.4 times than that of bare Zn//Zn. The modified CeO₂@Zn coupled with α-MnO₂ cathode presented excellent reversibility and greatly improved long cycling stability with almost no decay after 600 cycles compared with bare Zn. Our work provides a fundamental understanding and an essential solution to deal with the balance between rapid desolvation and inhibition of the hydrogen evolution reaction, which is important for promoting the practical application of rechargeable Zn batteries.

4. Experimental and methods

4.1. Chemicals

Deionized water (18.2 MΩ) was used for all experiments. Zn foil (20 μm, 80 μm, 99.9%) was bought from Guangsheng New Materials Co. Ltd. ZnSO₄·7H₂SO₄ (99.0%), MnSO₄ and Ti foil (10 μm, 99.99%) were bought from Aladdin Reagent Co. LTD. Hydrophobic carbon paper was bought from Shanghai Hesen Electric Co., Ltd. Glass fiber membrane (Whatman GF/D, glass microfiber filters, diameter 47 mm) was brought from Shanghai Yuling Filtering Equipment Ltd. N-Methyl-2-pyrrolidone (NMP, >99.5%) and PVDF (M_w = 8900–9800) were bought from Shanghai Aladdin Bio-tech Co. Ltd.

4.2. Characterization of the morphology and structure

XRD patterns were recorded using a Bruker-AXS micro-diffractometer (D8 ADVANCE) with Cu-K_α radiation (λ = 1.5406 Å) from 10° to 90°. The contact angle between the electrolyte and the Zn anode was measured using a contact angle measuring instrument (JC2000D1, Shanghai Powereach Digital Technology Equipment Co., Ltd.) An optical microscope (6XB-PC, Optical Instrument Factory) was used to observe in situ the deposition and exfoliation of Zn. A homemade optical cell was fabricated using Zn plates (100 mm × 100 mm × 50 mm) fixed on a transparent glass plate for the in situ optical analysis.

4.3. The synthesis of electrode materials

The synthesis of α-MnO₂. α-MnO₂ was synthesized according to a previous report [Nature Energy, 2016, 1, 16039], 0.5 M H₂SO₄ (2 ml) was added into 0.003 M MnSO₄·H₂O (90 ml) and magnetically stirred. Then, 0.1 M KMnO₄ (20 ml) aqueous solution was slowly added into the above solution. The solution was transferred to a Teflon-lined autoclave and kept at 120 °C for 12 h after being stirred for 2 h. Then the obtained material was collected by vacuum filtration and washed three times with water, and dried in a vacuum oven.

The preparation of CeO₂@Zn anode. Zn foil was polished using emery paper, and then washed with ethanol. 4 wt% PVDF was prepared by dissolving PVDF in NMP at 40 °C under magnetic stirring. CeO₂ and PVDF solution were mixed together in the ratio CeO₂ : PVDF (9 : 1) and then 100 μl of the mixture was drop cast onto Zn or Ti foil, and the resultant electrodes were dried in an oven at 80 °C, overnight to remove the NMP completely.

The preparation of the PVDF@Zn anode. All the procedures followed were the same as that for the above CeO₂@Zn foil except that CeO₂ was not added.

4.4. The assembly of batteries and electrochemical measurements

All cell measurements (galvanostatic charge–discharge, linear polarization and chronoamperograms) were performed on a Neware Battery Tester (Shenzhen, China). Corrosion analysis and cyclic voltammetry of full cells were tested at a scan rate of 0.1 mV s⁻¹ and the EIS spectra were recorded on an electrochemical workstation (VMP-300, Bio-Logic Science Instruments Co.) with a frequency range from 100 kHz to 0.01 Hz using a BioLogic electrochemistry workstation.

HER measurements were conducted in a three electrode configuration, in which bare Zn and coated Zn plate were used as the working electrode, the Zn plate as the counter electrode, and saturated Ag/AgCl as the reference electrode. The corrosion potential and corrosion current were calculated from the Tafel fit system in the electrochemical workstation.

The electrochemical performance of symmetrical Zn//Zn (or CeO₂@Zn//CeO₂@ Zn) cell batteries. A symmetrical Zn//Zn cell was assembled using the cleared Zn foil (80 μm, Φ16 mm) as both the anode and cathode, 2 M ZnSO₄ as the electrolyte (200 μl) and a glass fiber membrane as the membrane (Φ19 mm). All coin cells used in our experiment were 2032-type. Long-term cycling was measured under (2 mA cm⁻², 1 mA h cm⁻²), (5 mA cm⁻², 2.5 mA h cm⁻²) (5 mA cm⁻², 10 mA h cm⁻²), while for the deep-discharge tests, Zn foil was used (25 μm) under 10 mA cm⁻². Zn//Ti (or Zn//CeO₂@Ti) cells were tested under the current density of 5 mA cm⁻² for 0.5 h for the CE of Zn anodes.

The electrochemical performance of Zn (or CeO₂@Zn) //MnO₂ batteries. α-MnO₂ electrodes were fabricated by mixing α-MnO₂ powder, carbon black and PVDF at a weight ratio of 7 : 2 : 1 in NMP solvent, then coating the slurry onto hydrophobic carbon paper using a razor blade. The α-MnO₂ mass loading was about 1–3 mg cm⁻². Zn/MnO₂ (or CeO₂@Zn//MnO₂) batteries were performed as CR2032 type coin cells with the α-MnO₂ electrodes as the cathode, glass fiber as the separator and Zn foil as the anode. The electrolyte was 2 M ZnSO₄ with 0.1 M MnSO₄ aqueous solution (200 μl) at 0.2 C with a voltage range of 1.0–1.8 V.

The calculation of DoD for full cells³⁷. The formula used to calculate the DOD is as following:
where x (μm) is the thickness of the Zn foil and y (mA h cm⁻²) represents the Zn areal capacity used in the electrochemical testing. Here the DoD was 1% as shown in Fig. 4e.

Author contributions

J. Li. and C. H. conceptualised the study. X. X. and H. J. obtained the funding. S. W. and Y. Y. provided resources. X. X., Z. Z., G. X. and D. W. conducted the experiments.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article and its ESI.†

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (52272088) and the China Postdoctoral Science Foundation (220708). We further thank Tingting He for the help with the schematic part in Fig. 1.

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Footnote

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d4nr02385d

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