High performance, binder-free electrodes with single atom catalysts on doped nanocarbons for electrochemical water splitting synthesized using one-step thermally controlled delamination of thin films†
Abstract
Developing high performance catalysts for electrochemical water splitting is critical for an efficient and sustainable route to hydrogen production. For this, single-atom catalysts (SACs) are the best candidates, as they offer the highest atom efficiency. However, current methods to produce SACs involve a complex synthesis, often requiring multiple lengthy and expensive steps and yielding an insufficient density of single atoms. Here, we report a one-step chemical vapor deposition (CVD) synthesis to produce free-standing (FS) electrodes with Ni SACs on a matrix of sulfur-doped carbon nanofibers (CNFs), referred to as SACs@nanocarbon. The mechanism is based on a temperature-controlled delamination of thin films, with Au in contact with a SiO2 substrate, leading to the nucleation and growth of SACs@nanocarbon. Advanced characterization methods indicate the presence of Ni and Au single atoms and larger gold aggregates on the CNF matrix surface. These non-platinum group metal (non-PGM) electrodes showed exceptional performance for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). They performed for over 20 000 cycles with negligible change in overpotential at higher currents, with low onset overpotentials of 305 mV at 10 mA cm−2 for the OER and 40 mV at 17 mA cm−2 for the HER. The overpotential decreased to 195 mV at a current density of 100 mA cm−2. Remarkably, the electrode performance improved over cycling, while gold was dissolving in the electrolyte. This novel synthesis yielding SACs@nanocarbon could pave the way for the development of non-PGM, high performance electrodes for many other electrocatalytic applications. Additionally, the new paradigm of temperature-controlled delamination of thin films could be used to synthesize new materials.
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