Transition Metal Carbides Electrocatalysts for Water Splitting

Abstract

Abstract Electrochemically splitting water into its two elemental components, hydrogen and oxygen, is being heavily investigated as a path toward renewable energy. Hydrogen has been viewed as an energy carrier which could store wind, solar, and other forms of renewable energy for later use. In order to develop the hydrogen economy, new stable, and economical water splitting catalysts need to be developed. Transition metal carbides (TMC) are robust materials consisting of only metal and carbon atoms. These compounds are electrically conducting, and resistant to degradation in conditions typical of electrochemical water splitting reactions. TMCs have been found to have an electronic structure that is similar to Pt and are being investigated as cost‐effective, stable materials for both hydrogen and oxygen reactions. These TMC catalysts have been modified using several approaches including forming nanoparticles to increase surface area, adding conducting carbon and doped carbon support materials, doping the metal carbide to alter the electronic structure, and creating heterointerfaces with other metals and compounds. Fundamental studies on the nitrogen (N‐doped) carbon composites have shown a significant synergistic effect by modifying the electronic structure and thus the hydrogen binding energy. The nitrogen sites also provide a unique and beneficial binding site for H atoms during the electrochemical process. The most challenging but promising area of study focuses on the combination of TMC compounds with another catalyst material to create optimized interfaces. These heterointerface materials are difficult to probe experimentally and further optimize but with advances in density‐functional theory (DFT) calculations, several predictive models have been established. Through these modifications, several catalyst systems have shown catalytic activity and stability that rivals precious metal catalysts at greatly reduced cost. In addition, some of the synthetic methods could be easily scaled for industrial applications. The future of TMC catalysts is extremely promising and with improvements in scalable synthesis methods, activity, and stability, these carbide catalysts will likely be utilized in commercial electrolysis applications.