Electrocatalysis for water splitting and CO2 reduction
To achieve high conversion efficiency from electrical energy to chemical energy, it is crucial to develop highly efficient electrocatalysts. The processes of our interest include water electrolyzer and CO2 reduction, which are all relevant to the sustainable energy demand. The materials are also required to be durable for long-term reactions and versatile to various reaction conditions. Furthermore, such processes are often operated at large scale, and therefore use of abundant elements is preferred to reduce cost of the devices.
Recent progress in the nanomaterials synthesis enables us to investigate materials with ubiquitous elements for catalytic and electrocatalytic properties because they essentially have high surface area and work with active sites for catalysis. A novel preparation technique using sol-gel method, electro-deposition, hydrothermal, and hard-template methods are studied to synthesize nano-oxide, -nitride, -carbide and their carbon composites. These materials serve as new types of non-noble metal catalysts for various catalytic reactions and electrocatalytic reactions, including hydrogen evolution reaction, CO2 reduction reaction, and oxygen evolution reaction.
Our group claims importance of "electrolyte engineering" where supporting electrolyte, at especially near-neutral pH, determines the overall electrocatalytic performance. It affects mass transfer of ions, working as a reactant, buffering action, and adsorption/inhibition of electrode surface, etc. The scheme illustrates an example of supporting ion effects on water electrolysis.