Importance of Water Structure and Catalyst–Electrolyte Interface on the Design of Water Splitting Catalysts

Hydrogen production technologies have attracted intensive attention for their potential to cope with future challenges related to renewable energy storage and conversion. However, the significant kinetic barriers associated with the oxygen evolution reaction (OER), one of the two half reactions at the heart of water electrolysis, greatly hinder the sustainable production of hydrogen at a large scale. A wide variety of materials have thus been designed and explored as OER catalysts. In this perspective, we briefly review the development of Ir-based OER catalysts in acidic conditions and discuss the limitations of a design strategy solely based on the physical and electronic properties of OER catalysts, highlighting the importance of understanding the catalyst–electrolyte interface which affects the stability and activity of the catalyst. We then share our perspective on a group of crystalline, bulk protonated iridates obtained via cation exchange in acidic solutions to be used as promising stable and active OER catalysts. Finally, we discuss the advances recently made in understanding the impact of the active site environment on the OER kinetics, emphasizing the influence of the water structure and/or solvation properties of ions in the electrolyte. We highlight the importance of developing a better understanding of these influencing factors and incorporate them into our design of OER catalysts with enhanced properties.