Effective utilization of renewable energy such as water electrolysis driven by various renewable energy sources has become an essential strategy to resolve environmental issues and dependence on fossil fuels. Among several water splitting technologies, alkaline water electrolyzers have the advantage of using cost-effective transition metal electrodes. Although considerable efforts have been devoted to the study of catalysts for alkaline water electrolysis, the development of more active and durable catalysts is still needed. Recently, hybrid catalysts consisting of metal nanoparticles on a metal oxide support have been considered as a promising approach for designing active and stable catalysts for water splitting including both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, the structures of both metal nanoparticles and oxide support materials change simultaneously during the electrocatalytic reactions, making it difficult to understand the role of metal–oxide interactions in enhancing catalytic activity.

In this talk, I will discuss the OER and HER mechanisms of hybrid catalysts designed through the in situ exsolution process of metallic nanoparticles on a B-site Ni-substituted lead ruthenate pyrochlore oxide. Using density functional theory calculations in addition to systematic electrochemical characterization and operando X-ray absorption spectroscopy measurements, the origin of the enhanced catalytic activities of hybrid catalyst systems was demonstrated by understanding synergistic metal-oxide interactions. These results highlight the importance of understanding the interactions between metal nanoparticles and metal oxide support in order to design high-performance hybrid catalysts.