Precatalysts: A Missing Link in Efficient Oxygen Evolution Electrocatalysis

The pursuit of sustainable energy has spurred extensive research into water electrolysis, focusing on the oxygen and hydrogen evolution reactions, processes that necessitate efficient catalysts to enhance selectivity and reaction kinetics. Precatalysts, often underemphasized in electrocatalysis, hold significant promise due to their potential for in situ transformation into active catalytic species. This Review aims to explore and highlight this transformative potential. Specifically, it addresses the critical role of precatalysts, emphasizing their distinct characteristics compared to active catalysts and their transformative capacity in catalytic reactions. The Review systematically examines synthesis strategies for precatalysts effective under both alkaline and acidic conditions, underscoring their importance in catalyst design. A comprehensive analysis of in situ and ex situ characterization techniques, coupled with density functional theory calculations, machine learning, and electrochemical studies, elucidates their activation mechanisms. Recent advancements in precatalyst development are evaluated, showcasing their performance under diverse pH conditions. Finally, key findings are summarized, and perspectives on future research directions in this field are presented.