Atomically dispersed hybrid nickel-iridium sites for photoelectrocatalysis

Atomically dispersed supported catalysts can maximize atom efficiency and minimize cost. In spite of much progress in gas-phase catalysis, applying such catalysts in the field of renewable energy coupled with electrochemistry remains a challenge due to their limited durability in electrolyte. Here, we report a robust and atomically dispersed hybrid catalyst formed in situ on a hematite semiconductor support during photoelectrochemical oxygen evolution by electrostatic adsorption of soluble monomeric [Ir(OH)₆]^2- coupled to positively charged NiO_x sites. The alkali-stable [Ir(OH)₆]^2- features synergistically enhanced activity toward water oxidation through NiO_x that acts as a "movable bridge" of charge transfer from the hematite surface to the single iridium center. This hybrid catalyst sustains high performance and stability in alkaline electrolyte for >80 h of operation. Our findings provide a promising path for soluble catalysts that are weakly and reversibly bound to semiconductor-supported hole-accumulation inorganic materials under catalytic reaction conditions as hybrid active sites for photoelectrocatalysis.