Bimetallic Synergy in Ultrafine Cocatalyst Alloy Nanoparticles for Efficient Photocatalytic Water Splitting

Abstract Herein, PtRu solid‐solution alloy nanoparticles enable high‐performance H 2 evolution reaction cocatalysts through the transfer of knowledge from electrocatalysis to photocatalysis. Ultrafine PtRu alloy nanoparticles (1.0 ± 0.2 nm in diameter) are synthesized by using a chemical polyol method and used for electro/photo‐catalyses. Integration of PtRu nanoparticles with carbon and Al‐doped SrTiO 3 powders via liquid‐phase adsorption and successive two‐step air and H 2 annealing ensures uniform deposition of PtRu alloy nanoparticles (<2 nm) with a solid‐solution structure. The PtRu alloy nanoparticles exhibit higher electrocatalytic activity for the hydrogen evolution reaction than monometallic Pt counterparts. Modifying Al‐doped SrTiO 3 with PtRu alloy nanoparticles results in efficient photocatalytic overall water‐splitting activity with an apparent quantum yield of 65% at 365 nm and a solar‐to‐hydrogen energy conversion efficiency of 0.45%, which are the highest values among SrTiO 3 ‐based photocatalytic water splitting systems with Rh‐free cocatalysts. Transient diffuse reflectance spectroscopy reveals that the PtRu nanoparticles have a superior electron‐capturing ability than the Pt counterparts, probably due to the decreased work function of Pt by alloying with Ru. This work establishes a framework to elucidate catalytic trends and provides rational design guidance toward the development of bimetallic solid‐solution nanoparticles as cost‐effective and highly active cocatalysts for overall water splitting.