Bridging the Gap Between Photocatalytic Water Oxidation Half-Reaction and Stoichiometric Pure Water Splitting Over Ta3N5 via Cocatalyst Engineering.

Despite significant progress in photocatalytic half-reactions and photoelectrochemical water oxidation, achieving stable photocatalytic pure water splitting over Ta3N5 remains a long-standing challenge. Herein, the incompatibility of cocatalysts between alkaline photocatalytic water oxidation systems and pure water splitting is identified as a critical bottleneck, leading to serious N2 generation through photocorrosion. To address this challenge, a highly dispersed RuCoOx cocatalyst is developed via a multi-step incipient wetness impregnation strategy. The optimized Pt@Cr2O3/Ta3N5/RuCoOx achieves stoichiometric pure water splitting with an apparent quantum yield of 0.72% at 420 nm, representing the highest value reported for Ta-based nitride/oxynitride photocatalysts to date. Mechanistic studies reveal that an enhanced interfacial electric field facilitates hole extraction, while a reduced formation barrier of key intermediates accelerates surface reaction kinetics, thereby overcoming the long-standing bottleneck in photocatalytic pure water splitting over Ta3N5. This work establishes cocatalyst compatibility as a key design consideration for stable photocatalytic pure water splitting and provides mechanistic insight for the rational design of advanced nitride and oxynitride photocatalysts.