Highly Active GaN‐Stabilized Ta3N5 Thin‐Film Photoanode for Solar Water Oxidation

Abstract Ta 3 N 5 is a very promising photocatalyst for solar water splitting because of its wide spectrum solar energy utilization up to 600 nm and suitable energy band position straddling the water splitting redox reactions. However, its development has long been impeded by poor compatibility with electrolytes. Herein, we demonstrate a simple sputtering‐nitridation process to fabricate high‐performance Ta 3 N 5 film photoanodes owing to successful synthesis of the vital TaO δ precursors. An effective GaN coating strategy is developed to remarkably stabilize Ta 3 N 5 by forming a crystalline nitride‐on‐nitride structure with an improved nitride/electrolyte interface. A stable, high photocurrent density of 8 mA cm −2 was obtained with a CoPi/GaN/Ta 3 N 5 photoanode at 1.2 V RHE under simulated sunlight, with O 2 and H 2 generated at a Faraday efficiency of unity over 12 h. Our vapor‐phase deposition method can be used to fabricate high‐performance (oxy)nitrides for practical photoelectrochemical applications.