Ta3N5 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 Ta3N5 film photoanodes owing to successful synthesis of the vital TaO delta precursors. An effective GaN coating strategy is developed to remarkably stabilize Ta3N5 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/Ta3N5 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.