Ta3N5 photoanodes for water splitting prepared by sputtering

Ta3N5 thin-film photoelectrodes were prepared using a reactive sputtering technique, and their properties for photoelectrochemical water splitting under visible light were investigated. The crystal phases of the films were dependent on the sputtering conditions, such as the N2/O2 ratio of the sputtering atmosphere and the substrate temperature (Ts). Single-phase Ta3N5 films were obtained by sputtering at N2/O2 = 30 and Ts = 1013 K with post-annealing in an NH3 flow. The Ta3N5 photoelectrodes had an anodic photoresponse in water photoelectrolysis, although the photocurrent rapidly decreased because of self-oxidation of the photoanode by photogenerated holes. However, modification of the NH3-treated Ta3N5 films with IrO2 promoted the oxidation of water and suppressed the self-oxidation of Ta3N5.