A mixed oxynitride, with the formula In-Ni-Ta-O-N, has been examined and used in the preparation of photoelectrodes for water splitting. The material belongs to a monoclinic crystal system and has a layered structure. The nitrogen content is determined by a thermogravimetric method. The flat band of the material is determined with a Mott-Schottky plot and is located at +0.3 V vs. RHE. Cyclic voltammograms and XPS spectra prove that the material catalyzes a self-transformation, forming NiOOH at the surface, which acts as the active oxygen evolution site. Under simulated sunlight, the material exhibits stable hydrogen (62.4 mu mol h(-1) g(-1)) and oxygen (29.6 mu mol h(-1) g(-1)) evolution rates from water without any sacrificial reagent and without any additional co-catalyst. The open-circuit photovoltage measurement indicates that the low concentration of photogenerated charge carriers limits the performance of the material as a photoelectrode. Furthermore, two different sacrificial reagents are applied to show that the hydrogen evolution reaction is the rate-determining step in water splitting under visible light. (C) 2014 Elsevier Inc. All rights reserved.