Direct synthesis of BaTaO2N nanoparticle film on a conductive substrate for photoelectrochemical water splitting

•BaTaO2N nanoparticle film is directly synthesized on a metal substrate a co-evaporation and nitridation method for PEC water splitting.•The crystallinity, morphology, and defect density of the synthesized BaTaO2N nanoparticle films are varied by controlling the Ba:Ta ratios in the co-evaporated precursor films.•Photoanode based on the optimized BaTaO2N nanoparticle film achieves a photocurrent density of 4.7 mA cm−2 at 1.23 VRHE and a maximum applied bias photon-to-current efficiency of 1.18%.