Fast solvent evaporation of phase pure CuBi2O4 photocathodes for photoelectrocatalytic water splitting

•P-type metal oxide semiconductor CuBi2O4 exhibits excellent energy band structures and photoelectrochemical performance.•Phase-pure CuBi2O4 film were prepared via spray pyrolysis by adjusting the evaporation rate of the atomized droplets.•Increasing the evaporation rate decreases the time available for the establishment of the segregation gradient.•CuO was used as a hole transport layer to promote the collection and transfer of photogenerated charge carriers.