Photoelectrocatalytic methodologies are attractive for the longstanding storage of renewable energy via direct transformation of solar energy into fuels and chemicals. Controlled electrodeposition of thin and homogeneous nickel hydroxylphosphate (Ni-OH-Pi) nanoparticle films on Zr:BiVO4 photoanodes was achieved, wherein the Ni-OH-Pi co-catalyst increased the photoelectrochemical (PEC) water oxidation and stability of photoanodes comprising silver phosphate (AgPi) on Zr:BiVO4 (AgNi-OH-Pi/Zr:BiVO4). Evaluation of the optical, structural, and morphological properties revealed that the AgNi-OH-Pi/Zr: BiVO4 photoanodes exhibited enhanced PEC behavior with photocurrent densities (J(ph)) of similar to 3.14 mA cm(-2) for water oxidation with long-term stability over 60 h and similar to 4.15 mA cm(-2) for hydrogen peroxide (0.5 M H2O2) oxidation. The enhanced PEC of the fabricated AgNi-OH-Pi/Zr:BiVO4 photoanodes was attributed to the synergetic influence of strong visible-light absorption, enhanced charge separation-transport, and exceptional surface properties. Considering their comparatively superior photocatalytic activity, the AgNi-OH-Pi/Zr:BiVO4 photoanodes are potential electrode candidates in solar water splitting, dye-sensitized solar cells, and photocatalysis. (C) 2019 Elsevier Inc. All rights reserved.