A Copper phosphide (Cu3P) micro-rod (MR) array, with coverage by an n-Cu2O thin layer by electrodeposition as a photocathode, has been directly fabricated on copper foil via simple electro-oxidation and phosphidation for photoelectrochemical (PEC) hydrogen production. The morphology, structure, and composition of the Cu3P/Cu2O heterostructure are systematically analyzed using a scanning electron microscope (SEM), X-ray diffraction and X-ray photoelectron spectra. The PEC measurements corroborate that the p-Cu3P/n-Cu2O heterostructural photocathode illustrates efficient charge separation and low charge transfer resistance to achieve the highest photocurrent of 430 mu A cm(-2) that is greater than other transition metal phosphide materials. In addition, a detailed energy diagram of the p-Cu3P/n-Cu2O heterostructure was investigated using Mott-Schottky analysis. Our study paves the way to explore phosphide-based materials in a new class for solar energy applications. (c) 2018 Elsevier Inc. All rights reserved.