Herein, we report a novel heterojunction photocathode for the photoelectrochemical water splitting reaction. The photocathode of NiO loaded with WO3 was prepared for the first time. Its photoelectrocatalytic activity is higher than that of the pristine NiO under simulated sunlight lighting. The photoelectrochemical (PEC) property of NiO/WO3 shows a much higher current density (-23.39 mu A/cm(-2)) at 1.20 V vs. RHE under simulated sunlight compared to the unmodified NiO photoelectrode, which are only -5.93 mu A/cm(-2). High separation efficiency and high transmission efficiency of the photogenerated electron-hole pairs and enhanced light absorption lead this PEC property of NiO/WO3 heterojunction photocathode. This result indicates that incorporating additional material is one of the effective ways to improve property of NiO photocathode in PEC water splitting. (C) 2018 Elsevier B.V. All rights reserved.