We developed a two-step method to prepare Mo-doped CuWO4 NF array films, which involved a hydrothermal process to grow Mo-doped WO3 NF arrays and a follow-up thermal solid-state reaction to convert WO3 to CuWO4. The obtained Mo-doped CuWO4 NF array films retained the network structure of crosslinked CuWO4 NEs when the Mo-to-W atomic ratio in precursor solution is lower than 2 : 3. Mo doping not only narrowed the bandgap of CuWO4 but also significantly improved its electron density, both benefiting the photoelectrochemial (PEC) performance for oxygen evolution reaction (OER). The Mo-doped CuWO4 NF array films exhibited a high catalytic activity toward PEC OER, and the activity varied as a function of the Mo doping concentration. The highest activity was obtained on 32 at.% Mo-doped samples, with photocurrent densities of 0.62 mA cm(-2) and 1.23 mA cm(-2) at 1.23 V and 1.60 V vs RHE, respectively, which are the highest values among those reported in literature. Moreover, even at high OER overpotentials, the Mo-doped CuWO4 NF array films showed an excellent stability in weak alkaline solution. This work indicates that cation doping is an effective strategy to prepare highly efficient CuWO4-based photoanodes for PEC OER. (C) 2019 Elsevier Ltd. All rights reserved.