In this study, we report for the first time the controlled Co-doping in TiO2 nanowire (NW) arrays grown on the FTO substrate for highly efficient photoelectrochemical (PEC) water splitting. The Co/TiO2 and pristine TiO2 are single crystalline with a tetragonal rutile structure, while the primary peaks were transformed to (0 0 2) with the adding of Co. Compared to pristine TiO2 NW photoanode, the photocurrent of as-prepared Co/TiO2 NW arrays electrodes show a higher PEC activity with up to similar to 150% of photocurrent density increase under simulated solar radiation. The Co-doping enabled to control the charge dynamics in TiO2 photoanode and thus can achieve an enhanced photocurrent density. The electrochemical impedance measurement indicates that the density of photogenerated carriers can be significantly increased by the Co doping. The Co/TiO2 NW photoanodes exhibit high stability in photoelectrochemical conversion and show great potential for a variety of solar energy driven applications. (C) 2018 Elsevier Inc. All rights reserved.