The BiVO4 was firstly prepared by modification's metal organic decomposition method followed by electrodepositing rGO and Cu2O on BiVO4 to construct the rGO decorated BiVO4/Cu2O n-n heterojunction triadic photoanode for photoelectrochemical (PEC) water splitting. The structure and PEC properties of the photoanode were characterized and measured by various spectral analysis and three electrode system. The highest photocurrent density of the triadic photoanode achieves 2.2 mA/cm(2) at 1.8 V (vs. RHE) that is closely 2 folds of single BiVO4 photoanode. The photoanode has the highest IPCE value of 42.0% at 400 nm. The enhanced PEC properties come from the valid separation of the photogenerated electron-hole pair and enhancement of surface oxidation kinetics due to the formation of n-n heterojunction and rGO act as the role of electronic migration mediator accelerates charge carrier transfer, which has been demonstrated by calculated the decrease of charge transfer resistance at electrode/electrolyte interface and prolonging of charge carriers lifetimes. (C) 2019 Elsevier Ltd. All rights reserved.