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• The photocurrent density of WO 3 /RGO/Ni:FeOOH increased by a factor of 2.05. • The onset potential of WO 3 /RGO/Ni:FeOOH negatively shifted 83 mV. • Ni:FeOOH acts as a bi-functional modifier. • Ni:FeOOH improves light absorption and charge transfer process. • RGO as a conductive bridge-linker promote charge separation. The instability and low activity of WO 3 is the hot-topic for photoelectrochemical (PEC) water splitting, which is decreased by a sluggish interfacial kinetics and incomplete water oxidation. Aiming at such issues, we designed a ternary WO 3 /RGO/Ni:FeOOH photoanode, which exhibits 2.05 times larger photocurrent (1.32 mA cm−2) than the WO 3 NFs in 0.5 M Na 2 SO 4 electrolyte solution, accompanied with 83 mV cathodic shift of onset potential. These results demonstrates PEC response can occurs only in Ni:FeOOH but not FeOOH. Therefore, Ni:FeOOH acting as bi-functional modifier, can not only increase light absorption but also promote charge transfer process by forming p-n heterojunction with the WO 3 NFs. Besides, RGO forming a continuously conducting network can further improve charge separation process. Owing to their synergistic effects, the Faradaic efficiency and stability are both improved compared to its counterparts and the bare WO 3 NFs. This work may inspire the PEC application in other co-catalyst decorated systems. [ABSTRACT FROM AUTHOR]