Construction of inorganic–organic 2D/2D WO3/g-C3N4 nanosheet arrays toward efficient photoelectrochemical splitting of natural seawater

Abstract

Hydrogen production from seawater and solar energy based on photoelectrochemical cells is extremely attractive due to earth-abundance of seawater and solar radiation. Herein, we report the successful fabrication of novel inorganic–organic 2D/2D WO₃/g-C₃N₄ nanosheet arrays (WO₃/g-C₃N₄ NSAs) grown on a FTO substrate via a facile hydrothermal growth and deposition-annealing process, and their application in natural seawater splitting. The results indicate that the WO₃/g-C₃N₄ NSAs exhibit a photocurrent density of 0.73 mA cm⁻² at 1.23 V versus RHE under AM 1.5G (100 mW cm⁻²) illumination, which is 2-fold higher than that of WO₃ NSAs. More importantly, the WO₃/g-C₃N₄ NSA photoanode is quite stable during seawater splitting and the photocurrent density does not substantially decrease after continuous illumination for 3600 s. The remarkably enhanced performance originates primarily from the formation of the WO₃/g-C₃N₄ heterojunction between WO₃ and g-C₃N₄ nanosheets, which accelerates charge transfer and separation, and prolongs the lifetime of electrons as demonstrated by EIS and Mott–Schottky analyses. Finally, a possible mechanism for the improved performance was proposed and discussed.