Unique three dimensional architecture using a metal-free semiconductor cross-linked bismuth vanadate for efficient photoelectrochemical water oxidation

In this study, we report a unique design of nano-porous bismuth vanadate (BiVO₄) photoelectrode decorated with graphene linked carbon nitride (GCN) nanosheets and their potential application in solar driven photoelectrochemical water oxidation. Especially, an integrated sandwich-like heterojunction with highly interconnected porous structure, comprising two dimensional GCN sheets and three dimensional BiVO₄ was successfully synthesized with significantly enhanced photoelectrochemical activity. The prepared photoelectrode achieves up to 1.98 mA cm^-2 (1.23 V vs RHE) under AM 1.5G solar light irradiation, 2.06 times compared with pristine BiVO₄ (0.96 mA cm^-2 at 1.23 V vs RHE). After deposition of cobalt phosphate nanoparticles as water-oxidation electrocatalyst, a plateau photocurrent of 3.42 mA cm^-2 (1.23 V vs RHE) with a maximum photo-conversion efficiency of 1.28% was achieved on the prepared photoanode. The highly improved photoelectrochemical performance can be attributed to suitable band matching facilitating efficient charge separation between GCN and BiVO₄ as well as the desirable incorporation of rational designed dimensionality-dependent heterojunction for promoted solar energy utilization. More importantly, the combined experimental results and computational simulations reveal that the strong donor-acceptor coupling between GCN sheets and porous BiVO₄ facilitates the separation and transfer of photoinduced electron-hole pairs, accounting for the highly promoted photoelectrochemical performance.