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 BiVO4was 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-2at 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 BiVO4as 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 BiVO4facilitates the separation and transfer of photoinduced electron-hole pairs, accounting for the highly promoted photoelectrochemical performance.