A graphene oxide–molecular Cu porphyrin-integrated BiVO4 photoanode for improved photoelectrochemical water oxidation performance

Abstract

Monoclinic bismuth vanadate (BiVO₄), as a rising star in light-catching materials, has been researched in many fields, such as photoelectrochemical water splitting. To date, it is still noteworthy that the photogenerated electron–hole fast recombination and the slow kinetic rate impede the photoelectrochemical performance of BiVO₄. Herein, a composite material of graphene oxide (GO) and molecular Cu porphyrin (CuTCPP)-modified BiVO₄-based photoanode was prepared and characterized by various relevant physical tests. The photoelectrochemical performance measurements show that the assembled CuTCPP/GO/BiVO₄ photoanode has an admirable photocurrent density value, which is far better than that of pristine BiVO₄. Under AM 1.5G, 100 mW cm⁻² Xe lamp, the photocurrent density of the CuTCPP/GO/BiVO₄ photoanode reached 5.0 mA cm⁻², which was 4-fold enhancement than that of pristine BiVO₄. In addition, the optimized CuTCPP/GO/BiVO₄ photoanode displays an evident negative shift of the onset potential of around 400 mV, and it presents a fascinating charge injection efficiency of 92%. The fine photoelectrochemical performance is due to more active sites provided by the molecular catalyst CuTCPP and excellent electrical conductivity and fast charge separation rate offered by GO. Furthermore, GO and CuTCPP form strong conjugate systems, which effectively inhibit the photogenerated electron–hole recombination. These results offer a new concept of assembling a composite photoanode for efficient energy devices.