On the improvement of photoelectrochemical performance and finite element analysis of reduced graphene oxide–BiVO4 composite electrodes

Incorporation of thermally reduced graphene oxide (RG-O) into the metal oxide semiconductor BiVO4 improves its photoactivity by about three times for sulfite oxidation. The enhancement of photoactivity is attributed to reduced electron–hole recombination of BiVO4 using the RG-O as a conductive matrix in the composite photocatalyst. Photoelectrochemical behavior of the BiVO4 and RG-O/BiVO4 composite electrodes were simulated using finite element analysis to obtain the carrier mobility and its lifetime in the photoelectrodes. In contrast with sulfite oxidation, the improvement of photocurrent for water oxidation of RG-O/BiVO4 composite electrode was not significant because of the slower kinetics for water oxidation. To address the kinetic limitations, platinum (Pt) as an effective electrocatalyst was photodeposited on the RG-O/BiVO4 electrode. Addition of the Pt significantly improved water oxidation photocurrent of the Pt/RG-O/BiVO4 electrode. RG-O/W–Mo-doped BiVO4 composite electrodes were also prepared to investigate a further enhancement of photoactivity of W–Mo-doped BiVO4. The behavior obtained from RG-O/W–Mo-BiVO4 and RG-O/BiVO4 electrodes provides a valuable insight into the role of RG-O as a conducting additive and the role of W and Mo as dopants into BiVO4.