Architectural engineering of reduced graphene oxide in BiVO4 photoanodes for enhanced photoelectrochemical performance

Bismuth vanadate (BiVO 4 ) is a promising photoanode material for solar water splitting due to its visible-light absorption and earth-abundant composition. Herein, we investigate how the spatial positioning of reduced graphene oxide (rGO) influences the photoelectrochemical performance of hydrothermally synthesized BiVO4 photoanodes. Two heterostructures were examined, with rGO incorporated either beneath the BiVO 4 layer (BVO/rGO/FTO) or on the surface (rGO/BVO/FTO). Both architectures exhibit enhanced photocurrent densities compared to pristine BiVO 4 . Surface-deposited rGO primarily improves interfacial charge extraction, resulting in the highest photocurrent and interfacial efficiencies exceeding 25–30%. In contrast, buried rGO enhances bulk charge separation and electron transport, leading to a nearly twofold increase in charge-transport efficiency and an fourfold enhancement in photovoltage. IPCE values increased by more than one order of magnitude relative to pristine BiVO 4 , demonstrating the importance of heterointerface engineering for optimizing charge-transfer pathways in ceramic photoanodes.