Embedding cobalt polyoxometalate in polypyrrole shell for improved photoelectrochemical performance of BiVO4 core

Bismuth vanadate (BiVO4), as an appropriate semiconducting material with a narrow band gap and high light-harvesting, suffers from a high charge recombination rate and low photoactivity. To address these issues, in this work, the embedded cobalt polyoxometalate (POM) within the network of polypyrrole (PPy) coated on BiVO4 has been proposed to promote charge injection and separation. The photoanode based on BiVO4 was fabricated by electrophoretic deposition (EPD) under the optimized conditions. Conducting a comprehensive and fundamental study, we also implemented experiments to achieve the best conditions for BiVO4 preparation and the creation and optimization of PPy heterojunction with and without POM. The photoelectrochemical and physical analysis results revealed that the simultaneous incorporation of PPy and POM makes BiVO4 experience an impressive current enhancement, a 900% increase relative to bare BiVO4. Moreover, the hole extraction efficiency was enhanced to 93.7% from 15.12% (BiVO4), and charge separation yielded 33.83% from 24.47% (BiVO4). This study inspires promising studies on heterojunction formation through inorganic/organic semi-conductor hybridization, achieved by molecular water oxidation co-catalysts like POM.