Doping strategy to promote the charge separation in BiVO4 photoanodes

We fabricated Mo:BiVO4/Co:BiVO4 photoanodes by depositing Co:BiVO4 layers on top of Mo:BiVO4 layers, and demonstrated the enhanced PEC performances with improved charge separation both in the bulk and at the interface by doping strategy in this work. Co:BiVO4 layers in Mo:BiVO4/Co:BiVO4 photoanodes were found to be important for the enhanced charge separation efficiencies. The surface exposed Co2+ ions in Co:BiVO4 layers can act as reactive sites for water oxidation to promote the interfacial charge separation. While, the Co2+ doping inside Co:BiVO4 cannot only tune the built in electric fields in Mo:BiVO4/Co:BiVO4 homojunctions, but also be able to optimize the charge transport in Co:BiVO4 layers to facilitate the bulk charge separation. By optimizing the Co contents and the number of Co:BiVO4 layers in Mo:BiVO4/Co:BiVO4 photoanodes, 3Mo-1Co-6% consisted of 3 layers of 3% Mo:BiVO4 and 1 layer 6% Co:BiVO4 yields the highest photocurrent of 2.09 mA/cm2 at 1.23 V vs RHE, with a ηb and ηi value of 77.8% and 86.5%, respectively. This work provides a new thread for the design and fabrication of photoanode with high charge separation efficiencies by doping strategy, which could be helpful for the further improvement of PEC water splitting performances.