Spray-deposited Co-Pi Catalyzed BiVO_4: a low-cost route towards highly efficient photoanodes

摘要

Bismuth vanadate (BiVO_4) thin films are deposited by a low-cost and scalable spray pyrolysis method. Its performance under AM 1.5 illumination is mainly limited by slow water oxidation kinetics. We confirm that cobalt phosphate (Co-Pi) is an efficient water oxidation catalyst for BiVO_4. The optimum thickness of BiVO_4 is 300 nm, resulting in an AM 1.5 photocurrent of 1.9 mA/cm~2 at 1.23 V vs. RHE when catalyzed with Co-Pi. Once the water oxidation limitation is removed, the performance is limited by low charge separation efficiency. This causes more than 60% of the electron-hole pairs to recombine before reaching the respective interfaces. The slow electron transport is shown to be the main cause of this low efficiency, and future efforts should therefore be focused on addressing this key limitation.