Crystal size-controlled growth of bismuth vanadate for highly efficient solar water oxidation

Fabricating robust and flat photoactive materials is essential for high-performance PEC water splitting and other photovoltaic systems. Herein, we demonstrate a new method for the fabrication of flat and bulky BiVO4 (BVO) crystallites on an FTO substrate. This highly reproducible method can prepare highly active and bulky crystalline BVO (diameter ≤ 4 μm) with abundant oxygen vacancies for PEC water splitting. Moreover, the crystal size and oxygen vacancies of BVO can be controlled by adjusting the pH value of the electrodeposition electrolyte of the Bi precursor. For PEC performance, the FTO/BVO-3 photoanode shows the highest photocurrent (∼1.25 mA cm−2) among the samples in water splitting and 1.75 mA cm−2 with the aid of the impregnated Fe–Pi co-catalyst at 1.23 V vs. RHE under AM 1.5 G illumination. The new findings provide a simple yet efficient method to fabricate bulky and high-performance semi-transparent BVO photoanodes for BVO-based multi-layered tandem solar cell devices for commercial applications.