Room-temperature photodeposition of conformal transition metal based cocatalysts on BiVO₄ for enhanced photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting using semiconductors offers a promising way to convert renewable solar energy to clean hydrogen fuels. However, due to the sluggish reaction kinetics of water oxidation, significant charge recombination occurred at the photoanode/electrolyte interface and cause decrease of its PEC performance. To reduce the surface recombination, we deposit different transition metal complexes on BiVO₄ nanocone arrays by a versatile light driven in-situ two electrode photodeposition approach without applied bias. Conformal cobalt phosphate "Co-Pi" , nickel borate "Ni-Bi" and manganese phosphate "Mn-Pi" complexes were deposited on BiVO₄ nanocone arrays to form core-shell structure photoanode, all of which lead to enhanced photoelectrochemical performance. The photocurrent of the Co-Pi/BiVO₄ photoanode under front-side illumination for 5 min is increased by 4 folds comparing to that of bare BiVO₄ photoanode at 0.6 V vs. RHE, reaching a hole transfer efficiency as high as 94.5% at 1.23 V vs. RHE. The proposed photodeposition strategy is simple and efficient, and can be extended to deposite cocatalyst on other semiconductors with a valence band edge located at a potential more positive than the oxidation potential of transition metal ion in the cocatalyst.