Boosting photoelectrochemical activity of bismuth vanadate by implanting oxygen-vacancy-rich cobalt (oxy)hydroxide

Surface charge recombination is regarded as a detrimental factor that severely downgrades the photoelectrochemical (PEC) performance of bismuth vanadate (BiVO₄). In this work, we demonstrate defect-rich cobalt (oxy)hydroxides (Co(O)OH) as an excellent cocatalyst nanolayer sheathed on BiVO₄ to substantially improve the PEC water oxidation activity. The self-transformation of metal-organic framework produces an ultrathin Co(O)OH layer rich in oxygen vacancies, which could serve as a powerful hole extraction engine to promote the charge transfer/separation efficiency as well as an excellent oxygen evolution reaction catalyst to accelerate the surface water oxidation kinetics. As a result, the BiVO₄/Co(O)OH hybrid photoanode achieves remarkably inhibited surface charge recombination and presents a prominent photocurrent density of 4.2 mA cm^-2 at 1.23 V vs. RHE, which is around 2.6-fold higher than that of the pristine BiVO₄. Moreover, the Co(O)OH cocatalyst nanolayer significantly reduces the onset potential of BiVO₄ photoanodes by 200 mV. This work provides a versatile strategy for rationally preparing oxygen-vacancy-rich cocatalysts on various photoanodes toward high-efficient PEC water oxidation.