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 (BiVO). In this work, we demonstrate defect-rich cobalt (oxy)hydroxides (Co(O)OH) as an excellent cocatalyst nanolayer sheathed on BiVO 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 BiVO/Co(O)OH hybrid photoanode achieves remarkably inhibited surface charge recombination and presents a prominent photocurrent density of 4.2 mA cm at 1.23 V vs. RHE, which is around 2.6-fold higher than that of the pristine BiVO. Moreover, the Co(O)OH cocatalyst nanolayer significantly reduces the onset potential of BiVO 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.