Surface Reconstruction and Passivation of BiVO₄ Photoanodes Depending on the "Structure Breaker" Cs⁺

Monoclinic BiVO4 is one of the most promisingphotoanodematerials for solar water splitting. The photoelectrochemical performanceof a BiVO4 photoanode could be significantly influencedby the noncovalent interactions of redox-inert metal cations at thephotoanode-electrolyte interfaces, but this point has not beenwell investigated. In this work, we studied the Cs+-dependentsurface reconstruction and passivation of BiVO4 photoanodes.Owing to the "structure breaker" nature of Cs+, the Cs+ at the BiVO4 photoanode-electrolyteinterfaces participated in BiVO4 surface photocorrosionto form a Cs+-doped bismuth vanadium oxide amorphous thinlayer, which inhibited the continuous photocorrosion of BiVO4 and promoted surface charge transfer and water oxidation. The resultingcocatalyst-free BiVO4 photoanodes achieved 3.3 mA cm(-2) photocurrent for water oxidation. With the modificationof FeOOH catalysts, the photocurrent at 1.23 V-RHE reached5.1 mA cm(-2), and a steady photocurrent of 3.0 mAcm(-2) at 0.8 V-RHE was maintained for 30h. This work provides new insights into the understanding of Cs+ chemistry and the effects of redox-inert cations at the electrode-electrolyteinterfaces.