Surface Modulation Inducing Bismuth-Rich Surface Composition in BiVO₄ for Efficient Photoelectrochemical Water Splitting

Surface engineering affects the photoelectrochemical properties of multinary oxide photoelectrodes. Here, we report a simple alkaline solution treatment of the (010) faceted bismuth vanadate (BiVO4) photoanode to increase the surface ratio of bismuth to vanadium, thus improving the performance of photoelectrochemical water oxidation. This study demonstrates that the preferential vanadium dissolution occurs in an alkaline solution, resulting in a bismuth-rich surface on the outer region of the pristine BiVO4 to afford the formation of homojunction within BiVO4. The homojunction promotes the charge separation efficiency of the treated BiVO4 photoanode to reach an almost ∼100% enhancement at 1.23 VRHE under simulated sunlight. Upon further loading NiFeOx cocatalyst, the maximum applied-bias photon-to-current conversion efficiency (ABPE) of treated BiVO4 photoanode also shows a further 100% enhancement in 0.1 M KPi electrolyte. This study sheds light on the critical role of surface termination/composition on the photoelectrochemical properties of the BiVO4 photoanode. This essential surface property can be modulated through a simple strategy to improve its charge transport for efficient water oxidation.