Boosting Photoelectrochemical Catalytic Ability of Bismuth Vanadate toward Water Oxidation via Synergistic Surface Defect Engineering and MXene-Assisted Charge Transport.

Bismuth vanadate (BiVO) is regarded as a promising photoanode material for solar-driven photoelectrochemical (PEC) water oxidation, due to its visible-light absorption and favorable band edge positions. However, the practical application is hindered by limited charge carrier mobility and significant surface recombination. In this study, a dual-modification strategy is applied by combining alkaline etching and MXene integration to enhance surface reactivity and charge transport properties of BiVO. Alkaline etching introduces structural defects and active sites on BiVO surface, which promote hole accumulation and facilitate interfacial redox reactions. Meanwhile, incorporating MXene forms a conductive interface that accelerates hole extraction and suppresses recombination. Although alkaline etching slightly reduces light absorption due to morphological restructuring, the subsequent MXene addition recovers and enhances photon harvesting. In the absence of hole scavengers, the pristine BiVO electrode achieves a photocurrent density of 4.65 mA/cm at 1.23 V vs RHE at AM 1.5G, which increases to 5.13 mA/cm for alkaline-etched BiVO and further to 6.15 mA/cm for alkaline-etched BiVO coupled with MXene (MXene/E-BVO). Moreover, the MXene/E-BVO electrode retains 93.4% of its initial photocurrent after continuous illumination for 10,000 s. These results confirm the effectiveness of combining surface and interfacial engineering to improve PEC water splitting performance of BiVO.