Construction of a Co-MOF/MXene/BiVO4 Composite Photoanode for Efficient Photoelectrochemical Water Splitting

BiVO4 shows great potential as a high-quality material for photoelectrochemical applications, but its severe charge recombination and slow surface reaction kinetics seriously hinder its broader application. Herein, a high-performance Co-metal-organic framework (MOF)/MXene/BiVO4 composite photoanode was prepared by using a facile spin-coating and water bath deposition method. With the synergistic modification of MXene and Co-MOF, the high current density of the Co-MOF/MXene/BiVO4 photoanode is 4.26 mA/cm(2) at 1.23 V vs the reversible hydrogen electrode (RHE), which is 4.7 times higher than that of the pure BiVO4 photoanode (0.90 mA/cm(2)). Furthermore, compared with the bare BiVO4, there is a significant cathodic shift of 357 mV. Moreover, the Co-MOF/MXene/BiVO4 photoanode exhibits excellent water splitting performance, as demonstrated by its high applied bias photon-to-current conversion efficiency of 1.78% at 0.589 V vs RHE, impressive incident photon-to-current conversion efficiency of 76.7% at 420 nm, and a remarkable injection efficiency of 92.2%. Various physiochemical characterizations revealed that Co-MOF significantly improves the surface kinetics as an oxygen-evolving catalyst, while MXene modification can form a built-in electric field to effectively promote charge separation and accelerate charge-transfer efficiency. Our work presents a simple and effective method for preparing high-performance photoanodes, which has the potential to advance the large-scale photoelectrochemical water splitting applications.