Construction of MXene–BiVO4–FeOOH composite photoanode with ultra-low onset potential: performance, DFT calculation and mechanism

Synergistic enhancement of carrier separation-transport and acceleration of water oxidation kinetics is an effective way to boost the current density of photoanode. Therefore, in this work, we constructed Ti3C2Tx MXene conductive framework by cyclic voltammetric (CV) deposition within BiVO4 to force carrier separation-transfer while also depositing O-vacancied FeOOH by in situ self-hydrolysis to accelerate water oxidation kinetics. Predictably, the constructed MXene–BiVO4–FeOOH composite photoanode exhibits an impressive current density of 4.95 mA/cm2 (1.23 V vs. RHE) and 4.1 times higher than that of pristine BiVO4, as well as an ultra-low onset potential and high stability. This fantastic enhancement is attributed to the MXene conductive framework avoiding carrier recombination, tightening the interface of BiVO4–FeOOH, moreover O-vacancied FeOOH improves the adsorption of H2O to accelerate the water oxidation kinetics. This work demonstrates a successful method for constructing efficient and stable photoanodes as well as diversifying the application of MXene in photoelectrocatalysis.