Creation of oxygen vacancies to activate 2D BiVO4 photoanode by photoassisted self‐reduction for enhanced solar‐driven water splitting

Abstract BiVO4 is regarded as a promising photoanode material because of its narrow band gap (∼ 2.4 eV). However, the poor bulk carrier transport capacity severely limits the actual performance of BiVO4 in photoelectrochemistry (PEC) water splitting. Here, we tried to synthesize two-dimensional (2D) morphology by adding structure-directing agents to hydrothermal solution and introduce oxygen vacancies by photoassisted self-reduction. In the scheme, the 2D morphology can shorten the carrier diffusion length and the construction of oxygen vacancies can increase the bulk carrier concentration. Through the combined effect of both, the inherent poor carrier transport capacity of BiVO4 has been improved, which has been proven by Electrochemical Impedance Spectroscopy (EIS), Intensity Modulated Photocurrent Spectroscopy (IMPS) and Mott-Schottky (M-S) plots. At 1.23 V vs. RHE, the photocurrent density increases from ∼1.60 mA/cm2 (2D BiVO4) to ∼2.30 mA/cm2 [2D BiVO4(Vox)], which is 8 times larger than that of bare BiVO4(0.3 mA/cm2). The incident photon-to-current efficiencies (IPCE) of 2D BiVO4(Vox) have reached the value of 46% (at 350 nm). The carrier separation efficiency (ƞsep) and carrier injection efficiency (ƞinj) have been improved up to 49% and 68%, respectively.