Vacancy engineered BiVO4 photoanode realizes efficient photoelectrochemical CH3OH oxidation in near-neutral media: Active site regulation improves HCHO selectivity

Abstract

Photoelectrochemical (PEC) CH3OH oxidation holds great promise for sustainably obtaining high value-added HCHO. Low HCHO yield and selectivity are two major constraints to the development of PEC CH3OH oxidation. Herein, we deliver the first report of efficient PEC CH3OH oxidation catalyzed by vacant BiVO4 (BVO) photoanode derived from electrolyte photooxidation and disclose the oxygen vacancy (OV)-induced catalytic sites shift for HCHO selectivity modulation. The near-neutral electrolyte solution provides an excellent environment for alcohol-aldehyde conversion and stable performance of BVO photoanode. OVs promote photogenerated carrier separation, thus ensuring a high photocurrent density and efficient HCHO production for the BVO photoanode. More importantly, the introduction of OV changes the adsorption site for CH3OH molecules from the Bi site to V site of BVO, which enhances the adsorption of CH3OH molecules, and reduces the key C-H activation energy barrier and the energy required for HCHO desorption, collectively boosting the evolution rate and selectivity of HCHO. Thus, OV engineered BVO photoanode exhibits tunable Faraday efficiencies for CH3OH oxidation of 88.4%, 94.7% and 85.6% at 0.8 VRHE, 1.0 VRHE and 1.2 VRHE, respectively, and achieves a prominent HCHO production rate of 579.9 mmol m-2h−1 and a stable photocurrent density of 3.4 mA cm−2 at 1.2 VRHE in near-neutral electrolyte. This work may inspire the future work for PEC chemicals high value-added conversion by using vacancy engineering and matching suitable electrolyte solution.