Ultrathin FeOOH nanosheets as an efficient cocatalyst for photocatalytic water oxidation

Abstract

Water oxidation is a crucial step in photocatalytic water splitting and CO₂ reduction with H₂O, but is generally hindered by slow kinetics. Herein, ultrathin FeOOH nanosheets (FeOOH NSs, 1.8 nm) with abundant oxygen vacancies are composited with BiVO₄via an electrostatic adsorption method, and the resulting composite demonstrates a remarkable enhancement in visible-light photocatalytic and photoelectrochemical oxygen evolution, approximately 2-fold and 9-fold higher than that of pristine BiVO₄, respectively. The kinetics study shows that FeOOH NS loading leads to a 90% decrease in apparent activation energy compared to that of pristine BiVO₄. The prominent cocatalyst effect of FeOOH NSs is further validated in RhB degradation with an 8-fold apparent rate constant enhancement. Effective charge carrier separation and transfer are clarified by photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) characterization. The oxygen vacancies, systematically studied by X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) and extended X-ray absorption fine structure (EXAFS) characterization, are experimentally and theoretically demonstrated to be crucial for facilitating photocatalytic water oxidation.