Highly enhanced photoelectrocatalytic activity of NiFe/Ni/BiVO4 photoanode by a facile photoelectron-activation process in neutral solution

Abstract

Photoelectrocatalytic water splitting is a promising approach to convert solar energy to hydorgen energy. Delicate design of photoanode is crucial for the excellent catalytic activity. Here, a NiFe-LDH/Ni/BiVO₄ composite photoanode was prepared by magnetron sputtering of Ni followed by electrochemical deposition of NiFe-LDH on BiVO₄ photoelectrode. Interestingly, after a concise photoelectron-activation process, a photocurrent of 4.9 mA/cm² (1.23 V vs. RHE) was obtained in neutral solution, which is 4 times of the pristine BiVO₄ photoanode. The photoelectro-activation process not only enhances the photocurrent, but also significantly supresses the positive spiking phenomenon of the photocurrent. A series of characterizaitons including XRD, SEM, EDX, HRTEM, and XPS ect. were performed, which revealed that the photoelectron-activation process led to the reconstruction of the surface structure of NiFe-LDH/Ni/BiVO₄. The dynamic characterizaitons including stepped potential chronoamperometry, steady-state photoluminescence (PL) spectra, open-circuit potential diagrams, and electrochemical impedance spectroscopy (EIS) ect. were performed. It indicates that the activated samples can provide an enhanced internal electric field and enable the charge carriers being efficiently injected into the electrode/electrolyte interface to promote the water oxidation reaction. This investigation provided a facile activation method for BiVO₄-based composite photoanode, and highly increase the PEC performance in neutral condition.