NiFe MOF modified BiVO4 photoanode with strong π-π conjugation enhances built-in electric field for boasting photoelectrochemical water oxidation

Abstract

The photoelectrochemical (PEC) performance ofBiVO₄ is limited by sluggish kinetics and poor stability. In this work, a novel high-performance BiVO₄/NiFe MOF(BPDC) photoanode is constructed by loading NiFe MOF with biphenyl-4,4'-dicarboxylic acid (BPDC) as an organic ligand on BiVO₄ by a simple one-step hydrothermal method. The XPS, OCP, UPS, and KPFM show that the enhanced π-π conjugation effect causes more electrons transfer from the BiVO₄ to the MOFs and affects the magnitude of the work function, leading to a strong built-in electric field to drive carrier separation and migration. Therefore, the BiVO₄/NiFe MOF(BPDC) has a strong hole extraction and carrier separation capability to enhance photoelectrochemical water oxidation and improve photostability. The BiVO₄/NiFe MOF(BPDC) photoanode has an enhanced photocurrent density of 4.16 mA cm^-2 at 1.23 V_RHE, which is 4.33 times higher than that of the pure BiVO₄ (0.96 mA cm^-2) photoanode with a negative shift of 376 mV in the onset potential plot, exhibiting excellent photostability of 7 h at 1.23 V_RHE. This work demonstrates that the composite photoanodes constructed by BiVO₄ and the MOFs with strong π-π conjugation are promising, which provides an effective strategy for the preparation of efficient and stable photoanodes.

Keywords: BiVO(4); Built-in electric field; Heterojunction; Metal-organic frameworks; Photoelectrochemical water splitting; π-π conjugation.