Ultrathin layer TAFC on BiVO4 with ligand-to-metal charge transfer enhances built-in electric field for boosting photoelectrochemical water oxidation

Hongcheng Huang; Zimu Zhang; Wenhui Xie; Ben Fan; Cheng Wu; Ronghua Jiang; Jun Huang; Boge Zhang; Yanping Hou; Zebin Yu

doi:10.1016/j.jcis.2024.04.190

Ultrathin layer TAFC on BiVO₄ with ligand-to-metal charge transfer enhances built-in electric field for boosting photoelectrochemical water oxidation

J Colloid Interface Sci. 2024 Aug 15:668:551-564. doi: 10.1016/j.jcis.2024.04.190. Epub 2024 Apr 27.

Authors

Hongcheng Huang¹, Zimu Zhang¹, Wenhui Xie¹, Ben Fan¹, Cheng Wu¹, Ronghua Jiang², Jun Huang³, Boge Zhang¹, Yanping Hou¹, Zebin Yu⁴

Affiliations

¹ School of Resources, Environment and Materials, Guangxi University, State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, Nanning 530004, China.
² School of Chemical and Environmental Engineering, Shaoguan University, Shaoguan 512005, China.
³ School of Civil Engineering and Architecture, Guangxi Minzu University, Nanning 530004, China.
⁴ School of Resources, Environment and Materials, Guangxi University, State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures, Nanning 530004, China. Electronic address: xxzx7514@hotmail.com.

PMID: 38691964
DOI: 10.1016/j.jcis.2024.04.190

Abstract

To reveal the mechanism of charge transfer between interfaces of BiVO₄-based heterogeneous materials in photoelectrochemical water splitting system, the cocatalyst was grown in situ using tannic acid (TA) as a ligand and Fe and Co ions as metal centers (TAFC), and then uniformly and ultra-thinly coated on BiVO₄ to form photoanodes. The results show that the BiVO₄/TAFC achieves a superior photocurrent density (4.97 mA cm^-2 at 1.23 V_RHE). The charge separation and charge injection efficiencies were also significantly higher, 82.0 % and 78.9 %, respectively. From XPS, UPS, KPFM, and density functional theory calculations, Ligand-to-metal charge transfer (LMCT) acts as an electron transport highway in TAFC ultrathin layer to promote the concentration of electrons towards metal center, leading to an increase in the work function, which enhances the built-in electric field and further improves the charge transport. This study demonstrated that the LMCT pathway on TA-metal complexes enhances the built-in electric field in BiVO₄/_TAFC to promote charge transport and thus enhance water oxidation, providing a new understanding of the performance improvement mechanism for the surface-modified composite photoanodes.

Keywords: BiVO(4); Ligand-to-metal charge transfer (LMCT); Photoelectrochemical water splitting; Schottky heterojunction; Tannic complex.