New Insights into Se/BiVO₄ Heterostructure for Photoelectrochemical Water Splitting: A Combined Experimental and DFT Study

Abstract

Monoclinic clinobisvanite BiVO 4 is one of the most promising materials in the field of solar water splitting due to its band gap and suitable valence band maximum (VBM) position. We have carried out comprehensive experimental and periodic density functional theory (DFT) simulations of BiVO 4 heterojunction with selenium (Se-BiVO 4 ), to understand the nature of the heterojunction. We have also investigated the contribution of Se to higher performance by effecting morphology, light absorption, and charge transfer properties in heterojunction. Electronic properties simulations of BiVO 4 show that its VBM and conduction band minimum (CBM) are comprised of O 2p and V 3d orbitals, respectively. The Se/BiVO 4 heterojunction has boosted the photocurrent density by 3-fold from 0.7 to 2.2 mA cm –2 at 1.3 V vs SCE. The electrochemical impedance and Mott–Schottky analysis result in favorable charge transfer characteristics, which account for the higher performance in Se/BiVO 4 as compared to the BiVO 4 and Se. Finally, spectroscopic, photoelectrochemical, and DFT show that Se makes a direct Z-scheme (band alignments) with BiVO 4 where the photoexcited electron of BiVO 4 recombines with the VB of Se, giving electron–hole separation at Se and BiVO 4, respectively; as a result, enhanced photocurrent is obtained.