New insights into Se/BiVO4 heterostructure for photoelectrochemical water splitting: a combined experimental and DFT study

Monoclinic clinobisvanite BiVO4 is one of the most promising materials in the field of solar water splitting due to its band gap and suitable VBM position. We have carried out a comprehensive experimental and periodic density functional theory (DFT) simulations of BiVO4 heterojunction with Selenium (Se/BiVO4), to understand the nature of heterojunction. We have also investigated contribution of Se to higher performance by effecting morphology, light absorption and charge transfer properties in heterojunction. Electronic properties simulations of BiVO4 shows that its VBM and CBM are comprised of O 2p and V 3d orbitals, respectively. The Se/BiVO4 heterojunction has boosted the photocurrent density by three fold from 0.7 to 2.2 mAcm-2 at 1.3 V vs. SCE. The electrochemical impedance and Mott-Schottky analysis consequence favorable charge transfer characteristics which account for the higher performance in Se/BiVO4 compared to the BiVO4 and Se. Finally, spectroscopic, photoelectrochemical and DFT evident that Se makes a direct Z-scheme (band alignments) with BiVO4 where the photoexcited electron of BiVO4 recombine with the VB of Se, consequences electron-hole separation at Se and BiVO4, respectively as a result enhanced photocurrent is obtained.