The Electronic and Transport Properties of Sr2Sb2O2Q3 (Q=S,Se) for Photocatalytic Water Splitting

Hydrogen is a green fuel source, as no carbon emissions are produced upon combustion or conversion within a fuel cell. However, the most common source of hydrogen is from steam-reforming of hydrocarbons, which is not a zero-carbon method. The photocatalytic splitting of water is a heavily researched green alternative for the generation of hydrogen. A successful material for photocatalytic water splitting requires an appropriate band gap to absorb in the visible light region, and the correct alignment of the valence band maximum (VBM) and conduction band minimum (CBM) with the redox potential of water¹. <br/>Recently, Sr₂Sb₂O₂S₃ and Sr₂Sb₂O₂Se₃ were highlighted as promising candidates for photocatalytic water splitting². They were reported to possess bandgaps of 2.44 eV and 1.72 eV for Sr₂Sb₂O₂S₃ and Sr₂Sb₂O₂Se₃, respectively – well within the ideal region for photocatalytic materials^1,2. In addition to this, UV-vis measurements indicate promising photocatalytic efficiency for both materials. In this presentation, we have conducted a comprehensive computational analysis of the electronic properties of both materials through density functional theory (DFT) and the Vienna ab initio simulation package (VASP), utilising the hybrid functional HSE06. Analysis includes the electronic structure and band alignment for both structures. Additionally, the electronic transport properties have been investigated using the first principles package, AMSET, to elucidate carrier properties for the material and better characterise the material. The phonon band structure and optical properties of the materials have also been analysed using DFT. We demonstrate that these materials possess ideal direct band gaps and disperse band edges for a high mobility photocatalyst. <br/> <br/>1. M. G. Walter, E. L. Warren, J. R. McKone, S. W. Boettcher, Q. Mi, E. A. Santori and N. S. Lewis, Chem. Rev., 2010, 110, 6446–6473 <br/>2. S. Al Bacha, S. Saitzek, P. Roussel, M. Huvé, E. E. McCabe and H. Kabbour, Chem. Mater., 2023, 35, 9528–9541.