Comparison between hydrogen production via H2S and H2O splitting on transition metal-doped TiO2 (101) surfaces as potential photoelectrodes

Doping is an effective way to engineer the electronic band structure of semiconductor materials and consequently their photocatalytic activity for hydrogen generation. In this work, periodic Density Functional Theory (DFT) was employed to compare the adsorption of H2S and H2O molecules on TiO2(101) anatase surfaces compared to four transition metal-doped TiO2(101) anatase surfaces; Cr4+-TiO2, V4+-TiO2, Mn4+-TiO2, and Nb4+-TiO2. The defect formation energy, molecular adsorption energy, hydrogen splitting energies, geometrical changes, electronic structure and charge transfer characteristics were investigated to determine and compare the changes in adsorption of H2S and H2O on the pristine vs. doped surfaces. The defect formation energy calculations revealed the Nb4+-TiO2 surface resulted in the highest stability, smallest change in neighboring bond lengths and the highest dopant to surface charge transfer. However, upon H2S and H2O adsorption, the calculations concluded that the V4+-TiO2 surface resulted in the most stable structure for adsorbed H2S and lowest hydrogen splitting energy requiment compared to the other dopant metals and the lowest for H2S vs H2O, indicating its potential catalytic activity for facile dehydrogenation for industrial applications. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.