Modification of TiO₂ with metal chalcogenide nanoclusters for hydrogen evolution

Abstract

Using density functional theory, corrected for on-site Coulomb interactions (DFT + U), we have investigated surface modification of TiO2 with metal chalcogenide nanoclusters for hydrogen evolution. The nanoclusters have composition M4X4 (M = Sn, Zn; X = S, Se) and are adsorbed at the rutile (110) surface. The nanoclusters adsorb exothermically, with adsorption energies in the range −2.8 eV to −2.5 eV. Computed density of states (DOS) plots show that cluster-derived states extend into the band-gap of the rutile support, which indicates that modification produces a redshift in light absorption. After modification, photoexcited electrons and holes are separated onto surface and cluster sites, respectively. The free energy of H adsorption is used to assess the performance of metal chalcogenide modified TiO2 as a catalyst for the hydrogen evolution reaction (HER). Adsorption of H at nanocluster (S, Se) and surface (O) sites is considered, together with the effect of H coverage. Adsorption free energies at cluster sites in the range −0.15 eV to 0.15 eV are considered to be favourable for HER. The results of this analysis indicate that the sulphide modifiers are more active towards HER than the selenide modifiers and exhibit hydrogen adsorption free energies in the active range, for most coverages. Conversely, the adsorption free energies at the selenide nanoclusters are only in the active range at low H coverages. Our results indicate that surface modification with small, dispersed nanoclusters of appropriately selected materials can enhance the photocatalytic activity of TiO2 for HER applications.

Synthesis and Applications of TiO2‐based Nanostructures as Photocatalytic Materials

“…It is easy to recombine, so that the quantum efficiency becomes very low, thereby affecting the photocatalytic efficiency. In order to improve the photocatalytic activity of TiO 2 , a lot of studies have been carried out on the modification of TiO 2 [109–114] . This section briefly introduces metal doping, non‐metal element modification, recombination of TiO 2 with other semiconductors, and multi‐component co‐doping.…”

“…In order to improve the photocatalytic activity of TiO 2 , a lot of studies have been carried out on the modification of TiO 2 . [109][110][111][112][113][114] This section briefly introduces metal doping, non-metal element modification, recombination of TiO 2 with other semiconductors, and multicomponent co-doping.…”

Understanding the prototype catalyst TiO2 surface with the help of density functional theory calculation

“…The free energy of H adsorption can be used to assess the performance of the HER. Adsorption of H at nanocluster (S, Se) and surface (O) sites is taken into consideration by Rhatigan et al in the study of M 4 X 4 (M = Sn, Zn; X = S, Se) doped rutile (110) surface 189 . The results indicate that the sulfide modifiers are more active toward HER than the selenide modifiers and exhibit hydrogen adsorption free energies in the active range for most coverages of H. Zhuang et al 183 demonstrated that the active site of HER in Ni n supported TiO 2 (101) and (001) surfaces is the O 2c atoms binding near the Ni n cluster, and the loaded Ni n clusters significantly reduce the HER Gibbs free energy when compared to clean surfaces.…”