Design and construction of an O-Au-O coordination environment in Au single atom-doped Ti4+ defected TiO2 for an enhanced oxidative ability of lattice oxygen for Hg0 oxidation

Abstract

Transition metal oxide (TMO)-decorated TiO2 catalysts excel at low-temperature Hg0 oxidation. However, TMOs are typically found in large nanoparticles (NPs), resulting in a lower atom utilization efficiency. The current paper presents the design of an Au single atom (SA)-doped Ti4+ defected TiO2 (Au SAC-Ti1-xO2) and investigations concerning the influence of an O-Au-O coordination environment on Hg0 oxidation. Au SAC-Ti1-xO2 was designed using an O-Au-O coordination environment and the O-Au-O orbital interaction was elucidated using density functional theory (DFT). The enhanced oxidative capability of lattice oxygen atoms and the interaction between Hg0 and oxygen atoms were investigated. The O-Au-O coordination environment containing Au SAC Ti1-xO2 was then synthesized and characterized using X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), etc. Finally, Hg0 oxidation catalytic activity was determined. Due to the increasing population of Au-O antibonding orbital interactions in the valence band, the bond order of O-Au-O in Au SAC Ti1-xO2 decreased significantly, thereby enhancing the oxidation ability of its adjacent oxygen atoms. Au SA and ultra-small Au clusters coexisted on a Ti1-xO2 catalyst, and the Hg0-oxidation efficiency at 150–200 °C was 14 times and 1.5 times greater than those of TiO2 and 0.1 % Au/TiO2, respectively. Furthermore, Au SAC Ti1-xO2 was more resistant to the inhibition of SO2 and NO. It provides an efficient method for developing highly active SA catalysts for Hg0 oxidation.