Au atoms doped in Ti₃C₂T_x MXene: Benefiting recovery of oxygen vacancies towards photocatalytic aerobic oxidation

Photocatalytic aerobic oxidation by using oxygen molecules (O₂) as green and low-cost oxidants is of great attraction, where the introduction of irradiation has been proved as an efficient strategy to lower reaction temperature as well as promote catalytic performance. Moreover, the oxygen vacancies (OVs) of catalyst are highly active sites to adsorb and activate O₂ during photocatalytic aerobic oxidation. However, OVs are easily blocked by oxygen atoms from active oxygen species during the catalytic process, leading to the deactivation of catalysis. Herein, a promising catalyst toward photocatalytic aerobic oxidation was successfully developed by recovering the OVs through doping Au atoms into Ti₃C₂T_x MXene (Au/Ti₃C₂T_x). Impressively, Au/Ti₃C₂T_x exhibited remarkable activity under full-spectrum irradiation towards photooxidation of methyl phenyl sulfide (MPS) and methylene blue (MB), attaining a conversion of >90% at room temperature. Moreover, Au/Ti ₃C₂T_x also manifested remarkable stability by maintaining >95% initial activity after 10 successive reaction rounds. Further mechanistic studies indicated that the OVs of Au/Ti ₃C₂T_x served as the active centers to efficiently adsorb and activate O₂. More importantly, the doped Au atoms of Au/Ti₃C₂T_x were conducive to the recovery of OVs during photocatalytic process from the results of theoretical and experimental aspects. The recovered OVs of Au/Ti₃C₂T_x continuously and efficiently activated O₂, directly contributing to the remarkable catalytic activity and stability.