Synergistic Integration of AuCu Co-Catalyst with Oxygen Vacancies on TiO 2 for Efficient Photocatalytic Conversion of CO 2 to CH 4

Photocatalytic reduction of CO 2 toward eight-electron CH 4 product with simultaneously high conversion efficiency and selectivity remains great challenging owing to the sluggish charge separation and transfer kinetics and lack of active sites for the adsorption and activation of reactants. Herein, a defective TiO 2 nanosheet photocatalyst simultaneously equipped with AuCu alloy co-catalyst and oxygen vacancies (AuCu-TiO 2– x NSs) was rationally designed and fabricated for the selective conversion of CO 2 into CH 4 . The experimental results demonstrated that the AuCu alloy co-catalyst not only effectively promotes the separation of photogenerated electron–hole pairs but also acts as synergistic active sites for the reduction of CO 2 . The oxygen vacancies in TiO 2 contribute to the separation of charge carriers and, more importantly, promote the oxidation of H 2 O, thus providing rich protons to promote the deep reduction of CO 2 to CH 4 . Consequently, the optimal AuCu-TiO 2– x nanosheets (NSs) photocatalyst achieves a CO 2 reduction selectivity toward CH 4 up to 90.55%, significantly higher than those of TiO 2– x NSs (31.82%), Au-TiO 2– x NSs (38.74%), and Cu-TiO 2– x NSs (66.11%). Furthermore, the CH 4 evolution rate over the AuCu-TiO 2– x NSs reaches 22.47 μmol·g –1 ·h –1, which is nearly twice that of AuCu-TiO 2 NSs (12.10 μmol·g –1 ·h –1 ). This research presents a unique insight into the design and synthesis of photocatalyst with oxygen vacancies and alloy metals as the co-catalyst for the highly selective deep reduction of CO 2 .