Copper Vacancy and LSPR-Activated MXene Synergistically Enabling Selective Photoreduction CO₂ to Acetate

Photocatalytic CO₂ conversion towards C₂₊ fuels is a promising technology for simultaneously achieving carbon neutrality and alleviating the energy crisis. However, this strategy is inefficient due to the difficulty of both multi-electron transfer and C-C coupling during C₂₊ formation. In this work, CuInS₂/MXene heterostructure with Cu vacancy is rationally designed by in situ hydrothermal synthesis. The V_Cu-CuInS₂/MXene heterostructure has a suitable band structure and tight interface contact. Catalytic performances under different testing conditions, in situ spectroscopy, and COMSOL simulation reveal that LSPR-activated MXene promotes the formation of crucial intermediate CH₂* and triggers the C-C coupling process under near-infrared light, as the key to acetate. Moreover, in situ XPS analysis, DFT calculations, and photoelectrochemical characterizations unveil that copper vacancy can promote charge transfer from CuInS₂ to MXene and boost local electron aggregation on the MXene, further enhancing the photocatalytic efficiency and selectivity of C₂ products. Contributing to the synergistic effect of copper vacancy and plasmonic MXene, V_Cu-CuInS₂/MXene achieved excellent CO₂RR activity with an acetate evolution rate of 250.0 μmol/h/g and a selectivity of 97.5 % under the full spectrum irradiation, which is 38.8 and 3.3 times higher than that of V_Cu-CuInS₂ and CuInS₂/MXene, respectively.