Synergistic Mechanisms of Dual-Metal Single-Atoms Catalysts for Promoting CO₂ Photoreduction: Bifunctional, Intersite Distance, and Electronic Effects

The CO2 photoreduction reaction involves a series of processes, such as adsorption and activation of CO2 molecules, proton-coupled electron transfer, and desorption of target products. Conventional single-metal atom catalysts cannot adequately meet the demands of efficient CO2 photoreduction, although they are characterized by high atom utilization of single-metal atom catalysts. However, interacting dual-metal single-atom catalysts exhibit a synergistic dual-metal atom multiplying effect─proving that two heads are better than one─which significantly enhances the CO2 photoreduction efficiency. However, few reviews have been reported around the discussion of the constitutive relationship of bimetallic atom catalysts in the CO2 photoreduction process and their potentiation mechanism. Therefore, this review focuses on the synergistic mechanisms generated by the interactions between dual-metal single-atoms: bifunctional, intersite distance, and electronic effects, which are described in detail in the study of the application of the three effects in CO2 photoreduction. The mechanisms to enhance the catalytic efficiency by optimizing the adsorption model of CO2 and intermediates, regulating the reaction pathways, and optimizing the reaction kinetics are described in detail. This review aims to fill the gap in the current review of bimetallic atomic catalysts applied to CO2 photoreduction, aiming to help readers gain a deeper understanding of the principle of efficiency enhancement of bimetallic atomic catalysts in the CO2 photoreduction process. On this basis, it provides theoretical guidance and research ideas for the design and preparation of customized high-performance catalytic materials oriented to the needs of different reaction pathways and promotes the further development of photocatalytic CO2 reduction technology.