Driving CO₂ Conversion to C₁ and C₂ Products on Single-Atom Catalysts: Recent Experimental and Theoretical Insights

Efficient catalyst design for conversion of carbon dioxide (CO₂) into value-added chemicals through photo- and electroreduction has garnered considerable attention due to the urgent need to address rising global warming, primarily driven by the surge in CO₂ emissions from residential and industrial sources. This method could be more advantageous, particularly when employing catalysts that can substantially lower production costs, enhance the use of precious metals, achieve high selectivity, ensure uniform active sites, and approach near 100% atomic efficiency. Single-atom catalysts (SACs) fit perfectly into such a class of catalysts, possessing unique electronic features and tunable activity. Moreover, SACs provide a hybrid approach that leverages the advantages of both homogeneous and heterogeneous catalysis to drive the CO₂ reduction reaction (CO₂RR), offering the potential for high efficiency and selectivity. In this review, we present the up-to-date advances made in the design of the most efficient transition metal (Co, Ni, and Cu)-based SACs for CO₂ reduction (CO₂R) to various C₁ and C₂ products from both experimental and theoretical perspectives. We extensively discuss the role of various main group element-based SACs toward CO₂ reduction and the critical role of factors such as the nature of the supporting material and coordination environment (CE) engineering on the activity and selectivity of SACs toward the CO₂RR. Furthermore, the use of activity descriptors based on different features of SACs and machine learning (ML) techniques to predict the CO₂R activity of SACs is also presented. Finally, the major theoretical and experimental obstacles along with the potential uses of SACs in future CO₂ reduction-related applications are presented. We anticipate that this review will stimulate the rational synthesis and design of extremely potent next-generation SACs for the CO₂RR.