Stabilization and activation of single-atom sites for efficient CO2 reduction in Zn-CO2 battery

초록

The fundamental challenges for zinc-carbon dioxide (Zn-CO2) batteries lies in the sluggish kinetics of CO2 reduction reaction (CO2RR) that directly affects the faradaic efficiency, product selectivity, and long-term cycle life stabilization. While single-atom catalysts (SACs) have enhanced atomic-utilization and well-defined active sites, the chemistry is limited by lack of intrinsic stability-activity matching. Specifically, thermodynamic instability of isolated metal atoms leads to aggregation during electrochemical operation, and the energetic favourability of *COOH intermediate towards CO formation is constrained by a high-energy transition state, especially at the cathode-electrolyte interface. This review provides a critical perspective on making atomic scale SAC engineering an intrinsic advantage for overcoming these two barriers by enabling both stabilization of single-atom sites and higher CO2RR kinetics. The review identifies axial heteroatomic linkage engineering, along with in-plane coordination modulation and defect-mediated stabilization, as critical levers that modulate elec-tronic structure, adsorption configuration, and reaction energetics. We discuss major unresolved mechanisms associated with interfacial charge transfer, dynamic metal-support bonding to lock in atomic diffusion sup-pression, and vacancy-assisted electron redistribution enabled by strong metal-support interactions. The work also highlights a mechanistic framework connecting atomic coordination descriptors with the battery perfor-mance to identify key design principles for long-lasting and kinetically viable energy storage systems.

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