Lanthanide single-atom catalysts for efficient CO₂-to-CO electroreduction

Single-atom catalysts (SACs) have received increasing attention due to their 100% atomic utilization efficiency. The electrochemical CO₂ reduction reaction (CO₂RR) to CO using SAC offers a promising approach for CO₂ utilization, but achieving facile CO₂ adsorption and CO desorption remains challenging for traditional SACs. Instead of singling out specific atoms, we propose a strategy utilizing atoms from the entire lanthanide (Ln) group to facilitate the CO₂RR. Density functional theory calculations, operando spectroscopy, and X-ray absorption spectroscopy elucidate the bridging adsorption mechanism for a representative erbium (Er) single-atom catalyst. As a result, we realize a series of Ln SACs spanning 14 elements that exhibit CO Faradaic efficiencies exceeding 90%. The Er catalyst achieves a high turnover frequency of ~130,000 h^-1 at 500 mA cm^-2. Moreover, 34.7% full-cell energy efficiency and 70.4% single-pass CO₂ conversion efficiency are obtained at 200 mA cm^-2 with acidic electrolyte. This catalytic platform leverages the collective potential of the lanthanide group, introducing new possibilities for efficient CO₂-to-CO conversion and beyond through the exploration of unique bonding motifs in single-atom catalysts.