Universal Formation of Single Atoms from Molten Salt for Facilitating Selective CO 2 Reduction.

Clarifying the formation mechanism of single-atom sites guides the design of emerging single-atom catalysts (SACs) and facilitates the identification of the active sites at atomic scale. Herein, a molten-salt atomization strategy is developed for synthesizing zinc (Zn) SACs with temperature universality from 400 to 1000/1100 °C and an evolved coordination from Zn-N 2 Cl 2 to Zn-N 4 . The electrochemical tests and in situ attenuated total reflectance-surface-enhanced infrared absorption spectroscopy confirm that the Zn-N 4 atomic sites are active for electrochemical carbon dioxide (CO 2 ) conversion to carbon monoxide (CO). In a strongly acidic medium (0.2 m K 2 SO 4 , pH = 1), the Zn SAC formed at 1000 °C (Zn 1 NC) containing Zn-N 4 sites enables highly selective CO 2 electroreduction to CO, with nearly 100% selectivity toward CO product in a wide current density range of 100-600 mA cm -2 . During a 50 h continuous electrolysis at the industrial current density of 200 mA cm -2 , Zn 1 NC achieves Faradaic efficiencies greater than 95% for CO product. The work presents a temperature-universal formation of single-atom sites, which provides a novel platform for unraveling the active sites in Zn SACs for CO 2 electroreduction and extends the synthesis of SACs with controllable coordination sites.