KOH-Enabled Axial-Oxygen Coordinated Ni Single-Atom Catalyst for Efficient Electrocatalytic CO 2 Reduction.

Precise control of the coordination structure of metal centers is an ideal approach to achieve reasonable selectivity, activity, and stability in the electrochemical reduction of CO 2 . In this work, the KOH activation strategy for preparation of hierarchically porous material containing Ni single-atoms with axial-oxygen coordination is reported. Spectroscopic measurements reveal the multiple roles of KOH as oxygen source, pore-making reagent and promoter for the formation of key phthalocyanine structure. It exhibits superior surface area (1801 m 2  g -1 ) and electrocatalytic performance (Faradaic efficiency of 94%, Turnover frequency of 11 362 h -1 ). Notably, KOH-enabled architecture with abundant pores benefits the anchoring of Ni atoms and mass transfer for high activity and selectivity. Density functional theory calculations suggest that the axial-oxygen ligand can promote the electronic delocalization of the Ni site for facilitating the *COOH formation and *CO desorption to efficiently produce CO.