Rearranging spin electrons by axial-ligand-induced hybridization state transition to boost the activity of nickel single-atom-catalysts for electrochemical CO 2 reduction

A Cl axial ligand breaks the D 4h symmetry of Ni–N 4 , inducing Ni orbital hybridization and spin rearrangement. The Ni magnetic moment and d-band center spin difference are universal descriptors for the eCO 2 RR to CO on Ni–N 4 with various axial ligands.