Near- and Long-Range Electronic Modulation of Single Metal Sites to Boost CO Electrocatalytic Reduction.

Tuning the electronic structure of the active center is effective to improve the intrinsic activity of single-atom catalysts but the realization of precise regulation remains challenging. Herein, a strategy of "synergistically near- and long-range regulation" is reported to effectively modulate the electronic structure of single-atom sites. ZnN sites decorated with axial sulfur ligand in the first coordination and surrounded phosphorus atoms in the carbon matrix are successfully constructed in the hollow carbon supports (ZnN S /P-HC). ZnN S /P-HC exhibits excellent performance for CO reduction reaction (CO RR) with a Faraday efficiency of CO close to 100%. The coupling of the CO RR with thermodynamically favorable hydrazine oxidation reaction to replace oxygen evolution reaction in a two-electrode electrolyzer can greatly lower the cell voltage by 0.92 V at a current density of 5 mA cm , theoretically saving 46% of energy consumption. Theoretical calculation reveals that the near-range regulation with axial thiophene-S ligand and long-range regulation with neighboring P atoms can synergistically lead to the increase of electron localization around the Zn sites, which strengthens the adsorption of *COOH intermediate and therefore boosts the CO RR.