Low‐Valence Znδ+ (02 Reduction

Abstract A nitrogen‐stabilized single‐atom catalyst containing low‐valence zinc atoms (Zn δ+ ‐NC) is reported. It contains saturated four‐coordinate (Zn‐N 4 ) and unsaturated three‐coordinate (Zn‐N 3 ) sites. The latter makes Zn a low‐valence state, as deduced from X‐ray photoelectron spectroscopy, X‐ray absorption spectroscopy, electron paramagnetic resonance, and density functional theory. Zn δ+ ‐NC catalyzes electrochemical reduction of CO 2 to CO with near‐unity selectivity in water at an overpotential as low as 310 mV. A current density up to 1 A cm −2 can be achieved together with high CO selectivity of >95 % using Zn δ+ ‐NC in a flow cell. Calculations suggest that the unsaturated Zn‐N 3 could dramatically reduce the energy barrier by stabilizing the COOH* intermediate owing to the electron‐rich environment of Zn. This work sheds light on the relationship among coordination number, valence state, and catalytic performance and achieves high current densities relevant for industrial applications.