Low-Valence Znδ+ (0<δ<2) Single-Atom Material as Highly Efficient Electrocatalyst for CO2 Reduction

A nitrogen-stabilized single-atom catalyst containing low-valence zinc atoms (Zn delta+-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 delta+-NC catalyzes electrochemical reduction of CO2 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 delta+-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.

Automated summary

The nitrogen-stabilized single-atom catalyst Zn delta+-NC containing low-valence zinc atoms shows excellent catalytic performance in the electrochemical reduction of CO2 to CO. The unsaturated three-coordinate sites on Zn play a key role in reducing the energy barrier and achieving high CO selectivity. This work sheds light on the relationship between coordination number, valence state, and catalytic performance, with potential industrial applications for high current densities.