Single-Product Faradaic Efficiency for Electrocatalytic of CO2 to CO at Current Density Larger than 1.2 A cm−2 in Neutral Aqueous Solution by a Single-Atom Nanozyme

Abstract

Electroreduction of CO2 to CO is a promising approach for the cycling use of CO2, while it still suffers from impractical current density and durability. Here we report a single-atom nanozyme (Ni−N5−C) that achieves industrial-scale performance for CO2-to-CO conversion with a Faradaic efficiency (FE) exceeded 97 % over −0.8–−2.4 V vs. RHE. The current density at −2.4 V vs. RHE reached a maximum of 1.23 A cm−2 (turnover frequency of 69.7 s−1) with an FE of 99.6 %. No obvious degradation was observed over 100 hours of continuous operation. Compared with the planar Ni−N4 site, the square-pyramidal Ni−N5 site has an increase and a decrease in the (Formula presented.) and dxz/yz orbital energy levels, respectively, as revealed by density functional theory calculations. Thus, the Ni−N5 catalytic site is more superior to activate CO2 molecule and reduce the energy barriers as well as promote the CO desorption, thus boosting the kinetic activation process and catalytic activity.