Dual Role of Pyridinic-N Doping in Carbon-Coated Ni Nanoparticles for Highly Efficient Electrochemical CO₂ Reduction to CO over a Wide Potential Range

Abstract

Developing efficient and stable electrocatalysts within a wide potential range is vital for the mature applications of the electrocatalytic CO2 reduction reaction (CO2RR) into value-added chemical products. Herein, we engineered a NC@Ni/C nano-composite featuring a core–shell structure of a pyridinic-N-rich carbon layer encapsulating Ni nanoparticles (NPs) as a highly effective electrocatalyst for CO2RR to CO over a wide potential range. The catalyst demonstrates a high CO Faradaic efficiency (FECO) of >90% in a wide potential range from −0.65 to −1.45 V [vs reversible hydrogen electrode (RHE)] with the maximum FECO of 97% at −1.05 V (vs RHE). Strikingly, it exhibits an excellent stability with a constant current density and a FECO > 95% for 92 h at −1.05 V (vs RHE). Structural studies and DFT calculations further reveal that pyridinic-N doping in the carbon shell of Ni NPs plays a dual role in promoting the CO2RR activity. It not only alleviates the mass transfer limitation of CO2 by enhancing the CO2 adsorption capacity, but it also lowers the reaction energy barrier of the *COOH formation rate-determining step with the electronic structure modulation by Ni. This work may shed more light on the seeking of practical catalysts for high-efficiency electrochemical CO2 reduction over a broad potential window.