Understanding the role of metal and N species in M@NC catalysts for electrochemical CO2 reduction reaction

The electrochemical CO 2 reduction reaction (CO 2 RR) that transforms CO 2 to CO has attracted great interest. Transition metal nanoparticles encapsulated in nitrogen-doped carbon (M@NC) catalysts exhibit outstanding catalytic performance. However, the role of metal and N species in M@NC catalysts remains unclear. In this work, Co@C, Co@NC, Ni@C, and Ni@NC catalysts were achieved and employed in CO 2 RR. The Ni@NC catalyst exhibits an industry level current density of 220 mA cm −2 and a high Faradaic efficiency of 98% for CO production at − 0.87 V vs. RHE for 100 h. In addition, the N species, especially the pyrrolic-N in the shell of Ni@NC material provide active sites for adsorbing and activating CO 2 molecules, and metal nanoparticles improve the electronic structure of N species, thereby decreasing their ability for radical attack (*COOH, *CO, and *H). Consequently, this work can guide the design of M@NC catalyst for CO 2 RR to CO. • Different kinds of metal nanoparticles encapsulated within carbon shells are achieved. • The Ni@NC catalyst exhibits a large current density of 220 mA cm –2 and a high FE CO % of 98%. • The Ni@NC catalyst has excellent stability in CO 2 RR. • The pyrrolic-N in the shell of Ni@NC material provides active sites for CO 2 molecules. • The decrease of adsorption for radical attack (*COOH, *CO, and *H) improves the catalytic performance of CO 2 RR.