Elucidating the origin of catalytic activity of nitrogen-doped carbon coated nickel toward electrochemical reduction of CO2.

[Display omitted] • N -doped carbon coated nickel (Ni@NC) is prepared for electrochemical CO 2 reduction (ECRR). • There is a synergistic effect between Ni and N to ECRR activity. • The effect of pickling on ECRR performance of Ni@NC is revealed. • The adsorbed Cl on Ni@NC surface after pickling improves the ECRR performance. • The origin of the activity and selectivity of the pickling Ni@NC for ECRR is elucidated. Converting CO 2 into valuable chemicals and fuels through clean and renewable energy electricity provides a way to achieve sustainable development for human societies. In this study, carbon coated nickel catalysts (Ni@NCT) were prepared by solvothermal and high-temperature pyrolysis methods. A series of Ni@NC-X catalysts were obtained by pickling with different kinds of acids for electrochemical CO 2 reduction reaction (ECRR). The results show that Ni@NC-N treated with nitric acid has the highest selectivity but lower activity, Ni@NC-S treated with sulfuric acid has the lowest selectivity, and Ni@NC-Cl treated with hydrochloric acid shows the best activity and good selectivity. At –1.16 V, Ni@NC-Cl has a considerable CO yield of 472.9 μmol h−1 cm−2, which is significantly superior to Ni@NC-N (327.5), Ni@NC-S (295.6) and Ni@NC (270.8). The controlled experiments show that there is a synergistic effect between Ni and N. The chlorine adsorbed on the surface can promote the performance of ECRR. The poisoning experiments indicate that the contribution of surface Ni atoms to the ECRR is very small, and the increase of activity is mainly due to the nitrogen doped carbon coated Ni particles. The relationship between activity and selectivity of ECRR on different acid-washed catalysts was correlated by theoretical calculations for the first time, which is also in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]