A Ni nanoparticles encapsulated in N-doped carbon catalyst for efficient electroreduction CO2: Identification of active sites for adsorption and activation of CO2 molecules

Electrochemical CO2 reduction (ECR) offers a promising strategy to achieve global carbon balance and mitigate the global climate. However, it is still a challenge to fabricate excellent catalyst and illustrate the active site for adsorption and activation of CO2 molecules. Herein, we develop a reduced graphene oxide-supported N-doped carbon-encapsulated nickel (Ni@N-C/rGO) catalyst for ECR to CO. The optimal Ni@N-C/rGO(4,4'-bipy) catalyst exhibits high catalytic activity, selectivity and stability with a current density of 20 mA cm(-2) and Faradaic efficiency of 88% toward CO at -0.97 V vs. RHE for 10 h. The well-designed poisoning and control experiments deduce that the catalytic activity originates from the N-doped carbon layer coated on Ni particles. Density functional theory calculations suggest that pyrrolic-N is the optimal active site for the adsorption and activation of CO2 molecules, and the spontaneous charge transfer from Ni 3d electrons to the n orbitals of the N-C skeleton promotes the easy desorption of *CO from the active sites, thereby improving the ECR activity.