Highly stable and electron-rich Ni single atom catalyst for directed electroreduction of CO2 to CO

Transition metal-nitrogen-carbon (M-N-C) are considered as promising candidates for the electrochemical conversion of inert CO2 into high value-added CO products. However, previous reports have focused on Ni single- atom sites (Ni SAs) and the role of Ni nanoparticles (Ni NPs) in CO2 electroreduction reaction (CO2RR) has been overlooked. Herein, we prepared a series of Ni, N-codoped porous carbon (NiNC-T, T represents the temperature) catalysts by combining Ni phthalocyanine pyrolysis and acid etching strategy, which either contain only Ni SAs or both Ni SAs and Ni NPs. Notably, the NiNC-1100 catalyst with both Ni SAs and Ni NPs exhibited 99 % CO faradaic efficiency (FECO) at-0.66 V versus reversible hydrogen electrode (vs. RHE) and FECO above 98 % over a wide potential range (-0.66 V similar to-1.06 V). Moreover, the FECO of NiNC-1100 remained above 95 % after 100 h of continuous electrocatalysis, which was significantly superior to that of the most advanced Ni single atom electrocatalysts. The systematic characterization results showed that the introduction of Ni NPs can promote the adsorption and activation of CO2 by increasing the electron cloud density of Ni SAs, thus enhancing the CO2RR catalytic performance.