Highly dispersed atomic-level Ni active sites confined in defects for efficient electrocatalytic reduction of carbon dioxide

Electrocatalytic CO2 reduction reaction (eCO2RR) presents a promising approach for harnessing renewable energy and converting greenhouse gas (CO2) into high value-added CO products. N-doped single atom (SA) and atomic-level metal nanocluster (MN) tandem catalysts with rich defects for eCO2RR are reported, which achieved a maximum CO Faraday efficiency (FECO) of 97.7% (−0.7 V vs. RHE) in the H-type cell and maintained over 95% FECO at potentials from −0.18 to −0.73 V vs. RHE in the flow cell. Furthermore, the catalyst in the flow cell demonstrated a remarkably low onset potential of −0.14 V vs. RHE and the current density was approximately three times that of the H-type cell. Interestingly, XPS analysis indicates that carbon substrates containing defects have more pyridine-N content. DFT calculations and in-situ attenuated total reflection Fourier transform infrared support this finding by showing that the Ni-(N-C2)3 active sites with defect favors preferentially convert CO2-to-CO.