Sulfur-doped unsaturated Ni-N3 coordination for efficient electroreduction of CO2

Tuning coordination environment of metal atoms in catalysts can improve intrinsic performance of CO2 reduction and accelerate kinetics of CO formation. However, constructing unsaturated coordination configuration of metal single-atom by heteroatom doping still remains a challenge. Herein, a novel electrocatalyst of S/N co-coordinated Ni single-atom (denoted as Ni-SNC) was synthesized by calcining SO42- doped Zn/Ni ZIF for electrocatalytic CO2 reduction. The existence of single-atom Ni was verified by HAADF-STEM, while formation of “unsaturated” Ni-N3-S active sites was confirmed by XANES and EXAFS. The energy barrier of pivotal steps in CO2RR reaction process was reduced on “unsaturated” Ni-N3-S active sites, and sulfur doping improved current density of electrocatalytic process. The energy barrier of CO2→COOH* over Ni-SNC catalyst was only +0.69 eV, which was much less than that (+2.02 eV) over Ni-NC catalyst. The Ni-SNC exhibited CO Faradaic efficiency (FECO) of >90% at -0.6 ∼ -0.9 V vs. RHE with the highest FECO of 95% at −0.8 V.