Tuning N coordination environment in Ag[sbnd]N[sbnd]C single atom catalysts for efficient electrochemical CO2-to-Ethanol conversion

Abstract

The rational modulation of the coordination environment of the active center of single-atom catalysts (SACs) is a potential strategy to improve the activity and selectivity of electrocatalytic CO2 reduction. We developed a series of single-atom Ag-anchored on N-doped carbon catalysts with different N-coordination environments by regulating the carbon source (glucose/graphene oxide, GO). Results demonstrated that the CO2-to-CO/C2H5OH pathway can be converted through reasonable regulation of the content of pyrrolic N and pyridine N. At a highly dominant pyrrolic N content of 40.0 %, the electrocatalyst of Ag-N-rGO0.025 M facilitates the formation of CO with a Faradaic efficiency (FE) of 69.7 %. By contrast, when the pyridine N content is 70.5 %, the best Ag-N-C0.05 M catalyst in the H-cell shows an FE of 42 % for C2H5OH at −0.97 V vs. RHE; moreover, the FE is stable at 40 % within 31 h. Density functional theory calculations further confirm that the pyrrolic N site is conducive to the conversion of CO2 to intermediate *CO, whereas pyridine N exhibits the highest binding energy (ΔG = -4.73 eV) to hold *CO intermediates for dimerization, consequently steering the pathway to the formation of C2H5OH. The results of this study provide novel insights into the rational design of carbon-based SACs based on efficient electrochemical CO2 reduction reaction and the regulation of CO2 selectivity and activity for C2H5OH production.