Figure 1.

Evaluation of activity and selectivity for electrochemical CO₂ reduction by Ni–N–C-low, Ni–N–C-high, Ni₃S₂/C, and N–C (a catalyst synthesized without Ni). (a) Overall geometric current density. (b) Faradic efficiency toward CO production. (c) Faradic efficiency toward H₂ production. (d) Comparison of CO and H₂ production at −0.67 V vs RHE. Note that in some instances significantly less than 100% faradic efficiencies were reported owing to low current densities that resulted in H₂ concentrations in the effluent from the reactor below the detection limit of the thermal conductivity detector.