Ni-FeS showed higher organic product formation and overall faradaic efficiency for CO2 reduction at same electrochemical conditions than FeS (Figures and). We also detected that under nanoamp current, the faradaic efficiencies were much higher for the organic production, mainly for Ni-FeS. That indicates that Ni atoms enhanced the interaction of mackinawite with CO2 for its electrochemicallyinduced reduction, as shown in other works, and how specific currents, not necessarily the higher ones, may result in better efficiencies. For acetic acid formation, Ni-FeS shows a higher performance on mediating its formation. However, under condition of a fixed voltage of -500 mV (Table , entries 1 and 3), we see a different pattern, where FeS shows higher capacity to form formic and acetic acid. That altered pattern was detected on formic acid production under -2.0 V (Table , entries 2 and 4).