Controlled potential electrolysis (CPE) at different potentials between -0.88 and -1.18 V vs. RHE coupled with quantification of CO2 reduction gaseous products has been carried out to evaluate the catalytic CO2 reduction reaction (Fig. ). The potentials tested are in line and well-positioned with a previous report using similar catalysts. The current density increases with increasing potential as a driving force. Currents up to 32 mA/cm 2 combined with FE for CO of up to ~90% were achieved at the more cathodic potential. In all the experiments, only CO and H2 were detected as gaseous products and traces of formic acid (< 0.1% FEHCOOH) as liquid products were detected by 1 H-NMR in the spent electrolyte. Figure shows a higher current density was achieved for the plasma-treated Ag200P36 sample compared to the untreated material at higher potentials. The faradaic efficiency towards CO is similar for both electrodes with only slightly higher FE towards CO for the Ag200P36. Figs. 5(a) and 5(b) show the evolution of the current density and of the FE for CO and H2 with time on stream for the Ag200 and Ag200P36 electrodes, respectively. Firstly, the current density is higher for the plasma-treated electrode, attributed to the enhancement of the electrochemically active area. The initial value of the FECO is similar for both electrodes (~90%). However, for the Ag200 electrode the FECO decreases faster, attaining ~70% FECO after 24 hours. For the Ag200P36 electrode, the FECO attains ~80% after the same time. Concomitantly, the FEH2 increases with time on stream, attaining nearly 20% for Ag200 and 10% for Ag200P36. The total FE is below 100%, which can be due to resistive losses in the system.