CO
2 is electrocatalytically reduced in aqueous solutions (NaHCO3 and Na2SO4) at polycrystalline
gold (Au) both bare and modified with copper nanoparticles (nano-Cu) (nano-Cu/Au). Copper
nanoparticles were deposited by the cycling of potential in the range (–0.2–0.7 V) for various potential cycles. The effect of the electrolyte, as well as the nano-Cu loading on the electroreduction of
CO
2, has been investigated. Nano-Cu/Au electrode has been voltammetrically and morphologically
characterized. It has been found that the type of electrolyte, that is, NaHCO3 and Na2SO4, is critical
in the electrochemical reduction of CO
2; for instance, the CO2 reduction is obscured by hydrogen
evolution in NaHCO
3 solutions (pH 9.2) at both electrodes, that is, bare Au and nano-Cu/Au electrodes, the well-defined redox peak is obtained at both electrodes in Na2SO4 solution (pH 7), even
though the pH of Na2SO4 is smaller. The extent of catalysis is based on the copper loading at the
nano-Cu/Au electrode as well.