The catalytic properties of polycrystalline copper toward the electrochemical reduction of carbon dioxide in aqueous hydrogen carbonate and buffered phosphate solution have been studied. It was found that carbon dioxide was reduced at copper in both aqueous solutions under conditions where the copper surface was polarised at high cathodic potential for prolonged time to produce carbon monoxide which adsorbed on copper in linearly and bridged bonded fashions at high negative potentials and at low temperature, 0 °C. At high temperatures, only bridge-bonded CO adsorbed on the copper surface. At low negative potentials, CO interacts with oxidised copper to form copper(I)-carbonyl which exists in both temperatures. The pH of the solution does not seem control the reduction process. Nevertheless, it has a major impact on the chemical nature of the surface and on competing Faradaic reactions. The magnitude of the applied negative potential has a remarkable impact on the quantity and the nature of the reduction products and points to the presence of a competition between the reduction of CO2 and adsorption of anions. Carbon monoxide was confirmed as an intermediate in the mechanism of the reduction of CO2 on polycrystalline copper. This intermediate effectively interacts with metallic Cu inhibiting the hydrogen evolution reaction. It is found that the adsorption of CO is greatly influenced by the existence of pre-adsorbed anions such as hydroxide, phosphate and carbonate on the surface. Both adsorbed CO, linearly and bridged bonded behave differently toward the applied potentials or polarisation potential, duration of the potential polarisation and CO concentration in the solution. Both species are involved in interconversion of the binding sites under such conditions. The studies confirm that linearly bonded CO is weakly adsorbed whereas the bridge bonded CO is strongly adsorbed on the copper surface. Moreover copper(I)-carbonyl exists as a soluble species which is easily removed from the surface. Impedance studies confirm that the presence of pre-adsorbed anions on the copper surface even at the potential near the hydrogen evolution region, which hampers the reduction of CO2 or the adsorption of CO. Polarisation of the copper confirms that the adsorption of anions is depressed through the adsorption of CO either in one or in both linearly and bridged types. At more positive potentials the blocking process from the copper oxides is also reduced by the polarisation of the copper surface at high negative potential through the formation of soluble and insoluble copper species. Corrosion and pitting processes in tum exhibit additional problem in the reduction of CO2.