Global warming has been a severe problem over the past few decades, which is mainly caused by the massive emissions of CO2 due to large-scale consumptions of fossil fuels. The electrochemical reduction of CO2 is a promising way to produce synthetic fuels or chemicals and mitigate the greenhouse effect. Cu catalyst is unique for its ability to convert CO2 to value-added C2 products including ethylene and ethanol. However, the poor selectivity limits the effectiveness of this catalyst. In this thesis, we report a simple method to improve C2 selectivity to ~75% by employing pulsed potentials on a (100)-orientated polycrystalline Cu foil. We also find the selectivity between ethylene and ethanol can be simply tuned by controlling the temperature. The enhanced C2 selectivity can be explained by the improved CO dimerization kinetics on the (100) facets with reduced hydrogen adsorbates and the selectivity between ethylene and ethanol by the reducibility of the Cu(_) species under pulsed potentials. Our work demonstrates a route to improve the ethylene selectivity and identifies Cu(I) as the species responsible for ethanol production.