Influence of adsorption processes on the CO2 electroreduction: An electrochemical mass spectrometry study

The reduction of CO2 in sulfuric and perchloric acid electrolytes on a polycrystalline Cu surface has been investigated, using the online electrochemical mass spectrometry method (EC/MS). Gaseous products, such as CH4, C2H4 and highly volatile products such as CH3OH, HCHO, are formed at overpotentials of hydrogen evolution reaction. The EC/MS results suggest that the reduction products formed depend on the presence of preadsorbed sulfate on the surface. The adsorbed anion from the electrolyte plays a role at the potential where HCHO formation occurs on copper. A mechanism for this process, based on electrocatalytic hydrogenation, is proposed.