Electrochemical Reduction of CO2 on Supported Cu2O Catalysts

Abstract

We have examined Cu-based catalyst materials that enable the conversion of CO2 to useful products such as fuels and chemical feedstocks by electrochemical reduction. In particular, we compared the electrocatalytic activity of supported Cu2O particles prepared using electrodeposition and wet chemical methods. The particles had cubic structure, ranging in size from 40 nm to 900 nm and consisting of low index planes. We observed significantly different product distribution on these catalysts compared to polycrystalline Cu, specifically for methane and ethylene formation. While Cu particles showed higher faradaic efficiency for methane formation compared to ethylene formation, we observed that Cu2O particles were more selective to ethylene than methane. For example, the C2H4/CH4 ratio on Cu was 0.2 while the C2H4/CH4 ratio on both electrodeposited Cu2O film and colloidal Cu2O particles was around 60. The Cu2O particles were reducible and the derived particles consisted of higher number of low-coordinated active sites than Cu which we propose are responsible for the increased ethylene selectivity. At -1.5VNHE, electrodeposited Cu2O film and colloidal Cu2O particles achieved highest average ethylene faradaic efficiency of 9.4% and 38% respectively while Cu foil only showed 1.2%. The colloidal Cu2O particles also exhibited better CO selectivity than Cu. While Cu showed 5.5% CO faradaic efficiency, colloidal Cu2O particles achieved highest average CO faradaic efficiency of 22%. Product distribution on Cu2O catalysts was primarily influenced by potential and was kinetically dynamic. Nafion mixed with Cu2O particles was shown to enhance and stabilize ethylene formation.