NUS scientists have found a new mechanism for a selective electrochemical discount of carbon dioxide (CO2) to ethanol using copper-silver (Cu-Ag) composite catalysts.
Electrochemical reduction of CO2 to fuels and chemicals, when powered by renewable electricity, is a step forward in assuaging carbon emissions. Copper (Cu) supplies are choice catalysts for this process because they’ve the highest electrochemical actions towards multi-carbon merchandise.
Nevertheless, their selectivity towards ethanol (C2H5OH), a useful fuel and chemical feedstock, is always lower than towards ethylene (C2H4). The preference in the direction of production of ethylene compared to ethanol arises from the CO dimerization mechanism for producing C2 molecules from CO2, where the formation of ethylene, which has a lower energy barrier, is favored over ethanol.
An analysis team headed by Prof Yeo Boon Siang, Jason from the Division of Chemistry at NUS, in collaboration with a group guided by Dr. Federico Calle-Vallejo from the University of Barcelona, has proven that an influx of CO molecules, offered by silver (Ag) co-catalysts, activates an otherwise-locked mechanistic pathway on Cu which converts CO2 gas to ethanol.
A series of Cu-Ag composite catalysts, fabricated from a mixture of oxide-derived Cu nanowires and Ag powders, had been tested for their electrochemical CO2 reduction actions. During CO2 reduction, Ag converts CO2 to CO, and these CO molecules migrate to the Cu active sites for additional reduction to hydrocarbons (ethylene) and alcohols (ethanol).