(Invited) Electrochemical Reduction of Carbon Dioxide to Oxygenates and Hydrocarbons

Abstract

Currently, more than 80% of the world’s energy needs are met by burning fossil fuels. Supplies of these fuels are intrinsically limited and will eventually run out. Combustion of fossil fuels also generates carbon dioxide, whose rapidly increasing atmospheric concentration contributes to global warming. One solution for mitigating atmospheric concentrations of CO2 is to electrochemically reduce these molecules into chemicals and fuels. If the energy used for these processes is generated from renewable sources such as solar and wind, we can envisage a chemical production cycle that is closed-loop with net zero carbon emission.In this talk, we share our recent works related to the development of catalysts for the selective electroreduction of CO2 to oxygenates and hydrocarbons. We shall show the pathway by which CO2 could be converted to 1-butanol, a C4 alcohol. Through a series of control experiments and density functional theory (DFT) calculations, we pinpoint that its C4 backbone was formed from a surface-mediated aldol condensation of acetaldehyde formed from CO2 reduction, rather through the coupling of four CO intermediates. We also discuss how CO2 could be reduced to methanol through a tandem process - CO2 was first reduced to formic acid, and the latter can be reduced to methanol using anodized titanium. For the latter step, experiments and DFT calculations identify Ti3+ and oxygen vacancies (TOV) as the active sites in a vacancy-filling pathway mediated by *H2COOH. We also give screening rules based on the *HCOOH and *H2COOH binding energies alongside TOV formation energies. These can facilitate the high-throughput automated design of catalysts for CH3OH synthesis from tandem CO2 electrolysis. In the last part of our talk, we show how molecules not commonly observed during CO2 reduction such as propylene and other C4-C6 products could be formed.