Electroreduction of Carbon Dioxide to Methane on Copper, Copper–Silver, and Copper–Gold Catalysts: A DFT Study

2013-04-25T00:00:00Z (GMT) by Pussana Hirunsit
The electrochemical reduction of CO<sub>2</sub> is a promising process capable of efficiently recycling CO<sub>2</sub> waste and converting it into hydrocarbon fuel. To date, copper is the best metal catalyst; however the overpotential to achieve this reaction on Cu is excessively high. It follows that the development of a catalyst to efficiently catalyze the conversion with a low overpotential at a reasonable current density is needed. Many aspects of the molecular details of the reaction are still unclear. In this work, DFT calculations are applied to investigate CO<sub>2</sub> electroreduction to CH<sub>4</sub> over Cu<sub>3</sub>Ag and Cu<sub>3</sub>Au stepped surfaces (211) compared to that over Cu(211). In the resulting analysis, the Cu<sub>3</sub>Ag surface shows a slightly lower overpotential and suppresses OH poisoning compared to the Cu surface, yet the selectivity toward H<sub>2</sub> increases. The Cu<sub>3</sub>Au is not a good candidate due to higher overpotential and a relatively weak CO adsorption resulting in CO desorption rather than further reduction. The CO desorption can also be problematic on Cu<sub>3</sub>Ag as well. The thermodynamics and kinetics of the nonelectrochemical hydrogenations are also examined to explore alternative paths which might result in an absence of formaldehyde intermediate production during CO<sub>2</sub> reduction on Cu.