Electrochemical Methanation of Carbon Dioxide with Highly Dispersed Copper Nanocatalysts

Although the vast majority of fuels and hydrocarbon products are presently derived from petroleum, there is immense interest in the development of alternate routes for synthesizing these products by hydrogenating carbon oxygenates. Electrochemical methods of reducing carbon dioxide could serve as a method of storing electrical energy derived from intermittent sources like solar and wind if efficient catalysts with high hydrocarbon selectivity are developed. Although metals in the form of foils are increasingly well-characterized as electrocatalysts for carbon dioxide reduction, the activity and stability of their nanoscale counterparts remain poorly understood. We present an understanding of the electrochemical conditions and catalyst architectures that afford control over the selectivity of copper nanoparticles for electrochemical methanation. Highly dispersed copper nanoparticles supported on glassy carbon exhibit enhanced Faradaic efficiencies for methanation compared to copper foils. The improved hydrocarbon selectivity for the copper nanoparticles is due to an underlying difference in the mechanism by which electrochemical carbon dioxide reduction proceeds on the nanoparticle surface. Our understanding of highly dispersed copper nanoparticles for electrochemical methanation is a first step towards their incorporation into membrane-electrode assemblies in practical electrolyzers.