Chemical Engineering Seminar

The electrochemical conversion of carbon dioxide into hydrocarbons is an alternative route for producing fuels and feedstocks that are typically derived from oil or natural gas. This route also represents a potential strategy to store electrical energy derived from intermittent, renewable sources like solar and wind. Although metals in the form of foils are increasingly well-characterized as electrocatalysts for carbon dioxide reduction, their nanoscale counterparts remain poorly understood. This presentation focuses on a mechanistic understanding of the factors that influence the activity, selectivity, and stability of gold and copper nanoparticles for electrochemical carbon dioxide reduction. The mobility of nanoparticles along a support is typically thought to be limited at room temperature; in contrast, our experimental and simulation results demonstrate that nanoparticle catalysts readily diffuse along the support, collide with neighboring particles, and fuse to form dendritic structures during electrochemical carbon dioxide reduction. An in-depth understanding of the polarization-dependent surface chemistry of gold nanoparticles has been used to develop strategies to limit the dendritic assembly process, thereby increasing the surface area for catalysis. In addition, highly-dispersed copper nanoparticles are found to exhibit the highest selectivity reported to date for electrochemical methanation. Detailed kinetic studies reveal that electrochemical methanation on copper nanoparticles proceeds through a mechanism involving intermediates that are distinct from those thought to occur on copper foils. The improved understanding of the catalytic behavior of gold and copper nanoparticles for electrochemical carbon dioxide reduction is a first step towards their incorporation into membrane-electrode assemblies for electrolyzers.