The Role of Mesostructure for CO2 Reduction on Dendritic Copper Electrocatalysts

Abstract

Electrochemical reduction of CO2 for production of fuels has been a promising field of research for simultaneously decreasing carbon emissions and storing solar energy in dense chemical bonds. Copper is an important electrocatalyst for this process because it catalyzes a broad range of hydrocarbons and alcohol CO2 reduction products. The structure of copper catalysts can affect product selectivity through several known strategies. Hierarchically structured copper foams incorporate several strategies for the production of high value products, including the diffusive trapping of products such as CO and HCOOH into further reduced products. During fabrication of the electrocatalyst, hydrogen evolution (HER) is responsible for the formation of the large-scale morphology of the electrode, but also promotes the formation of electrode areas that are particularly effective at HER. Here, we explore alternative fabrication strategies for dendritic Cu electrocatalysts by modifying the pH of the solution to control hydrogen bubbling during synthesis. We describe the synthesis and structural characterization of the catalyst surfaces as a function of pH. We also show that the branching ratios and Faradaic efficiency of CO2 reduction can be controlled through the conditions of electrode synthesis. Based on these results, we consider the relationship between electrode mesostructure and electrolytic branching ratios in order to tailor the selectivity of Cu electrocatalysts for the CO2 reduction reaction.