Electrodes Modified with Overlayers for Enhanced CO2 Reduction Selectivity

Abstract

Like many electrocatalytic reactions involving the transfer of multiple protons and electrons, the CO2 reduction reaction frequently exhibits poor selectivity among many possible products. In this presentation, I will describe our laboratory’s efforts to design electrochemical platforms that enable the control over proton transfer dynamics to electrocatalysts using molecular and polymeric overlayers with the goal of increasing product selectivity and understanding reaction mechanism. This platform is generally applicable to both molecular and metallic systems, and we demonstrate how it can be used to improve the selectivity of nonprecious metal O2 reduction and NO3 - reduction catalysts.For the CO2 reduction reaction, this strategy as applied to metal electrodes is also broadly germane and is used to modulate catalyst reactivity such that it results in the selective production of ethylene, ethanol, methanol, carbon monoxide, and methane, with examples for each with Faradaic efficiencies in excess of 70%. A common theme is that the hydrophobicity of the metal-overlayer interface frequently controls product selectivity and can steer the site of protonation events at intermediates. In this manner, for example, the selectivity of catalysts between the C2 products ethanol and ethylene can be dictated. To aid in mechanistic understanding and catalyst characterization, the majority of these studies are conducted on nominally flat metal electrodes. However, we will also describe ongoing efforts to nanostructure these CO2 reduction systems to develop selective catalysts that operate at high current densities.