(79f) Single Atom Catalysts for Electrochemical Reduction of CO2

Electrochemical reduction of CO₂ offers a sustainable route to mitigate the problem of rising in CO₂ concentration in the atmosphere. Among the various electrocatalysts studied for the conversion of CO₂ to hydrocarbons, supported metal catalysts have played an important role in enhancing the rate of chemical reactions compared to bulk unsupported metals. Broadening this distribution of metal to make supported isolated atoms is a novel approach to heterogeneous catalysis. The reduction in the size of the catalyst not only enlarges its specific area, but also increases the number of under coordinated sites, and the HOMO-LUMO gap. This can improve the activity and selectivity of the catalyst. In this work, η⁶-functionalized graphene which includes transition metal single-atom (SA) layer is used as the cathode for electrochemical reduction of CO₂. The η⁶ chemistry retains graphene’s 2D structure and high electronic properties (high carrier mobility and high electric conductivity), which contributes to a high catalytic activity with a large surface area. Moreover, the transition metal is grafted on graphene by coordination bonds, so that the adsorption energy of CO₂ reduction intermediates is increased and further the energy barrier for hydrogenation is reduced. Such single metal atom supported electrocatalysts offer a higher activity to transition metals as compared to their bulk counterparts. The use of SA catalysts also means that lesser quantities of metals being used per unit weight of the electrode resulting in cheaper catalysts with superior performance. Due to only recent advances in the synthesis of stable SA catalysts, the application of single-atom catalysis for electrochemical reduction of CO₂ seems promising. To study the behavior of single-atom catalysts for CO₂ reduction, we present a design of a compact electrochemical cell with carbon supported single-atom transition metal atoms on graphene as the Rotating Disk Electrode (RDE). An RDE is chosen as it minimizes the cathode polarization and enables the measurement of intrinsic kinetic activity. A product distribution of CO₂ reduction products at near-neutral pH, their partial current density, and Faradaic efficiencies at different potentials will also be reported in this work.