(62f) Mechanistic Insight into CO2 Electroreduction over Single-Atom Catalyst Platform Via Operando Infrared Spectroscopy

Electrochemical conversion of CO₂ into value-added chemicals offers a sustainable route to mitigate the rising atmospheric CO₂ levels. Developing highly active, selective, inexpensive, stable, and readily available electrocatalysts for CO₂ reduction reaction (CO2RR) is therefore of significant importance. Many transition metals like Cu, Ag, and Au are known to be selective to produce hydrocarbons, however, any practical implementation of such catalysts would require large quantities of metal which will make it economically non-viable. Therefore, attention has been directed to the development of high surface area supported catalysts. Reducing the size of the catalyst not only reduces the amount of metal used, but also increases the specific area, increases the number of unsaturated sites, and the HOMO-LUMO gap, which in turn, increases the activity of the catalyst. Dispersing isolated atomic clusters is, therefore, a novel approach to heterogeneous catalysis. In this work, η6-functionalized graphene with transition metal single-atom (SA) layer is used as a 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. We present operando attenuated total reflectance- Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy to understanding the behavior of single-atom catalysts for CO2RR by observing the adsorption of the intermediate species on the catalyst surface. A distribution of CO2RR products at near-neutral pH using gas chromatography (GC) and high-pressure liquid chromatography (HPLC), their partial current density, and Faradaic efficiencies at different potentials is also reported as a part of this work.