Electrochemical CO₂ Reduction Reaction over Cu Nanoparticles with Tunable Activity and Selectivity Mediated by Functional Groups in Polymeric Binder

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The electrochemical carbon dioxide reduction reaction (CO₂RR) using copper (Cu)-based catalysts has received significant attention mainly because Cu is an element capable of producing hydrocarbons and oxygenates. One possible way to control the CO₂RR performance at the electrode interface is by modifying catalysts with specific functional groups of different polymeric binders, which are necessary components in the process of electrode fabrication. However, the modification effect of the key functional groups on the CO₂RR activity and selectivity is poorly understood over Cu-based catalysts. In this work, the role of functional groups (e.g., -COOH and -CF₂ groups) in hydrophilic and hydrophobic polymeric binders on the CO₂RR of Cu-based catalysts is investigated using a combination of electrochemical measurements, in situ characterization, and density functional theory (DFT) calculations. DFT results reveal that functional groups influence the binding energies of key intermediates involved in both CO₂RR and the competing hydrogen evolution reaction, consistent with experimental observation of binder-dependent product distributions among formic acid, CO, CH₄, and H₂. This study provides a fundamental understanding that the selection of desired polymeric binders is a useful strategy for tuning the CO₂RR activity and selectivity.