Modulating CO2 electroreduction pathways through controlled ionomer arrangement on catalyst surfaces via solvent dispersion

Ionomers play a vital role in the preparation of electrodes for CO₂ electroreduction, and controlling the ionomer configuration on the catalyst surface offers an effective strategy for adjusting the surface microenvironment of the electrode, thereby influencing the distribution of CO₂ electroreduction products. In this study, we demonstrate that Nafion, a commonly used ionomer, exhibits distinct aggregation behaviors in solvents with different dielectric constant (ε) values. These differences in aggregation result in varied Nafion arrangements on the catalyst surface, which in turn affect the binding of ∗CO and ∗H intermediates, enabling control over product distribution. For example, over a Cu nanosheet catalyst at 800 mA cm^-2, the Faradaic efficiency for multicarbon products increases from 67.5% to 90.5% simply by changing the dispersion solvent from low-ε dimethyl sulfoxide to moderate-ε isopropanol. This work introduces a novel approach for fine-tuning CO₂ electroreduction product distribution through manipulation of the dispersion solvent without requiring modifications to the catalyst or ionomer.