Protic ionic liquids as binders for carbon paste electrode fabrication

Enhancing electron transfer rates is a critical challenge in improving electrochemical efficiency and advancing energy storage technologies. Ionic liquids (ILs), which can significantly enhance charge transport and interfacial electron transfer, have emerged as versatile components in electrochemical systems, particularly as binders in carbon paste electrodes (CPEs). We combined molecular dynamics (MD) simulations with experiments to further elucidate how aprotic quaternary ammonium (QA) ionic liquids can function as binders CPEs. Simulation revealed QA-ILs films selectively wet graphite basal planes while leaving edge sites exposed, unlike paraffinic binders that uniformly coat all surfaces. This interfacial selectivity supports the hypothesis of edge-plane exposure in enhancing electron-transfer kinetics. Additionally, peak-widths of correlation function indicate that the aliphatic QA cation experiences low friction on graphite, enabling barrierless "gliding" motion, in contrast to the rigid, hopping behavior of aromatic imidazolium ILs. Together with charge delocalization in the flexible [NTf₂]^- anion, this promotes rapid ion dynamics at the graphite interface. Cyclic voltammetry confirms fast electron transfer and a pronounced non-Faradaic response for QA-IL-based CPEs relative to pyridinium- and imidazolium-derived systems. These results identify QA-ILs as promising binders for next-generation supercapacitors and high-performance electrochemical devices.