A molecular dynamics study of graphyne-based electrode and biocompatible ionic liquid for supercapacitor applications

Abstract

• Graphyne as a promising candidate for electrochemical energy storage systems. • Electrolytes based on aqueous mixtures of the biodegradable ionic liquid. • Efficiency of low toxicity cholinium-based ionic liquids electrolytes in supercapacitor. Atomistic molecular dynamics simulations were used to investigate the properties of electrolytes based on aqueous mixtures of the biodegradable ionic liquid [Ch][Gly] with the ionic liquid [Bmim][PF 6 ] as electrolytes in graphyne supercapacitors. Energetic, structural, and electrostatic analyses were performed to describe de Electrical Double Layer (EDL) formed near de graphyne electrodes revealing preferential adsorption of [Bmim][PF 6 ] additive in both, positive and negative electrodes. From the energetic analysis, we found that although the structure and formation of the EDL are governed by the complex interaction network of both van der Waals and electrostatics, its interaction with the electrode is drastically dominated by van der Waals interactions. From electrostatic results, we found a reduction in total capacitance as the concentration of [Bmim][PF 6 ] increases but overall, we observed that cholinium-based electrolytes can perform as well as most conventional ionic liquids, but with the advantage of having a low toxicity. The comparison between graphene and graphyne supercapacitors revealed a higher capacitance for graphyne, with 2.4 μF cm −2 at 2 V, even when we compare similar values for the drop potential (which occur for different values of charge density) the higher performance of the graphyne electrode is maintained; a result that corroborates the previous findings and that indicates graphyne as a promising candidate for electrochemical energy storage systems.