title: Temperature effects on the capacitance of an imidazolium-based ionic liquid on a graphite electrode: a molecular dynamics simulation.
abstract: Temperature-dependent electric double layer (EDL) and differential capacitance-potential (C(d)-U) curves of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM(+)/PF6(-)) were studied on a graphite electrode by molecular dynamics simulations. It was found that all C(d)-U curves were asymmetric camel-shaped with higher C(d) at negative polarization, attributed to the specific adsorption of BMIM(+). In addition, the maxima of Cd at the negative polarization decrease monotonically with temperature due to the thicker EDL, whereas at the positive polarization they gradually increase from 450 to 550 K and decrease at 600 K. Such temperature effects at positive polarization may be understood in terms of the competition between two aspects: the weakening specific adsorption of BMIM(+) allows more effective screening to the positive charge and overall increasing EDL thickness. Although the former dominates from 450 to 550 K, the latter becomes dominant at 600 K.
authors.affiliation: Tianjin Key Laboratory of Metal- and Molecular-based Material Chemistry, Key Laboratory of Advanced Energy Materials Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, Institute of New Energy Material Chemistry, College of Chemistry, Nankai University, Tianjin 300071 (PR China).
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Liu
authors.forename: Yining
authors.initials: Y
authors.lastname: Han
authors.forename: Tianying
authors.initials: T
authors.lastname: Yan
keywords: differential capacitance; electric double layer; ionic liquids; molecular dynamics; temperature effects