The Role of Ion-Ion Correlations for the Differential Capacitance of Ionic Liquids

Autor(es)

Downing, Rachel ^[1] ; Bossa, Guilherme Volpe ^[2] ; May, Sylvio ^[1]

Afiliação do(s) autor(es)

^[1] North Dakota State Univ, Dept Phys, Fargo, ND 58108 - USA

^[2] Sao Paulo State Univ UNESP, Dept Phys, Inst Biosci Humanities & Exact Sci, BR-15054000 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry C; v. 122, n. 50, p. 28537-28544, DEC 20 2018.
• Citações Web of Science: 3

Resumo

We employ the quasi-chemical approximation to incorporate ion ion correlations into a lattice gas model for the electric double layer formed by a compact, size-symmetric ionic liquid. The resulting differential capacitance, which we calculate for planar and weakly curved electrodes up to first order in curvature, transitions from a bell shape to a camel-shape profile for increasing correlation strength. No such transition is present if the quasi-chemical approximation is replaced by a random mixing approximation. The bell-to-camel shape transition is, up to first order, independent of curvature. If Coulomb interactions dominate on molecular length scales, the differential capacitance has a tendency to adopt a camel-shape profile. Hence, our model offers a physical interpretation for the observed camel shape (or even U-shape) of the differential capacitance in many ionic liquids. Correlations also cause ``underscreening{''} where the characteristic decay length of the electric double layer grows with the correlation strength and can become much larger than the size of a single ion. (AU)

• Processo FAPESP: 17/21772-2 - Extensões da Teoria de Poisson-Boltzmann para o estudo da capacitância diferencial de uma dupla camada elétrica
• Beneficiário: Guilherme Volpe Bossa
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado