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Differential capacitance of an electrical double layer with asymmetric ion sizes in the presence of hydration interactions

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Autor(es):
Bossa, V, Guilherme ; Caetano, Daniel L. Z. [1] ; de Carvalho, Sidney J. [1] ; May, Sylvio [2]
Número total de Autores: 4
Afiliação do(s) autor(es):
[1] Bossa, Guilherme, V, Sao Paulo State Univ UNESP, Dept Phys, Inst Biosci Humanities & Exact Sci, Sao Jose Do Rio Preto - Brazil
[2] North Dakota State Univ, Dept Phys, Fargo, ND 58108 - USA
Número total de Afiliações: 2
Tipo de documento: Artigo Científico
Fonte: Electrochimica Acta; v. 321, OCT 20 2019.
Citações Web of Science: 0
Resumo

The differential capacitance is a fundamental property of an electrical double layer and thus important for the development of more efficient and environment-friendly energy storage devices. In addition to the bare electrostatic interactions, the differential capacitance is affected by a complex interplay of ion-specific effects that arise from ion size, shape, and hydration. We employ Monte Carlo simulations to calculate the differential capacitance for size-asymmetric spherical ions, thereby modeling hydration-mediated interactions using Yukawa pair potentials. We also propose a corresponding mean-field theory that includes ion-specific Yukawa pair potentials and accounts for ion size mismatch on the basis of a recently proposed lattice model. Comparison of the two approaches - Monte Carlo simulations and mean-field theory - yields qualitative agreement, irrespective of ion size and size mismatch between cations and anions. The agreement includes the regime of weakly charged electrodes, where we find a growing differential capacitance with growing ion sizes, a behavior that is not consistent with the widely used Stern layer concept. Hence, our study reinforces the predictive power of mean-field theory, but only when the influence of correlations due to excluded volume interactions is diminished by the presence of soft, hydration-mediated ion-ion interactions. (C) 2019 Elsevier Ltd. All rights reserved. (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
Linha de fomento: Bolsas no Brasil - Pós-Doutorado
Processo FAPESP: 18/01841-2 - Estudo por Simulação Computacional da Interação entre Polieletrólitos e Macromoléculas
Beneficiário:Sidney Jurado de Carvalho
Linha de fomento: Auxílio à Pesquisa - Regular