The impact of steric repulsion on the capacitance and total free energy\n of electrochemical systems

2021/08/27 by Dagmawi Berhanu Tadesse, Tadesse, Dagmawi Berhanu, Drew F. Parsons +1
Chemistry · Engineering · Physics and Astronomy · #Applied Physics (physics.app-ph) #Electrostatics and Colloid Interactions #FOS: Physical sciences #Nanopore and Nanochannel Transport Studies #Spectroscopy and Quantum Chemical Studies

paper · pdf · doi:10.48550/arxiv.2108.12253

openalex publication_date 2021/08/27 · openalex created_date 2022/07/25 · openalex updated_date 2026/07/28

Abstract

We present a modified Poisson-Boltzmann model that adds steric repulsion of\nions, providing an approximation to ion-ion correlations. Controlled by\nspecific ion sizes, this steric contribution provides a concentration cap.\nImportantly, the steric contribution to the total free energy is comparable in\nsize to the electrostatic contribution and exceeds the classical energy\n1/2CV². Capacitance varies non-monotonically with voltage, with a maximum\nnear 0.2-0.3V depending on the ion size. An analytic expression for the total\nfree energy is derived in terms of the size of the counterion, surface\npotential, and charge density at each electrode.\n

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