The capacitance of the electrical double layer of valence-asymmetric salts at low reduced temperatures

Abstract

The low temperature anomalies in the double layer properties of electrolytes have been observed in recent simulations and reproduced by a number of theoretical methods. This anomaly means that the capacitance of the electrical double layer increases with increasing reduced temperature when the reduced temperature is small, while the behaviour is the reversed at high reduced temperatures. In this paper, we give a concise overview of Monte Carlo simulation results for a 1:1 electrolyte together with the results of various theories such as the Gouy–Chapman theory, various versions of the mean spherical approximation, density functional theories, the modified Poisson–Boltzmann theory, and a field theoretical approach. We report our simulation results for the reduced temperature dependence of the capacitance of 2:1 and 3:1 electrolytes. Finally, we investigate the effect of a concentration dependent dielectric constant by means of a Parsons–Zobel plot.