The differential capacitance of an electrical double layer is a topic of great importance to developing more efficient and environment-friendly energy storage devices: the supercapacitors. In addition to electrostatic interactions, several theoretical and experimental works have suggested that the differential capacitance is affected by a complex interplay of ion-specific solvent-mediated interactions and the structure of the ion close to charged surfaces. In line with this, in this project we present a theoretical model that incorporates non-electrostatic interactions into the Poisson-Boltzmann theory by means of Yukawa potentials; we thus focus on the electric double layer formed at the vicinity of an electrode which surface is covered by ionizable groups. We analyze the effects of salt concentration, finite ionic size and, more importantly, how the affinity of the ion-electrode interaction can be tuned to optimize the capacitance.
News published in Agência FAPESP Newsletter about the scholarship: