In situ analysis of pore size effect of ionic solvation during the formation of double electric layers

Abstract Electrochemical quartz crystal microbalance (EQCM) technique was used to characterize the influence of pore size and ion size and, solvation effect on the formation of electric double-layer capacitors (EDLCs). Based on quantitative calculation and analysis, the apparent molecular mass (Msx) was calculated from the slope of the electrode mass change (Δm) vs. the charge (ΔQ) passed in the electrode during charging/discharge. Comparing Msx with the molar mass of bare ion, the value of specific solvation number(x)was deduced. Findings indicate that the formation of double layers at electrode interface by ionic absorption was accompanied by solvation effect. The solvation effect was weakened as the pore size of the electrode decreased, concluding that the pore size effect exist concurrently with solvation effect during ionic adsorption. The pore size effect was influenced by the size of the counter-ions, polarity of solvent molecules and ionic concentrations.