Effect of capillary waves on the double layer capacitance of the interfacebetween two immiscible electrolytes

The effect of capillary waves on the double layer capacitance of the interf ace between two immiscible electrolytes has been studied. We have found tha t a corrugation of the interface due to capillary waves leads to an increas e in the capacitance, as compared with the Gouy-Chapman result for a flat i nterface. The theory offers a concept of a roughness function. (R) over til de, which determines the deviation of capacitance from the Gouy-Chapman res ult. R is a function of Debye lengths of the two immiscible electrolytes. A nalytical expression for the roughness function has been derived which show s a strong dependence of R on the interfacial tension and the dielectric co nstants of contacting solutions. Predictions amenable to experimental tests have been discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.