Measurement of double-layer capacitance and investigation of exchange reactions at selected electrodes in aqueous solution

Differential capacitance curves for the metals, lead, cadmium, zinc, silver and tin have been determined in a number of ultra-pure aqueous electrolytes. In the absence of adsorption at the electrode, conclusions are drawn regarding the relationship between a metal’s crystal structure and the shape of the differential capacitance curves and also between the melting point of a metal and the value of its differential capacitance. The kinetics of the rate-controlling exchange reaction at cadmium and lead electrodes have been investigated using two different experimental techniques. The rate-controlling reaction at a lead electrode in nitrate-supporting electrolyte was shown to be charge transfer. The reaction at calcium electrodes in both simple perchlorate electrolytes and complex cyanide electrolytes was complex. Equilibration processes on electrode surfaces are discussed.