Preparation of a high surface area nickel electrode by alloying and dealloying in a ZnCl2-NaCl melt

An electrochemical method of preparing a high surface area nickel electrode by NiZn alloy formation and subsequent dealloying in ZnCl2-NaCl (60-40 mol%) at 450degreesC was studied. A nickel electrode was kept at 0.22 V vs. Zn in ZnCl2-NaCl(sat) where gamma-NiZn alloy was formed, and then at 0.5 V where partial dealloying occurred to yield alpha-NiZn alloy. Scanning electron microscope observation showed that the microporous structure was formed on the surface. The roughness factor of a sample was determined to be 240 from the double layer capacitance obtained in the ac impedance measurement. Thickness, porosity, and pore size of the surface layer were estimated. (C) 2003 The Electrochemical Society.