Electrochemical formation of porous nickel in zinc chloride-alkali chloride melts

An electrochemical method of preparing a porous nickel electrode by NiZn alloy formation and subsequent dealloying in zinc chloride-alkali chloride (60-40 mol %) melts at 350-450 degrees C was studied. X-ray diffraction measurements at different stages of dealloying suggested that two step transformation from gamma- to beta(1)- and from beta(1)- to alpha-NiZn alloy occurred. Dealloyed material exhibited well-developed porous structure of hundreds of nanometers in size. Electron probe microanalysis of a partially dealloyed layer showed that the dissolution of zinc occurred relatively uniformly throughout the alloy layer. Scanning electron microscopy of samples obtained at different temperatures showed that the size of porous structure (crevices and pores) was smaller at lower temperatures. The porous nickel electrode showed relatively low overvoltages in the hydrogen evolution reaction in 1 M KOH aqueous solution. (c) 2006 The Electrochemical Society.