Fabrication of Microporous Palladium by Selective Anodic Dissolution of Ag-Pd Alloy in Alkali Chlorides Melt

Abstract

The electrochemical dealloying of Ag40Pd60 alloy in (LiCl)57(CsCl)26(KCl)17 melt with the addition of 3 mol% silver chloride has been studied. Selective anodic dissolution of the alloy was carried out both in the potentiostatic and in galvanostatic regimes at temperatures ranging from 300 to 500 °C. The obtained voltammetry characteristics of the initial alloy, chronoamperograms and chronopotentiogram during the dealloying are presented and discussed. At a temperature near 500 °C, the second maximum was observed in the chronoamperograms at two different values of the set potential. The unusual shape of the current curves is due to the superposition of several diffusion processes, which intensities in this case are greater than at lower temperatures. Bi-continuous structures of practically pure palladium with pores and ligaments of sizes ranging from a few to tens of micrometers were obtained in the potentiostatic regime. As the dealloying temperature increased, the sizes of pores and ligaments increased naturally. The same effect was also caused by the increase in applied potential. In the galvanostatic mode similar metallic structures were obtained, but the residual silver content reached 5%, and, in addition, the effects of samples sintering appeared.