Pd-Al Alloys Formation by Aluminium Underpotential Deposition on Palladium from Equimolar AlCl3+NaCl Melt

The possibility of electrochemical underpotential deposition of aluminium onto palladium from equimolar AlCl3+NaCl melts at temperatures between 200 degrees and 300 degrees C was investigated. Electrochemical techniques used were cyclic voltammetry, chronoamperometry, potentiodynamic polarization and open circuit measurements. The results were analyzed by SEM, EDX and XRD. It was found that aluminium deposits underpotentially onto palladium at around 0.200 V vs. Al from the chloroaluminate melt used. It was established that under the given conditions, Al underpotential deposition onto the palladium substrate can result in AlPd and Al3Pd4 alloy synthesis by solid-state interdiffusion. The surface alloys synthetized are well adhering, microcrystalline deposits, having highly developed surface area suitable for applications such as hydrogen purification filters.