Electrochemical Behavior of a Pd Thin Film Electrode in Concentrated Alkaline Media

Abstract

Pd limited volume electrodes (LVE) were obtained electrochemically from the PdCl2 aqueous solution. Hydrogen absorption was performed using cyclic voltammetry and chronoamperometry in concentrated (6 M) alkaline solutions (KOH, NaOH, the mixture of 2M LiOH + 4M KOH) and results were compared with 0.5 M H2SO4. It was found that hydrogen pretreatment procedure is crucial for further examination of hydrogen absorption in Pd electrodes. After many cycles of hydrogen absorption/desorption in Pd, these processes become electrochemically more reversible—faster than in a freshly prepared electrode. Results obtained for Pd electrodes in different concentrated alkaline media subjected to hydrogen pretreatment procedure are comparable with those for an acidic solution (e.g., α→β phase transition potential equals to ca. 0.050 V vs. RHE). The continuous Pd electrode cycling does not affect significantly the amount of absorbed hydrogen (ca. 0.72–0.74). The surface roughness factor in basic solutions decreases after multiple hydrogen sorption as in case of an acidic solution.