Influence of temperature on hydrogen electrosorption into palladium-noble metal alloys. Part 3: Palladium-rhodium alloys

Hydrogen electrosorption into Pd-Rh alloys (containing more than 60 at.% Pd in the bulk) was studied in acidic solution (0.5 M H2SO4) using cyclic voltammetry and chronoamperometry. Alloys were obtained by electrodeposition from baths containing PdCl2, RhCl3 and HCl. The influence of temperature (in range between 283 K and 328 K) and alloy bulk composition on parameters of hydrogen sorption in Pd-Rh alloys was examined. It has been found that for the temperature range studied the maximum hydrogen absorption capacity is the highest in 283 K and decreases with temperature increase. It has been established that potentials of hydrogen phase transitions (α → β and β → α) are shifted negatively with increasing temperature. The potential of absorbed hydrogen oxidation peak is shifted negatively with increasing temperature. With increasing Rh bulk content the phase transition potentials and hydrogen oxidation peak are shifted into lower potentials. An alloy containing 92.6 at.% Pd is characterized by the highest hydrogen absorption capacity with H/M ratio exceeding 0.80.