Influence of temperature on hydrogen electrosorption into palladium-noble metal alloys. Part 1: Palladium-gold alloys

摘要

Hydrogen electrosorption into Pd-rich (>70at.% Pd in the bulk) Pd-Au alloys obtained by electrodeposition was studied in acidic solutions (0.5 M H_2SO_4) using cyclic voltammetry and chronoamperometry. The influence of temperature (in the range between 283 and 313 K) on the amount of absorbed hydrogen, the potential of the α-β phase transition, absorption-desorption hysteresis and the potential of absorbed hydrogen oxidation was examined. It was found that for the temperature range studied the potentials of the α → β and β → α phase transitions are shifted negatively with increasing temperature and positively with decreasing Pd content in the alloy bulk. Thermodynamic parameters (Gibbs free energy, enthalpy and entropy) of the β-phase formation and decomposition were determined from the temperature dependence of the potential of the α-β phase transition. The absolute values of enthalpy and entropy of the β-phase formation and decomposition increase with the decrease in Pd bulk concentration in Pd-Au alloys. The maximum hydrogen absorption capacity of Pd-Au alloys slightly decreases with increasing temperature. The potential of absorbed hydrogen oxidation peak is shifted negatively with increasing temperature and decreasing Pd bulk content.