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

Hydrogen electrosorption into Pd-rich (>70 at.% Pd in the bulk) Pd–Au alloys obtained by electrodeposition was studied in acidic solutions (0.5 M H2SO4) 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.