Determination of change in enthalpy and entropy for hydride formation and decomposition of palladium using in-situ electrical resistance measurement with various hydrogen pressures

Abstract

Detection of hydride formation and decomposition of palladium is performed on pure palladium in the hydrogen gas atmosphere up to 0.5 MPa between room temperature and 673 K using an in-situ electrical resistance measurement system. Introduction of hydrogen gas increases the electrical resistance about 1.1 time higher than that in vacuum. Electrical ratio-temperature plot gives a peak during heating and cooling with the temperature changing ration of 0.067 K/s under hydrogen gas, which are associated with the hydride composition and decomposition. Change in enthalpy ΔH and entropy ΔS are determined using van't Hoff plot, and the values were comparable to the reported ones obtained by pressure-composition-temperature measurements. Those for hydride decomposition are 45.6±2.6 (kJ/mol) and 104.8±5.3 (J/mol), respectively, and those for hydride formation are -29.4±2.1 (kJ/mol) and 73.8±4.6 (J/mol), respectively. Furthermore, the measurement method is relatively simple and easy compared with pressure-composition-temperature measurements.