Electrical resistivity due to dissolved H in Pd

Peculiarities of the electrolytic hydrogenation of Pd as revealed by resistivity measurements

“…On the charging curve with 1 mA/cm 2 denoted by squares, the break at a concentration of c(␣ max ) = 1.54 at.%H (0.016H/M) identified by the intersection of the two linear sections corresponds to the start of the formation of the ␤-phase. The slopes of curves 1 and 1 are around 0.43 cm/at.%H and this is in very good agreement with the results of previous electrolytic [10,22] and gas-phase [14] charging experiments. We can also establish that the slope is independent of the charging current density in the wide range investigated.…”

“…In the experiment denoted by circles, the absorption up to c ≈ 0.58 at.%H (= 0.006H/M) was promptly followed by desorption at the same current density (0.1 mA/cm 2 ). The absorption and desorption resistivity data show complete coincidence with each other as also found by Szõkefalvi-Nagy et al [10]. This is a good indication for the validity of Faraday's law with 100% current efficiency and it justifies the calculation of the H content in this manner for the ␣-phase range.…”

“…They demonstrated that if the hydrogenation is performed under equilibrium conditions from the gas phase in the usual manner by which pressure-composition (p-c) isotherms are obtained (i.e., by continuously increasing the H-content in very small steps from 0 up to the pure ␤-phase region), the resistivity variation with hydrogen content matches very closely the behaviour of the corresponding p-c isotherm. In the ␣-phase, they found a resistivity variation very similar to that observed in previous experiments by electrolytic hydrogenation [1,9,10]. In the mixed ␣ + ␤ region, however, the rate of resistivity increase was strongly diminished and a similar plateau was observed as in the p-c isotherm.…”

“…In the present study, the hydrogen content assigned was obtained from Faraday's law by assuming 100% current efficiency for both the absorption and desorption processes. With reference to the results described in Section 3.1, it can be established that this H concentration deviation cannot come from an inappropriate application of Faraday's law since in the ␣-phase region we have very accurately reproduced the slope of the resistivity increment reported in previous studies [10,14,22].…”

“…In early experiments on studying the influence of hydrogen on the electrical resistivity of Pd, the electrolytic hydrogenation technique was mainly applied [1,9,10]. It was found in these studies that the resistivity increases linearly with increasing H-content in the ␣-phase region, the rate of increase being as high as 0.42 cm/at.%H [10].…”