Some problems on the resistance method in the in situ measurement of hydrogen content in palladium electrode

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Vol. 528; no. 1; pp. 1 - 17
• Main Authors: Zhang, Wu-Shou, Zhang, Zhao-Fu, Zhang, Zhong-Liang
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 14.06.2002; Elsevier Science
• Subjects: Chemistry; Concentration-cell; Diffusion; Electrochemistry; Electrodes: preparations and properties; Exact sciences and technology; General and physical chemistry; Hydrogen evolution; Other electrodes; Pd electrode; Resistance; Resistance; Concentration-cell; Pd electrode; STM, scanning transmission microscope; Hydrogen evolution; ISRM, in situ resistance measurement; emf, electromotive force; dc, direct current; ecd, electrolysis current density; Diffusion; ec, electrolysis current; her, hydrogen evolution reaction; Measurement in situ; Platinoid Compounds; Temperature dependence; Electrical properties; Transition metal Compounds; Electric resistivity; Solid electrode; Electrodiffusion; Experimental study; Palladium hydride; Wire electrode
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/S0022-0728(02)00845-8

Some problems on the resistance method in determining the hydrogen content in PdH x electrodes are discussed. First, the resistivity ratio of PdH x , the temperature coefficient of resistivity and the resistance of PdH x , and the resistance of Pd having undergone hydriding–dehydriding cycles are discussed. It is found that the resistivity ratio is somewhat higher than the resistance ratio with the same x value and their difference depends on the internal stress-state arising from hydrogen insertion. Another fact that has been omitted in past work is that the temperature coefficients of PdH x resistance and resistivity increase while x 0.7. The Pd resistance decreases with hydriding–dehydriding cycle number due to the shape deformation of the electrode, which occurs. Second, the effect of the non-uniform distribution of x in the electrode on determining the hydrogen content is discussed theoretically. It is proved that errors are particularly significant when the Pd+H system is in the mixed α+β phase or the resistance is near the maximum value. Finally, we calculate the additional potential drop and hence the apparent resistance of the PdH x electrode caused by the co-conduction of electrolyte, the concentration-cell effect, the collection of electrolysis current and other imperfect configurations of the electrode in the in situ measurement of electrode resistance, using a direct current. It is found that an electrode with a large ratio of length to radius, an active surface, a surrounding electrolyte with high conductance and a high electrolysis current will all induce substantial additional resistance. At the same time, some advice on measuring the PdH x resistance is presented.