Use of a coulometric assay technique to study the variables affecting deuterium loading levels within palladium electrodes

Abstract

We report in this paper measurements of hydrogen (H) and deuterium (D) loading stoichiometries in Pd electrodes. We accomplished these analyses using an electrochemical method developed for in situ determination of palladium deuteride stoichiometries. The electrochemical method quantifies the amount of deuterium incorporated into the metal lattice by collecting the charge released during the potential controlled discharge of deuterium loaded Pd electrodes. In addition, ex situ gravimetric analyses were used to confirm electrochemically measured D/Pd atom ratios. Gravimetric analyses were also used in cases where the diameter of the Pd electrode precluded the relatively slow diffusion-limited electrochemical discharge method. A variety of electrolytic factors were studied to determine what conditions, if any, promote the greatest absorption of deuterium into the Pd lattice. We observed loading values of 0.73 ± 0.02 deuterium atoms per Pd lattice atom under all the electrolytic conditions studied in LiOD and D 2SO 4 solutions. As found in previous studies, H/Pd values were approximately 10% higher than D/Pd values. These measurements of D/Pd stoichiometries indicate that interfacial parameters, current density, pD, charging time and surface purity have negligible effect on the maximum deuterium concentration within Pd electrodes.