Parameters Affecting the Loading of Hydrogen Isotopes into Palladium Cathodes

We have tested our new Degree of Loading (DoL) cell design which can be directly transferred to the SRI mass flow calorimeter. We have shown that appropriately prepared Pd cathodes can reach high loadings in this new design and that the cells can be transferred to the calorimeter without degrading the cathode’s or cel’s performance. In al of the experiments the cathode deloaded at higher current densities, and ostensibly identical cathodes yield significantly different D:Pd loading/current density profiles. In the new cell design high purity Pd from IMRA Materials and Johnson Matthey have generally loaded better than recent lots of 99.9% Engelhard Pd. Pd that IMRA Materials cast in air with added CaB6 held its loading best at higher current densities. Electrolyte additives Al, Si, Nd and Sm had no perceptible effect on loading behavior. The regular addition of Cl ion, similar to what might happen when topping up open cells, can increase or maintain loading. The presence of Cu is detrimental to good loading. Electrochemical surface potential (Esurf) measurements made in H2SO4 yield potentials similar to those predicted by high pressure H2 loading experiments. LiOH (LiOD) significantly affects Esurf but that effect may be deconvolved to allow an estimate of the surface loading in alkaline electrolytes.