Electrochemical hydrogen absorbing behavior of Pd and Pd-Li alloys in a molten LiCl-KCl-LiH system

Electrochemical hydrogen absorption and desorption into/from Pd and Pd-Li alloys were studied in a molten LiCl-KCl-LiH system (5 mole percent LiH added) at 673 K. A cyclic voltammogram for a Pd electrode indicates that the current is largely due to a hydrogen-related reaction and partly due to a Li-related reaction. Pd spontaneously changes into PdLiHx merely by immersion into the molten LiCl-KCl-LiH system, because the anodic hydrogen absorption and the cathodic lithium deposition occur on the same surface. By chronopotentiometry, H/Pd ratios were estimated for Pd, Pd7Li, Pd2Li, and PdLi electrodes after hydrogen charging at 0.6 V for 0.5 h as 0.05, 0.08, 0.27, and 0.74, respectively. These results show that the hydrogen absorbing ability of the alloys increases as the Li concentration increases. These characteristics can be explained by the stronger interaction of Li-H than of Pd-H.