An Overview of Experimental Studies on H/PD Over-Loading with thin PD Wires and Different Electrolytic

Hundreds of electrolytic loading tests of thin Pd wires in different experimental conditions have been performed in order to find out the best procedures for stable, high hydrogen overloading into the palladium lattice. In a very dilute acid solution thin Pd cathodes (50 or 100 μm in diameter) and thick Pt anodes (0.5 mm in diameter) were used in a parallel or coaxial geometry. Normalised resistance (R/R_0) of the Pd cathode was on-line and continuously measured in order to determine the actual H/Pd values. Different electrolytic solutions have been tested by adding to the acid solution very low amounts of Ca, Sr, Li, and Hg ions; high loading H/Pd ratios have been achieved with a satisfactory grade of reproducibility. Several loading procedures have been performed in a wide range of electrolysis current (from a few mA up to 100mA) and at different Hg ion concentrations. The obtained results allowed for the definition of a loading protocol that ensures very high H/Pd over-loading. Stable R/R_0 ≤ 1.2 values (corresponding to H/Pd ratios $≥1) can be currently achieved with an extremely low power electrolytic supply (10V;5mA)