If one subscribes to a Millsean approach, palladium is somewhat unique In the Periodic Table in that it is relatively non-reactive with oxygen or other oxidants while having an ionization potential which is near the first Rydberg level at 27.2 eV. Nickel alone has no such “entry level” Rydberg value …
The four other metal substitutes for Pd at the first Rydberg level are Mo, Zn, Cu and Cs – and all of them plus bare protons have assorted chemical reactivity problems meeting requirements for catalyzing the first drop in orbital according to Mills. This is according to my older version of his theory which may have changed. Hydrogen ions (bare protons) also qualify as self-catalytic but they are usually too reactive. Any of these metals would be interesting as a catalyst substitute for expensive palladium – but all are relatively reactive in ways which could quench the effect. The best realistic catalytic fit is molybdenum and as an inexpensive di-sulfide it would be interesting to try. It is commonly available as a lubricant and relatively unreactive. From: Nicholas Cafarelli Recent posts make me wonder if the Palladium is required. What would happen if the Nickel mesh were only burnished with a Nickel rod after the tap water treatment? Is this an example of simplication? Simplification through elimination.