one of the materials that could possibly be used in place of nickel is tungsten
***I hadn’t heard that. Got any links? I had heard that Rossi used tungsten to separate H2 gas into H1 monoatomic gas and that was his initial secret “catalyst”...
Tungsten has been known to soak up huge quantities of hydrogen since the experiments of Irving Langmuir when he was trying to find the perfect fill gas for the electric light bulb.
There are "some" indications that Langmuir thought he had sometimes gotten more energy out of his tungsten-hydrogen system than he had put in. He asked one of the top physicists of the day (Bohr??) and was told that such was "impossible"....so he dropped it (sound familiar???).
I'll see if I can dredge up a link or two...but it has been some time back that I read it.