It seems that the catalysts used for steam reformatting are a mixture of copper, aluminum (oxide) and zinc. (oxide)
Which explains why the "diffuse" (is the term I think the paper used) layer of copper plating,
that left both some aluminum (oxide) exposed and exposed copper,
worked as well as it did on that research engine.
ie:
It's likely that pure copper pre-chambers wont be as effective as that diffuse layer used in the research engine.
Also Copper powder alone in the fuel pre heater probably wont work/help, whereas a mixture of copper, zinc and aluminum powder, with some 'air time' would..?
https://www.sciencedirect.com/scienc...21951724006353
https://www.sciencedirect.com/scienc...60544224008636
https://www.sciencedirect.com/scienc...66821124000437
https://www.sciencedirect.com/science/article/abs/pii/0926860X9385197W