stolfi@jumbo.dec.com (Jorge Stolfi) (04/05/89)
I vaguely recall a posting to sci.space several months ago saying that
the chemical reaction
H + H -> H2
is very exothermic, to the point that atomic hydrogen---if it could be
stored in large quantities---would make an even better rocket fuel than
H2 + F2.
If this is true, maybe this explains the amazing amounts of energy
claimed by Fleischman and Pons. A block of palladium saturated with
atomic hydrogen in close to 1:1 atomic ratio may well pack more
chemical energy than the same volume of TNT. This seems enough to blow
up a lab bench and blast small holes in concrete.
From my armchair laboratory, I conjecture that hydrogen can be absorbed
into palladium in two forms, as isolated atoms (as in the F&P
experiment) or as H2 molecules (as in the usual pressure-driven
absorption). In the F&P experiment, once the electrode is saturated
with atomic hydrogen, any additional H atoms that are forced into it
will react exothermically with the absorbed H to form adsorbed H2.
This could be the source of the extra heat measured at low-power
experiments.
The power surges and explosions could also be explained if the single-H
hydride is less stable than the H2 form at higher temperatures.
In fact, it could also explain why power surges happen when the current
is reduced (particularly with spongy electrodes): the atomic H starts
to diffuse out of the palladium, and recombines as soon as it reaches
the surface. The heat thus produced raises the temperature of the
eletrode, which drives more H out, which produces more heat, and so on.
If this makes sense, then the extra energy detected by F&P is
energy that was stored into the electrode during the charging period.
I believe that in normal electrolysis the reactions at the hydrogen
electrode are something like this
H3O+ + e- + electrical energy --> H2O + H
H + H --> H2 + heat
which add up to
2H3O+ + 2e- + electrical energy --> 2H2O + H2 + heat
In the F&P experiment, during the "charging" phase, the reactions are
something like
H3O+ + e- + electrical energy --> H2O + H
H + Pd --> PdH (single-H form)
and during the "production" phase
2 (PdH) --> Pd2H2 (molecular-H form) + heat
Does this make any sense? (As you can tell, I am no chemist.)
Jorge Stolfi @ DEC Systems Research Center
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On the whole, though, the reaction was excellent in the scientific
world, and from there it passed on to the general public who took a
passionate interest in the question. That was important, since the
masses were expected to subscribe huge sums.
--Verne, _From the Earth to the Moon_ (1865)
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