
New concepts emerge for generating clean, inexpensive fuel from water - DrScump
http://news.uchicago.edu/article/2015/10/29/new-concepts-emerge-generating-clean-inexpensive-fuel-water
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zeofig
Seems cool, although it's quite misleading to say the fuel is generated form
water when the energy really comes from sunlight.

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JoachimS
A bit like Feynmans description of burning logs as a way to release stored sun
energy.

Yes, the energy for splitting the molecule comes from the sun. This makes it
possible to store the energy for later release when the captured hydrogen is
made to combine with oxygen.

So energy conversion into a more useful form. And if one wants to pull this
all the way, it really started with other hydrogen atoms that due to gravity
was forced close enough to form helium and in the process release photons.
Which happened thousands of years and eight light minutes away. So it really
is gravity. ;-)

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JoachimS
(Some midnight random thinking)

I'm curious on how easy it is for the hydrogen to diffuse through the water
and to the surface where it can be captured.

In the picture the electrodes looks like the typical rods suspended vertically
at each end of a relatively deep container. For any hydrogen molecule
generated at the bottom it would have to travel a long way and possibly be
caught by other atoms, molecules on the way to the surface. Would it be better
to have the electrodes close to each other and parallel with the surface. And
possibly having the water flow between the electrodes?

Basically, can the process be made more or less efficient by altering
container shape, placement and area of electrodes and how the water is
handled?

Oh, and how is the hydrogen then collected efficiently - a minor vacuum to
pull it away? What about the exygen?

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jgamman
good question. complex answer. you need to have a good surface area on the
electrodes. the hydrogen ions will bond on the surface to form H2 which will
eventually bubble and literally float to the top. O2 on one electrode and H2
on the other - split the gas collectors and you have pure-ish H2 and O2
seperated. and the volume of h2 is twice that of o2... ;-) hydrogen ion
migration is a weird one - unlike most things that you think of as migrating
through water, H+ ions seem to be about 10x faster. last i heard (20 year ago
memory here) is that the electric field actually messes with the hydrogen
bonding in water so instead of migrating the h+ atom from one place to
another, you flip the H --- O.....H hydrogen bonds along the line of potential
and hey presto a bond where there used to be a hydrogen bond and a hydrogen
bond at the other end. to the casual observer it looks like the H+ atom
whipped from end to the other super fast. the problems associated with using
hydrogen as an energy storage medium are still being ignored though. we don't
know how to make it, store it, transport it or use it - IMHO it's a dead end
for the sorts of applications its being sold for, worse it's distracting and
costly use of time/$/people when decarbonising the energy system is running
out of time.

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msandford
Basically, they doped their material. Interesting. I'm kind of surprised that
people haven't been doing this for a while. Seems like there might be a dozen
PhDs to be had.

