

Nanosheet Catalyst Discovered To Sustainably Split Hydrogen From Water - pwg
http://www.bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=1414

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alephnil
There are perfectly good industrial electrolysis cells that can split water
with 85% efficiency, and that does not require platinum, only nickel (and by
that I mean elemental nickel, not nickel-molybdenum-nitride). They need to be
big and operate under high temperature and use sodium or potassium hydroxide
in the water, so for industrial purposes only, but essentially a solved
problem.

The unsolved problem is a good catalyst for the reverse process that takes
place in hydrogen fuel cells. For that platinum is currently required, and no
alternatives are known. I have read dozens of reports of catalysts for
electrolysis, but not a single one for a replacement catalyst in hydrogen fuel
cells. That would actually be a breakthrough.

Even with the latter problem solved (where I'm optimistic), the problem of
storing hydrogen in an efficient way is way harder, and there I'm less
optimistic. For that reason alone I'm very sceptic to how realistic a hydrogen
economy is.

~~~
dojomouse
It's only far away if you want to work in pure hydrogen, which is
ideologically simple but not really required. Synthesis of methane from
hydrogen is easy and efficient and (pretty) cheap - use atmospheric co2 as
carbon feedstock. A German company is working on this and has proven solution
at small scale, I'm sure they're not the only ones.

More of a pain than simply burning/recombining hydrogen with oxygen, but has
the upside that there is already a huge and established global network for
transport and storage of methane - cheap and proven and currently being
rapidly scaled.

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patrickgzill
So what is the idea?

You place a bunch of solar panels in a sunny place that also has water.

Then you directly power the grid when it is sunny and all power is needed.

When not needed, you power the catalyst, storing the hydrogen.

When it is dark, you use the hydrogen to create power and (maybe) heat.

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uvdiv
Besides the current costs (especially the solar PV part), there's the problem
that you're throwing away most of your energy in the [electricity => hydrogen
=> electricity] loop. Electrolysis isn't perfect [1], but the big waste is
electricity generation, with the best hydrogen fuel cells being only 50-60%
efficient [2, SOFC "predicted"] (turbines smaller than utility scale would be
far worse). In the most optimistic case you lose half of your stored energy
(more likely 2/3rd).

Realistically you'd have to store almost all of your electricity -- compare
solar output, a very short midday peak, with electricity demand, which in many
places is nearly constant over time. Almost of all of it would go through the
50%+ storage losses, which means the solar part (PV + inverter + etc.) of your
costs are more than doubled, amortized per kWh. So economically, practically
anything is better than local hydrogen storage. (Under the premise that solar
PV is _not_ effectively free, which is an understatement to put it mildly).

[1]
[http://en.wikipedia.org/wiki/Electrolysis#Electrolysis_of_wa...](http://en.wikipedia.org/wiki/Electrolysis#Electrolysis_of_water)

[2]
[http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/f...](http://www1.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html)

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planetguy
Punchline: nearly as good as platinum, without being expensive like platinum.
Not sure whether it's actually easy and cheap to make in large quantities.
Still lots of other problems with hydrogen as a fuel.

If it were _really_ likely to be incredibly useful, there'd be a patent number
in this article, not a reference to a publication in Angewandte Chemie.

~~~
ams6110
Also: _requires external electricity ... exceeding the minimum required by
thermodynamics_

Of course, there's no getting around those pesky laws of thermodynamics.

~~~
dReid1991
Right, so with the perfect catalyst, you get as much energy out as you put in.
With imperfect catalysts (anything real), you have to apply a voltage higher
than when thermodynamics says is necessary to get the reaction to happen at an
appreciable rate. The excess voltage cannot be recovered. The better the
catalyst, the lower the excess voltage necessary, so a cheap and very
effective catalyst essentially promises an efficient way to store and
transport energy as hydrogen gas, which would be excellent.

