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Solar fuel cells

Maria Forsyth helps us take a look at how fuel cells work.
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Just tell us a little bit about fuel cells. OK, so fuel cells, of course, are like a battery. Except, they’re constantly supplying, for example, in a hydrogen fuel cell, you have a hydrogen gas, the oxygen gas, and you’re making effectively making water. And you– so the reaction H2 and O2, it produces electricity. But in this case, you have to actually carry the fuel much like gasoline. Carry it with you. So you’d have a hydrogen supply and an oxygen supply. One of the problems at the moment is that Toyota’s car for example, has quite large, compressed hydrogen cylinders in the vehicle. Safety wise, I guess gasoline is probably not particularly safe either.
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But still, these big cylinders of gas are in the vehicle. And the fuel cell operates by having a platinum catalyst, which catalysed the reactions that you want, the hydrogen reduction hydrogen oxidation ,oxidation yes and oxygen reduction reactions. And you have to have a membrane, which separates the gases that also allows permeation of acid H+ basically. Now you could replace that hydrogen with ammonia– people talking about ammonia fuel cell. Ethanol fuel cells, you have different fuels. The premise being that you react the fuel to form electricity.

In the video above, Prof. Maria Forsyth discusses whether storing energy in solar fuels is as good as using batteries. If we could make fuels like H2 from only sunshine and water, how sustainable would that be?

Plants split water into H+ and O2 using natural catalysts that are renewed every 30 minutes. We can already do the same thing very easily using electricity and metal electrodes in a process called electrolysis (water splitting) but this is very expensive in both energy and materials cost. To store solar energy in a H2 fuel on a large scale to meet the Terawatt challenge, we need to be able to split water with renewable energy or a solar driven process using inexpensive materials. This is indeed what a number of researchers, startup and established companies around the world are currently working hard to achieve.

Yet, if H2 is a fuel that’s storing energy, how do we get the energy back out?

That’s easy using fuel cells that produce electricity by doing exactly the opposite of splitting water – reacting H2 and O2 to form water again as in the animation below that shows the operation of one cell in a fuel cell stack. So fuel cells run by consuming hydrogen, a ‘zero-emission’ fuel and produce only water and electricity.

Fuel Cell
A larger image can be found on the bottom of this page (Fuel cell technology)

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How to Survive on Earth: Energy Materials for a Sustainable Future

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