Re: photochemical advance

From: Robert J. Bradbury (
Date: Sat Dec 08 2001 - 10:44:58 MST

On Sat, 8 Dec 2001, Mike Lorrey wrote:

> >
> >
> > <<Solar cell edges towards endless energy
> >
> > 7 December 2001
> >
> > Zou and colleagues point out that although their set-up is only 0.66%
> > efficient, they are confident that this will improve when they increase
> > the surface area of the semiconductor, and adjust its layout.
> So, you could use solar cells at 10-35% efficiency to power they
> electrolysis of water into hydrogen and oxygen, or you can use this
> 'catalyst', for a far lower rate of efficiency.

I'm not buying it at all. I just did the calculations and an H-O bond
at 464 kJ/mol of bond energy which works out to 770.5 zJ/bond (4.81 eV).
That ends up being in the UV-C region of the spectrum (@ 0.258 mu-m).

Unless they make the case that the material is going to be able to absorb
and store the energy from multiple photons (exactly what the photosynthetic
reaction centers in plants do) they *aren't* going to be able to up the
efficiency by much. I don't doubt that some point we will be able
to grab multiple photons, store the energy efficiently, then redirect
it to split water, but I've got my doubts that it will be a "simple"
material to develop.


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