Artificial leaves make fuel from sunlight

[fritzd]

---

Some interesting development.

Artificial leaves make fuel from sunlight

Jul 20, 2011 3 comments
New solar cells liberate hydrogen

Two teams of researchers in the US have taken important steps towards the creation of commercially viable "artificial leaf" – a hypothetical device that can turn sunlight into electrical energy or fuel by mimicking some aspects of photosynthesis.

More here:
Artificial leaves make fuel from sunlight - physicsworld.com
http://www.rsc.org/images/Energy_Che...m18-151116.pdf

[rodsky]

A conversation between me and my late mother inside a jeepney on our way to the marketplace, 25 years ago, on artificial plants, has now become reality.

"Any sufficiently high level of technology is indistinguishable from magic." - Arthur C. Clarke

-RODION

[observer]

This is a step in the right direction. The science has always been there for splitting water molecules to form hydrogen fuel. But the key is that it has to be economically viable. If you pump in more energy just to extract a fraction of that input energy in fuel, it's not practical. That's the problem with those so-called water-powered cars; you burn a lot of fossil fuel just to get a handful of hydrogen fuel. Harnessing the sun, which we consider 'free energy', has to be one of the solutions. But you must do it cheaply too. If one were to rely on rare metals, as John Turner and Oscar Khaselev did (as stated in that article), that too poses practicality issues.

It did the job, producing hydrogen four times more efficiently than photosynthesis. Unlike photosynthesis, however, their system used rare metals and wasn’t stable even for a day.

Dan Nocera's breakthrough system, about which the article wrote, is inexpensive and stable, but it needs to work on one downside (below is the section which talked about Nocera's invention):

According to Nocera, the oxygen evolving half of the reaction is the most difficult – and one of the unique things about his catalyst is that it works under ambient conditions.

‘That’s really different and special,’ he says. ‘Nobody’s been able to make an inexpensive catalyst that operates efficiently in an open glass of water. And that means it’s at pH 7, at ambient pressure and room temperature – that’s how photosynthesis works.’

Although the exact mechanism is unknown, Nocera thinks positively charged cobalt ions must pull electrons from the hydrogen atoms of water molecules, releasing oxygen in the process. Impressively, oxygen is formed at a rate rivalling that of photosynthesis. But according to Nocera, the most exciting thing about the catalyst is its ability to self-repair, which is analogous to that of the leaf.

‘In photosynthesis, the leaf repairs every half an hour,’ he explains. ‘It takes out the subunit that the oxygen evolving complex is in and makes a whole new protein that it inserts. And this catalyst is doing it better than the leaf – if cobalt falls out of the catalyst, then it gets oxidised and the phosphate brings it back to the electrode.’

The only downside is that the electricity needed to generate the cobalt ions, which are formed when a current is run through an electrode in the solution, still comes from fossil fuels through a socket in the wall. ‘This catalyst doesn’t work unless we find the main material, that light absorbing material which is driven by some kind of energy,’ Turner points out. ‘You can shine light on this catalyst and nothing happens.’

I hope they do find "that light absorbing material which is driven by some kind of energy". Who knows how much more oil is left in our oil wells? A technology like this would go a long way to decrease our dependence on fossil fuels.

[xmasher05]

..........................................