Using sunlight to split water is a monster job, but a team of chemists is striving to crack this problem in their attempt to save the world.
Daniel Nocera, at MIT, has taken the latest step in his part of the project, known as “Powering the planet”. His task is to find a catalyst to make oxygen molecules once the water has been split into its constituent parts (hydrogen and oxygen). Elsewhere, Harry Gray at Caltech is looking for a hydrogen catalyst, and the final part of the puzzle, the photovoltaic medium that will separate the two catalysts is being investigated by Nathan Lewis.
In case that didn’t make sense, the three-part system works like this: sunlight hits the PV material, which converts the light into current – or holes and electrons. The holes go towards the oxygen catalyst, where water is split into oxygen. The remaining protons scoot off to the hydrogen catalyst to be turned into molecular hydrogen, which can be stored in some other molecular form until the energy is needed.
Yesterday’s afternoon session was something of a double act between Nocera and Gray, both doing incredible chemistry, and both very funny men. Nocera showed us his various oxygen-trapping molecules, one called a ‘Hangman’ and one ‘Pacman’. He is about to publish the hangman version – which is based on a stripped down version of cytochrome p450. In it, a water molecule dangles above an oxygen atom – hard to do apparently. This isn’t going to be the final answer, but Nocera says it’s important because it highlights that key intermediates in these energetically uphill processes are being identified.
Nocera also showed his ruthenium pacman catalyst candidate, and hinted to me after the session that this might just be the catalyst that works. How intriguing. Except, it isn’t strictly true – because an environmentally friendly catalyst is never goin to be ruthenium based – it needs to be a metal that can be dug out of the ground – iron or manganese, perhaps.
But Nocera’s claims will please Harry Gray, who spent a lot of his talk (that he described as “the technical version of Dan’s talk”) reminding Nocera that an oxygen catalyst was needed – and soon.
I’m very interested to see what happens as these three elements conitue to be developed. Nocera is certain that if (and it’s a big if) the chemistry community really take this idea seriously, we could have our solar powered water-splitting energy supply within 10 years. I’m going to be paying close attention.
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