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Freely Speaking: What is an Artificial Leaf?

It's been a while again since I last posted here. Writing my thesis and preparing for the actual defense in July are taking most of my time. However, I wanted to at least share an interesting idea I came across in the last couple of months before this month is over.

And so today, I'll write about the artificial leaf which Professor Nocera at MIT was researching. It's been all over the science news: an alloy made of nickel and cobalt acts as a catalyst to split water into hydrogen and oxygen similar to what plant leafs do when they perform photosynthesis.

After the coolness of the words "artificial leafs" wore off, I started to wonder what is so special about an artificial leaf. After all, doesn't an artificial leaf just do electrolysis? Couldn't I just achieve the same by connecting solar panels to a container with water and two electrodes?

Apparently, the answer is yes and no. By applying a current to water, electrolysis could indeed be performed producing oxygen and hydrogen. The current produced could even come from the solar panels. However, Nocera's artificial leafs work slightly differently:

First: The nickel-cobalt alloy with the catalyst, can directly break water into hydrogen and oxygen without the need for any apparent electrodes. It's "wireless" electrolysis if you will.

Second: It's all about efficiencies. While photovoltaics could be used to split water, by itself this is not a very efficient process. The secret is in the catalyst which lowers the activation energy of splitting water sufficiently to make photo-catalysis (in this case we are breaking things down) feasible.

The Implications

One of the weaknesses of using photovoltaics is that electricity generation drops to 0 when there is no sun. Artificial leafs could fill this gap by storying part of the energy captured during the day in form of hydrogen and oxygen. In the evening, electricity could be generated again from the stored energy. Nocera has also stated that he hopes these materials are cheap enough so that people in 3rd world countries could easily and cheaply obtain artificial leaves that could be used to power a light source at night.

All in all, very cool research and technology. I will try to keep my eye on this for the future.

Sources:
http://news.cnet.com/8301-11128_3-20047814-54.html
http://www.eurekalert.org/pub_releases/2011-03/acs-dot031811.php

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