Saturday, April 9, 2011

Synthetic Photosynthesis

Very much like my undergrad research days, light shining on a
semiconductor drives reactions -- in this case electrolysis of water.
When I was a senior in college I worked on semiconductor photocells that could be used for solar cells. These were solar cells immersed in water not the dry kind.

Now I see there was an announcement of an apparent  breakthrough in that field, Prof Nocera of MIT, made a catalyst/silicon composite that splits H2O water into hydrogen and oxygen. The hydrogen is valuable as a fuel; of course oxygen is just floating around in the air.

Nocera's company Sun Catalytix calls this an "Artificial Leaf," which it isn't. A leaf makes sugar not hydrogen. Interestingly Indian conglomerate Tata is a big investor in Sun Catalytix.

The technology the "leaf" uses is vague probably because they have not had any patents issued -- I could not find any.  Nickel and cobalt are used rather than platinum as a catalyst, and an electric current must be applied to keep the device at the right potential for electrolysis of water.  Others have used quantum dots to absorb energy, and then simple mineral catalysts like iron sulfide to reduce hydrogen ions.

David Wendel at the University of Cincinnati uses enzymes and foam to make sugars via artificial photosynthesis. This is reportedly 18 times more efficient than a natural cell, because all the synthetic "cell" does is make sugar. It does not grow or feed other cells. See also.

I have often thought that an engineered synthetic "cell" could be more efficient than a natural cell. If people could not make a cell better then that would be an argument for intelligent design.

The Department of Energy has a research center on artificial photosynthesis in California which opened in 2010. They have some plans, but not much in terms of actual results so far. They will do research in the different components of a synthetic photosynthesis system: light collection, energy conduction, catalysis and membranes.
Schematic of artificial photosynthesis. Link.