Fuel Made by Sun, Water, Carbon Dioxide, and Nanotechnology

fuel from water carbon solar photo
photo felix @ flickr

Trees use sunlight to forge carbon dioxide and water into a useful fuel. It is an elegantly simple strategy, using renewable energy and common non-toxic elements that has worked for millions of years. Why don’t we do the same thing, and create fuel from the sun? Scientists are rapidly advancing our ability to work on the same scale as nature, but are we moving in the right direction? New research highlights the opportunities and some potential missteps of this exciting field.Life is built at the nanoscale, from the smallest virus to the largest sequoia. Our ability to peer into this world has rapidly advanced in the past fifty years, yet our ability to manipulate matter on this scale is just beginning to emerge. The potential for nanotechnology, such as that being developed by materials scientist Craig Grimes and his colleagues at Pennsylvania State University show some of the brighter possibilities.

Creating Fuel From The Sun
The group has found a way to generate hydrocarbons 20 times faster than previous attempts. The researches use titanium dioxide, the same stuff we have seen put into pollution eating concrete, dye sensitized solar cells, and super tough paper. Except this time the titanium dioxide arrives in the form of nanotubes about 135 nanometers wide and a tenth of a millimeter long. The researchers added nitrogen to the nanotubes, and also loaded copper and platinum nanoparticles on the surface.

Typically our titanium dioxide applications use ultraviolet light to activate the catalyst. However, the additions of nitrogen and copper to these nanotubes are thought to shift the spectrum to longer wavelengths of visible light. The copper and platinum particles are included to speed up the later stages of the process.

The researchers aren’t fully sure why the process works. They think that when sunlight falls on the nanotubes it is able to split water molecules into two compounds, hydroxide radicals and hydrogen ions. The hydrogen ions will join up to form hydrogen gas. The researches think the carbon dioxide also splits (this is the part they are not too clear on yet) to form oxygen and carbon monoxide, which reacts with the hydrogen gas to form methane and water.

Missteps of Nanotechnology?
The use of platinum in these tubes, in my estimation, is an unfortunate knee jerk reaction. Platinum, while extremely useful is also expensive. Inherently, building an energy capture and storage technology that is based on platinum will be tough to make affordable. If we look to the materials life uses in photosynthesis we will not find platinum or copper, but instead we find manganese, magnesium, or calcium. I’m not a physical chemist or a materials scientist, but I know life has figured out how to do it with these elements – can we?

Physical chemist Michael Grätzel at the Federal Polytechnic School of Lausanne in Switzerland says that the results "are fundamental work that shows that nanotubes might get you a better conversion efficiency than prior approaches". He points out that the efficiency of the catalyst is still quite low, but is optimistic that further work can improve it.

Grimes and colleagues estimate that with their current technology a square meter of the nanotube film, if supplied with pure carbon dioxide and water along with a solar concentrator could yield 500 liters of methane over the course of eight hours. Grimes has his hopes set on improving the copper coating for use to pull out carbon dioxide from coal plants. I would suggest he set longer term goals, such as avoiding both copper and coal plants, neither of which plays much of a role in life’s energy budget - but that is from a biologists point of view. What do you think?

via Nature News
More on Titanium Nanotechnology
Doubling the Efficiency of Dye-Sensitized Solar Cells
It Slices, It Dices: Pollution Eating Concrete
Titanium Fiber Paper; Tough Stuff
Consumer Group Questions Safety of Nanoparticles in Sunscreens

Related Content on Treehugger.com