Scientist at Sandia National Laboratory develop photosynthetic energy production

Fuel Cell Today ^ | 13 February 2004 | Stefan Geiger

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Researchers from the Department of Energy’s Sandia National Laboratories and the University of New Mexico have developed a new way of mimicking photosynthetic proteins to manipulate platinum at the nanoscale. The method has the potential of deliver a form of energy manufacture. The idea for the technique is similar to photosynthesis, in which plants use the energy from sunlight to produce sugar. But instead of manufacturing sugar, the new method changes a platinum ion to the neutral metal atoms. The photosynthetic protein mimicks this repeatedly, allowing metal to be deposited as desired at the nanoscale.

The method involves putting porphyrins — the active part of photosynthetic proteins — along with the platinum salt in an aqueous solution of ascorbic acid at room temperature. The porphyrins are placed in specific locations in the solution where it is intended that metal should be deposited. For example, the porphyrins may be confined to micelles or liposomes. Micelles are spherical assemblies of detergent molecules in which the heads are exposed to the water and the tails stick together in the interior. Liposomes are similar structures but they are larger and have water on the inside and outside separated by a closed membrane — sort of like a cell. The membrane is composed of two layers of detergent molecules, with the heads on the inner and outer surface facing the water and the tails forming the interior of the membrane.

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You left out the neat part (“Fuel Cell Today” isn’t on the mean-people list):

“When light is shined on the porphyrins located in these detergent structures, the porphyrins excite, becoming catalysts for platinum reduction and deposition. As this occurs, the metal grows onto the surfaces of the surfactant structures as a thin sheet or in other ways.

For the metals platinum and palladium that form these nanostructures, it is enough for the porphyrin molecule to grow only a small metal “seed” particle composed of about 500 atoms. When it reaches this size, the seed starts to catalyze its own rapid growth (by oxidation of ascorbic acid), budding off arms in all directions and creating the ball-like nanostructures.

Since the porphyrin remains attached to the platinum nanostructure and active in the presence of light, it can also perform other functions besides growing itself. For example when illuminated with light, the platinum nanostructure evolves hydrogen from water. This reaction is similar to one of interest to car manufacturers looking to new ways to build automobiles powered by hydrogen fuel cells.”

This comes on the heels of Polyfuel’s good news last month:

“The PolyFuel DMFC membrane delivers substantial performance and system cost advantages over both traditional lithium ion batteries and existing fuel cell membrane technology. PolyFuel is currently supplying its DMFC membrane samples to the world's leading consumer electronics manufacturers and other developers of DMFC systems.

Leading consumer electronics manufacturers acknowledge that limited battery runtimes today restrict the functionality that can be built into portable devices such as laptop computers, tablet PCs, PDAs and mobile phones," said Jim Balcom, President and Chief Executive Officer of PolyFuel. "This problem will only get worse as wireless and other capabilities are added to these devices. The solution to this problem is the direct methanol fuel cell, a new approach to portable power. The PolyFuel DMFC membrane will enable the development of highly efficient, simple, cost effective, small, light and quiet portable fuel cell power systems that will deliver unlimited, unplugged runtimes for consumers."