Obviously, plants have a much better solution and we have written about it often - artificial photosynthesis - but despite nature being our best example of efficiency, she isn't easy to duplicate. But a group of chemists say they have made a step towards that, by discovering a new way to pass electrons back and forth between two molecules. Understanding the electron transfer processes in these molecules provides a way to design organic materials for storing electrical energy that could then be retrieved for later use - an organic battery.
When molecules meet, they often form new compounds by exchanging electrons and in some cases, that transfer process creates one molecule with a positive charge and one molecule with a negative charge. Molecules with opposite charges are attracted to each other and can combine to form something new. In their research, the chemists created two molecules that could meet and exchange electrons but don't unite to form a new compound.
Illustration of an assembled set of different molecules. These molecules meet, exchange electrons and then disassemble because chloride ions, which are represented as green spheres, are present. If these chloride ions are removed, the entire process can be reversed. Credit: Jung Su Park
"These molecules were effectively spring-loaded to push apart after interacting with each other," says Bielawski, professor of chemistry at University of Texas at Austin and co-author of the study in Science. "After electron transfer occurs, two positively charged molecules are formed which are repelled by each other, much like magnets held in a certain way will repel each other. We also installed a chemical switch that allowed the electron transfer process to proceed in the opposite direction."
Bielawski says this system gives important clues for making an efficient organic battery. "I would love it if my iPhone was thinner and lighter, and the battery lasted a month or even a week instead of a day. With an organic battery, it may be possible. We are now starting to get a handle on the fundamental chemistry needed to make this dream a commercial reality."
The next step, he says, is to demonstrate these processes can occur in a condensed phase, like in a film, rather than in solution.
Organic batteries are made of organic materials instead of heavy metals. They could be lightweight, could be molded into any shape, have the potential to store more energy than conventional batteries and could be safer and cheaper to produce.
The molecular switch could also be a step toward developing a technology that mimics plants' ability to harvest light and convert it to energy. With such a technology, fuel could be produced directly from the sun, rather than through a plant mediator, such as corn.
"I am excited about the prospect of coupling this kind of electron transfer 'molecular switch' with light harvesting to go after what might be an improved artificial photosynthetic device," says Sessler. "Realizing this dream would represent a big step forward for science."
Comments