Jeffrey Grossman thinks we've been looking at coal all wrong. Instead of just setting it afire, thus ignoring the molecular complexity of this highly varied material, he says, we should be harnessing the real value of that diversity and complex chemistry. Coal could become the basis for solar panels, batteries, or electronic devices, he and his research team say.
As a first demonstration of what they see as a broad range of potential high-tech uses for this traditionally low-tech material, Grossman, doctoral student Brent Keller, and research scientist Nicola Ferralis have succeeded in making a simple electrical heating device that could be used for defrosting car windows or airplane wings, or as part of a biomedical implant. In developing this initial application, they have also for the first time characterized in detail the chemical, electrical, and optical properties of thin films of four different kinds of coal: anthracite, lignite, and two bituminous types. Their findings have just been reported in the journal Nano Letters.
"When you look at coal as a material, and not just as something to burn, the chemistry is extremely rich," says Grossman, the Morton and Claire Goulder and Family Professor in Environmental Systems in the Department of Materials Science and Engineering (DMSE). The question he wanted to ask is, "Could we leverage the wealth of chemistry in things like coal to make devices that have useful functionality?" The answer, he says, is a resounding yes.
It turns out, for example, that naturally occurring coal varieties, without the purifying or refining that is needed to make electronic devices out of silicon, have a range of electrical conductivities that spans seven orders of magnitude (ten million times). That means that a given variety of coal could inherently provide the electrical properties needed for a particular component.