13 July 2012
University of Wisconsin-Milwaukee (UWM) researchers have identified an inexpensive nanorod catalyst with efficiencies rivaling that of platinum. Composed of nitrogen-enriched iron-carbon nanorods, the new catalyst holds the promise of cheaper, more efficient microbial fuel cells (MFCs) that generate their own hydrogen from waste water.
The hydrogen fuel cell is the holy grail of green energy. It burns hydrogen and gives off nothing but water. What could be more environmentally friendly than that? The problem is, hydrogen isn’t just lying about in the ground like oil or natural gas. True, it’s the most abundant element in the universe, but on Earth all of it is locked up in water and other chemicals. To be used as an energy source, the hydrogen has to be extracted and, unfortunately, the main source of most commercial hydrogen today comes from fossil fuels – which sort of defeats the purpose.
One alternative is microbial fuel cells, which use microorganisms to break down waste water into hydrogen and oxygen. That’s a step in the right direction, but there’s still a snag. To reach practical efficiency, an MFC needs a catalyst to goose along one of the chemical reactions involved in the process. That catalyst is usually platinum, which does its job very well, but is also extremely expensive at over US$1,200 per ounce. It also doesn’t help that platinum, like many catalysts, is susceptible to poisoning by impurities coating its surface, resulting in a very pricey replacement job.
In contrast, the UWM nanorod catalyst is composed of cheap, common elements. It consists of nitrogen bonded to the surface of a carbon rod with a core of iron carbide. According to the UWM researchers, this structure is optimal for electron transport. The upshot is that over three months of testing, the new catalyst demonstrated consistent performance that was superior to platinum and has every indication of being stable and scalable. More importantly, it’s much more economical. Platinum makes up 60 percent of the cost of an MFC and with the UMW catalyst only five percent the cost of a platinum catalyst, the savings are obvious.
According to nanorod creator Professor Junhong Chen,“fuel cells are capable of directly converting fuel into electricity. With fuel cells, electrical power from renewable energy sources can be delivered where and when required, cleanly, efficiently and sustainably.” With a view toward making the UMW catalyst practical, Professor Chen and his team are now concentrating on studying the exact characteristics of the catalyst and making it suitable for mass production.