Golden goose eggs and the Midas touch are the stuff of fairy tales, but the cool reality of platinum-based catalysts is a major part of C.J. Zhong’s research into next-generation fuel cells that could help break America’s dependence on petroleum products.
Zhong says hydrogen-powered fuel cells work something like a conventional battery, with one major exception: they never run out. The fuel cell has two electrodes, an anode and a cathode, separated by a membrane. Oxygen passes over one electrode and hydrogen over the other.
The hydrogen reacts on a catalyst on the electrode anode that converts the hydrogen gas into negatively charged electrons (e-) and positively charged ions (H+).
The electrons flow out of the cell to be used as electrical energy. The hydrogen ions move through the electrolyte membrane to the cathode electrode where they combine with the reduced oxygen species to produce water. It’s an approach that scientists agree will ultimately produce clean and low-cost energy.
And, of all metals, the catalyst platinum turns out to be the best at speeding up the necessary chemical reaction within hydrogen-powered fuel cells. But, platinum’s superior ability to catalyze the combination of the oxygen from the atmosphere with hydrogen, which can be released from a water-electrolyzer that has been exposed to sunlight, is offset by both economics and chemistry, Zhong explained.
“Platinum is expensive, twice the market price of gold, and there is also a limited quantity, which further drives up the price,” he said. “Reforming of natural gas is one of the main sources of hydrogen, but that process also creates carbon monoxide as a by-product and carbon monoxide also destroys the platinum’s catalytic activity.”
Zhong’s research into refining platinum’s capacity as a fuel-cell catalyst has several goals. Besides reducing the amount of platinum used in the catalyst, he is also exploring how to increase its activity and stability. Improving its stability is key because consumers will reasonably expect the fuel cell to last at least two to three years before any maintenance.
Discovering a new catalyst material is challenging, he said, and in addition to doing that, his research will be more productive by focusing on reducing platinum load with increased activity and stability, because the catalyst could work better when there is less platinum present.
This metallic marvel currently comprises about 30 percent of the cost in manufacturing fuel cells. Zhong is well aware of the consumer mindset that demands a low price point before adopting a new technology, no matter how much people would prefer to switch from carbonbased fuel sources to the so-called “hydrogen economy.”
To reduce the cost of fuel cells that use platinum catalysts, Zhong is pursuing two distinct avenues of research. The first focuses on alloy creation, in which less expensive metals such as nickel and iron are added to the platinum. Carbon is also added to the mix because it disperses the catalysts so that more surface areas can be exposed.
The second technique exploits the latest advance in the growing field of nanotechnology for the design and fabrication of nanostructured catalysts
“It’s partially about surface area,” Zhong said. “When you use nanoparticles of platinum, you increase the surface areas significantly without increasing the total amount of platinum.”
To advance his research in this project, Zhong received a major National Science Foundation (NSF) grant in September 2007, valued at $1 million over four years. It represents the first award from the NSF’s Nanoscale Interdisciplinary Research Team (NIRT) program won by Binghamton University.
page 1 | page 2