Student-led team brings fuel cell research to fruition
By Steven Powell, email@example.com, 803-777-1923
A refined approach to purifying hydrogen gas at the University of South Carolina could be a boon for energy production. A student-led team in the College of Engineering and Computing is developing a new catalyst for fuel cells with both enhanced reactivity and longevity.
Hydraulic fracturing – fracking – has changed the global energy landscape in many ways. Prices for natural gas have dropped considerably in recent years because of fracking, and inexpensive natural gas is reducing prices for another fuel as well: hydrogen.
Through steam reforming and the water-gas shift reaction, the methane that makes up natural gas can provide copious quantities of hydrogen gas. If you want to use that hydrogen to provide electricity in the most efficient manner possible, though – namely, harness it in a fuel cell – there’s a bit of a hitch.
“The hydrogen gas will have impurities in it, especially carbon monoxide,” said William Rigdon, a graduate student in USC’s College of Engineering and Computing. “That affects the catalysts, like platinum, that are used in these devices. It affects their activity, and cleaning up the impurities causes corrosion.”
And there are several other largely untapped sources of hydrogen as well, according to Rigdon, who will finish his doctoral work in assistant professor Xinyu Huang’s laboratory at USC this fall.
“Hydrogen is used in semiconductor manufacturing, for example, and currently a lot of it is just wasted after it’s used,” said Rigdon. “It’s also used in metals refining and steel manufacturing for iron reduction. They’d both be good sources for recycled hydrogen, but the contaminants cause problems.”
With all that fuel readily available, it’s no surprise that efforts are under way to harness it more effectively. Rigdon is leading a student team at USC that earned a $25,000 grant in the 2012 Fuel Cell Collaborative's Fuel Cell Challenge to address that need. Throughout the spring semester, he and undergraduate Diana Larrabee worked in Huang’s laboratory refining a new approach to improving both the longevity and efficacy of electrochemical hydrogen pumps.
The target of their work was not the platinum catalyst itself, but rather the support on which the catalyst rests. The team began with carbon nanotubes, which serve as an ideal surface to build upon, given that they have long-range order and fewer defects than traditional high-surface-area carbon.
Carbon nanotube surfaces can be functionalized for chemical modification with titanium oxide through covalent linkages, forming a composite that can anchor platinum to the support through stronger bonding than provided by carbon. Moreover, the team substituted niobium for titanium in small doses (about 10 percent) to improve electronic conductivity.
The team found success with the doped catalyst. “The metal oxide can contribute to reactivity through a bifunctional mechanism while also preventing detachment of the catalyst in corrosive conditions.” Rigdon said. “What we found is that those niobium-doped composite samples were both more tolerant catalysts as well as more durable in this application for the anode.”
Sustainable Innovations, a manufacturer of electrochemical hydrogen pumps and components for fuel cells based in Glastonbury, Conn., submitted an “industry challenge” to the Fuel Cell Collaborative's Fuel Cell Challenge in 2012, looking for a solution to the problem of short-lived catalysts for hydrogen pumps used to purify and pressurize the gas. The USC team, dubbed Team CapItalIs, will follow up its successful laboratory work in addressing that challenge by providing Sustainable Innovations with the composite catalysts to be manufactured into functioning membrane electrode assemblies. The results will be demonstrated at the 2013 Fuel Cell Seminar and Energy Exposition in Columbus, Ohio, in October.
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