2:07 p.m., Nov. 29, 2010----Jingguang G. Chen, Claire D. LeClaire Professor in the Department of Chemical Engineering at the University of Delaware, is co-author of a paper demonstrating a new way to save platinum commonly used as a catalyst in hydrogen production.

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Chen's paper, entitled “Low-Cost Hydrogen Evolution Catalysts Based on Monolayer Platinum on Tungsten Monocarbide (WC) Substrates,” appears as the cover feature in a December issue of Angewandte Chemie International Edition, the leading high impact journal in the world on applied chemistry.

Co-authors of the paper include Robert W. Birkmire, professor of materials science and engineering and director of the Institute of Energy Conversion (IEC); Kevin D. Dobson, IEC research associate; students Daniel V. Esposito, Sean T. Hunt and Alan L. Stottlemyer; and Brian E. McCandless, IEC associate scientist.

Chen explains that when powered by renewable energy sources such as wind- or solar-based technologies, the generation of hydrogen from the electrolysis of water produces a high-energy-density mobile energy carrier without any associated carbon dioxide emissions. At low temperatures, this water-splitting process can take place in a variety of electrochemical devices, however, the catalyst used to initiate the hydrogen-evolution reaction (HER) can have a profound influence on cost, lifetime and efficiency of the device.

Platinum is a very active and commonly used HER catalyst, says Chen, but its high price and limited world-wide supply prohibit its use to mass produce hydrogen by water electrolysis. One approach to overcoming the challenges associated with platinum HER catalysts is to increase the surface bulk atomic ratio of platinum, allowing a lower metal loading to be used without compromising electrolysis efficiency.

Experiments conducted by the research team explored the lower limits of platinum loading for HER by using nearly all platinum atoms in the form of an atomic layer, or monolayer (ML), on low-cost tungsten monocarbide (WC) substrates. The research was led by Esposito, a fifth-year graduate student.

WC is known for its “platinum-like” catalytic properties. It also exhibits good stability in a wide-range of acidic environments and shows great promise as a support material for platinum particles.

Using a combination of experimental and theoretical approaches, their results confirm that surface electronic and chemical properties of ML platinum on bulk WC substrate are strikingly similar to those of bulk platinum. This similarity demonstrates the possibility that all but the topmost layer of platinum can be replaced by WC, thereby decreasing platinum loading and associated platinum costs without compromising its very high HER activity.

Further work is needed to develop high-surface-area ML Pt-WC systems structures for high-current-density applications and to investigate the long-term stability of this type of HER catalyst. Other electrochemical and photoelectrochemical applications may also exist, says Chen.

Chen and his research group at UD have been investigating the use of tungsten carbide as an alternative to more expensive platinum-based catalysts for more than a decade, with demonstrated results of the utility of these materials for fuel cell applications. In 2008, his research focused on directly converting biomass to useful chemical compounds using tungsten carbide as a catalyst was also featured as an Angewandte Chemie cover story.

Chen received his bachelor's degree from Nanjing University and his doctorate from the University of Pittsburgh. After a year in Germany as a Humboldt postdoctoral fellow, he began his career in industry in 1989 at the Exxon Research and Engineering Co. in Annandale, N.J. He joined the UD faculty in 1998 and served as director of the Center for Catalytic Science and Technology from 2000 through 2007. He served as the interim director of the UD Energy Institute from 2008 to 2010.

Widely published and cited with more than 200 articles in refereed journals and more than 5,000 research citations, Chen holds 19 U.S. patents and has served on the editorial boards of several surface science and catalysis journals. He also serves on the board of directors of the North American Catalysis Society and formerly was the catalysis secretary-general of the American Chemical Society. He has served as co-director of the Energy Frontier Research Center on Biomass Conversion since 2009.

Article by Karen B. Roberts