New catalysts designed and investigated by Tufts University School of Engineering researchers and collaborators from other university and national laboratories have the potential to greatly reduce processing costs in future fuels, such as hydrogen.
The catalysts are composed of a unique structure of single gold atoms bound by oxygen to several sodium or potassium atoms and supported on non-reactive silica materials. They demonstrate comparable activity and stability with catalysts comprising precious metal nanoparticles on rare- earth and other reducible oxide supports when used in producing highly purified hydrogen.
The work, which appears in the November 27, 2014, edition of Science Express, points to new avenues for producing single-site supported gold catalysts that could produce high-grade hydrogen for cleaner energy use in fuel-cell powered devices, including vehicles.
"In the face of precious metals scarcity and exorbitant fuel-processing costs, these systems are promising in the search for sustainable global energy solutions," says senior author Maria Flytzani-Stephanopoulos, the Robert and Marcy Haber Endowed Professor in Energy Sustainability and professor in the Department of Chemical and Biological Engineering at Tufts.
Flytzani-Stephanopoulos's research group has been active in designing catalysts requiring a lower amount of precious metals to generate high-grade hydrogen for use in fuel cells. The water-gas shift reaction, in which carbon monoxide is removed from the fuel gas stream by reacting with water to produce carbon dioxide and hydrogen, is a key step in the process. Catalysts, such as metal oxide supported precious metals like platinum and gold, are used to lower the reaction temperature and increase the production of hydrogen.
The Tufts group was the first to demonstrate that atomically dispersed gold or platinum on supports, such as cerium oxide, are the active sites for the water-gas shift reaction. (doi:10.1126/science.1192449). Metal nanoparticles are "spectator species" for this reaction.
Flytzani-Stephanopoulos says the new research suggests single precious metal atoms stabilized with alkali ions may be the only important catalyst sites for other catalytic reactions. "If the other particles are truly 'spectator species', they are therefore unnecessary. Future catalyst production should then focus on avoiding particle formation altogether and instead be prepared solely with atomic dispersion on various supports," says Flytzani-Stephanopoulos.
The just published research describes how single gold atoms dispersed on non-reactive supports based on silica materials can be stabilized with alkali ions. As long as the gold atoms, or cations, are stabilized in a single-site form configuration, irrespective of the type of support, the precious metal will be stable and operate for many hours at a range of practical temperatures.
"This novel atomic-scale catalyst configuration achieves the maximum efficiency and utilization of the gold," says Flytzani-Stephanopoulos, who directs the Tufts Nano Catalysis and Energy Laboratory. "Our work showed that these single-site gold cations were active for the low-temperature water-gas shift reaction and stable in operation at temperatures as high as 200°C."
"Armed with this new understanding, practitioners will be able to design catalysts using just the necessary amount of the precious metals like gold and platinum, dramatically cutting down the catalyst cost in fuels and chemicals production processes," she adds.
Paper co-authors Professor Manos Mavrikakis at the University of Wisconsin-Madison and Assistant Professor Ye Xu at Louisiana State University used theoretical calculations to predict the stability and thermochemical properties of the single-site configuration. Researchers Larry Allard at Oak Ridge National Laboratory and Sungsik Lee at Argonne National Laboratory used atomic resolution electron microscopy and x-ray absorption spectroscopies, respectively, to demonstrate the existence and stability of the single-site gold species. Co-author Jun Huang, a lecturer at the University of Sydney, synthesized and characterized the silica materials used as supports. Several graduate students were involved in all aspects of the research both at Tufts and the University of Wisconsin-Madison.
The paper appears in the November 27, 2014, edition of Science Express (doi:10.1126/science.1260526). This research is primarily supported by the U.S. Department of Energy under grant # DE-FG02-05ER15730.
Located on Tufts' Medford/Somerville campus, the School of Engineering offers a rigorous engineering education in a unique environment that blends the intellectual and technological resources of a world-class research university with the strengths of a top-ranked liberal arts college. Close partnerships with Tufts' excellent undergraduate, graduate and professional schools, coupled with a long tradition of collaboration, provide a strong platform for interdisciplinary education and scholarship. The School of Engineering's mission is to educate engineers committed to the innovative and ethical application of science and technology in addressing the most pressing societal needs, to develop and nurture twenty-first century leadership qualities in its students, faculty, and alumni, and to create and disseminate transformational new knowledge and technologies that further the well-being and sustainability of society in such cross-cutting areas as human health, environmental sustainability, alternative energy, and the human-technology interface.
Kim Thurler | EurekAlert!
Molecular Force Sensors
20.09.2017 | Max-Planck-Institut für Biochemie
Foster tadpoles trigger parental instinct in poison frogs
20.09.2017 | Veterinärmedizinische Universität Wien
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
20.09.2017 | Life Sciences
20.09.2017 | Power and Electrical Engineering
20.09.2017 | Physics and Astronomy