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Researchers Discover More Efficient Way to Split Water, Produce Hydrogen

September 19, 2016
Researchers Discover More Efficient Way to Split Water, Produce Hydrogen

Inexpensive, Nontoxic Catalyst Could Help Reduce Global Reliance on Fossil Fuels

Hydrogen is often considered a fuel for the future, in the form of fuel cells to power electric motors or burned in internal combustion engines. But finding a practical, inexpensive and nontoxic way to produce large amounts of hydrogen gas - especially by splitting water into its component parts, hydrogen and oxygen - has been a challenge.

A team of researchers from the University of Houston and the California Institute of Technology has reported a more efficient catalyst, using molybdenum sulfoselenide particles on three-dimensional porous nickel diselenide foam to increase catalytic activity.

The foam, made using commercially available nickel foam, significantly improved catalytic performance because it exposed more edge sites, where catalytic activity is higher than it is on flat surfaces, said Zhifeng Ren, MD Anderson Professor of physics at UH.

Ren is lead author of a paper in Nature Communications describing the discovery. Other researchers involved include Haiqing Zhou, Fang Yu, Jingying Sun, Ran He, Shuo Chen, Jiming Bao and Zhuan Zhu, all of UH, and Yufeng Huang, Robert J. Nielsen and William A. Goddard III of the California Institute of Technology.

For more information, read the original news release.

Houston scientist Dr. Paul Chu upends the physics world

July 24, 2016
Houston scientist Dr. Paul Chu upends the physics world

Thousands of scientists crammed the hallways of the Hilton Hotel in New York, jockeying for a seat inside the ballroom. Televisions were set up for the unlucky who couldn't squeeze inside for the event, which would later be dubbed the "Woodstock of Physics."

For more information, read the original news release.

New Superconducting Coil Improves MRI Performance

July 20, 2016
New Superconducting Coil Improves MRI Performance

A multidisciplinary research team led by University of Houston scientist Jarek Wosik has developed a high-temperature superconducting coil that allows magnetic resonance imaging (MRI) scanners to produce higher resolution images or acquire images in a shorter time than when using conventional coils.

Wosik, a principal investigator at the Texas Center for Superconductivity at UH, said test results show the new technology can reveal brain structures that aren't easily visualized with conventional MRI coils. He also is a research professor in the UH Department of Electrical and Computer Engineering.

The cryo-coil works by boosting the signal-to-noise ratio (SNR) - a measure of the strength of signals carrying useful information - by a factor of two to three, compared with conventional coils. SNR is critical to the successful implementation of high resolution and fast imaging.

Wosik said the cryo-coil reveals more details than a conventional coil because of its enhanced SNR profile. Where a conventional coil does not have enough sensitivity to "see," a superconducting coil can still reveal details. These details will remain hidden to conventional coils even when image acquisition is repeated endlessly.

For the initial tests, the probe was optimized for rat brain imaging, useful for biomedical research involving neurological disorders. But it also has direct implications for human health care, Wosik said.

"Research in animal models yields critical information to improve diagnosis and treatment of human diseases and disorders," he said. "This work also has the potential to clearly benefit clinical MRI, both through high quality imaging and through shortening the time patients are in the scanner."

Results from preliminary testing of the 7 Tesla MRI Cryo-probe were presented at the International Symposium of Magnetic Resonance in Medicine annual meeting in May. The coil can be optimized for experiments on living animals or brain tissue samples, and researchers said they demonstrated an isotropic resolution of 34 micron in rat brain imaging. In addition to its use in MRI coils, superconductivity lies at the heart of MRI scanning systems, as most high-field magnets are based on superconducting wire.

In addition to Wosik, collaborators on the project include Ponnada A. Narayana, director of the Magnetic Resonance Imaging Center and a professor in the Department of Diagnostic and Interventional Imaging at the University of Texas Health Science Center at Houston; Kurt H. Bockhorst, senior research scientist at UT Houston; Kuang Qin, a graduate student working with Wosik; and I-Chih Tan, assistant professor in the Department of Neuroscience at Baylor College of Medicine.

Compared to corresponding standard room temperature MRI coils, the performance of the cooled normal metal and/or the high-temperature superconducting receiver coils lead either to an increase in imaging resolution and its quality, or to a very significant reduction in total scan time," Wosik said.

For more information, read the original news release.

UH Physicist Joins Project to Develop New High Thermal Conducting Material

July 19, 2016
UH Physicist Joins Project to Develop New High Thermal Conducting Material

A University of Houston physicist will participate in a $7.5 million collaboration to develop a new material with thermal conductivity higher than that of diamonds.

The work, funded by the U.S. Navy's Multidisciplinary University Research Initiative, involves researchers from around the country, working to create an effective and affordable thermal conductor of boron arsenide.

Zhifeng Ren, MD Anderson Professor of physics at UH, said previous research predicted that boron arsenide would perform better than diamond as a thermal conductor. A thermal conductor allows energy, in the form of heat, to be transferred within the material; electronic devices require high thermal conductors in order to avoid overheating.

Ren will receive $1.3 million to study the material in single crystals or thin film.

The project is led by Li Shi, professor of mechanical engineering at the University of Texas at Austin. Other participating universities include Boston College, the Massachusetts Institute of Technology, the University of Illinois at Urbana-Champagne, and the University of California at Los Angeles.

Shi noted that Ren's research group has reported the first thermal conductivity measurement of boron arsenide. "They have proposed novel methods to grow this and other potentially ultrahigh thermal conductivity materials," he said. "Their efforts are instrumental for the success of this multidisciplinary project."

Diamond is considered one of the best thermal conductors at room temperature, with thermal conductivity of more than 2,000 watts per meter per Kelvin. That's five times higher than copper.

But it's expensive, and Ren said researchers hope to prove a theory developed by Boston College physicist David Broido that cubic boron arsenide could deliver thermal conductivity on par with the industry standard set by diamond, potentially allowing for improved high tech cooling applications.

Ren's lab began experimenting with the compound last year, making a single crystal of the material. The crystal had defects but reached thermal conductivity of 200 watts/meter/Kelvin, about 10 percent of what Broido predicted, he said.

It indicated they were on the right track, however. "This was very preliminary work, so there is hope that this material can have very high thermal conductivity," he said. "If we are successful, it would be a big improvement for high-powered electronics."

Making the material is difficult, as boron has a high melting point - almost 2,075 degrees Centigrade, or 3,767 degrees Farenheit - while arsenic vaporizes between 400 degrees and 500 degrees C. Beyond those complications, Ren's group will have to produce a crystal between 10 and 100 times larger than that created last year - or about one millimeter - in order to accurately measure the results.

"We have to demonstrate we can make bigger crystals, and that the crystals have thermal conducting properties that are truly high," he said.

For more information, read the original news release.

UH Researchers Discover Key Mechanism for Producing Solar Cells

July 18, 2016
UH Researchers Discover Key Mechanism for Producing Solar Cells

Researchers from the University of Houston have reported the first explanation for how a class of materials changes during production to more efficiently absorb light, a critical step toward the large-scale manufacture of better and less-expensive solar panels.

The work, published this month as the cover story for Nanoscale, offers a mechanism study of how a perovskite thin film changes its microscopic structure upon gentle heating, said Yan Yao, assistant professor of electrical and computer engineering and lead author on the paper. This information is crucial for designing a manufacturing process that can consistently produce high-efficiency solar panels.

Last year Yao and other researchers identified the crystal structure of the non-stoichiometric intermediate phase as the key element for high-efficiency perovskite solar cells. But what happened during the later thermal annealing step remained unclear. The work is fundamental science, Yao said, but critical for processing more efficient solar cells.

“Otherwise, it’s like a black box,” he said. “We know certain processing conditions are important, but we don’t know why.”

Other researchers involved with the project include first author Yaoguang Rong, previously a postdoctoral fellow at UH and now associate professor at Huazhong University of Science and Technology in China; UH postdoctoral fellows Swaminathan Venkatesan and Yanan Wang; Jiming Bao, associate professor of electrical and computer engineering at UH; Rui Guo and Wenzhi Li of Florida International University, and Zhiyong Fan of Hong Kong University of Science and Technology.

Yao is also a principal investigator at the Texas Center for Superconductivity at UH, which provided funding for the work.

The work also yielded a surprise: the materials showed a peak efficiency – the rate at which the material converted light to electricity – before the intermediate phase transformation was complete, suggesting a new way to produce the films to ensure maximum efficiency. Yao said researchers would have expected the highest efficiency to come after the material had been converted to 100 percent perovskite film. Instead, they discovered the best-performing solar devices were those for which conversion was stopped at 18 percent of the intermediate phase, before full conversion.

“We found that the phase composition and morphology of solvent engineered perovskite films are strongly dependent on the processing conditions and can significantly influence photovoltaic performance,” the researchers wrote. “The strong dependence on processing conditions is attributed to the molecular exchange kinetics between organic halide molecules and DMSO (dimethyl sulfoxide) coordinated in the intermediate phase.”

Perovskite compounds commonly are comprised of a hybrid organic-inorganic lead or tin halide-based material and have been pursued as potential materials for solar cells for several years. Yao said their advantages include the fact that the materials can work as very thin films – about 300 nanometers, compared with between 200 and 300 micrometers for silicon wafers, the most commonly used material for solar cells. Perovskite solar cells also can be produced by solution processing at temperatures below 150 degrees Centigrade (about 300 degrees Fahrenheit) making them relatively inexpensive to produce.

At their best, perovskite solar cells have an efficiency rate of about 22 percent, slightly lower than that of silicon (25 percent). But the cost of silicon solar cells is also dropping dramatically, and perovskite cells are unstable in air, quickly losing efficiency. They also usually contain lead, a toxin.

Still, Yao said, the materials hold great promise for the solar industry, even if they are unlikely to replace silicon entirely. Instead, he said, they could be used in conjunction with silicon, boosting efficiency to 30 percent or so.

For more information, read the original news release.

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