New, inexpensive production materials boost promise of hydrogen fuel

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Generating electricity is not the only way to turn sunlight into energy we can use on demand. The sun can also drive reactions to create chemical fuels, such as hydrogen, that can in turn power cars, trucks and trains.The trouble with solar fuel production is the cost of producing the sun-capturing semiconductors and the catalysts to generate fuel. The most efficient materials are far too expensive to produce fuel at a price that can compete with gasoline.”In order to make commercially viable devices for solar fuel production, the material and the processing costs should be reduced significantly while achieving a high solar-to-fuel conversion efficiency,” says Kyoung-Shin Choi, a chemistry professor at the University of Wisconsin-Madison.In a study published last week in the journal Science, Choi and postdoctoral researcher Tae Woo Kim combined cheap, oxide-based materials to split water into hydrogen and oxygen gases using solar energy with a solar-to-hydrogen conversion efficiency of 1.7 percent, the highest reported for any oxide-based photoelectrode system.Choi created solar cells from bismuth vanadate using electrodeposition — the same process employed to make gold-plated jewelry or surface-coat car bodies — to boost the compound’s surface area to a remarkable 32 square meters for each gram.”Without fancy equipment, high temperature or high pressure, we made a nanoporous semiconductor of very tiny particles that have a high surface area,” says Choi, whose work is supported by the National Science Foundation. “More surface area means more contact area with water, and, therefore, more efficient water splitting.”Bismuth vanadate needs a hand in speeding the reaction that produces fuel, and that’s where the paired catalysts come in.While there are many research groups working on the development of photoelectric semiconductors, and many working on the development of water-splitting catalysts, according to Choi, the semiconductor-catalyst junction gets relatively little attention.”The problem is, in the end you have to put them together,” she says. “Even if you have the best semiconductor in the world and the best catalyst in the world, their overall efficiency can be limited by the semiconductor-catalyst interface.”Choi and Kim exploited a pair of cheap and somewhat flawed catalysts — iron oxide and nickel oxide — by stacking them on the bismuth vanadate to take advantage of their relative strengths.”Since no one catalyst can make a good interface with both the semiconductor and the water that is our reactant, we choose to split that work into two parts,” Choi says. “The iron oxide makes a good junction with bismuth vanadate, and the nickel oxide makes a good catalytic interface with water. So we use them together.”The dual-layer catalyst design enabled simultaneous optimization of semiconductor-catalyst junction and catalyst-water junction.”Combining this cheap catalyst duo with our nanoporous high surface area semiconductor electrode resulted in the construction of an inexpensive all oxide-based photoelectrode system with a record high efficiency,” Choi says.She expects the basic work done to prove the efficiency enhancement by nanoporous bismuth vanadate electrode and dual catalyst layers will provide labs around the world with fodder for leaps forward.”Other researchers studying different types of semiconductors or different types of catalysts can start to use this approach to identify which combinations of materials can be even more efficient,” says Choi, whose lab is already tweaking their design. “Which some engineering, the efficiency we achieved could be further improved very fast.”Story Source:The above story is based on materials provided by University of Wisconsin-Madison. The original article was written by Chris Barncard. Note: Materials may be edited for content and length.


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Evidence mixed on the usefulness of echinacea for colds

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For people seeking a natural treatment for the common cold, some preparations containing the plant Echinacea work better than nothing, yet “evidence is weak,” finds a new report from The Cochrane Library. The evidence review revealed no significant reductions in preventing illness, but didn’t rule out “small preventive effects.”The six authors conducted reviews on this subject in 1998, 2006 and 2008 and wanted to do an update to include several new trials conducted since then. “We’ve been doing this for so long and are very familiar with past research — which has been mixed from the very beginning,” said author Bruce Barrett, M.D., Ph.D. in the department of family medicine at the University of Wisconsin in Madison.The research team reviewed 24 randomized controlled trials to determine whether Echinacea was a safe and effective cold prevention and treatment. Trials included 4631 participants and 33 preparations, along with placebo. Echinacea products studied in these trials varied widely according to characteristics of three different plant species, the part of the plant used and method of manufacturing.People who get colds spend $8 billion annually on pharmaceutical products, including supplements such as Echinacea, Barrett noted. The authors’ meta-analyses suggest that at least some Echinacea preparations may reduce the relative risk of catching a cold by 10 to 20 percent, a small effect of unclear clinical significance. The most important recommendation from the review for consumers and clinicians is a caution that Echinacea products differ greatly and that the overwhelming majority of these products have not been tested in clinical trials.Barrett added that “it looks like taking Echinacea may reduce the incidence of colds. For those who take it as a treatment, some of the trials report real effects — but many do not. Bottom line: Echinacea may have small preventive or treatment effects, but the evidence is mixed.”"The paper does support the safety and efficacy of Echinacea in treating colds and highlights the main issue of standardizing herbal medicines,” commented Ron Eccles, Ph.D., director of the Common Cold Centre & Healthcare Clinical Trials at Cardiff University’s School of Biosciences in Wales.Story Source:The above story is based on materials provided by Health Behavior News Service, part of the Center for Advancing Health. …


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