Nanowire solar cells raise efficiency limit

Scientists from the Nano-Science Center at the Niels Bohr Institut, Denmark and the Ecole Polytechnique Fédérale de Lausanne, Switzerland, have shown that a single nanowire can concentrate the sunlight up to 15 times of the normal sun light intensity. The results are surprising and the potential for developing a new type of highly efficient solar cells is great.

Due to some unique physical light absorption properties of nanowires, the limit of how much energy we can utilize from the sun's rays is higher than previous believed. These results demonstrate the great potential of development of nanowire-based solar cells, says PhD Peter Krogstrup.

Now, ride to your office on electric skateboard

Soon, you can skate to work! Researchers are developing a skateboard which they claim will be the world's lightest electric vehicle and will be capable of travelling up to 9 kilometres. The Stanford University team behind the 'Boosted Board' said it could reach speeds of 32km/hr and be used by tourists, commuters and for everyday getting around, the Daily Mail reported.
The 'Boosted Board' prototype is built on a standard longboard, and weighs around 5 kilogrammes. Two brushless motors are used to drive the rear wheels, creating 2000 watts. Regenerative braking used to recharge the battery while moving. Lithium batteries which can be recharged in two hours, giving 9 kilometres of use. The team recently launched a Kickstarter fund to build the gadget - and have already raised over $2,60,000 - more than double their initial aim.

The search for new materials for hydrogen storage

Hydrogen is the ideal fuel for new types of fuel cell vehicles, but one problem is how to store hydrogen. In his doctoral dissertation Serhiy Luzan studies new types of materials for hydrogen storage. He also shows that new materials with interesting properties can be synthesized by the reaction of hydrogen with carbon nano-structured materials. The dissertation will be publicly defended on September 28 at Umeå University.

New car engines that run on hydrogen produce only water as exhaust and are three to four times more efficient than ordinary internal combustion engines. Just one “small” problem is hampering the development of hydrogen-powered vehicles: there is no good method for storing sufficient amounts of hydrogen, as it is a gas of very low density.

Serhiy Luzan devotes the first part of his dissertation to studies of hydrogen storage in exciting new types of materials: metal-organic frameworks (MOFs). They consist of zinc- and cobalt-based metal clusters linked together via organic linkers, and they are extremely porous. One gram of MOF has a hydrogen-absorbing surface that is larger than a football field! Dozens of new MOF materials are synthesized each year, which is highly promising for the next generation of hydrogen storage materials.

Serhiy studied the hydrogen absorption of several new MOFs and researched the effects of different surface areas, pore volumes, and pore forms on the hydrogen storage parameters. MOFs can store record amounts of hydrogen at very low temperatures, but the hydrogen capacity at room temperature is not good enough. Luzan therefore studied new methods to enhance this capacity. Addition of metal catalysts has previously been reported to improve hydrogen storage considerably.

“But in my study, the effect of metal catalysts addition on hydrogen absorption in MOFs was not confirmed,” says Serhihy Luzan.

Hydrogen is of interest not only as a fuel but also for chemical modification of nano-structured carbon materials, such as carbon nanotubes, fullerenes, and graphene. Graphene is a single layer of carbon atoms. Carbon nanotubes also consist of pure carbon, in the form of graphene layers rolled into a cylinder. Fullerene, C60, consist of sixty carbon atoms arranged in five- or six-vertices figures, just like the pattern on a soccer ball. There are carbon materials that are stronger than steel, conduct current better than copper, and diffuse heat better than diamond.

In the second part of the dissertation Luzan describes the materials he created by the reaction of hydrogen with fullerenes and carbon nanotubes.

Luzan studied the reaction between fullerene C60 and hydrogen at elevated temperatures and hydrogen pressures, with and without the addition of metal catalysts. The reaction resulted in the formation of hydrogenated fullerenes, C60Hx. Upon extended hydrogen treatment, the fullerene structure fragmented and collapsed. This outcome shows that it is possible to break down fullerenes stepwise into smaller cup-like molecules, which are stabilized by hydrogen atoms. This is a structure that was previously difficult to achieve.

“With this method, we should be able to use fullerenes as a relatively inexpensive source material for creating new molecules that hopefully would retain interesting properties from the original carbon nano-material,” says Serhihy Luzan.

Hydrogenated graphene (graphane) is expected to be an ideal material for new carbon-based electronics, but graphane is difficult to synthesize by a direct reaction between graphene and hydrogen. It is much easier first to hydrogenate carbon nanotubes and then to cut them along the tube axis into so-called nanoribbons, which have hydrogen covalently bonded to the surface.

Luzan’s experiments showed that the reaction between single-wall carbon nanotubes and hydrogen is possible if a suitable catalyst is used, and he was able to observe that some of the nanotubes were converted to graphene or graphane nanoribbons.

Safe, Portable Fuel Cell Can Charge Smartphones-A research team led by Rohm Co. announced it has developed a portable hydrogen-powered fuel cell

TOKYO (Nikkei)–A research team led by Rohm Co. (6963) announced Tuesday that it has developed a portable hydrogen-powered fuel cell that is lightweight, inexpensive and safe, aiming for commercialization by next spring.

Power your smartphone with hydrogen.

The team, which also includes Kyoto University and fuel-cell start-up Aquafairy Corp., has devised a hydrogen generator that uses a sheet of calcium compound solidified by resin. It generates 4.5 liters of hydrogen from 3 grams of calcium compound through a chemical reaction with water.

Combined with the polymer electrolyte power generation technology, the fuel cell can produce 5 watt-hours of electricity, enough to charge a smartphone in two hours.

The team plans to commercialize a credit card-sized smartphone charger that weighs less than 100 grams as well as a 200-watt portable generator to be used for emergencies.

Nanotechnology turns plants into common plastic

Dutch scientists have found a way of turning plant matter into the building blocks of common plastics using a nanotechnology process that offers an alternative to oil-based production.

The team from Utrecht University and Dow Chemical Co produced ethylene and propylene - precursors of materials found in everything from CDs to carrier bags and carpets - after developing a new kind of iron catalyst made of nanoparticles.

Existing bioplastics, which are made from crops such as corn and sugar, have only limited use as they are not exact substitutes for oil-based products.

The new system, by contrast, produces chemicals that are the same as those made in petrochemical works, allowing them to be used in a wide range of industries.

This also means they will not be biodegradable, although they will be made from renewable resources.

Researcher Krijn De Jong and his colleagues envisage using non-food sources of biomass for the new process, such as fast-growing trees or grasses, rather than traditional crops, in order to reduce competition for resources between food and fuel.

Plastics made from biomass could, however, be vulnerable to the same criticism that has beset biofuel production.

Critics say the production of some biofuels can occupy land that would otherwise be used for agricultural purposes, thus limiting food and water resources for a rapidly rising world population.

Some biofuel production could also increase carbon emissions, especially if rainforests are cut down to facilitate production.

The research by De Jong and his colleagues, which was published Thursday in the journal Science, is still at an early stage. It now requires larger-scale testing and pilot projects, so it will not reach the market for several years.

RISING DEMAND

Diminishing reserves of fossil fuels and rising greenhouse gas emissions suggest there should be increased demand for bioplastics. But that argument could be disrupted by recent vast finds of shale gas, which now provide a cheap alternative feedstock for ethylene in the United States.

The Dutch-designed catalysts consist of tiny nanoparticles separated from each other on carbon nanofibers. In laboratory tests, the catalysts proved highly effective at converting biomass-derived synthesis gas - a mix for hydrogen and carbon monoxide - in ethylene and propylene.

Importantly, the process worked without producing large amounts of methane, an unwanted byproduct of another catalytic process using large iron particles.

The team now plan to increase catalyst production by linking with experts from Johnson Matthey, the world's largest supplier of catalytic converters for vehicles.

Nanotechnology, which involves designing and manufacturing materials on the scale of one-billionth of a meter, is a rapidly expanding area of materials science with applications in medicine, electronics and coatings.