Researchers generate hydrogen without the carbon footprintJuly 16, 2008A greener, less expensive method to produce hydrogen for fuel may eventually be possible with the help of water, solar energy and nanotube diodes that use the entire spectrum of the sun's energy, according to Penn State researchers. "Other researchers have developed ways to produce hydrogen with mind-boggling efficiency, but their approaches are very high cost," says Craig A. Grimes, professor of electrical engineering. "We are working toward something that is cost effective." Currently, the steam reforming of natural gas produces most of our hydrogen. As a fuel source, this produces two problems. The process uses natural gas and so does not reduce reliance on fossil fuels; and, because one byproduct is carbon dioxide, the process contributes to the carbon dioxide in the atmosphere, the carbon footprint.
Grimes' process splits water into its two components, hydrogen and oxygen, and collects the products separately using commonly available titanium and copper. Splitting water for hydrogen production is an old and proven method, but in its conventional form, it requires previously generated electricity. Photolysis of water solar splitting of water has also been explored, but is not a commercial method yet. Grimes and his team produce hydrogen from solar energy, using two different groups of nanotubes in a photoelectrochemical diode. They report in the July issue of Nano Letters that using incident sunlight, "such photocorrosion-stable diodes generate a photocurrent of approximately 0.25 milliampere per centimeter square, at a photoconversion efficiency of 0.30 percent." "It seems that nanotube geometry is the best geometry for production of hydrogen from photolysis of water," says Grimes In Grimes' photoelectrochemical diode, one side is a nanotube array of electron donor material - n-type material - titanium dioxide, and the other is a nanotube array that has holes that accept electrons - p-type material - cuprous oxide titanium dioxide mixture. P and n-type materials are common in the semiconductor industry. Grimes has been making n-type nanotube arrays from titanium by sputtering titanium onto a surface, anodizing the titanium with electricity to form titanium dioxide and then annealing the material to form the nanotubes used in other solar applications. He makes the cuprous oxide titanium dioxide nanotube array in the same way and can alter the proportions of each metal. While titanium dioxide is very absorbing in the ultraviolet portion of the sun's spectrum, many p-type materials are unstable in sunlight and damaged by ultraviolet light, they photo-corrode. To solve this problem, the researchers made the titanium dioxide side of the diode transparent to visible light by adding iron and exposed this side of the diode to natural sunlight. The titanium dioxide nanotubes soak up the ultraviolet between 300 and 400 nanometers. The light then passes to the copper titanium side of the diode where visible light from 400 to 885 nanometers is used, covering the light spectrum. The photoelectrochemical diodes function the same way that green leaves do, only not quite as well. They convert the energy from the sun into electrical energy that then breaks up water molecules. The titanium dioxide side of the diode produces oxygen and the copper titanium side produces hydrogen. Although 0.30 percent efficiency is low, Grimes notes that this is just a first go and that the device can be readily optimized. "These devices are inexpensive and because they are photo-stable could last for years," says Grimes. "I believe that efficiencies of 5 to 10 percent are reasonable." Grimes is now working with an electroplating method of manufacturing the nanotubes, which will be faster and easier. Penn State Science News and Science Current Events Tag Cloud This tag cloud is a visual representation of term frequencies of random science news topics with common terms grouped together and emphasized by their display size. Heart Surgery Shark Attack Amygdala Vitamin C Earthquakes Atomic Clock Nanotechnology Influenza Biosensor Cassini Nervous System Bone Formation Wine Restless Legs Syndrome Bone Density Brachytherapy Zebrafish Quarks Bird Species Cholera Retinoic Acid Bladder Cancer Memories Autophagy Medication
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Related Titanium Dioxide Current Events and Titanium Dioxide News Articles Memory with a twist: NIST develops a flexible memristor Electronic memory chips may soon gain the ability to bend and twist as a result of work by engineers at the National Institute of Standards and Technology (NIST). Novel approach estimates nanoparticles in environment Without knowing how much of an industrial chemical is being produced, it is almost impossible for scientists to determine if it poses any threat to the environment or human health. Nano-sandwich Triggers Novel Electron Behavior A material just six atoms thick in which electrons appear to be guided by conflicting laws of physics depending on their direction of travel has been discovered by a team of physicists at the University of California, Davis. Working with computational models, the team has found that the electrons in a thin layer of vanadium dioxide sandwiched between insulating sheets of titanium dioxide exhibit one set of properties when moving in forward-backward directions, and another set when moving left to right. Ancient diatoms lead to new technology for solar energy Engineers at Oregon State University have discovered a way to use an ancient life form to create one of the newest technologies for solar energy, in systems that may be surprisingly simple to build compared to existing silicon-based solar cells. Dancing 'adatoms' help chemists understand how water molecules split Single oxygen atoms dancing on a metal oxide slab, glowing brighter here and dimmer there, have helped chemists better understand how water splits into oxygen and hydrogen. In the process, the scientists have visualized a chemical reaction that had previously only been talked about. The new work improves our understanding of the chemistry needed to generate hydrogen fuel from water or to clean contaminated water. Sunlight turns carbon dioxide to methane Dual catalysts may be the key to efficiently turning carbon dioxide and water vapor into methane and other hydrocarbons using titania nanotubes and solar power, according to Penn State researchers. Nanostructure boosts efficiency in energy transport Overcoming a critical conductivity challenge to clean energy technologies, Boston College researchers have developed a titanium nanostructure that provides an expanded surface area and demonstrates significantly greater efficiency in the transport of electrons. Rivers are carbon processors, not inert pipelines Microorganisms in rivers and streams play a crucial role in the global carbon cycle that has not previously been considered. Solar Power Game-Changer: "Near Perfect" Absorption of Sunlight, From All Angles Researchers at Rensselaer Polytechnic Institute have discovered and demonstrated a new method for overcoming two major hurdles facing solar energy. New efficiency benchmark for dye-sensitized solar cells In a paper published online June 29 in the journal Nature Materials, EPFL professor Michael Graetzel, Shaik Zakeeruddin and colleagues from the Changchun Institute of Applied Chemistry at the Chinese Academy of Sciences have achieved a record light conversion efficiency of 8.2% in solvent-free dye-sensitized solar cells. More Titanium Dioxide Current Events and Titanium Dioxide News Articles |
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