Sunday, February 5, 2012

Titanium Dioxide and sunlight produce hydrogen from water

Titanium Dioxide Key to Producing Hydrogen Fuel from Sunlight
Published on August 26, 2004 at 11:46 PM
A team of Australian scientists predicts that a revolutionary new way to harness the power of the sun to extract clean and almost unlimited energy supplies from water will be a reality within seven years.

Using special titanium oxide ceramics that harvest sunlight and split water to produce hydrogen fuel, the researchers say it will then be a simple engineering exercise to make an energy-harvesting device with no moving parts and emitting no greenhouse gases or pollutants.

It would be the cheapest, cleanest and most abundant energy source ever developed: the main by-products would be oxygen and water. Rooftop panels placed on 1.6 million houses, for example, could supply Australia's entire energy needs.

"This is potentially huge, with a market the size of all the existing markets for coal, oil and gas combined," says Professor Janusz Nowotny, who with Professor Chris Sorrell is leading a solar hydrogen research project at the University of NSW Centre for Materials and Energy Conversion. The team is thought to be the most advanced in developing the cheap, light-sensitive materials that will be the basis of the technology.

"Based on our research results, we know we are on the right track and with the right support we now estimate that we can deliver a new material within seven years," says Nowotny.

Sorrell says Australia is ideally placed to take advantage of the enormous potential of this new technology: "We have abundant sunlight, huge reserves of titanium and we're close to the burgeoning energy markets of the Asia-Pacific region. But this technology could be used anywhere in the world. It's been the dream of many people for a long time to develop it and it's exciting to know that it is now within such close reach."

The results of the team's work will be presented this week at an international conference.

Eminent delegates from Japan, Germany, the United States and Australia will be in Sydney on August 27 for a one-day International Conference on Materials for Hydrogen Energy at UNSW.

Among them will be the inventors of the solar hydrogen process, Professors Akira Fujishima and Kenichi Honda. Both are frontrunners for the Nobel Prize in chemistry and are the laureates of the 2004 Japan Prize.

Since their 1971 discovery that allowed the splitting of water into hydrogen and oxygen, researchers have made huge advances in achieving one of the ultimate goals of science and technology - the design of materials required to split water using solar light.

The UNSW team opted to use titania ceramic photoelectrodes because they have the right semiconducting properties and the highest resistance to water corrosion.

Professors Nowotny and Sorrell say that with appropriate government support and financial backing, their technology could help Australia become part an OPEC of the future.

"We have a solar energy empire in Australia and have a moral obligation to utilise this," says Nowotny. "The very same sentiments were shared by David Sukuzi when he visited Sydney recently. He said he hoped Australia would serve as an example to the rest of the world."

Solar hydrogen, Professor Sorrell argues, is not incompatible with coal. It can be used to produce solar methanol, which produces less carbon dioxide than conventional methods. "As a mid-term energy carrier it has a lot to say for it," he says.

At present, the UNSW work is backed by Rio Tinto, Sialon Ceramics and Austral Bricks A major producer of titania slag, Rio Tinto hopes that an early outcome will be a more environmentally friendly and economically attractive local source of fuel for its remote mining operations while Sialon Ceramics is interesting in production and marketing of a solar-hydrogen production device.


Isolation: titanium is readily available from commercial sources so preparation in the laboratory is not normally required. In industry, reduction of ores with carbon is not a useful option as intractable carbides are produced. The Kroll method is used on large scales and involves the action of chlorine and carbon upon ilmenite (TiFeO3) or rutile (TiO2). The resultant titanium tetrachloride, TiCl4, is separated from the iron trichloride, FeCl3, by fractional distillation. Finally TiCl4 is reduced to metallic titanium by reduction with magnesium, Mg. Air is excluded so as to prevent contamination of the product with oxygen or nitrogen.
Hydrogen production under sunlight with an electrochemical photocell
Fujishima, A.; Kohayakawa, K.; Honda, K.
Electrochemical Society, Journal, vol. 122, Nov. 1975, p. 1487-1489.

Three methods of forming oxide film on metal, electrochemical formation, thermal formation in an electric furnace, and thermal formation by simple heating, were studied as possible means of producing titanium dioxide electrodes. The maximum photocurrents produced by potentiostatically or galvanically formed oxide film electrodes under anodic polarization were 1/10 that of single crystal rutile electrodes, and similar results were obtained using electrodes formed in an electric furnace to which oxygen was supplied. Those produced in a reducing atmosphere produced slightly greater photocurrents. The oxide film layers formed by heating in a gas burner were thicker than those obtained by other methods, and produce anodic photocurrents comparable to those produced by a single crystal rutile electrode. A photocell containing titanium dioxide film anodes was developed on the basis of these results and collected hydrogen at the rate of 6.6l of H2/sq mm of titanium dioxide.



Before its discovery, most of its properties had been predicted and described in the classic articles about elements natural system and its application for describing yet no discovered elements by Dmitri Mendeleev, who called the hypothetical element eka-aluminium, on the basis of its position in his periodic table. His prediction was brilliantly when the new element was discovered spectroscopically by Paul-Emile Lecoq de Boisbaudran in 1875 by its characteristic spectrum in an examination of a zinc blend from the Pierrefitte Mountain in Pyrenees. He called the new-discovered element gallium (Latin Gallia meaning Gaul (essentially modern France); also gallus, meaning "rooster"), the French for which is "le coq", mentioning the Lecoq de Boisbaudran's surname.

Gallium's discovery had been the greatest Gallium triumph of Mendeleev's periodic system.
Gallium is a typical trace element, poor metal, sometimes considered as a rare element. Its crustal abundance is quite big, 1.5x10-3 mass %. However gallium does not exist in free form in nature, and concentration is less than 100 ppm or 0.01% of a rock's composition. Gallium minerals were unknown even 100 years ago before Ramdorf's report about new mineral species of gallium ores from Tsumeb, Namibia and Kipushi mine in Zaire. It was gallium and copper sulphides mixture CuS2 called gallite and described by Strunz, Geier and Seeliger in 1958. Primary zinc-rich ore body contains the minerals sphalerite, cobalt-bearing chalcopyrite, germanite and gallite. Sphalerite from floutite-sulphide deposits is especially rich by gallium. Gallium is found and extracted as a component in bauxite, germanite, and sphalerite. Apatite-nepheline ores deposited in Khibin range of the Kola region of Russia are also very rich by gallium (0.01 - 0.04%). Gallium's concentrations in other minerals are as follows: sphalerite (ZnS) - 0.001%, pyrite (S2) - 0,001%, germanite (Cu3S4) - 1.85%, zircon (zirconium silicate ZrSiO4) - 0.001 - 0.005%, spodumene (LiAlSi2O6) - 0.001 - 0.07%. Some flue dusts from burning coal esp. in England have been shown to contain small quantities of gallium, typically less than 1.5% by weight.

Gallium abundance in Universe is estimated to be 10-6% by mass or 2x10-7% (by atom.); 4x10-6% (mass.) or 6x10-7% (atom) on the Sun; in meteorites 7.8x10-4% by mass and in seawater 3x10-9% by mass.

Gallium'a role for life processed is not understood. According to some hypotheses gallium's presence in English coal is a result of some vital processes. Galium is needed for some fungi such as myco Aspergillus which is a close relative to mold and for Lemna minor, lesser duckweed, which is one the world's smallest flowering wetland plants.

Aluminum mixed with gallium will react with water to produce hydrogen and aluminum oxide so has been considered by (Purdue) and others as a fuel candidate as gasoline becomes either scarce or expensive.

[From the internet]
"Their (Purdue) hydrogen-releasing formula, which is patent-pending, is 90 percent bulk aluminum and 10 percent liquid metal alloy, consisting of gallium, indium and tin. The gallium dissolves the aluminum, allowing it to react with the oxygen in the seawater. The hydrogen atoms break free from the water molecule. The end product is aluminum hydroxide, which can be recycled back into aluminum.

Despite their seawater hydrogen recipe calling for indium, which has supply issues, the researchers contend it could be cost-competitive."

Hydrogen is often advocated as an energy medium. Here are some relevant facts.

Hydrogen is the lightest of the elements with an atomic weight of 1.0. Liquid hydrogen has a density of 0.07 grams per cubic centimeter, whereas water has a density of 1.0 g/cc and gasoline about 0.75 g/cc. These facts give hydrogen both advantages and disadvantages. The advantage is that it stores approximately 2.6 times the energy per unit mass as gasoline, and the disadvantage is that it needs about 4 times the volume for a given amount of energy. A 15 gallon automobile gasoline tank contains 90 pounds of gasoline. The corresponding hydrogen tank would be 60 gallons, but the hydrogen would weigh only 34 pounds.

New fuel for 21st century -- aluminum +(gallium, indium,tin) alloy pellets?
"Pellets made out of aluminum and gallium can produce pure hydrogen when water is poured on them, offering a possible alternative to gasoline-powered engines, U.S. scientists say.

Hydrogen is seen as the ultimate in clean fuels, especially for powering cars, because it emits only water when burned. U.S. President George W. Bush has proclaimed hydrogen to be the fuel of the future, but researchers have not yet found the most efficient way to produce and store hydrogen.

The metal compound pellets may offer a way, said Jerry Woodall, an engineering professor at Purdue University in Indiana who invented the system.

"The hydrogen is generated on demand, so you only produce as much as you need when you need it," Woodall said in a statement. He said the hydrogen would not have to be stored or transported, taking care of two stumbling blocks to generating hydrogen.

For now, the Purdue scientists think the system could be used for smaller engines like lawn mowers and chain saws. But they think it would work for cars and trucks as well, either as a replacement for gasoline or as a means of powering hydrogen fuel cells.

"It is one of the more feasible ideas out there," Jay Gore, an engineering professor and interim director of the Energy Center at Purdue's Discovery Park, said in a telephone interview on Thursday. "It's a very simple idea but had not been done before."

On its own, aluminum will not react with water because it forms a protective skin when exposed to oxygen. Adding gallium keeps the film from forming, allowing the aluminum to react with oxygen in the water.

This reaction splits the oxygen and hydrogen contained in water, releasing hydrogen in the process.

"I was cleaning a crucible containing liquid alloys of gallium and aluminum," Woodall said. "When I added water to this alloy -- talk about a discovery -- there was a violent poof."

What is left over is aluminum oxide and gallium. In the engine, the byproduct of burning hydrogen is water.

"No toxic fumes are produced," Woodall said.

"When and if fuel cells become economically viable, our method would compete with gasoline at $3 per gallon even if aluminum costs more than a dollar per pound."

Recycling the aluminum oxide byproduct and developing a lower grade of gallium could bring down costs, making the system more affordable, Woodall said.

The Purdue Research Foundation holds title to the primary patent, which has been filed with the U.S. Patent and Trademark Office. An Indiana startup company, AlGalCo LLC., has received a license for the exclusive right to commercialize the process."


Gallium oxide is precipitated in hydrated form upon neutralization of acidic or basic solution of gallium salt. Also, it is formed on heating gallium in air or by thermally decomposing gallium nitrate at 200-250˚C. It can occur in five different modifications, α,β,δ,γ and ε. Of these modifications β-Ga2O3 is the most stable form.[3]

[edit]Preparation Methods for the Five Modifications

β-Ga2O3 is prepared by heating nitrate, acetate, oxalate or other organic derivatives above 1000˚C.
α-Ga2O3 can be obtained by heating β-Ga2O3 at 65kbars and 1100˚C for 1 hour giving a crystalline structure. The hydrated form can be prepared by decomposing precipitated and "aged" gallium hydroxide at 500˚C.
γ-Ga2O3 is prepared by rapidly heating the hydroxide gel at 400˚C-500˚C.
δ-Ga2O3 is obtained by heating Ga(NO3)3 at 250˚C.
ε-Ga2O3 is prepared by briefly heating δ-Ga2O3 at 550˚C for 30 minutes.[4