Promise of hydrogen fuel may become a reality with cheap production materials

February 24, 2014 by  
Filed under Solar Energy Tips

According to a news release from the University of Wisconsin-Madison, the sun can drive reactions to make chemical fuels, like hydrogen, that can in turn power a variety of cars and trucks. However, the cost of producing the sun-capturing semiconductors and the catalysts to generate fuel is prohibitive.

The U.S. Department of Energy’s www.fueleconomy.gov, the official U.S. government source for fuel economy information, notes the hydrogen is being investigated as a fuel for passenger cars, adding that it is an environmentally friendly fuel that has the potential to significantly lower our dependence on imported oil. However, major challenges, some of which are discussed in this article, must be overcome before it can be widely used.

“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,” posits Kyoung-Shin Choi, a chemistry professor at the University of Wisconsin–Madison.

Choi and postdoctoral researcher Tae Woo Kim combined cheap, oxide-based materials to split water into hydrogen and oxygen gases utilizing solar energy with an impressive solar-to-hydrogen conversion efficiency of 1.7 percent.

Choi developed solar cells from bismuth vanadate utilizing electrodeposition to enhance the compound’s surface area to an outstanding 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,” notes Choi. “More surface area means more contact area with water, and, therefore, more efficient water splitting.”

Bismuth vanadate requires help in speeding the reaction that generates fuel, and that’s where the paired catalysts come in.

“The problem is, in the end you have to put them together,” Choi explains. “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.”

The researchers stacked inexpensive and slightly flawed catalysts — iron oxide and nickel oxide — on the bismuth vanadate to benefit from their relative strengths.

“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,” Choi notes.

“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,” she adds.

Choi expects that other researchers can begin to utilize this technique to determine which combinations of materials can be even more effective.

According to the Alternative Fuels Data Center, hydrogen is considered an alternative fuel under the Energy Policy Act of 1992. The attraction of hydrogen as an alternative transportation fuel comes from its ability to power fuel cells in zero-emissions electric vehicles, its potential for domestic production, and the fuel cell vehicle’s potential for high efficiency.

Read more about the study’s findings here.

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