The study, funded by the U.S. Department of Energy with additional funding from the National Science Foundation, appears in the February 3 issue of Science.

The research team developed a family of molecularly engineered, polar, rubbery copolymer membranes that selectively remove larger gases such as carbon dioxide and hydrogen sulfide from the smaller hydrogen. These reverse-selective materials purify hydrogen more efficiently than existing methods, producing hydrogen at high pressures without requiring expensive recompression.

"One of the major barriers to hydrogen as alternative motor fuel has been the cost of purifying it," said Raghubir Gupta, Ph.D., director of energy research and development at RTI and co-author on the paper. "Because of the high production volume of hydrogen, even a small improvement in purification efficiency could substantially reduce costs. These next-generation membranes could be a huge step in forming the basis of a purification process that makes hydrogen an affordable energy alternative."

The new membranes, which were developed in the lab of Chemical Engineering Professor Benny Freeman in Austin and tested there and at RTI, take advantage of plasticization by gases such as carbon dioxide and water vapor to enhance their separation performance. Traditionally, plasticization was viewed as a detrimental effect on membrane selectivity.

These efficient membranes also can be used to purify other gases, such as natural gas and value-added chemical products of carbon dioxide and other polar gases.

The research is part of the president�s 2003 Hydrogen Fuel Initiative that dedicated $1.2 billion to reverse America's growing dependence on foreign oil by developing the technology needed to make hydrogen cost-competitive with gasoline by 2010.

Because hydrogen is pollution free and can be produced from abundant domestic energy resources including fossil fuel, nuclear power and renewable energy, it has been considered a leading choice in the search for alternative energy sources.

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