In the long term, hydrogen is expected to be the fuel of choice for both the power and transportation industries. Just as conventional cars need gas stations, hydrogen-powered fuel cell cars will need an infrastructure. Hydrogen separation technology is integral to successful fossil-based hydrogen production technologies. Thin, dense composite membranes fabricated from ceramic and hydrogen-transport metal may provide a simple, efficient means for separating hydrogen from fossil-based gas streams. New ceramic-metal composite (cermet) membranes developed at Argonne, called hydrogen transport membranes, could eliminate the need for costly, conventional hydrogen-manufacturing facilities; the membranes could one day be small and efficient enough to be installed at every gas station.
Membranes currently used by industry to separate gases are not selective enough to isolate pure hydrogen—the simplest and smallest of all elements. Argonne has developed a composite cermet that transports only atomic hydrogen, allowing the membrane to separate pure hydrogen for use as a clean-burning fuel and in production of fertilizers and other products. The new membrane material works on a different principle than conventional porous membranes; hydrogen is the only species that passes through it because it dissolves in, and diffuses rapidly through, the metal phase in the composite. Unlike most membrane systems, Argonne's hydrogen membrane tolerates temperatures as high as 900 degrees Celsius. Such elevated temperatures push more hydrogen atoms into the membrane, accelerating the rate of gas separation.
The most likely raw feedstock material for hydrogen separation is syngas, a mixture of hydrogen and carbon monoxide made by reacting natural gas with oxygen. Because syngas can be expensive to produce, Argonne is exploring the use of another membrane to extract oxygen. The team has demonstrated that the oxygen membranes successfully separate oxygen and that this separated oxygen, when reacted with methane, forms syngas. Because Argonne's oxygen and hydrogen membranes both function at the same high temperatures, they can work in tandem: one membrane adding oxygen to methane to create syngas and the other extracting hydrogen from the syngas.