Nanotech Energizes Hydrogen Fuel Cells

By Matthew Burns  

For decades, the world has relied primarily on hydrocarbons for fuel, developing a dependence that has caused political upheaval and environmental pollution. Nanotechnology might be able to minimize those global problems, Dr. Xiangwu Zhang says, simply by replacing hydrocarbons with hydrogen made by using carbon.

Clean-burning hydrogen energy is seen by many as the gold standard for future U.S. energy policy. It would reduce the nation's reliance on foreign oil and slash greenhouse-gas emissions. Producing energy from hydrogen easily and cheaply has been the primary obstacle, but Zhang, an assistant professor in the Department of Textile Engineering, Chemistry and Science at NC State, believes carbon nanofibers can solve that production problem and help store the energy.

By combining additives with nanofibers, Zhang has created lithium-ion batteries that can store energy for longer periods. Photos by Roger Winstead.

Zhang – a materials scientist by training – and his research team are synthesizing the nanofibers by electrospinning polyacrynitrile polymer and platinum salt. The resulting carbon filaments are covered with platinum nanoparticles and can be made into nonwoven fabrics and used as electrode layers in a hydrogen fuel cell. The platinum acts as a catalyst, he says, separating electrons from hydrogen atoms so they can be discharged as electricity. The carbon nanofibers transport the electrons out of the fuel cell, but more importantly, their large surface area provides a base for the chemical reaction to occur.

Zhang is testing several fabrication methods to maximize the surface area on the nanofibers without trapping the platinum particles inside the carbon matrix, where they can't produce a chemical reaction. The small fuel cells his team has built have only enough juice to run an electric clock or small appliance, so they are trying to scale up the science – without a proportional increase in cost – to a point where the device could power a car.

"To be practical," Zhang says, "the fuel cells can't cost so much that people can't afford them."

Once electricity is produced by fuel cells or other means, he says, carbon nanofibers can also help store the energy by making batteries more efficient. His team has created energy-storage nanofibers by blending in active materials as the filaments are spun. When the fibers are layered in an electrode of a lithium-ion battery, Zhang says, the nanofiber structure increases the stability of the lithium atoms, so they can hold more energy for a longer time.

"We need to change the economic and political impacts of energy in our society," he says. "Nanotechnology lets us create novel materials and new energy solutions."

Link:

• The Year of Energy

• Dr. Xiangwu Zhang