Fuel cells generate electricity through an electrochemical exchange between oxygen and hydrogen. The devices have long supplied electricity on spacecraft and are becoming the favored backup source in electric power plants. Now, the cells are poised to become the automotive power source of the future.

Fuel cells are comprised of tightly compressed stacks of 12-inch by 12-inch carbon plates, which function as bipolar anode and cathode electrodes. The plates are sandwiched between polymer proton exchange membranes. The bigger the stack, the more power is generated. Three-hundred fuel cells in a stack generate approximately 50 hp.

Hydrogen is fed into one side of the membrane and oxygen from the opposite side. Platinum coating on the membrane catalyzes these gases, releasing free electrons and protons. The electrons form the cell's electrical output, which is transmitted through an external circuit to power the vehicle. Protons migrate through the membrane where they are combined with oxygen and expelled through the tailpipe as harmless water and heat.

Tight, reliable, fail-safe sealing is critical to cell performance, says Joe Ballantine, director of automotive marketing at Loctite. "All of these new power sources will require specialty adhesives, sealants and coatings to enable them to function reliably and efficiently," he says. "Loctite intends to be the primary supplier of these materials."