Fuel cells and their ability to cleanly produce electricity from hydrogen and oxygen are what make hydrogen attractive as a "fuel" for transportation use particularly, but also as a general energy carrier for homes and other uses, and for storing and transporting otherwise intermittent renewable energy. Fuel cells function somewhat like a battery—with external fuel being supplied rather than stored electricity—to generate power by chemical reaction rather than combustion.
Hydrogen fuel cells, for instance, feed hydrogen gas into an electrode that contains a catalyst, such as platinum, which helps to break up the hydrogen molecules into positively charged hydrogen ions and negatively charged electrons. The electrons flow from the electrode to a terminal that connects to an external circuit, creating an electrical current. Meanwhile, the hydrogen ions pass through an electrolyte—a conductive material, in this case usually a solid polymer membrane—to reach the other electrode, where they combine with oxygen to form water. Electrons flow from the external circuit into this other electrode to complete the electrical circuit. Many such "cells" are typically assembled together to form a "stack," which combines the voltage of the individual cells to form a high-voltage fuel cell.
There are a variety of different fuel cell types, generally characterized by what fuel they consume and what electrolyte they use. The above example, for instance, is often called a hydrogen fuel cell, but can also be referred to as a polymer electrolyte membrane (PEM) fuel cell.
NREL's current fuel cell work is primarily on developing durable, less-expensive materials for fuel-cell components. Platinum and other current electrode catalysts are costly (particularly for low-operating-temperature fuel cells) and conditions can be highly corrosive (particularly for high-operating-temperature fuel cells) both for electrodes and membranes. Fuel cell design options and their relation to other vehicle operating systems are quite complex. NREL is also applying its analytical capabilities to fuel-cell system analysis to help the U.S. Department of Energy (DOE) and industry partners identify critical areas for improvement and the most effective operating parameters for whole vehicle systems. See NREL's Fuel Cells Research webpage.
For more information on fuel cells, see: