Fuel Cells 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. They typically consist of numerous small cells in layers though, rather than a single large one. There are several different types of fuel cells using different catalysts (chemicals, in this case probably metals, that trigger a chemical reaction without themselves being used up by it) and electrolytes (non-metallic conductors of electrical ions, classically in a solution, but for fuel cells more likely in a solid membrane). In one type, for example, however, hydrogen fed to one catalyst- containing electrode splits to a positively charge hydrogen ion (proton) and a negatively charged electron. The positive ions travel through the electrolyte to the other catalyst electrode where they combine with oxygen fed to that electrode—and electrons—to produce water and heat. The necessary electrons are drawn through an electric circuit external to the cell, creating the electrical generation. 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 fuel-cell system analysis to help DOE and industry partners identify critical areas for improvement and the most effective operating parameters for whole vehicle systems.