It is progress in the development of hydrogen-air PEM stacks that has made fuel cells a contender for powering automobiles of the future. For many years, the energy and power densities of PEM cells were so low and the amount of platinum catalyst required was so high that most commercial applications seemed out of the question. For example, the platinum requirements for the PEM cells used on Gemini space missions of the 1960s were on the order of 100 g/ kW, for a cost factor of $1500/kW (assuming a platinum cost of $15/g). A typical automotive fuel cell stack would be 80 kW, implying a cost of $120,000 for the catalyst material alone. By comparison, current automotive catalytic converters require roughly 0.05 g/ kW of platinum-group metals, costing on the order of $100 for an average car. More stringent emissions standards are pushing precious metal requirements higher, so that future gasoline vehicles may need 0.1 to 0.2 g/kW of platinum group metals. (more…)

Polymer Electrolyte Fuel Cells have high-power density, rapid startup, and low-temperature operation (around 80 to 120 C), and so are ideal for use in applications such as energy transport and battery replacement. The electrolyte used is a proton conducting polymer. This is typically a perfluorinated polymer, though other hydrocarbon-based membranes are under development in an attempt to reduce cost or to enable operation at temperatures approaching 200 C. The catalytically active layer sits adjacent to the membrane, supported on a PTFE treated carbon paper, which acts as current collector and gas diffusion layer. For operation on pure hydrogen, platinum is the most active catalyst, but alloys of platinum and ruthenium are used when higher levels of carbon monoxide are present (CO is a poison in all low temperature fuel cells). (more…)

Numerous other parts are needed for a complete fuel cell engine suitable for motor vehicles. These auxiliary components include many familiar pieces of equipment, such as blowers, pumps, heat exchangers, sensors, and controls. However, fuel cells have specialized performance requirements, so substantial engineering effort is needed to develop auxiliary systems suitable for fuel cell vehicles. (more…)