This invention relates in general to electrochemical systems and devices, and in particular to fuel cell components.
A fuel cell is an electrochemical “device” that continuously converts chemical energy into electric energy (and some heat) for as long as fuel and oxidant are supplied. Fuel cells are evolving. Some currently known categories of fuel cells include polymer electrolyte membrane (PEM), alkaline, phosphoric acid, molten carbonate, solid oxide, and biobased. All of these fuel cell types have the advantages of silent operation, high efficiency and zero emission capability. PEMs, however, offer several distinct advantages over the others. Some of these are low temperature operation (80-150 C), quick-start-up, compactness, and orientation independence.
At the heart of the PEM fuel cell is a membrane that has thin coatings of catalyst applied to both sides comprising a membrane electrode assembly (MEA). As hydrogen flows through the anode side of the MEA, a platinum-based catalyst facilitates the disassociation of the hydrogen gas into electrons and protons (hydrogen ions). The hydrogen ions pass through the thickness of the membrane and combine with oxygen and electrons on the cathode side, producing water and heat. The electrons, which cannot pass through the membrane, flow from the anode to the cathode through an external circuit containing an electric load, which consumes the power generated by the cell. FIG. 1 shows a detailed schematic of a PEM fuel cell. The illustrated fuel cell 10 includes a polymer electrolyte membrane 12, and catalyst layers 14 and 16 on opposing sides of the membrane. The anode side 18 of the fuel cell is shown on the left of the membrane. It includes a gas distribution layer 20 and a gas diffusion layer 22. The cathode side 24 of the fuel cell is shown on the right of the membrane.
Fuel cells have been around since 1839, but they have been hindered by component materials which are high in cost and suffer from poor durability. Nevertheless, they have attracted much interest in recent years for their ability to produce electricity and heat with higher efficiency and lower emissions than conventional energy technologies. However, the cost of fuel cells is still too high and technical breakthroughs are required before broad commercial application can become a reality.
Despite recent advances in the design of fuel cell components, further improvements are required to transform fuel cells from the fundamental sciences into enabling technologies.