Fuel Cells

Abstract

Abstract Fuel Cells. Fuel cells are electrochemical devices that convert the chemical energy of a fuel directly into electrical and thermal energy. In a typical fuel cell, gaseous fuels are fed continuously to the anode (negative electrode) compartment, and an oxidant, eg, oxygen or air, is fed continuously to the cathode (positive electrode) compartment. The electrochemical reactions take place at the electrodes to produce an electric (direct) current. The fuel cell theoretically has the capability of producing electrical energy for as long as the fuel and oxidant are fed to the electrodes. In reality, degradation or malfunction of components limits the practical operating life of fuel cells. Besides the direct production of electricity, heat is also produced in fuel cells. This heat can be effectively utilized for the generation of additional electricity or for other purposes, depending on the temperature. A practical consideration for fuel cells is compatibility with the available fuels and oxidants. One of the main attractive features of fuel cell systems is the expected high fuel‐to‐electricity efficiency. This efficiency, which runs from 40–60% based on the lower heating value (LHV) of the fuel, is higher than that of almost all other energy conversion systems. The two primary impediments to the widespread use of fuel cells are high initial cost and short operational lifetime. A variety of fuel cells has been developed for terrestrial and space applications. Fuel cells are usually classified according to the type of electrolyte used in the cells as polymer electrolyte fuel cell (PEFC), alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), and solid oxide fuel cell (SOFC). Fuel cells operating on pure H 2 and O 2 provide a useful power source in remote areas such as in space or under the sea where system weight and volume are important parameters. On the other hand, fuel cell power plants operating on fossil fuels and air offer the potential for environmentally acceptable, highly efficient, and low cost power generation. The minimum technical requirements for fuel cells for four different types of applications, ie, for buildings, industry, transportation, and utilities are given. From the standpoint of commercialization of fuel cell technologies, there are two challenges: initial cost and reliable life. Several activities, would strongly boost the prospects for fuel cell technology and include the development of (1) an active electrocatalyst for the direct electrochemical oxidation of methanol; (2) improved electrocatalysts for oxygen reduction; and (3) a more CO‐tolerant electrocatalyst for hydrogen.