PEMFCs Phosphorous-Acid FC a solid membrane of natural material, such as polystyrene sulfonic acid, is used as an electrolyte in a peMfc. this fc works at 40-60 °c, a low-temperature operation that allows the peMfc to start quickly and results in less wear on system components, resulting in better durability. an explanation of the peMfc on the basis of chemical equations is shown in figure 3. the phosphorous-acid fc (pafc) was invented in the 1980s. it comprises two electrodes of porous conducting material (usually nickel) to receive a charge, with concentrated phosphoric acid present between the electrodes to function as an electrolyte. a platinum catalyst is added to both electrodes to increase the rate of the reaction. the explanation of a pafc on the basis of chemical equations is shown in figure 5. AFC the afc is the most seasoned fc, using 40% of aqueous potassium hydroxide as an electrolyte. the working temperature is roughly 90 °c. the fuel of the afc technology is free of carbon dioxide. the afcs were used in the apollo shuttle to provide both power and drinking water. figure 4 explains the operation of the afc on the basis of chemical equations. Molten-Carbonate FC the molten-carbonate fc (Mcfc) uses carbonate of alkali metals in a molten state as an electrolyte. this requires the cell operation to occur over the melting point (roughly 600-700 °c) of the separate carbonates but does not require a catalyst due to the high temperature. figure 6 explains the Mcfc on the basis of chemical equations. Electron Flow Carbon Dioxide Bipolar Plates (Polymer/Graphite Composite) AGDL Plus Anode Catalyst (Platinum Alloy) Hydrogen Ions Electrolyte (Sulfophynelated Polysulfonic) CGDL Oxygen AGDL Methonal CGDL Plus Cathode Catalyst (Platinum Alloy) Water Bipolar Plates (Polymer/Graphite Composite) Figure 2. A portrayal of the internal operation of a DMFC. Electron Flow Oxygen Excess Bipolar Plates Hydrogen (Platinum/Graphite Composite) AGDL Plus Anode Catalyst (Platinum) Hydrogen Ions Electrolyte (Polystyrene Sulphonic Acid) CGDL AGDL Hydrogen CGDL Plus Cathode Catalyst (Platinum) Bipolar Plates Water (Platinum/Graphite Composite) Figure 3. A portrayal of the internal operation of a PEMFC. IEEE Electrific ation Magazine / ma r c h 201 8 29