FUEL CELL

Fuel cells are a source of electric power using hydrogen as fuel and oxygen as oxidant that produces exhaust is water, electrochemical energy is converted directly into electrical energy. In contrast to batteries that work is not continuous, the fuel cell can work continuously while fuel is supplied into the cell. The most important part in the fuel cell is two layers of electrodes and electrolyte. Electrolytes are substances that can conduct ions. Hydrogen gas (H₂) supplied to the anode, platinum (Pt) contained in the anode serves as a catalyst that will take electrons from hydrogen atoms. H⁺ ions are formed will pass through the electrolyte, while the electrons remain behind in the anode. Oxygen is supplied to the cathode, then H⁺ ions pass through the electrolyte binds with oxygen produces water (H₂O). This reaction would take place if there are electrons at the anode, while the cathode requires electrons. If the anode and the cathode connected to the electrons will flow and reduction-oxidation reactions will take place. The process is the basic principle of a fuel cell work.

One unit fuel cell consists of two electrodes and an electrolyte Pt – called single cell. The voltage obtained from a single cell is equal to about 1 volt dry cell, to be able to produce a high voltage or desired then the cells can be arranged in series or parallel. A collection of many single cell is called a stack. Stack made ​​of single cells and cell separator. Stack can be used for electronic equipment and household purposes, for example in mobile phones that require single cells, while for household use needed 20 more single cells and to car needed 200 more single cells. Currently the price of these materials are very expensive, so as to be applied to cars is still relatively expensive.

 

Figure 1.

Fuel Cell Structure

Based on the difference in electrolyte used, fuel cells can be divided into six types, i.e. polymer electrolyte fuel cell (PEFC), alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid oxide fuel cell (SOFC), and direct methanol fuel cell (DMFC). The sixth type, temperature and scale have different energy. Six types are then split into two, namely fuel cells working at high temperature and fuel cells that work at low temperatures. Every cell type has its own advantages and disadvantages. Excess cells work at temperatures below 2000 °C (AFC, PEMFC, DMFC and PAFC) is the start up and shut down faster, easy to make, and its use is widespread. The disadvantage, the catalyst is deactivated by impurities, especially CO in the hydrogen can react with the catalyst. Other losses are not able to use a liquid fuel directly. Cell SOFC and MCFC operates at temperatures above 2000 °C allows the use of solid fuels such as coal or liquid fuels such as gasoline directly without going through the reformer. Waste heat can be utilized as a steam generator. The catalyst does not need precious metals and catalysts are more resistant to CO. Weakness of these cells operate at high temperatures so that the start up and shut down a long, hard look for materials that are resistant to high temperature and because of the difference in temperature start up and shut down relatively large, it is possible that the cells will rupture. Use of a cell is limited to providing large-scale power centers e.g. power plants.