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alkaline fuel cell
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| An alkaline fuel cell consists of an alkaline electrolyte,
typically potassium hydroxide (KOH), sandwiched between an anode (negatively
charged electrode) and a cathode (positively charged electrode). The
processes that take place in the fuel cell are as follows: 1. Hydrogen
fuel is channeled through field flow plates to the anode on one side
of the fuel cell, while oxygen from the air is channeled to the cathode
on the other side of the cell. 2. At the anode, a platinum catalyst
causes the hydrogen to split into positive hydrogen ions (protons)
and negatively charged electrons. 3. The positively charged hydrogen
ions react with hydroxyl (OH-) ions in the electrolyte
to form water. 4. The negatively charged electrons cannot flow through
the electrolyte to reach the positively charged cathode, so they must
flow through an external circuit, forming an electrical current. 5.
At the cathode, the electrons combine with oxygen and water to form
the hydroxyl ions that move across the electrolyte toward the anode
to continue the process. |
AFCs' high performance is due to the rate at which chemical reactions take place in the cell. They have also demonstrated efficiencies near 60% in space applications.
The disadvantage of this fuel cell type is that it is easily poisoned by carbon dioxide (CO2). In fact, even the small amount of CO2 in the air can affect this cell's operation, making it necessary to purify both the hydrogen and oxygen used in the cell. This purification process is costly. Susceptibility to poisoning also affects the cell's lifetime (the amount of time before it must be replaced), further adding to cost.
Cost is less of a factor for remote locations, such as space or under the sea. However, to effectively compete in most mainstream commercial markets, these fuel cells will have to become more cost-effective. AFC stacks have been shown to maintain sufficiently stable operation for more than 8,000 operating hours. To be economically viable in large-scale utility applications, these fuel cells need to reach operating times exceeding 40,000 hours, something that has not yet been achieved due to material durability issues. This obstacle is possibly the most significant in commercializing this fuel cell technology.
Related category
• FUEL CELLSSource: U.S. Department of Energy
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