Fuel cells are ingenious devices that convert chemical energy into electricity. They work by oxidizing fuel at the anode and reducing oxygen at the cathode , with electrons flowing through an external circuit to generate power.
The key components of a fuel cell are the electrolyte , electrodes, and catalyst. These work together to facilitate the electrochemical reactions, with the anode oxidizing fuel and the cathode reducing oxygen to produce water as the main byproduct.
Fuel Cell Components and Operation
Principles of fuel cell operation
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Convert chemical energy directly into electrical energy through electrochemical reactions
Fuel (hydrogen) oxidized at anode releases electrons and produces protons (H+)
Oxidant (oxygen from air) reduced at cathode consumes electrons and combines with protons forming water
Electrochemical reactions occur at electrode-electrolyte interface
Anode reaction: H 2 → 2 H + + 2 e − H_2 \rightarrow 2H^+ + 2e^- H 2 → 2 H + + 2 e −
Cathode reaction: 1 2 O 2 + 2 H + + 2 e − → H 2 O \frac{1}{2}O_2 + 2H^+ + 2e^- \rightarrow H_2O 2 1 O 2 + 2 H + + 2 e − → H 2 O
Overall reaction: H 2 + 1 2 O 2 → H 2 O H_2 + \frac{1}{2}O_2 \rightarrow H_2O H 2 + 2 1 O 2 → H 2 O
Electrons flow through external circuit from anode to cathode generating electric current
Protons migrate through electrolyte from anode to cathode completing the circuit
Components of fuel cells
Electrolyte
Conducts ions (protons) between anode and cathode
Separates fuel and oxidant preventing direct mixing and combustion
Common electrolytes include polymer electrolyte membranes (PEM) and solid oxide electrolytes (SOFC)
Electrodes (anode and cathode)
Provide sites for electrochemical reactions
Anode: site of fuel oxidation reaction, releases electrons
Cathode: site of oxidant reduction reaction, accepts electrons
Typically made of porous materials with high surface area (carbon, metal foams)
Catalyst
Facilitates and accelerates electrochemical reactions at electrodes
Lowers activation energy barrier allowing reactions at lower temperatures
Common catalysts include platinum, palladium, and their alloys
Often dispersed as nanoparticles on electrode surface maximizing active surface area
Anode vs cathode reactions
Anode reaction
Oxidation of fuel (hydrogen)
Releases electrons to external circuit
Produces protons that migrate through electrolyte to cathode
Example: H 2 → 2 H + + 2 e − H_2 \rightarrow 2H^+ + 2e^- H 2 → 2 H + + 2 e −
Cathode reaction
Reduction of oxidant (oxygen from air)
Accepts electrons from external circuit
Combines protons from electrolyte with oxygen forming water
Example: 1 2 O 2 + 2 H + + 2 e − → H 2 O \frac{1}{2}O_2 + 2H^+ + 2e^- \rightarrow H_2O 2 1 O 2 + 2 H + + 2 e − → H 2 O
Fuel and oxidant supply
Continuous supply of fuel and oxidant essential for sustained fuel cell operation
Fuel (hydrogen) must be continuously fed to anode
Oxidant (oxygen from air) must be continuously fed to cathode
Fuel and oxidant flow rates affect fuel cell performance
Insufficient flow rates lead to mass transport limitations and reduced power output
Excessive flow rates lead to inefficient fuel utilization and increased system complexity
Fuel and oxidant purity crucial for optimal fuel cell performance
Impurities can poison catalyst reducing effectiveness and lifetime
Fuel impurities (carbon monoxide) adsorb onto catalyst surface blocking active sites
Oxidant impurities (sulfur compounds) degrade catalyst and electrolyte
Fuel and oxidant humidification may be necessary for certain fuel cell types
Polymer electrolyte membrane fuel cells require proper humidification maintaining ionic conductivity
Insufficient humidification leads to membrane dehydration and increased ohmic losses
Excessive humidification leads to flooding of electrodes and mass transport limitations