Get to Know About Fuel Cell Thermodynamics

A fuel cell is an electrochemical cell that creates electrical energy from the fuel through an electrochemical process. These cells require a constant supply of fuel and an oxidising agent to maintain the reactions that generate electricity (generally oxygen). As a result, these cells will continue to create electricity even if their fuel and oxygen supplies are turned off.

A fuel cell is similar to an electrochemical cell in that it has a cathode, an anode, and an electrolyte. In these cells, the electrolyte allows protons to move about.

Working of Fuel Cell

The reaction between hydrogen and oxygen can be used to generate power in a fuel cell. Such a cell was utilised in the Apollo space programme and served two purposes: as a source of fuel and as a source of drinking water.

This fuel cell worked by transferring hydrogen and oxygen into a concentrated sodium hydroxide solution via carbon electrodes. The cells’ response can be written as follows:

Cathode Reaction – O2 + 2H2O + 4e– → 4OH–

Anode Reaction – 2H2 + 4OH– → 4H2O + 4e–

Net Cell Reaction – 2H2 + O2 → 2H2O

This electrochemical response, on the other hand, has a slow reaction rate. This difficulty can be solved by using a catalyst such as platinum or palladium. To maximise the effective surface area, the catalyst is finely split before being integrated into the electrodes.

Types of Fuel Cells

Fuel cells come in a variety of shapes and sizes, but they all work in the same way. Some of these fuel cell types are discussed in this section :- 

The Polymer Electrolyte Membrane (PEM) Fuel Cell

• These cells are also known as proton exchange membrane fuel cells (or PEMFCs).
• These cells work at temperatures ranging from 50 to 100 degrees Celsius.
• The electrolyte in PEMFCs is a polymer that can conduct protons.
• A typical PEM fuel cell consists of bipolar plates, a catalyst, electrodes, and a polymer membrane.
• Despite its environmentally benign applications in transportation, PEMFCs can also be utilised for fixed and portable power generation.

Phosphoric Acid Fuel Cell

• The Phosphoric Acid Fuel Cell is a type of fuel cell that uses phosphoric acid
• The electrolyte in these fuel cells is phosphoric acid, which is used to channel H++.
• Working temperatures for these cells range from 150°C to 200°C.
• Because phosphoric acid is non-conductive, electrons are forced to travel to the cathode via an external connection.
• Due to the acidic nature of the electrolyte, the components of these cells corrode or oxidise over time.

Solid Acid Fuel Cell

• The electrolyte in these fuel cells is a solid acid substance.
• The molecular structures of these solid acids are organised at low temperatures.
• At higher temperatures, a phase shift can occur, resulting in a massive increase in conductivity.
• Solid acids such as CsHSO4 and CsH2PO4 are examples (cesium hydrogen sulphate and cesium dihydrogen phosphate respectively).

Alkaline Fuel Cell

• This is the fuel cell that was utilised as the major source of electricity in the Apollo space mission.
• In these cells, an aqueous alkaline solution is utilised to saturate a porous matrix, which is then used to separate the electrodes one by one.
• The operating temperatures of these cells are fairly low (about 90°C).
• These cells are incredibly effective.

Fuel Cells Based on Solid Oxide

• These cells are used with a solid oxide or ceramic electrolyte (such as yttria-stabilised zirconia).
• These fuel cells are both extremely efficient and reasonably priced (theoretical efficiency can even approach 85 percent 
• These cells operate at extremely high temperatures (lowest limit of 600°C, usual operating temperatures of 800 to 1000°C).
• Solid oxide fuel cells are confined to stationary applications due to their high operating temperatures.

Carbonate Molten Fuel Cell

• The electrolyte in these cells is lithium potassium carbonate salt. This salt becomes liquid at high temperatures, allowing carbonate ions to move around.
• These fuel cells, like SOFCs, have a comparatively high working temperature of 650°C.
• The anode and cathode of this cell are prone to corrosion due to the high operating temperature and presence of the carbonate electrolyte.
• These cells can be fueled by carbon-based fuels such as natural gas and biogas.

What are the Benefits of Using Fuel Cells?

• More Stable: The fuel cells ensure that the various components within and surrounding the cell move as little as possible. As a result, they are more dependable and convenient than a standard cell phone.
• Protects Natural Resources: The separation of atoms and generation of energy in fuel cells is a very clean and ergonomic technology. As a result, it is beneficial to natural resources.
• If the cell is to be integrated with other technologies, fuel cells are by far the most ergonomic choice. You may make your own combination of turbines and solar panels. As a result, it has been established as complementary.
• Fuel cells may create power at scales ranging from a few milliwatts to many megawatts. It also assists in the powering of a variety of gadgets, including mobile phones and dwellings. As a result, they’re scalable.

Conclusion

A fuel cell is an electrochemical cell that uses an electrochemical reaction to create electrical energy from fuel. To keep the processes that generate electricity going, these cells need a constant supply of fuel and an oxidising agent (usually oxygen). As a result, until the supply of fuel and oxygen is shut off, these cells can continue to generate power.Fuel cells, despite being conceived in 1838, did not enter commercial usage until a century later, when NASA utilised them to power space capsules and satellites. Many establishments, including businesses, commercial buildings, and residential buildings, now use these devices as a major or secondary source of electricity.

A cathode, anode, and electrolyte make up a fuel cell, which is comparable to an electrochemical cell. The electrolyte in these cells allows protons to travel around.