Fuel Cells in Chemistry: Definition, Working Principle & Examples

Fuel cell is a crucial topic in chemistry, linking real-life energy solutions to concepts like redox reactions, electrochemistry, and sustainable technology.

On this Vedantu page, you’ll learn all about fuel cells, their working, types, chemical reactions, and much more with easy explanations. Let’s explore fuel cells step-by-step and relate them to your Class 12 syllabus and competitive exam prep!

What is Fuel Cell in Chemistry?

A fuel cell is an electrochemical device that converts the chemical energy of a fuel (usually hydrogen) and an oxidizing agent (like oxygen) directly into electricity, water, and heat. Unlike ordinary batteries, fuel cells produce electricity continuously as long as they are supplied with fuel and oxidant. 

This topic is key in chapters like Electrochemical Cells, Redox Reactions, and energy conversion, forming a foundation for modern chemistry and technology studies.

Molecular Formula and Composition

The main fuel cell studied in school chemistry is the hydrogen-oxygen fuel cell. Its overall reaction is:
2H₂ + O₂ → 2H₂O
It contains two electrodes (anode and cathode) separated by an electrolyte. Most commonly, an alkaline solution or polymer membrane acts as the electrolyte, while platinum, palladium, or carbon is used as electrode material.

Preparation and Synthesis Methods

Fuel cells are manufactured by assembling an anode, cathode, and the correct electrolyte media (such as sodium hydroxide solution for alkaline fuel cells or a polymer membrane for PEM fuel cells). Hydrogen gas is supplied continuously to the anode and oxygen/air to the cathode. 

Electrodes are often coated with finely divided platinum to increase reaction rates. In real-world settings, hydrogen is obtained by electrolysis of water or industrial gas reforming methods.

Physical Properties of Fuel Cells

Fuel cells don’t have typical chemical properties like boiling/melting points, but their performance is defined by:
- Operating temperatures: From 50°C (PEM cells) up to 1000°C (solid oxide cells)
- Fuel types: Hydrogen, methanol, natural gas
- Electrolyte: Liquid alkaline, phosphoric acid, molten carbonate, or solid oxide
- Efficiency: Can reach 60–70% (much higher than combustion engines)

Chemical Properties and Reactions

A fuel cell relies on simultaneous oxidation (at anode) and reduction (at cathode). Here is the breakdown for a hydrogen-oxygen fuel cell using alkaline electrolyte:

1. Anode (Hydrogen side):
2H₂ + 4OH^– → 4H₂O + 4e^–

2. Cathode (Oxygen side):
O₂ + 2H₂O + 4e^– → 4OH^–

3. Net cell reaction:
2H₂ + O₂ → 2H₂O

Electrons travel through the external circuit, producing electricity directly from the chemical energy of the reactants.

Frequent Related Errors

• Assuming fuel cells store energy—they generate energy as long as fuel is supplied.
• Confusing fuel cells with batteries; batteries have limited internal chemicals, while fuel cells have external fuel supply.
• Mixing up the direction of electron flow (anode to cathode via external circuit).
• Forgetting to include the catalyst’s role in increasing reaction rate, especially at lower temperatures.

Uses of Fuel Cell in Real Life

Fuel cells are found in many modern applications due to their high efficiency and environmental friendliness:

• Powering electric vehicles (hydrogen fuel cell cars/trains)
• Backup power for hospitals and data centers
• Supplying electricity in spacecraft (e.g., Apollo missions)
• Portable and stationary energy generation
• Emerging technology for home energy systems

They are also studied extensively for future sustainable energy solutions, an area often discussed in Vedantu’s advanced chemistry sessions.

Relation with Other Chemistry Concepts

Fuel cells are closely linked to topics such as Electrochemical Cells, Batteries, and Faraday’s Laws of Electrolysis. 

Understanding oxidation-reduction reactions, electrode processes, catalysts, and energy conservation is crucial for mastering fuel cell concepts. Linking these ideas together helps with holistic chemistry learning and exam success.

Step-by-Step Reaction Example

1. Setup: Assemble two gas chambers (hydrogen and oxygen), a pair of electrodes, and electrolyte (such as KOH solution).

2. Anode Reaction: Hydrogen gas passes over the anode, splitting into protons and electrons. Reaction: 2H₂ + 4OH^– → 4H₂O + 4e^–

3. Electrons flow through external circuit to cathode, generating electric current.

4. Cathode Reaction: Oxygen reacts with water and incoming electrons. Reaction: O₂ + 2H₂O + 4e^– → 4OH^–

5. The cycle continues as long as fuel is supplied.

Final Answer: Electricity is produced with water as the only by-product.

Lab or Experimental Tips

To quickly remember fuel cell reactions, always start with the reactant gases (hydrogen and oxygen for school-level fuel cells) and follow the electrons from the anode to cathode. Label the external circuit and mention the catalyst used (often platinum).

Try This Yourself

• Draw a labelled diagram of a hydrogen-oxygen fuel cell and write both electrode reactions.
• List two advantages and two limitations of using fuel cells over convetional petrol engines.
• Compare a fuel cell and a battery using three key differences.

Final Wrap-Up

We explored fuel cells—their structure, working principle, reactions, advantages, and importance in the shift towards green energy. From powering cars to spacecraft, fuel cells offer a direct, pollution-free method of generating electricity. 

If you wish to master more topics such as Faraday’s laws, check out Vedantu’s online chemistry classes and NCERT-friendly resources. Keep learning and stay curious!