4.7.1 Advantages and Disadvantages of Fuel Cells

Advantages:

• Hydrogen-oxygen fuel cells are highly efficient since they convert fuel directly into electricity with very little waste.
• Fuel cells are a source of clean energy, as they do not produce harmful pollutants. They emit water vapour only.
• Fuel cells are highly reliable, as they have no moving parts.
• They also have a long life span with little maintenance.
• Hydrogen-oxygen used in fuel cells is obtained from renewable energy sources.

Disadvantages:

• Hydrogen is highly inflammable and explosive in nature.
• It requires careful handling for storage and use.
• So, it cannot be transported easily from one place to another.
• Hydrogen used in fuel cells is produced by electrolysis of water, which is very expensive.

Comparison with Gasoline Engines:

Unlike fuel cells, gasoline-powered combustion engines in vehicles emit pollutants, including:

• carbon dioxide
• oxides of nitrogen and sulphur

These pollutants cause pollution and create smog. These pollutants cause respiratory problems and other health issues. Moreover, gasoline is obtained from non-renewable sources of energy.

Summary Table

Intermediate Level

How a battery works:

• Anode is oxidized, releasing electrons.
• Electrons flow through the external circuit to the cathode.
• At the cathode, electrons reduce the oxidizing agent.

How a fuel cell works:

• Hydrogen is passed through the anode compartment.
• Oxygen is passed through the cathode compartment.
• The middle compartment contains hot aqueous KOH.
• At the anode, hydrogen is oxidized to water.
• At the cathode, oxygen is reduced to hydroxide ions.
• The energy released is converted to electrical energy.

Advantages of fuel cells:

• Highly efficient
• Clean energy (water vapour only)
• Reliable (no moving parts)
• Long life span
• Uses renewable energy sources

Disadvantages of fuel cells:

• Hydrogen is inflammable and explosive
• Requires careful handling
• Cannot be transported easily
• Hydrogen production by electrolysis is expensive

Important Points

• - Battery = galvanic cell or group of galvanic cells joined in series.
• - It generates electric current by a redox reaction.
• - Anode is oxidized, releasing electrons.
• - Electrons flow through the external circuit to the cathode.
• - At the cathode, electrons reduce the oxidizing agent.
• - Examples of batteries: dry cells, storage cells, mercury batteries.
• - Fuel cell = special galvanic cell based on the reaction between oxygen and hydrogen.
• - Hydrogen-oxygen fuel cell:
• - Three compartments separated by porous carbon electrodes
• - Electrodes contain platinum as a catalyst
• - Middle compartment contains hot aqueous KOH
• - Hydrogen passed through anode compartment
• - Oxygen passed through cathode compartment
• - At anode: hydrogen is oxidized to water
• - At cathode: oxygen is reduced to hydroxide ions
• - Only chemical product: water
• - Advantages of fuel cells: efficient, clean, reliable, long life, renewable
• - Disadvantages of fuel cells: hydrogen is explosive, expensive to produce, difficult to transport
• - Gasoline engines emit pollutants (CO₂, NOx, SOx) and use non-renewable sources.

Remember

• - Battery = galvanic cell or group of cells joined in series.
• - Battery generates electricity by a redox reaction.
• - Anode is oxidized; cathode is reduced.
• - Fuel cell = special galvanic cell using H₂ and O₂.
• - Product of H₂-O₂ fuel cell = water.
• - Fuel cell advantages: efficient, clean, reliable, long life.
• - Fuel cell disadvantages: hydrogen is explosive, expensive, difficult to transport.
• - Gasoline engines emit pollutants and use non-renewable sources.

Common Mistakes

Quick Revision

Battery — A Source of Electrical Energy:

A battery is a galvanic cell, or a group of galvanic cells joined in series. It generates electric current by a redox reaction. When connected in a circuit its anode is oxidised by releasing electrons. These electrons through the external circuit begin to flow towards the cathode. At the cathode, these electrons reduce the oxidizing agent present in the electrolyte. Examples of batteries are dry cells, storage cells, mercury batteries etc.

Fuel Cell:

A fuel cell is a special type of galvanic cell which is based upon the reaction between oxygen and a gaseous fuel hydrogen. When hydrogen burns in air, an exothermic reaction occurs and a lot of chemical energy is released in the form of heat and light. In this reaction, hydrogen is oxidized to water.

• 2H_2(g) + O_2(g) → 2H₂O_(g) + heat

The energy released from the reaction of hydrogen with oxygen to form water is converted to electrical energy. A hydrogen-oxygen fuel cell has three compartments separated from one another by porous carbon electrodes. These electrodes contain platinum as a catalyst. The middle compartment contains a hot aqueous solution of KOH. Hydrogen gas is passed through the anode compartment and oxygen is passed through the cathode compartment. At the anode, hydrogen is oxidized to water and at the cathode oxygen is reduced to hydroxide ions.

• Anode reaction:
• 2H_2(g) + 4OH^-_(aq) → 4H₂O_(g) + 4e^-

4.7.1 Advantages and disadvantages of fuel cells:

Hydrogen-oxygen fuel cells are highly efficient since they convert fuel directly into electricity with very little waste. Fuel cells are a source of clean energy, as they do not produce harmful pollutants. They emit water vapour only. Moreover, fuel cells are highly reliable, as they have no moving parts. They also have a long life span with little maintenance. Hydrogen-oxygen used in fuel cells is obtained from renewable energy sources.

Unlike fuel cells, gasoline-powered combustion engines in vehicles emit pollutants, including carbon dioxide, oxides of nitrogen and sulphur, which cause pollution and create smog. These pollutants cause respiratory problems and other health issues. Moreover, gasoline is obtained from non-renewable sources of energy.

Fuel cells have a few disadvantages. Hydrogen is highly inflammable and explosive in nature. It requires careful handling for storage and use. So, it cannot be transported easily from one place to another. Hydrogen used in fuel cells is produced by electrolysis of water which is very expensive.

60-Second Revision

• Battery = galvanic cell or group of cells joined in series.
• Battery generates electricity by a redox reaction.
• Anode is oxidized; cathode is reduced.
• Fuel cell = special galvanic cell using H₂ and O₂.
• Product of H₂-O₂ fuel cell = water.
• Fuel cell advantages: efficient, clean, reliable, long life.
• Fuel cell disadvantages: hydrogen is explosive, expensive, difficult to transport.
• Gasoline engines emit pollutants and use non-renewable sources.
• Examples of batteries: dry cells, storage cells, mercury batteries.
• ⚠️ Warning: hydrogen is highly inflammable and explosive — it must be handled carefully.