# Fuel Cell

## What is a Fuel Cell?

A fuel cell is that device which is widely used these days. By using fuel cells we can generate electricity through chemical reactions. Fuel cells are very helpful in thermal power plants. They are a pollution-free method of producing electricity and can produce 70% more electricity than other thermal plants that have an efficiency less than 40%. In general, the galvanic cells that convert the energy of combustion of fuels like hydrogen into electrical energy are called fuel cells.

### Working of a fuel cell

Let us study one of the most successful fuel cells which uses the reaction between hydrogen and oxygen. In Apollo space programme, the electrical power was provided by the same cell. It helped in two ways- when it was heated it was used as a fuel and after it was condensed it again added to the drinking water which helped the astronauts.
In this cell hydrogen and oxygen are passed through carbon electrodes into the concentrated sodium hydroxide solution. Catalysts are also used here that are finely divided platinum or palladium metal. They are fixed in the electrodes to increase the rate of reaction.

The reaction is-

Cathode: $O_2(g)+ 2H_2O(l) +4e^- \rightarrow 4OH^-(aq)$

Anode: $2H_2(g)+ 4OH^-(aq) 4H_2O(l) + 4e^-$

Overall reaction: $2H_2(g) + O_2(g) 2H_2O$

## Types of Fuel cells:

We know, fuel cells are electrochemical cells that convert chemical energy into electricity through an electrochemical reaction. They are named after their electrolyte. There are numerous fuel cell types that have a similar working pattern. They are stated below with a brief description.

### Polymer Electrolyte Membrane Fuel cell

Polymer electrolyte membrane (PEM) fuel cell is also termed as Proton exchange membrane fuel cells. It is a form of a fuel cell that is used to transfer applications, portable fuel cell applications, and stationary fuel cell applications. They are characterized by features such as polymer electrolyte membrane and pressure that range from 50° to 100° Celsius.

Various components of PEM is listed below:

• Current Collectors
• Electrodes
• Membrane
• Catalyst

### Phosphoric Acid Fuel Cells

It is a form of a fuel cell where liquid phosphoric acid is used as an electrolyte. The electrode is composed of carbon paper. It involves the following electrode reactions.

Anode: 2H2(g) → 4H+ + 4e‾

Cathode: O2(g) + 4H+ + 4e‾ → 2H2O

Overall: 2 H2 + O2 → 2H2O

PAFC has its applications in various fields. They are used in bus and stationary power generators. One of the disadvantages of phosphoric acid fuel cells is its use of an acidic electrolyte. Because when components are exposed to phosphoric acid, it leads to corrosion.

Solid Acid Fuel Cells

It is a form of fuel where the electrolyte is a solid acid material. It possesses a molecular structure similar to that of salts at low temperature. Following illustrates electrode reactions for solid acid fuel cells.

Anode: H2 → 2H+ + 2e

Cathode: ½O2 + 2H+ + 2e → H2O

Overall: H2 + ½O2 → H2O

SAFC finds its applications in various fields. It is well suited for remote places where other fuel cells are difficult to implant. They are used in military applications.

### Molten Carbonate Fuel Cell

Molten Carbonate Fuel Cells operates at a high temperature of six hundred degree Celsius. They are presently designed for military, natural gas, biogas, industries, and coal-based power plants. The electrode of a molten carbonate fuel cell is made up of molten carbonate salt mixture.

## Applications of fuel cells:

• Fuel cells are used in transportation.They are not used on a large scale today but automobile industries are planning to launch the vehicles which are run by fuel cells.
• As we know that fuel cells are portable i.e. it can be taken anywhere. This helps in military applications of fuel cells, they can also be used as torches. Fuel cells are used for electronic gadgets like camera, laptops etc.
• Fuel cells have many advantages over conventional cells as they produce very less amount of harmful greenhouse gases. The byproduct of fuel cells is only heat and water.