Chemical Cells and Fuel Cells

This section explains chemical cells and fuel cells covering, cells and batteries, fuel cells and hydrogen fuel cells. 

Cells and Batteries

A cell is a device that converts chemical energy into electrical energy through a chemical reaction. It consists of two electrodes (anode and cathode) and an electrolyte. When a chemical reaction occurs between the electrodes and the electrolyte, it produces an electric current.

• Primary cells (e.g., dry cells in non-rechargeable batteries) cannot be recharged after use, as the chemical reaction is irreversible.
• Secondary cells (e.g., rechargeable batteries in mobile phones, laptops, and electric cars) can be recharged because the chemical reactions that occur inside them are reversible.

Example of a common cell: A zinc-carbon cell, which is often found in household batteries, produces a current through the reaction between zinc and manganese dioxide.

Example of a rechargeable battery: A lithium-ion battery, commonly used in devices like smartphones and electric cars, allows the reversible flow of lithium ions between the anode and cathode.

Fuel Cells

A fuel cell is a type of cell that produces electricity through the chemical reaction between a fuel (often hydrogen) and oxygen, without burning the fuel. This process is more efficient than combustion and does not produce harmful emissions, making fuel cells an attractive alternative energy source.

Fuel cells work by allowing hydrogen gas to react with oxygen from the air to produce water, releasing energy in the form of electricity. This process can be summarised by the following equation:

Hydrogen Fuel Cell Formula:

$$2H_2 (g) + O_2 (g) \rightarrow 2H_2O (l) + \text{energy (electricity)}$$ 

In a hydrogen fuel cell:

• Hydrogen gas (H₂) is supplied to the anode, where it is split into protons (H⁺) and electrons (e⁻).
• The protons travel through an electrolyte to the cathode, while the electrons flow through an external circuit, generating electricity.
• Oxygen (O₂) from the air is supplied to the cathode, where it reacts with the protons and electrons to form water.

The main advantage of fuel cells is that their only waste product is water, making them a clean and sustainable energy source.

This reaction occurs in two half-reactions:

• At the Anode (oxidation):
• At the Cathode (reduction):

$$2H_2 (g) \rightarrow 4H^+ (aq) + 4e^-$$ 

Hydrogen molecules are split into protons (H⁺) and electrons (e⁻) at the anode.

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

Oxygen molecules react with protons (H⁺) and electrons (e⁻) at the cathode to form water.

The overall reaction shows the complete conversion of hydrogen and oxygen into water, with the production of electricity.

Summary of Key Points:

• Cells convert chemical energy into electrical energy, with primary cells being non-rechargeable and secondary cells being rechargeable.
• Fuel cells generate electricity by using a fuel (typically hydrogen) and oxygen, with the only by-product being water.
• The hydrogen fuel cell formula involves hydrogen reacting with oxygen to produce water and electricity.