What is a fuel cell?

A fuel cell is an electrochemical energy conversion device that transforms chemical energy into electrical energy. It works based on the continuous flow of a fuel (usually hydrogen) and an oxidant (usually oxygen) that undergo a chemical reaction and, as a result, supplies electrical current to an external circuit.

Unlike a conventional battery, a fuel cell doesn’t die or need to be recharged. The reagents that put it into operation are stored outside it, so the battery can work as long as there is a flow of reagents.

A fuel cell can process more fuels (any substance that can be oxidized in a chemical reaction and can be supplied continuously) and oxidants (any fluid that can be reduced in the chemical reaction) besides hydrogen and oxygen.

This electrochemical device has high efficiency and a low impact on the environment. Since the energy is obtained from a process that does not involve thermal changes, the devices achieve greater efficiency, so the fuel cell has been put forward as a clean, emission-free alternative to conventional combustion processes.

What are the parts of a fuel cell?

A fuel cell is composed of:

Negative electrode or anode.
Positive electrode or cathode.
Intercalated electrolyte between each electrode of a material that facilitates the passage of ions (positively or negatively charged atoms), but not electrons (which are conducted to generate electricity).

Depending on its parts, the operation of a fuel cell consists of fuel oxidation at the anode with which electrons are generated that travel through an external circuit. At the cathode, a reduction reaction occurs independently of the anode, so the oxidizer recognizes the electrons coming from the external circuit.

In order for the system to stay in continuous operation, an ion transit must occur between negative and positive electrodes. This is possible thanks to the intercalated electrolyte that also prevents the flow of electrons inside, thereby enabling the circuit to charge.

What types of fuel cells are there?

The main types are:

Alkaline fuel cell (AFC): the oldest type and the most economical to manufacture. It contains electrodes saturated with an alkaline solution and separated by a hydroxide electrolyte. This type of battery was used by NASA to generate electricity and water for the crew of the Apollo mission.
Solid oxide fuel cell (SOFC): it contains a solid ceramic electrolyte layer that is heated to temperatures above one thousand degrees Celsius to conduct oxygen ions. It is used to generate energy in residential and commercial areas. The high temperature needed for it to reach operation can pose a problem when combined with certain materials in the external circuit.
Proton exchange membrane fuel cell (PEMFC): it uses a special electrolytic membrane to conduct protons between the anode and the cathode. While it weighs less than the other types, it has a higher power density, making it ideal for use in the field of transportation.
Molten carbonate fuel cell (MCFC): like solid oxide batteries, this type of battery operates at high temperatures, although the origin of the electrolyte is different.
Phosphoric acid fuel cell (PAFC): phosphoric acid is the basis of the electrolyte and is used to generate stationary energy, or that which is in a power range of 100 to 400 kW.