What is a fuel cell? How is it different from a battery?

An electrochemical cell is a device that can convert chemical energy into electrical energy through a chemical reaction. This chemical reaction involves the transfer of electrons from one material to another through an external circuit. In other words, an electrochemical cell harnesses the power of chemical reactions to generate electricity.

Such cells consist of two electrodes, called an anode and a cathode. The anode undergoes oxidation (loses electrons) and the cathode undergoes reduction (gains electrons). These electrodes are often immersed in an electrolyte which contains ions that facilitate the flow of electrons within the cell. When the electrodes are connected by a wire, an electrical current is generated as electrons flow from the anode to the cathode.

Redox reactions, short for reduction-oxidation reactions, are the foundation of the operations within an electrochemical cell. These reactions involve the transfer of electrons between two substances. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons.

For instance, in a fuel cell utilizing hydrogen as the fuel, hydrogen atoms lose electrons (oxidation) and oxygen molecules gain electrons (reduction). This electron flow from hydrogen to oxygen generates an electric current that can be used to power devices or systems. Redox reactions are crucial because they facilitate the movement of electrons, and it is this movement that produces usable electric energy.

The process of converting chemical energy into electrical energy is key to the operation of both fuel cells and batteries. Chemical energy conversion involves transforming the energy stored in the chemical bonds of molecules into an electrical form that can power various devices.

In a battery, this conversion occurs through a chemical reaction in a closed system, meaning once the reactants are spent, the energy conversion process stops until the battery is recharged or replaced. In a fuel cell, however, the chemical energy conversion continues as long as fuel and oxidant are supplied, making it capable of producing electricity continuously without the need for recharging.

Generating electricity from fuel cells involves continuously supplying a fuel, typically hydrogen, and an oxidant, usually oxygen from the air, to the anode and cathode of the cell, respectively. Within the cell, the hydrogen fuel is oxidized at the anode, producing protons and electrons. The protons pass through an electrolyte to the cathode while the electrons flow through an external circuit, producing an electrical current. At the cathode, the protons, electrons, and oxygen combine to form water, which is often the only byproduct, making fuel cells an environmentally friendly source of power.

Fuel cells are distinct from batteries in that they do not store energy; they convert energy from external fuel sources into electricity as long as the fuel supply is maintained. This quality makes them ideal for applications where refueling is practical and for situations that demand clean energy solutions.