An electrode is a device that conducts electricity, typically used to make electrical connections or measure electrical potential. They are made of materials that are good conductors of electricity, such as metals.
Electrodes are used in many different applications, including batteries, fuel cells, electroplating, and welding. In these applications, electrodes play a critical role in transferring electrons between the device and an external circuit. For example, in a battery electrodes transfer electrons from the chemical reaction inside the battery to the load (e.g., light bulb) connected to the battery terminals.
In fuel cells and electrolyzers electrodes provide sites for reactions that generate or consume electric current respectively; these reactions occur at interfaces between an electrode material and an electrolyte through which ions can migrate.
Electrodes come in many shapes and sizes depending on their intended purpose.