What is an electrolyzer?
(What does it do and how does it work)?
Written by: Maya Ardon
Edited by: Vanessa Lu Langley
An electrolyzer is a unit that uses electricity to split water into hydrogen and oxygen in a process called electrolysis (Hydrogen and Fuel Cell Technologies Office, n.d.). Electrolysis is viewed as a viable option for carbon-free hydrogen production that uses renewable and nuclear resources (Hydrogen and Fuel Cell Technologies Office, n.d.). Electrolyzers mimic most fuel cells as they consist of an anode and a cathode:
Anodes are the electrodes in a fuel cell that release electrons, and produce oxygen (resulting in oxidation) (Ma et al., 2009).
Cathodes are the electrodes in which electrons enter the cell, and produce hydrogen (resulting in reduction) (Ma et al., 2009).
The anode and the cathode are separated by an electrolyte, which is a solution that allows for ion transportation between the anode and the cathode in a fuel cell (Sedlak et al., 1981).
Electrolyzers work in different ways, since electrolyte material and the type of ions conducted through the electrolytes vary through each kind of unit. One common type of such a unit is a polymer electrolyte membrane electrolyzer, which doesn’t use a liquid as an electrolyte and has been viewed as a more durable, compact, and highly-operating form of electrolysis compared to units that use alkaline electrolytes (Millet, 2015). PEM production, however, is limited by economic properties such as cost and efficiency, especially in obtaining and maintaining the right kind of deionized water for PEM usage (Millet, 2015).
Electrolysis can produce hydrogen in a manner that produces zero greenhouse gas emissions depending on the source of electricity used, which is why hydrogen production using this method is being pursued for renewable options – such as wind, solar, and hydrothermal energy – as well as nuclear energy. It is important to note that current grid electricity is not suitable for electrolysis because much of the electricity produced is not generated from these renewable sources and is rather produced in an energy-intensive manner (Hydrogen and Fuel Cell Technologies Office, n.d.). By making renewable-based electricity options more cost-effective and either fully separating the electricity from the grid or using a mix, hydrogen production via electrolysis can overcome its current limitations (Hydrogen and Fuel Cell Technologies Office, n.d.).
Hydrogen and Fuel Cell Technologies Office. (n.d.). Hydrogen production: Electrolysis. energy.gov. Retrieved September 18, 2022, from https://www.energy.gov/eere/fuelcells/hydrogen-production-electrolysis
Ma, Z., Venkataraman, R., & Farooque, M. (2009). Fuel cells – molten carbonate fuel cells | Modeling. Encyclopedia of Electrochemical Power Sources, 519–532. https://doi.org/10.1016/b978-044452745-5.00272-0
Millet, P. (2015). Hydrogen production by polymer electrolyte membrane water electrolysis. Compendium of Hydrogen Energy, 255–286. https://doi.org/10.1016/b978-1-78242-361-4.00009-1
Sedlak, J.M., Austin, J.F., & LaConti, A.B. (1981). Hydrogen recovery and purification using the solid polymer electrolyte electrolysis cell. International Journal of Hydrogen Energy, 6(1), 45-51. https://doi.org/10.1016/0360-3199(81)90096-3