Electrolysis is a process that uses an electric current to split water molecules into hydrogen and oxygen atoms. This process can be utilized at a commercial scale to convert electricity to hydrogen gas, often referred to as “power-to-gas.” Electrolysis itself does not produce any byproducts other than hydrogen and oxygen. The hydrogen produced through electrolysis can be used as a renewable energy source in various applications, including transportation, power generation, and industrial processes.

The principle mechanism of electrolysis is based on the fact that water is made up of hydrogen and oxygen atoms. When an electric current is passed through water, it causes the hydrogen and oxygen atoms to separate. The electric current is used to split the water molecule into its constituent parts, with the hydrogen ions (H+) moving towards the cathode and water react at the anode. At the cathode, the hydrogen ions combine with electrons to form hydrogen gas (H2), while at the anode, water combine with electrons to form oxygen gas (O2).

There are different types of electrolysis, including alkaline water electrolysis and proton exchange membrane (PEM) electrolysis. Alkaline water electrolysis is a key technology for large-scale hydrogen production powered by renewable energy. PEM electrolysis cells play a vital role in high-purity and sustainable hydrogen production by utilizing the DC power from renewable energy sources. The hydrogen produced through electrolysis can be used as a renewable energy source in various applications, including transportation, power generation, and industrial processes. However, it is important to note that it takes more energy to produce hydrogen through electrolysis than hydrogen produces when converted to useful energy; thus the hydrogen must be generated via the renewable energy sources for the sustainable energy.

PEM stands for Proton Exchange Membrane, which is a type of fuel cell technology that uses a solid polymer electrolyte to conduct protons from the anode to the cathode. PEM technology is used in various applications, including fuel cells and electrolyzers. PEM electrolyzers generally exhibit high energy conversion efficiency, allowing them to produce more hydrogen per unit of electricity input, and can quickly adapt to fluctuating power input from renewable sources, making them ideal for grid-balancing applications. Furthermore, the solid polymer electrolyte in PEM electrolyzers helps produce hydrogen with high purity, which is beneficial for certain applications, such as fuel cell vehicles and electronics.(1) Alkaline electrolysis is a type of electrolysis that uses an alkaline electrolyte solution, typically potassium hydroxide (KOH) or sodium hydroxide (NaOH), to conduct electricity and split water molecules into hydrogen and oxygen atoms. Alkaline electrolysis cells can achieve high energy conversion efficiency, allowing them to produce more hydrogen per unit of electricity input, and typically have lower capital costs than other types of electrolysis cells due to the use of inexpensive materials, such as nickel catalysts. However, alkaline electrolysis cells are sensitive to impurities in the feedwater, which can cause degradation of the catalyst and reduce system performance. (2)

(1) https://www.hydrogennewsletter.com/a-comprehensive-analysis-on-pem-electrolyzer-vs-aem-electrolyzer/
(2) https://www.energy.gov/sites/default/files/2022-02/7-TEA-Liquid%20Alkaline%20Workshop.pdf