An Electrolyzer is an electrochemical device to convert electricity and water into hydrogen and oxygen, these gases can then be used as a means to store energy for later use. This use can range from electrical grid stabilization from dynamic electrical sources such as wind turbines and solar cells to localized hydrogen production as a fuel for fuel cell vehicles.

The PEM electrolyzer utilizes a solid polymer electrolyte (SPE) to conduct protons from the anode to the cathode while insulating the electrodes electrically. With fast dynamic response times, large operational ranges, high efficiencies, and very high gas purities (99.999%), PEM electrolysis is a promising alternative for energy storage coupled with renewable energy sources. See the image on the right side for the operating principle and half cell reactions for anode and cathode electrodes.

Some of the advanced alkaline water electrolyzers would utilize a solid polymer electrolyte (in this case an anion exchange membrane or AEM) that would conduct hydroxyl ions from cathode to the anode while insulating the electrodes electrically.  AEM-based CCMs for alkaline electrolyzers would have superior performance compared to manually assembled membrane and electrode components because of the first one having the anode and cathode electrodes being immobilized directly on the membrane surface contrary to the later one having the catalyst material immobilized on the electrodes.