Steam at the cathode combines with electrons from the external circuit to form hydrogen gas and negatively charged oxygen ions.Solid oxide electrolyzers, which use a solid ceramic material as the electrolyte that selectively conducts negatively charged oxygen ions (O 2-) at elevated temperatures, generate hydrogen in a slightly different way. Newer approaches using solid alkaline exchange membranes (AEM) as the electrolyte are showing promise on the lab scale. Electrolyzers using a liquid alkaline solution of sodium or potassium hydroxide as the electrolyte have been commercially available for many years. Anode Reaction: 2H 2O → O 2 + 4H + + 4e - Cathode Reaction: 4H + + 4e - → 2H 2Īlkaline electrolyzers operate via transport of hydroxide ions (OH -) through the electrolyte from the cathode to the anode with hydrogen being generated on the cathode side. At the cathode, hydrogen ions combine with electrons from the external circuit to form hydrogen gas.

The electrons flow through an external circuit and the hydrogen ions selectively move across the PEM to the cathode.

Water reacts at the anode to form oxygen and positively charged hydrogen ions (protons).

In a polymer electrolyte membrane (PEM) electrolyzer, the electrolyte is a solid specialty plastic material. Polymer Electrolyte Membrane Electrolyzers Different electrolyzers function in different ways, mainly due to the different type of electrolyte material involved and the ionic species it conducts. Like fuel cells, electrolyzers consist of an anode and a cathode separated by an electrolyte.

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