An alkaline electrolyzer stack is a device that uses an aqueous alkaline solution to split water molecules into hydrogen and oxygen:

 An alkaline electrolyzer stack is a device that uses an aqueous alkaline solution to split water molecules into hydrogen and oxygen: 

Electrodes

Two metal electrodes, the cathode and anode, are dipped into the solution and separated by a diaphragm. The cathode produces hydrogen, and the anode produces oxygen. 

Diaphragm

A porous diaphragm separates the hydrogen and oxygen. It's typically made of chrysotile asbestos and is anion-selective. 

Electrolyte

The alkaline solution is usually 25–30 wt% NaOH or KOH. 

Current

When a DC voltage is applied between the electrodes, current flows through the cells and splits the water molecules. 

Gas collection

The gas from each cell is collected in ducts and fed into the electrolyte system. 

Electrolyte system

This system separates the gases from the lye, cools and circulates the lye back to the stack, and has water seals and gas separators. 

Pressurized Alkaline Electrolyser Stack for Green Hydrogen Generator

Alkaline electrolyzers are the oldest type of electrolyzer. They are the most advanced and produced in the highest volumes. The capital cost of alkaline electrolyzers is relatively low because of the low cost of the electrolyte and the use of lower-cost catalysts.