[3][4] Polymer electrolyte membrane electrolysis uses expensive platinum-group metals (PGMs) such as platinum, iridium, and ruthenium as a catalyst.

The diaphragm only allows water and hydroxide ions to pass through, but does not completely eliminate gas cross-over.

Oxygen gas can enter the hydrogen half-cell and react on the cathode side to form water, which reduces the efficiency of the cell.

[12] AEM based on an aromatic polymer backbone is promising due to its significant cost reduction.

Compare to Nafion membrane use in PEM, the production of Nafion required highly toxic chemicals, which increased the cost (>1000$/m2)[13][14] and fluorocarbon gas is produced at the production stage of tetrafluoroethylene, which poses a strong environmental impact.

[15] Fluorinated raw materials are inessential for AEM, allowing for a wider selection of low-cost polymer chemistry.

There is less academic literature on pure-water fed AEM electrolysers compared to the usage of KOH solution.

[11] The major technical challenge facing a consumer level AEM electrolyser is the low durability of the membrane, which refers to the short device lifetime or longevity.

[9] To overcome the obstacles for a large scale usage of AEM, increasing ionic conductivity and durability is essential.

The quaternary ammonium (QA) headgroup is commonly employed to attach polymer matrices in AEM.

A substrate must conduct electricity, support the catalyst mechanically, and remove gaseous products.

[17][11] Other methods include electrodeposition, magnetron sputtering, chemical electroless plating, and screen printing onto the substrate.

[11][20] Ionomers act as a binder for the catalyst, substrate support, and membrane, which also provide OH− conducting ions and increase electrocatalytic activities.