High-pressure electrolysis

[1] The difference with a standard proton exchange membrane (PEM) electrolyzer is the compressed hydrogen output around 12–20 megapascals (120–200 bar)[2] at 70 °C.

[6] There is also an importance for the electrolyser stacks to be able to accept a fluctuating electrical input, such as that found with renewable energy.

[8] At ultra-high pressures the water solubility and cross-permeation across the membrane of H2 and O2 is affecting hydrogen purity, modified PEMs are used to reduce cross-permeation in combination with catalytic H2/O2 recombiners to maintain H2 levels in O2 and O2 levels in H2 at values compatible with hydrogen safety requirements.

[10] Mitsubishi is pursuing such technology with its High-pressure hydrogen energy generator (HHEG) project.

[16] Honda installed its Smart Hydrogen Station (SHS) in Los Angeles for use by fuel cell automobiles.