For example, ultra-high purified hydrogen is needed for applications like proton exchange membrane fuel cells.
[1] The default large-scale purification of H2 produced in oil refineries exploits its very low boiling point of −253 °C.
[3][4] Pressure swing adsorption is used for the removal of carbon dioxide (CO2) as the final step in the large-scale commercial synthesis of hydrogen.
Impurities impact PEMFC using a range of mechanisms, these may include poisoning the anode hydrogen oxidation reaction catalysts, reducing the ionic conductivity of the ionomer and membrane, altering wetting behaviour of components or blocking porosity in diffusion media.
[8][9][10] While the hydrogen was generally found to be 'good'[8] violations of the standard have been reported, most frequently for nitrogen, water and oxygen.
[11] This standard has itself been criticised with revisions proposed to make it more lenient and therefore suitable for hydrogen distributed through a repurposed gas network.
[14] As the permissible concentrations for many impurities are very low this sets stringent demands on the sensitivity of the analytical methods.