Effect of metal–organic framework on hydrogen volume fraction in the oxygen-rich anode catalyst layer of proton exchange membrane water electrolyzer

Hydrogen permeation through the membranes in proton exchange membrane water electrolyzers (PEMWEs) poses a significant safety risk, as the mixing of hydrogen with oxygen at the anode can lead to dangerous concentration levels and potential explosion hazards. This study investigates the modification of the anode catalyst layer (CL) within the membrane electrode assembly (MEA) to enhance the operational safety of PEMWEs by incorporating metal–organic frameworks (MOFs) with H₂-adsorbing capabilities. We evaluate the effects of MOFs with various functional groups on the H₂ concentration in O₂ stream and the electrochemical performance of the anode CL. The amine-functionalized MOF leads to the highest reduction in the H₂ concentration in O₂ stream. Additionally, the reversibility of the H₂ adsorption properties of the MOFs with temperature changes are verified. The amine-functionalized MOF leads to a H₂ volume fraction in O₂ of less than 1.2 mol% at the anode, which is well below the lower explosion limit of 4 mol% and thus, ensures PEMWE safety. In contrast, carboxyl and sulfonic acid-functionalized MOFs result in H₂ volume fractions in O₂ of 1.9 mol% and 2.2 mol%, respectively, at 50 mA cm⁻². These results provide crucial insights for developing safer anode CLs for PEMWEs.