Incorporating MOF-NH 2 into the anode CL of PEMWE improved safety by preventing H 2 and O 2 mixing and demonstrated superior cycle performance compared to other functionalized MOFs. • Functional groups in the MOF effectively modified its surface area and pore size. • The functionalized MOF was integrated into the anode catalyst layer of PEMWE. • The MOF captured crossover hydrogen within the anode catalyst layer. • The H 2 concentration in O 2 was decreased to below the lower explosion limit (LEL). 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 H 2 -adsorbing capabilities. We evaluate the effects of MOFs with various functional groups on the H 2 concentration in O 2 stream and the electrochemical performance of the anode CL. The amine-functionalized MOF leads to the highest reduction in the H 2 concentration in O 2 stream. Additionally, the reversibility of the H 2 adsorption properties of the MOFs with temperature changes are verified. The amine-functionalized MOF leads to a H 2 volume fraction in O 2 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 H 2 volume fractions in O 2 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.

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