Introduction of proton‐exchange membranes as solid electrolytes has permitted the development of fuel cells that utilize hydrogen, reformate gas and methanol as reactants. Modern fuel cells have extended service life and reliability and increased power and energy density. The need for fuel cell operating in excess of 5000 h for transportation and 30 000 h for stationary applications has led to extensive investigations of the failure modes in an effort to understand the primary mechanical, chemical and electrochemical mechanisms. This chapter reviews the progress in understanding the limitations of fuel cell operation with historical and current state‐of‐the‐art membranes and suggests directions for achieving further improvement.

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Generating green hydrogen through proton exchange membrane electrolyzer cells (PEMECs) is promising to build future sustainable energy systems. Operating PEMECs at high current densities with high efficiency is a realistic strategy to reduce the capital costs of PEMECs and increase their sustainability. Herein, an Ir-integrated electrode was developed via facile electrodeposition as an efficient anode for PEMECs, successfully achieving high-current operation of up to 6 A/cm 2 . More importantly, the electrode shows excellent stability under an ultrahigh current density of 5 A/cm 2 , showing almost no performance loss after the stability test. Further studies indicate that a platinum protection layer on Ti substrates plays a crucial role in superior performance and stability, which not only provides electrodes with improved electrical conductivity resulting in improved catalyst activity but also enhances the crack-free catalyst layer achieving catalysts' adhesion improvement to the substrate and prevents substrate oxidation. With platinum, the cell voltage can be improved by 33, 59, and 87 mV at current densities of 2, 4, and 6 A/cm 2 , respectively. Overall, considering efficient high-current operation capability, remarkable stability, and significantly simplified and low-cost fabrication process with easy scalability, the developed integrated electrodes are believed to have great potential in future sustainable energy systems.

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