Optimizing Ionomer Distribution in Anode Catalyst Layer for Stable Proton Exchange Membrane Water Electrolysis.

The high cost of PEMWE originates from the usage of precious materials, insufficient efficiency and lifetime. In this work, we identified an important degradation mechanism of PEMWE caused by dynamics of ionomers over time in anode catalyst layer (ACL), which is a purely mechanical degradation of microstructure. Contrary to conventional understanding that the microstructure of ACL is static, the micropores are inclined to be occupied by ionomers due to the localized swelling/creep/migration, especially near the ACL/PTL (porous transport layer) interface, where they form transport channels of reactant/product couples. Consequently, the ACL with increased ionomers at PTL/ACL interface exhibited rapid and continuous degradation. Additionally, we discovered a close correlation between the microstructure of ACL and the catalyst ink. Specifically, if more ionomers migrate to the top layer of the ink, more ionomers accumulate at the ACL/PEM interface, leaving fewer ionomers at the ACL/PTL interface. Therefore, we successfully optimized the ionomer distribution in ACL, which exhibited reduced ionomers at the ACL/PTL interface and enriched ionomers at the ACL/PEM interface, reducing the decay rate by a factor of three when operation at 2.0 A/cm 2 and 80 °C. Our findings provide a general way to achieve low-cost hydrogen production. This article is protected by copyright. All rights reserved.