(Invited) Ionomer-Free Porous-Transport Electrode Design for Proton-Exchange-Membrane Water Electrolysis

Clean hydrogen, which is set to reduce the carbon footprint for hard-to-decarbonize sectors, relies on large-scale deployment of water-electrolysis technologies, particularly proton-exchange-membrane water electrolyzers (PEMWEs). However, as iridium-based electrocatalysts remain the only option for PEMWEs, its low abundance is likely to become the bottleneck for a sustainable hydrogen economy. Therefore, developing PEMWEs at low iridium loading is an urgent task. Herein, we propose a high-performing and durable ionomer-free porous transport electrode (Ir PTE) that is fabricated using a facile physical vapor deposition method. This fabrication method creates a thin layer of nanosized iridium catalyst that is well attached to the porous transport layer surface. The proposed Ir PTE at ~ 0.1 mg Ir /cm 2 demonstrates voltage reduction of > 600 mV compared to the traditionally coated PTE at 1.8 A/cm 2 , and cell voltage degradation of only 29 mV at average rate of 0.58 mV/1000-cycles after 50k cycles of accelerated-stress tests at 4 A/cm 2 . 1 By further designing nano-channel features of the ionomer-free PTE, we demonstrate expedited localized transport features that allow durable operation of PEMWE for over 2000h with degradation rate of 11.7 µV h -1 . Moreover, the ionomer-free feature of Ir PTE enables facile recycling of multiple components of PEMWEs, which is critical to enable circular clean hydrogen economy. Reference: Lee, J. K. et al. Ionomer-free and recyclable porous-transport electrode for high-performing proton-exchange-membrane water electrolysis. Nat. Commun. 14 , 1–11 (2023).