Ordered Membrane Electrode Assembly with Drastically Enhanced Proton and Mass Transport for Proton Exchange Membrane Water Electrolysis.

In this work, an ordered membrane electrode assembly (MEA) based on a cone Nafion array with gradient Nafion distribution, tightly bonded catalytic layer/proton exchange membrane (CL/PEM) interface, and abundant vertical channels has been engineered by an anodic aluminum oxide template and magnetron sputtering method. Benefiting from a highly efficient CL/PEM interface, plentiful proton transfer highways, and rapid oxygen bubble release, this ordered MEA achieves an ultralow Ir loading of 20.0 μg cm -2 and a high electrochemical active area by 8.7 times compared to traditional MEA with Ir loading of 1.0 mg cm -2 . It yields a mass activity of 168 000 mA mg Ir -1 cm -2 at 2.0 V, which is superior to most reported PEM electrolyzers. Notably, this ordered MEA maintains excellent durability at a current density of 500 mA cm -2 . This work opens a simple, cost-effective, and scalable route to design ordered MEAs for proton exchange membrane water electrolysis.