Nanomechanical and nanoelectrical analysis of the proton exchange membrane water electrolyzer anode – impact of reinforcement fibers and porous transport layer

Abstract

Understanding the aging of proton exchange membrane electrolyzer cells (PEMECs) is essential for durability enhancement. Therefore, a large-scale and long-term operated (>5000 h) web-woven reinforced membrane electrode assembly (MEA) anode was investigated using nanomechanical and nanoelectrical atomic force microscopy (AFM) techniques and nanoindentation. Web-woven fibers locally increase the reduced modulus and hardness and proved to be a suitable reinforcement for long-term operation. Interestingly, both pristine and operated anodes show slightly diminished electrically conductive surface areas above reinforcement fiber intersections. The homogeneous pristine anode heterogenizes with operation. Additional porous transport layer (PTL) related domains and increased statistical deviations are observed. Nanoindentation revealed a generally increased reduced modulus and hardness with operation, accompanied by a stiffening of the near surface catalyst shown by AFM. This effect is promoted by a loss of low stiffness ionomer, confirmed by the increase of electrically conductive anode surface area. The most significant anode aging effects were observed only at a small surface fraction—at certain PTL related marks. This study firstly analyzes a web-woven fiber reinforced MEA and enhances the understanding of anode aging related to reinforcement fibers and PTL.