Mechanically Stable Thinned Membrane For A High-Performance Polymer Electrolyte Membrane Fuel Cell Via A Plasma-Etching And Annealing Process

A thin electrolyte membrane is highly demanded for achieving high-performance polymer electrolyte membrane fuel cells (PEMFCs) by taking advantage of the reduced ohmic resistance-driven enhanced proton- and water-transport property during the PEMFC operation. However, the thin membrane inherently suffers from poor mechanical properties. In this study, we propose a simple methodological approach that combines the plasma etching and thermal annealing process to construct mechanically stable thinned membrane using commercially available Nafion membranes. The morphological, mechanical, and chemical properties of the modified Nafion membranes were characterized through diverse measurements including field-emission scanning electron microscopy, atomic force microscopy, stress-strain behavior test, and Fourier transform infrared spectrometry. We observed that the plasma etching process effectively reduced the membrane thickness; however, it induced spike-like structures with hundreds of nanometers in size on the membrane surface, which can cause stress-concentration-induced mechanical degradation of the membrane. By adopting a consecutive thermal annealing process, the roughened surface was flattened and mechanical properties including tensile strength and elongation to break were successfully recovered while maintaining the chemical composition of the Nafion. Interestingly, the modified 15 mu m-thick Nafion membrane with the plasma etching and thermal process showed a much enhanced maximum power density of 22.5 and 13.6% under the low and high humidity condition of RH 45% @89.5 degrees C and RH 92% @70 degrees C, respectively, compared to that of a pristine 25 mu m-thick Nafion membrane.