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Tuyet Anh Pham,Le Vu Nam,Segeun Jang(장세근),Sang Moon Kim(김상문) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
In polymer electrolyte membrane fuel cells (PEMFCs), a thin electrolyte membrane is highly preferable due to its reduced ohmic resistance which leads to enhanced kinetics of electrochemical reactions. On the other aspect, the mechanical properties of the thin membrane get significantly lowered which restricts the thickness of the membrane. In this work, we propose a simple process that combines plasma etching and annealing (E-T) process to fabricate thin Nafion® membranes with enhanced mechanical characteristics. The fabricated membranes are characterized through a tensile test, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and Fourier transform infrared spectrometry (FT-IR). The plasma etching process effectively reduces the membrane thickness, while generating nano-roughness on the surface. Furthermore, the roughened surface gets flattened during the annealing process, which also increases the tensile stress of the membrane by up to ~30 %. After constructing fuel cells with the fabricated membranes, the device performances are measured. Thanks to E-T process, the 15 µm-thick membrane shows maximum power density of 22.5 % higher in the condition of 70 ℃ and 92% relative humidity (RH), and 19.3 % higher in the condition of 89.5 ℃ and 45% RH, compared to that of a 25 µm-thick conventional membrane.
Le Vu Nam,Changwook Seol(설창욱),Tuyet Anh Pham,Segeun Jang(장세근),Sang Moon Kim(김상문) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
Elevated temperature operating polymer electrolyte membrane fuel cells have gained considerable interest owing to good electrode kinetics, high CO tolerance, and improved heat management. It was supposed that inserting inorganic fillers (SiO<SUB>2</SUB>, TiO<SUB>2</SUB>, etc.,) in the Nafion® membrane can retain water under higher temperature, low humidity operating condition. This incorporation would increase the electrochemical performance of the membrane. Conventionally, many researches inserted the inorganic fillers utilizing casting and evaporation approach. However, this method decreases proton pathways and induces agglomeration, thus would not significantly increase the efficiency of the membrane. Here in, homogeneous patterned TiO<SUB>2</SUB> have been added onto the anode side of the electrolyte membrane. The addition of patterned TiO<SUB>2</SUB> not only manages the agglomeration of inorganic filler but also maintains the ionic conductivity of the membrane. This resulted in enhanced the maximum power output of the membrane electrode assembly by more than 35% compare to the to the conventional Nafion® MEA under intermediate temperature.
Changwook Seol(설창욱),Le Vu Nam,Tuyet Anh Pham,Segeun Jang(장세근),Sang Moon Kim(김상문) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
Interface engineering based on the design and fabrication of micro-/nano-structures has received much attention as an effective way to improve the performance of polymer electrolyte membrane (PEM) fuel cells while using the same materials and quantity. Herein, we fabricated spatially hole-array patterned PEMs with different hole-depths by using both plasma etching process and micro-hole pattern polymer stencil inspired by nature. This approach exhibited high pattern-fidelity over large-area and controllability in pattern-depth while excluding the problems of contact-based conventional patterning processes. All the membrane electrode assembly (MEA) with the patterned PEMs with an etch depth of 4 μm (PE4-MEA), 8 μm (PE8-MEA), and 12 μm (PE12-MEA) showed higher performance than the reference MEA with pristine PEM. Among the modified MEAs, the PE8-MEA showed the highest performance enhancement due to the locally thinning effect of the PEM, geometrically favorable features for mass transport, and increased interfacial contact area between the PEM and the catalyst layer.