Department of Material Science and Chemical Engineering, Stony Brook University, Stony Brook, NY 11794, USA.
Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA.
Int J Mol Sci. 2022 Dec 3;23(23):15245. doi: 10.3390/ijms232315245.
Carboxycellulose nanofibers (CNFs) promise to be a sustainable and inexpensive alternative material for polymer electrolyte membranes compared to the expensive commercial Nafion membrane. However, its practical applications have been limited by its relatively low performance and reduced mechanical properties under typical operating conditions. In this study, carboxycellulose nanofibers were derived from wood pulp by TEMPO oxidation of the hydroxyl group present on the C6 position of the cellulose chain. Then, citric acid cross-linked CNF membranes were prepared by a solvent casting method to enhance performance. Results from FT-IR spectroscopy, C NMR spectroscopy, and XRD reveal a chemical cross-link between the citric acid and CNF, and the optimal fuel cell performance was obtained by cross-linking 70 mL of 0.20 wt % CNF suspension with 300 µL of 1.0 M citric acid solution. The membrane electrode assemblies (MEAs), operated in an oxygen atmosphere, exhibited the maximum power density of 27.7 mW cm and the maximum current density of 111.8 mA cm at 80 °C and 100% relative humidity (RH) for the citric acid cross-linked CNF membrane with 0.1 mg cm Pt loading on the anode and cathode, which is approximately 30 times and 22 times better, respectively, than the uncross-linked CNF film. A minimum activation energy of 0.27 eV is achieved with the best-performing citric acid cross-linked CNF membrane, and a proton conductivity of 9.4 mS cm is obtained at 80 °C. The surface morphology of carboxycellulose nanofibers and corresponding membranes were characterized by FIB/SEM, SEM/EDX, TEM, and AFM techniques. The effect of citric acid on the mechanical properties of the membrane was assessed by tensile strength DMA.
羧甲基纤维素纳米纤维（CNF）有望成为一种比昂贵的商业 Nafion 膜更具可持续性和成本效益的聚合物电解质膜替代材料。然而，其在典型工作条件下的性能相对较低，机械性能较差，限制了其实际应用。在这项研究中，通过 TEMPO 氧化纤维素链 C6 位上的羟基，从木浆中得到羧甲基纤维素纳米纤维。然后，通过溶剂浇铸法制备柠檬酸交联的 CNF 膜，以提高性能。FT-IR 光谱、C NMR 光谱和 XRD 的结果表明，柠檬酸与 CNF 之间存在化学交联，通过交联 70mL 0.2wt%CNF 悬浮液与 300µL 1.0M 柠檬酸溶液，获得最佳的燃料电池性能。在氧气气氛中运行的膜电极组件（MEA）在 80°C 和 100%相对湿度（RH）下，以 0.1mgcmPt 负载量在阳极和阴极上的柠檬酸交联 CNF 膜，其最大功率密度为 27.7mWcm，最大电流密度为 111.8mAcm，约为未交联 CNF 膜的 30 倍和 22 倍。具有最佳性能的柠檬酸交联 CNF 膜的最小活化能为 0.27eV，在 80°C 时的质子电导率为 9.4mScm。通过 FIB/SEM、SEM/EDX、TEM 和 AFM 技术对羧甲基纤维素纳米纤维和相应膜的表面形态进行了表征。通过拉伸强度 DMA 评估了柠檬酸对膜机械性能的影响。
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