Study of Nanocellulose as a New Proton Conducting Material for Fuel Cells and Electrolysers

以纤维素纳米纤维（CNF）和纤维素纳米晶体（CNC）膜为基准材料（结晶度下限和上限）。对先前制备的磺化纳米纤维素（S-CNF）进行了进一步的研究和表征。CNF膜具有较高的氧化稳定性，在Fenton试验中保留了大部分质量（97.5%），与Nafion膜（99.3%）相当。S-CNF稳定性较差（质量保持率为64.3%）。CNF、CNC和S-CNF的IEC分别为0.016、0.003和0.090 mmol g-1。用30微米厚的S-CNF膜制备的PEFC显示出大约。原位氢交叉比Nafion低2个数量级，满足DOE要求。为了研究结晶度对电导率的影响，制备了CNF和CNC共混物，并用EIS对其进行了电化学表征。随着CNC/CNF比的增加，质子电导率增加，接近纯CNC的电导率。阻断层测量证实了与Nafion相同的质子传导机制。平面内和平面通测量揭示了CNF和CNC的高电导率各向异性。制备了tempo氧化CNF。质子电导率增加了10倍（最大）。1.9 mS/cm（120℃时，活化能增加），膜保持较高的机械强度和弯曲能力。作为基准，利用Nafion和aquvion制备了水电解mea，并在80 ~ 120°C范围内对其性能和耐久性进行了研究。基于aquivon的MEA在120°C下表现出更好的性能和高耐久性，而基于nation的MEA在仅运行15h后就失效了。

Cellulose nanofibers (CNF) and cellulose nanocrystal (CNC) membranes were used as benchmark materials (lower and upper limit of crystallinity). Previously prepared sulfonated nanocellulose (S-CNF) was further investigated and characterized.The CNF membrane had high oxidative stability and retained most of its mass during Fenton test (97.5%), comparable to Nafion (99.3 %). S-CNF was less stable (64.3% mass-retention). The IEC of CNF, CNC and S-CNF are 0.016, 0.003 and 0.090 mmol g-1. A PEFC fabricated with a 30 micron thick S-CNF membrane showed an approx. 2 orders of magnitude lower in-situ hydrogen crossover than Nafion, meeting DOE requirements. In order to investigate the impact of crystallinity on conductivity, blends of CNF and CNC were prepared and electrochemical characterized via EIS. The proton conductivity increased with increasing CNC/CNF ratio, approaching the conductivity of pure CNC. Blocking layer measurements confirmed same proton conduction mechanism as in Nafion. In- and through-plane measurements unveiled high conductivity anisotropy in CNF and CNC. TEMPO-oxidized CNF was prepared. The proton conductivity increased by factor 10 (max. 1.9 mS/cm at 120°C, increased activation energy) and the membrane maintained high mechanical strength and bending capability.For benchmark reasons, water electrolysis MEAs were prepared using Nafion and Aquivion, and their performance and durability was investigated from 80 to 120°C. Aquivion based MEAs showed better performance and high durability at 120°C, whereas the Nafion-based MEA failed after only 15h operation.