Moehring Nicole K, Mansoor Basha Abdul Bashith, Chaturvedi Pavan, Knight Thomas, Fan Xiaozong, Pintauro Peter N, Boutilier Michael S H, Karan Kunal, Kidambi Piran R
Interdisciplinary Graduate Program in Materials Science, Vanderbilt University, Nashville, Tennessee 37235, United States.
Chemical and Biomolecular Engineering Department, Vanderbilt University, Nashville, Tennessee 37212, United States.
Nano Lett. 2025 Jan 22;25(3):1165-1176. doi: 10.1021/acs.nanolett.4c05725. Epub 2025 Jan 13.
Permeance-selectivity trade-offs are inherent to polymeric membranes. In fuel cells, thinner proton exchange membranes (PEMs) could enable higher proton conductance and increased power density with lower area-specific resistance (ASR), smaller ohmic losses, and lower ionomer cost. However, reducing thickness is accompanied by an increase in undesired species crossover harming performance and long-term efficiency. Here, we show that incorporating atomically thin monolayer graphene synthesized via scalable chemical vapor deposition (CVD) and tunable defect density into PEMs (Nafion, ∼5-25 μm thick) can allow for reduced H crossover (∼34-78% of Nafion of a similar thickness) while maintaining adequate areal proton conductance for applications (>4 S cm). In contrast to most prior work using >50 μm symmetric Nafion sandwich structures, we elucidate the interplay of graphene defect density and Nafion proton transport resistance on the performance of Nafion|graphene composite membranes and find high-quality low-defect density CVD graphene (G) supported on Nafion 211 (∼25 μm); i.e., N211|G has a high areal proton conductance (∼6.1 S cm) and the lowest H crossover (∼0.7 mA cm). Fully functional centimeter-scale N211|G fuel-cell membranes demonstrate performance comparable to that of state-of-the-art Nafion N211 at room temperature as well as standard operating conditions (∼80 °C, ∼150-250 kPa-abs) with H/air (power density ∼0.57-0.63 W cm) and H/O feed (power density ∼1.4-1.62 W cm) and markedly reduced H crossover (∼53-57%).
渗透选择性权衡是聚合物膜固有的特性。在燃料电池中，更薄的质子交换膜（PEM）能够实现更高的质子传导率，并通过降低面积比电阻（ASR）、减小欧姆损耗和降低离聚物成本来提高功率密度。然而，减小膜的厚度会伴随着不期望的物质渗透增加，从而损害电池性能和长期效率。在此，我们表明，将通过可扩展化学气相沉积（CVD）合成的具有可调缺陷密度的原子级薄单层石墨烯掺入PEM（厚度约为5 - 25μm的Nafion膜）中，可以减少氢气渗透（约为相同厚度Nafion膜的34 - 78%），同时保持适用于实际应用的面质子传导率（>4 S cm²）。与大多数使用厚度大于50μm的对称Nafion三明治结构的先前工作不同，我们阐明了石墨烯缺陷密度与Nafion质子传输电阻对Nafion|石墨烯复合膜性能的相互作用，并发现支撑在Nafion 211（约25μm）上的高质量、低缺陷密度的CVD石墨烯（G）；即，N211|G具有高面质子传导率（约6.1 S cm²）和最低的氢气渗透（约0.7 mA cm²）。全功能厘米级N211|G燃料电池膜在室温以及标准操作条件（约80°C，约150 - 250 kPa绝对压力）下，使用氢气/空气（功率密度约0.57 - 0.63 W cm²）和氢气/氧气进料（功率密度约1.4 - 1.62 W cm²）时，表现出与最先进的Nafion N211相当的性能，并且氢气渗透显著降低（约53 - 57%）。
