论文标题
使用磁共振成像同时对燃料电池的质子交换膜中的温度和水合映射
Simultaneous mapping of temperature and hydration in proton exchange membrane of fuel cells using magnetic resonance imaging
论文作者
论文摘要
质子交换膜（PEM）燃料电池的效率取决于PEM中质子的迁移率，这取决于膜的水合和温度。虽然光学技术，中子或X射线散射技术可用于研究PEM中水合和温度的不均匀性，但这些技术不能在测量分层PEM中提供3维空间分辨率。由于它们提供了非侵入性3D图像的能力，因此已建议在PEM中质子的旋转弛豫时间（T1）和自旋旋转弛豫时间（T2）对比度磁共振成像（MRI）作为在燃料电池中绘制水合的方法。我们表明，尽管T1和T2成像可用于在等热条件下的PEM中绘制水合，但质子T1和T2也是温度的函数。对于PEM燃料电池，当前密度较大并且预期热梯度的情况下，T1和T2松弛时间不能用于映射水合。但是，移动质子的化学位移是水合的强大功能，但不是温度的功能。因此，化学位移成像（CSI）可用于绘制水合。移动质子的扩散常数可以由脉冲场梯度NMR确定，随温度和水合都增加。因此，CSI随后通过脉冲场梯度进行扩散成像，可用于在PEM中单独映射水合和温度。在这里，我们在空间分辨率为1 mm x 1 mm，总扫描时间为3分钟，温度分辨率为6 K，水合不确定性不确定性，在15％以内的空间分辨率分辨率为1 mm x 1 mm，在16 x 16 x 16的像素MRI图映射。可以将所示的映射推广到成像交换任何燃料电池或流动电池的膜。
The efficiency of a proton exchange membrane (PEM) fuel cell depends on the mobility of protons in the PEM, which is determined by the hydration and temperature of the membrane. While optical techniques or neutron or x-ray scattering techniques may be used to study the inhomogeneities in hydration and temperature in PEMs, these techniques cannot provide 3 dimensional spatial resolution in measuring layered PEMs. Due to their ability to provide non-invasive 3D images, spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) contrast magnetic resonance imaging (MRI) of protons in PEMs have been suggested as methods to map hydration in the fuel cells. We show that while T1 and T2 imaging may be used to map hydration in PEMs under isothermal conditions, proton T1 and T2 are also a function of temperature. For PEM fuel cells, where current densities are large and thermal gradients are expected, T1 and T2 relaxation times cannot be used for mapping hydration. The chemical shift of the mobile proton is, however, a strong function of hydration but not temperature. Therefore, chemical shift imaging (CSI) can be used to map hydration. The diffusion constant of the mobile proton, which can be determined by pulsed field gradient NMR, increases with both temperature and hydration. Therefore, CSI followed by imaging of diffusion via pulsed field gradients can be used for separate mappings of hydration and temperature in PEMs. Here, we demonstrate a 16 x 16 pixel MRI mapping of hydration and temperature in Nafion PEMs with a spatial resolution of 1 mm x 1 mm, a total scan time of 3 minutes, a temperature resolution of 6 K, and an uncertainty in hydration within 15%. The demonstrated mapping can be generalized for imaging exchange membranes of any fuel cells or flow batteries.
