Chen Yen-Chun, Dörenkamp Tim, Csoklich Christoph, Berger Anne, Marone Federica, Eller Jens, Schmidt Thomas J, Büchi Felix N
Electrochemistry Laboratory, Paul Scherrer Institut CH-5232 Villigen PSI Switzerland
Chair of Technical Electrochemistry, Department of Chemistry and Catalysis Research Center, Technical University of Munich D-85748 Garching Germany.
Energy Adv. 2023 Jul 31;2(9):1447-1463. doi: 10.1039/d3ya00189j. eCollection 2023 Sep 14.
Product water transport the microporous layer (MPL) and gas diffusion layer (GDL) substrate during polymer electrolyte fuel cell (PEFC) operation was directly and quantitatively observed by X-ray tomographic microscopy (XTM). The liquid water distribution in two types of MPLs with different pore size distributions (PSDs) was characterized as a function of the inlet gas relative humidity (RH) and current density under humid operating conditions at 45 °C. During the first minute of PEFC operation, liquid water mainly accumulated at the catalyst layer (CL)/MPL interface and in the GDL substrate close to the flow fields. Furthermore, under all tested conditions, saturation in the MPL was low (<25%), whereas under the rib, the saturation in the GDL was up to 70%. Based on these XTM results, it is confirmed that in the high porosity MPLs, vapor transport was non-negligible even at high humidity conditions. Therefore, on top of the widely discussed MPL pore size and its distribution, it is proposed that the lower thermal conductivity from the high porosity of MPLs can also be a main cause of promoted vapor transport, reducing water saturation near the CL.
在聚合物电解质燃料电池（PEFC）运行过程中，通过X射线断层显微镜（XTM）直接且定量地观察了产物水在微孔层（MPL）和气体扩散层（GDL）基底中的传输情况。在45°C的潮湿运行条件下，研究了两种具有不同孔径分布（PSD）的MPL中液态水的分布与进气相对湿度（RH）和电流密度的关系。在PEFC运行的第一分钟内，液态水主要积聚在催化剂层（CL）/MPL界面以及靠近流场的GDL基底中。此外，在所有测试条件下，MPL中的饱和度较低（<25%），而在肋条下方，GDL中的饱和度高达70%。基于这些XTM结果，证实了在高孔隙率的MPL中，即使在高湿度条件下，蒸汽传输也不可忽略。因此，除了广泛讨论的MPL孔径及其分布外，还提出MPL高孔隙率导致的较低热导率也可能是促进蒸汽传输、降低CL附近水饱和度的主要原因。
