Temperature and Humidification Effect on Mass Transfer of PEMFC Via EIS and Soft X-Ray Measurement
Authors: Jao Ting-Chu , Sasabe Takashi , Uemura Suguru , Yoshida Toshihiko , Hirai Shuichiro 
Published: February 2020

In proton exchange membrane fuel cells (PEMFCs), appropriate water management is critical to achieve high power density operation with increased robustness. Proton exchange membranes (PEMs) require sufficient hydration to fulfill its function as proton conductor, while flooding at the cathode side can hamper the transport of reactant, resulting in deterioration of cell operation. Liquid water accumulation and its transportation is one of major issue for PEMFCs.

For diagnosis the water and mass transport ability the following experimental methods can be used: polarization, oxygen gain, limiting current density, calculate oxygen transportation resistance, electrochemical impedance spectrum (EIS), and visualization technique etc. However, there are not so many literatures point out where the water accumulation can cause the mass transport resistance arc. In this study, the cell operated temperature and cathode humidify has been selected as main parameters for investigating the mass transfer phenomenon. The EIS was using for indicating mass transport occurs condition and the soft X-ray radiography was using for verify the location of the water accumulation. The soft X-ray radiography [1-13] had been proved it is a powerful tool to investigate liquid water within membrane electrode assemblies (MEAs).

Fig. 1 (a) shows EIS and water extraction image with different humidification conditions. The liquid water accumulation within gas diffusion substrates/channel is barely effects nothing on the mass transport resistance art. The water extraction image implies the water accumulates within/nearby catalyst layer is the main reason to cause the mass transport resistance art. Fig. 1(b) shows EIS and water extraction image with different operating conditions. It is barely no mass transport resistance arc at high temperate condition, due to generation water is mainly as vapor form. This result indicates the mass transport resistance arc is important indicator which points out there are liquid water accumulate within/nearby catalyst layer.

Acknowledgement

This work has been supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

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Figure 1