High Performance of a Novel Polymer Electrolyte Fuel Cell with Proton and Hydroxyl Ion Conducting Membranes Under Non-Humidified Condition
Authors: Chae Ji Eon , Na Youngseung , Choi Jieun , Lee So Young , Han Jong Hee , Kim Hyoung-Juhn 
Published: February 2020

Fuel cells are high-efficiency, environment-friendly power generation systems which produce electricity and thermal energy through electrochemical reactions between hydrogen and oxygen. Unlike conventional generators, it produces electricity directly without the energy conversion process through combustion of fuel. It is attracting attention as a next generation energy source that has a low energy loss, high power generation efficiency, and can be used as a distributed power source. Up to date, a various types of fuel cells were developed and studied. However, the high cost of fuel cell systems which are composed of the precious metal catalyst, the perfluorosulfonic acid membrane such as Nafion, and humidifier etc. was the problem.

Especially, in regard to the humidification system, the hydration of membrane is significant for proton and hydroxyl ion conduction on the fuel cell operations. Therefore, the PEMFCs need a considerable size of humidifier which supplies moisture to the PEMFC. Due to the humidifier, the total fuel cell system becomes big and heavy. Because of the reason, it is difficult to load PEMFC in the system which requires the limit of weight and volume such as unmanned aerial vehicles.

In this work, a new type of polymer electrolyte fuel cell, which is composed of anion exchange membrane (AEM) and cation exchange membrane (CEM) at a one to one ratio (named half- half cell) as shown in Figure 1, is proposed for non-humidified system. As it occurs the electrochemical reactions in the anode (AEM) on hydrogen oxidation reaction (HOR) and in the cathode (CEM) on oxygen reduction reaction (ORR), water was generated on the dry condition and affected for the fuel cell operation. As shown in Figure 2 (a), the half- half cell was carried out for a long term test at 0.6 V constant voltage mode for 60 days and analyzed by current-voltage polarization, electrochemical impedance spectroscopy. And the each performance of AEM and CEM was investigated with specially produced and divided separator and measured. In current aspect, we ascertained that the overall cell performance comes from CEM part and the AEM part is just for pertaining to generate water in Figure 2 (b). For investigating the flow of generated water through the separator channel to the naked eye, the acrylic transparent single cell was used. Also, we compared the effect of the generated water on consumption alternately between CEM and AEM (orthogonal) and on passing through each membrane completely (parallel) by describing the calculated relative humidity in the cell. Finally, the MEAs were piled up in order of bipolar plates, and MEAs to 5 unit and put in one direction on the flow channel. The stack was tested with alternating nitrogen and fuel (hydrogen and oxygen) to observe how well the fully dried MEA could perform. The electrochemical reactions can be reoccurred and it was operated rapidly in a few minutes because of the already activated MEAs. We carried out the long-term durability of the stack through a repetitive cycle in the non-humidified condition for 210 h. The details will be discussed in presentation.

Figure 1