Measurements of the Temperature Distribution of PEMFC Catalyst Layer Using an Ultra Thin Thermocouple Array
Proton exchange membrane fuel cells (PEMFCs) are one of the most promising technologies for addressing the world’s energy needs, however, there are still many problems to be solved before they can be commonly used. One of the most serious issues concerns water management. For water management, knowledge of the temperature distribution inside the cell is extremely important due to the strong dependence of the water vapor saturation pressure on temperature. The cathode catalyst layer (CCL) generates the most heat during operation, and this heat could cause the proton transport path to dry out. Water is also generated by the chemical reactions, and an excess of accumulated water would block the transport of the reactant to the reaction site. Furthermore, the local temperature distribution is affected by the flow channels and ribs. Thus, it is important to determine the temperature distribution in the CCL, however, limited information about the temperature distribution and water transport near the CCL has been obtained to date. To acquire this information, six integral and in-line type Au-Ni thin film thermocouple (TFTC) arrays were constructed using a microelectromechanical system (MEMS) based fabrication technique. The total thickness of the sensors was no more than 3 ????m. The holes between the TFTCs were designed not to interfere with the mass and electron transport. Each thermocouple showed sufficient and nearly linear thermo-electromotive force, and their standard deviations were no more than 0.4 K, and their response time was less than 0.5 s. No overall performance decrement was observed with the insertion of the thermocouples. The temperature rise at the CCL was approximately 9 K at 1.2 A/cm2 with the supplied at 60% RH. The temperature under the channel often differed from that of under the rib, depending on operating conditions such as the current density and supplied humidity.