Investigation of Distribution Characteristics of Proton Exchange Membrane Fuel Cells Based on Localised Electrochemical Impedance Spectroscopy

Abstract

In recent years, as proton exchange membrane fuel cells (PEMFCs) have progressed toward commercialisation. The non-uniform performance output of PEMFCs, which influence the efficiency and lifespan, has become a significant problem. The current density distribution test is commonly used to assess this non-uniformity. Nevertheless, this method fails to identify the underlying causes of the uneven current distribution in PEMFCs. This study employs printed circuit board technology to obtain localised electrochemical impedance spectroscopy (EIS) measurements from various regions within a single PEMFC cell. It establishes and validates the mathematical relationship between the localised EIS of each region and the total EIS. Subsequently, the technique is employed to acquire in-situ EIS distribution and analyse the mechanisms behind uneven current distributions. Notably, the Warburg impedance at the outlet exhibits a significant increase, indicating that the elevated oxygen transport resistance is the primary cause of lower current density in that particular area. For the inlet, the low humility influences the location of high current density regions. Additionally, the load current also affects the distribution of current. For the low loading condition, PEMFC need a higher humidity air primarily due to a decrease in the water retention capacity of membrane. When the membrane thickness decreases, this effect becomes more pronounced. For the high loading condition, the thick membrane also need a higher humidity to reduce the resistance of membrane to improve its performance. With the decreasing of thickness, the lower resistance is easier to obtain, and a higher drainage capacity is needed. This study provides a theoretical foundation for designing and optimizing operating parameters and control systems for PEMFCs to increase its efficiency and service life.

Keywords: PEMFC, Localised EIS, Paraments distribution, Current density distribution, membrane thickness