Influence of Cathode Airborne Impurity Levels on PEMFC Durability during Accelerated Performance Testing

Imaging PEMFC performance heterogeneity by sensing external magnetic field

Performance analysis of PEM fuel cell in mobile application under real traffic and environmental conditions

Challenges and opportunities in modelling of proton exchange membrane fuel cells (PEMFC)

Study on the effect of NO2 impurity gas on the performance and local current density distribution of PEMFC

Proton exchange membrane fuel cells (PEMFCs) can intensely lessen the emissions from the energy sector through environmentally friendly attributes. This evaluation paper summarizes the key additives of the PEMFC which are associated with water formation and delivery inside the cell. The gas diffusion layer (GDL) plays a key role in reactant gas diffusion and water control in proton exchange membrane (PEM) fuel cells. This paper also reviews updated literature regarding various hydrophobic and hydrophilic materials used for the improvement of the GDL and overall PEMFC performance. A style of carbon and steel-based microporous substrates (MPS) and microporous layer (MPL) and their impact in GDL overall performance are provided. Materials' properties that affect the performance of the MPL consisting of pore sizes, porosity, and permeability are additionally reviewed. Visualization of water in the flow channel and techniques to understand the mechanism of flow is reported. The failure modes related to the membrane electrode assembly (MEA) and typical PEMFC degradation are discussed. Prospects for development and addressing the water management and degradation of PEMFC through the exploration of further experimental and numerical studies are presented. Highlights Proton exchange membrane fuel cells (PEMFCs) can be a good candidate for several applications The material property of the GDL influences the overall fuel performance Water transport if not properly managed can cause poor performance and failure of the fuel cell There is need to understand how the fuel cell failure is related to the PEMFC component materials

Effect of channel-rib width ratio and relative humidity on performance of a single serpentine PEMFC based on electrochemical impedance spectroscopy

Experimental study of the influence of dynamic load cycle and operating parameters on the durability of PEMFC

The proton exchange membrane fuel cell (PEMFC) is a promising substitute for classic energy converter machines. However, there are still concerns regarding reliability and durability of PEMFCs, and hence, various modeling methods have been employed. One of the effective methods used for analysis and diagnosis of the fuel cell and other electrochemistry systems is Electrochemical Impedance Spectroscopy (EIS) which has been well established due to its high speed and precision. In this paper, the temperature sensitivity of the EIS results at different current densities obtained for a high temperature PEMFC are studied using electrochemical impedances reported in the literature. The magnitude of different elements in the proposed equivalent circuit for different temperatures and current densities, and root mean squares of deviation of various measurements are extracted. Then, the significance of the variations for different temperatures is examined via t-test. Finally, the minimum temperature change at different currents that can be captured by EIS is determined considering the root mean squares of measured values.

As a critical component, the bipolar plate appreciably affects the performance of proton exchange membrane fuel cell (PEMFC). The flow field structure on the bipolar plate is significant in transporting the internal reaction gas and excess water. In the nature, the leaf veins provide efficient branch networks to the plant, contributing to distribute the nutrients in the whole system. By bionic means, a similar branching structure can be used to design flow channels on the bipolar plates for PEMFC, which helps distribute the reactant gas evenly and manage the water better. In this paper, a three-dimensional isothermal single phase model of the bio-inspired flow channel design based on the leaf vein pattern was presented. The effect of the angle between the main channel and sub-channels on the performance of PEMFC was studied at various cases. A PEMFC of 10.24cm2 activation area was assembled and examined experimentally. The results showed that increasing the angle appropriately was beneficial to improving the uniform oxygen distribution and excess water removal. After comprehensively analyzing the electrochemical performance, species distribution, and power loss of PEMFC, the optimal angle was presented.

Study on hydrophobicity degradation of gas diffusion layer in proton exchange membrane fuel cells

Water management is an important issue for proton exchange membrane fuel cells (PEMFC). The research mainly focuses on the diagnosis and treatment of faults. However, faults harm PEMFC and cause its durability decay, whatever duration they last. This study designs a closed-loop water management system to control the water content in a reasonable range which can not only avoid the faults of hydration and flooding but also improve the performance and durability of PEMFC. The proposed system introduces the measurement methodology based on the phase of single-frequency impedance, which corresponds numerically well with the water content. Moreover, two preferred operating conditions, cathode air stoichiometry and stack temperature, are adopted to regulate the water content with a trade-off between the time cost and power loss. The open-loop characteristics of water content on the temperature and air stoichiometry are studied to design the corresponding control strategy. Findings suggest that air stoichiometry is suitable for large regulation requirements of water content, while the temperature is suitable to meet small demands. Finally, the proposed closed-loop water management system is validated by experiments in variable-load and constant-load with disturbance situations. The results indicate that the proposed system effectively controls the water content within a 3% deviation from the desired value.

Vehicular application of Proton Exchange Membrane Fuel Cells (PEMFC) poses durability and stability issues toward the multiple start-stops operation. Start-stop cycle leads to performance decay for PEMFC over time. Considering its reliability, PEMFC's performance recovery becomes a major concern. In electrical vehicle which does not used hydrogen tank due to safety, PEMFC require fuel processor to produce hydrogen as fuel source from ethanol. Output temperature of hydrogen from fuel processor is about 80 °C, which is quite high for PEMFC. Temperature is alleged having an impact on the performance of PEMFC. This research is focused on studying the effect of start-stop cycle and hydrogen temperature on the performance of PEMFC under constant loads using electrochemical characterisation. The number of start-stop cycle was varied by 10, 20 and 30 cycles under constant loads of 1 and 0.5 ampere. The temperature that used for hydrogen was 40° C. The result shows that heating hydrogen to 40 °C does not have significant effect to PEMFC's performance. However, enhancing start-stop cycle number has increased degradation of PEMFC stack.

Enhancing PEMFC performance at high current density by incorporating PTFE emulsion into catalytic layer

As fuel cell technology moves toward a mass-production stage, research has to address issues relating to cost production, durability and stability of proton exchange membrane fuel cell (PEMFC) performance. Most fuel cells use ambient air as an oxidant, which contains a variety of contaminants originating from vehicle and industrial exhausts as well as from naturally occurring processes. It was shown that in addition to being expensive conventional Pt cathodes do not have a sufficient tolerance to major air pollutants (SO2, H2S, NH3, NOx) (1, 2). So attempts to replace Pt with non-platinum group metals have been pursued in order to reduce cost production and gain stability of PEMFC performance in harsh environments (3). The evaluation of fuel cell performance with a single, lumped cell does not reveal its spatial behavior. In contrast, a segmented cell system provides locally resolved voltage, current and impedance, which is a powerful tool for understanding the environmental adaptability, durability and poisoning mechanisms. In this work, the spatial performance of Pt and Fe/N/C cathode fuel cells exposed to 2-20 ppm SO2, NO2 and CO in air was comprehensively studied and compared using a segmented cell system and spatial electrochemical impedance spectroscopy (EIS) for the first time. A segmented fuel cell system was operated (4) with a commercially available Pt-containing (0.4 mgPt cm- 2 for anode and cathode) membrane/electrode assembly (MEA) and home-made MEA consisting of Fe/N/C (3 mg cm-2) cathode gas diffusion electrodes (GDEs), Pt anode GDE (0.04 mgPt cm-2, Alfa Aesar) and Nafion XL. The MEA was operated under galvanostatic control of the whole cell current, 80°C, 48.3 kPag or 2 atmg back pressure and 100/50-100% relative humidity for the anode and cathode, respectively. SO2/NO2/CO concentrations varied from 2 to 20 ppm. The dry contaminant was injected into the humidified cathode air stream. The exposure proceeded until the cell voltage reached a steady value. Subsequently, the contaminant injection was stopped to evaluate the cell recovery ability in air. Fig. 1 a) shows the voltage response and normalized current density for each segment vs. experiment time for the Pt cathode PEMFC at 1.0 A cm-2. For the first 16 h, the cell was operated with pure air resulting in a cell voltage of 0.665 V. The injection of 2 ppm SO2 significantly decreased the voltage during a transition period that lasted ~6-7 h eventually reaching a steady state of 0.370 V. The voltage decrease was accompanied by a significant change in the current density distribution which undergoes several steps. Recovery was only partial and took ~4 h, the cell voltage reached 0.475 V instead of initial performance of 0.665 V. Chemisorption of SO2 at intermediate potentials (0.4-0.8 V) most likely results in formation of zero-valent sulphur and leads to a decrease of the ECA, a shift of the oxygen reduction from a 4-electron to a 2-electron mechanism and an increase in H2O2 production, which negatively impact the PEMFC performance (5). Fig. 1 b) presents profiles of the segment voltages and normalized current densities for the Fe/N/C cathode PEMFC at 0.2 A cm-2. The injection of 10 ppm SO2 for 7 hours did not cause any noticeable changes in segments’ cell voltage and current distribution. Only segment 1 showed a slight variation in performance. Exposure of the Fe/N/C cathode to 2 and 10 ppm NO2 resulted in a performance loss of 30 and 70-75 mV, respectively, which is less than in a Pt cathode fuel cell with a performance drop of ~80 mV. Detailed analyses of the current density distribution, its correlation with spatial EIS results obtained during SO2, NO2 and CO exposure and density functional theory calculations will be presented and discussed. ACKNOWLEDGEMENTS We gratefully acknowledge ONR (N00014-12-1-0496), DOE EERE (DE-EE0000459) and Hawaiian Electric Company. REFERENCES J.M. Moore, P.L. Adcock, J.B. Lakeman, G.O. Mepsted, J. Power Sources, 85, 254 (2000).O.A. Baturina, Y. Garsany, B.D. Gould, K.E. Swider-Lyons, in: H. Wang, H. Li, X.-Z. Yuan (Eds.), PEM fuel cell failure mode analysis, CRC Press, 2011, p. 199.A. Serov, K. Artyushkova, P. Atanassov, Adv. Energy Mater., 4, 1301735 (2014).T.V. Reshetenko, G. Bender, K. Bethune, R. Rocheleau, Electrochim. Acta, 56, 8700 (2011).B.D. Gould, O.A. Baturina, K.E. Swider-Lyons, J. Power Sources, 89, 188 (2009). Figure 1

In the recent years, by increasing the consumption of fossil fuels, the carbon dioxide level increases, which affects human health and climate change. One of the important technologies to solve these problems is fuel cell vehicles (FCVs), and, due to low operating temperature and high efficiency, the proton exchange membrane fuel cells (PEMFCs) have been more considered among various types of FCVs. Computational fluid dynamics (CFD) and numerical modeling have a great potential to study the detailed physical phenomena in the fuel cells such as mass, heat and energy transport, electrode kinetics, and potential fields and can reveal which factors in a real system are most important from a sensitivity point of view We reviewed several existing works relevant to CFD simulation and mathematical modeling of PEMFCs, which were performed by different software and codes like ANSYS Fluent, COMSOL, lattice Boltzmann, MATLAB codes, and OpenFOAM. The key factors that affect performance and failure modes of PEMFCs were discussed based on these simulations. One of these factors is water management that can be improved by using appropriate flow field configuration. The various configurations were reviewed. In addition, the effect of humidification of inlet reactants on the performance of PEMFCs was discussed.