M. M. Mench

The University of Tennessee Medical Center at Knoxville, Knoxville, Tennessee, United States

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Publications (56)178.86 Total impact

  • Journal of The Electrochemical Society 08/2014; 161(12):X17-X17. DOI:10.1149/2.0461412jes · 3.27 Impact Factor
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    ABSTRACT: The present work demonstrates an innovative concept of obtaining enhanced performance via laser treatment of the cathode-side diffusion medium (DM) while mitigating identified degradation modes. A diffusion medium was modified such that hydrophilic heat affected zones (HAZ) were introduced, which led to localized water redistribution. However, no perforation was created, thus mitigating accelerated degradation of the catalyst layer and diffusion medium. This material was compared to a diffusion medium with 100-mu m diameter perforations that contained heat affected zones surrounding the perforations. In-situ net water drag experiments indicate that at low humidity and low-to-moderate current densities, a non-perforated microporous layer (MPL) forces more water to back diffuse from the cathode to the anode. However, when more water is produced at higher currents or the inlet streams are close to saturation, the non-perforated MPL acts as a barrier to prevent liquid water in the cathode DM from moving toward the anode. Furthermore, a computational model showed that the thermal gradients introduced as a result of the perforations can significantly change the water transport, particularly due to phase-change induced flow. This work adds understanding to the role of the MPL and the laser-induced heat affected zones in polymer electrolyte fuel cell performance. (c) 2014 The Electrochemical Society. All rights reserved.
    Journal of The Electrochemical Society 07/2014; 161(10):F1061-F1069. DOI:10.1149/2.0591410jes · 3.27 Impact Factor
  • G. Xu · J. M. LaManna · J. T. Clement · M. M. Mench
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    ABSTRACT: An experimental study to investigate the through-plane thermal conductivity of three different diffusion media (DM) used in polymer electrolyte fuel cells (PEFCs) as a function of compression (from 0.1 MPa to 2 MPa) and saturation (from 0 to 25%) was performed. Additionally, measurements to determine the stress–strain relationship for the materials were made using an optical microscope. Both compression and water content had a significant impact on the through-plane thermal conductivity, which should be accounted for in multiphase modeling efforts. An analytical expression for the theoretical maximum of the through-plane thermal conductivity, as a function of both compression and saturation, was developed to help understand the nature of liquid connectivity in saturated pores. Additionally, a relationship was developed to predict actual thermal conductivity of the tested materials as a function of both compression and saturation based on experimentally measured data.
    Journal of Power Sources 06/2014; 256:212–219. DOI:10.1016/j.jpowsour.2014.01.015 · 6.22 Impact Factor
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    ABSTRACT: We report results of polarization measurements resolved for the negative and positive electrodes of vanadium redox batteries (VRBs) using a dynamic hydrogen electrode in an operating battery cell. Electrochemical experiments with symmetric electrolyte feeds were also performed. Greater kinetic polarization is observed at the negative (V3/2+) electrode compared to the positive electrode (V5/4+), in contrast with previously reported ex situ measurements. For the positive electrode, the polarization in the low-current regime was modest and was not kinetically controlled. The relative rates of reaction are a surprise since it might be expected that the V3/2+ redox reaction is a simple outer-sphere electron transfer.
    ECS Electrochemistry Letters 12/2013; 2(3):A29-A31. DOI:10.1149/2.001303eel · 1.79 Impact Factor
  • Yasser Ashraf Gandomi · Mathew M. Mench
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    ABSTRACT: In high-power polymer electrolyte fuel cell systems, prevention of anode dry-out through enhanced back flux of water and restriction of evaporative losses is needed. One potential method to engineer the back flux of water to the anode is to utilize an asymmetric anode and cathode micro-porous layer configuration to independently tailor anode and cathode thermal and mass transport resistances. Extensive experimental tests have been performed to study the impact of asymmetric MPL configuration on the net water drag coefficient using sets of MPL with different thermal and mass transport resistances. It was observed that with asymmetric MPL alignment between the anode and cathode, the net water drag coefficient could be significantly altered, opening the door to enhanced high power performance at anode-dryout conditions.
    224th ECS Meeting; 10/2013
  • Che-Nan Sun · Mathew M. Mench · Thomas A. Zawodzinski
    224th ECS Meeting; 10/2013
  • AK K Srouji · Lijuan Zheng · Robert Dross · Mathew M. Mench
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    ABSTRACT: Limiting current measurements were used to evaluate oxygen transport resistance in the catalyst layer of a polymer electrolyte fuel cell (PEFC). The pressure independent oxygen transport resistance in the electrode was evaluated with two different cell architectures, and two different cathode Pt loadings (0.4 and 0.07 mgPt.cm-2). The total oxygen transport resistance is divided into intermolecular gas diffusion and a pressure independent component, which could be attributed to Knudsen diffusion or dissolution film resistance. The pressure-independent oxygen transport resistance in the catalyst layer was measured to vary between 13.3 and 34.4 s/m. It is shown that the pressure independent oxygen transport resistance increases with reduced Pt loading, but that effect is exacerbated by using conventional channel/lands. The results indicate that the open metallic element architecture improves the oxygen transport resistance in ultra-low Pt loading electrodes due to enhanced water management at the catalyst layer.
    224th ECS Meeting; 10/2013
  • Mathew M. Mench · Jason Clement · Thomas A. Zawodzinski
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    ABSTRACT: A printed circuit board with imbedded shunt resistors was developed and implemented to obtain distributed data in real time in an all-vanadium redox flow battery. This work discusses the development and design considerations for implementing this diagnostic approach. The in-situ data from this approach can be used to assess build quality, material performance, operating conditions, flow field design and degradation. In this work, the lateral current spread and influence of electrode material properties via a split electrode configuration was observed. It was shown that current shifts away from a hydrophobic electrode.
    224th ECS Meeting; 10/2013
  • 224th ECS Meeting; 10/2013
  • A.K. Srouji · L. J. Zheng · R. Dross · A. Turhan · M. M. Mench
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    ABSTRACT: Anode dry-out is the main mechanism identified to limit operation in an open metallic element (OME) PEFC. The fundamental water transport mechanisms in the OME PEFC were examined in order to engineer further improved performance and higher temperature operation required for efficient heat rejection. Specifically, the net water drag (NWD) was measured over a range of conditions and analyzed with respect to electrochemical impedance spectroscopy and performance. As the cell operating temperature was increased, the effect of back diffusion was reduced due to the diminishing liquid water content in the cathode catalyst layer, and at critical liquid water content, anode dry-out was triggered primarily through electro-osmotic drag. Addition of cathode humidity was shown to promote high temperature operation mostly due to improved water back diffusion. The same mechanism can be achieved by creating a pressure differential across the membrane, with higher pressure on the cathode side. Stable operation was demonstrated at 90 °C using a polymer electrolyte membrane. Real time NWD measurements during transient anodic dry-out conditions were consistent with gradual membrane dehydration. The trade-off between liquid water overshadowing cathode catalyst sites and its contribution in promoting back diffusion is a key factor in systems with anode dry-out limited operation.
    Journal of Power Sources 10/2013; 239:433–442. DOI:10.1016/j.jpowsour.2013.03.145 · 6.22 Impact Factor
  • M. P. Manahan · Q. H. Liu · M. L. Gross · M. M. Mench
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    ABSTRACT: In this study, the performance and reaction location in a VRFB was investigated with a carbon paper electrode that was modified to include a thin layer of multi-walled carbon nanotubes. The nanotube layer was introduced into the electrode at locations on the negative and positive electrode nearest the membrane and nearest the flow field. Results with the nanotube layer on the positive electrode yielded small changes in the performance, despite the location. However, when the nanotube layer was introduced on the negative electrode, the performance was greatly improved when it was closest to the current collector. In this configuration, an 8% increase in power density and a 65 mV increase in cell voltage were observed, compared to a cell with raw carbon paper. This is attributed to the increase in active area of the nanoporous structure in a location where the reaction is favored to occur.
    Journal of Power Sources 01/2013; 222:498–502. DOI:10.1016/j.jpowsour.2012.08.097 · 6.22 Impact Factor
  • L. J. Zheng · A. K. Srouji · R. Dross · A. Turhan · M. M. Mench
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    ABSTRACT: A comprehensive 2D + 1 multi-phase computational model has been applied to polymer electrolyte fuel cells with a porous metallic flow field to investigate operating strategies which enable high power density operation in dry, elevated temperature environment. Extensive experimental model validation has been completed under a wide range of temperature, pressure, stoichiometry and humidity conditions. Both qualitative and quantitative agreement has been achieved in regard to voltage, area-specific resistance, and net water drag coefficient. Internal water distribution predictions show that modest changes in operating parameters on the cathode side help maintain a hydrated anode stream and thus effectively push the envelope of stable operating temperature 20 degrees C higher, enabling more efficient heat dissipation in coolant system. Results also show that thermo-osmotic water flux across the membrane, as observed and measured experimentally, can be significant compared to electro-osmosis under high current (> 2 A/cm(2)) hot and dry conditions, even with thin electrolyte membranes.
    Journal of The Electrochemical Society 11/2012; 160(2):F119-F128. DOI:10.1149/2.056302jes · 3.27 Impact Factor
  • A.K. Srouji · L. J. Zheng · R. Dross · A. Turhan · M. M. Mench
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    ABSTRACT: Performance and mass transport of a polymer electrolyte fuel cell (PEFC) with an open metallic element (OME) flow field architecture were analyzed in comparison to a conventional parallel channel/land (C/L) fuel cell, using low humidity at the anode and dry oxidant at the cathode. Under identical conditions the OME cell was able to operate at a current density of 3 A cm−2, recording a peak power of 1.2 W cm−2, compared to 0.9 W cm−2 using a parallel cell. Area specific resistance (ASR) was lower for the OME cell as a result of more uniform compression and reduced contact resistance. Electrochemical impedance spectroscopy (EIS) revealed great improvement in mass transport compared to a parallel C/L cell. A heliox mixture at the cathode of both cells revealed improved mass transport for the parallel cell, but revealed no oxygen gas phase transport limitation at high current densities for the OME architecture. In fact, it was shown that with an OME architecture, limitation at ultra-high current density results from dehydration at the anode and not reactant mass transport. This also indicates that ionomer film resistances at the electrode do not preclude operation at extremely high currents.
    Journal of Power Sources 11/2012; 218:341–347. DOI:10.1016/j.jpowsour.2012.06.075 · 6.22 Impact Factor
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    ABSTRACT: The performance of a vanadium flow battery with no-gap architecture was significantly improved via several techniques. Specifically, gains arising from variation of the overall electrode thickness, membrane thickness, and electrode thermal treatment were studied. There is a trade-off between apparent kinetic losses, mass transfer losses, and ionic resistance as the electrode thickness is varied at the anode and cathode. Oxidative thermal pretreatment of the carbon paper electrode increased the peak power density by 16%. Results of the pretreatment in air showed greater improvement in peak power density compared to that obtained with pretreatment in an argon environment. The highest peak power density in a VRB yet published to the author's knowledge was achieved at a value of 767 mW cm(-2) with optimized membrane and electrode engineering.
    Journal of The Electrochemical Society 07/2012; 159(8):A1246-A1252. DOI:10.1149/2.051208jes · 3.27 Impact Factor
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    ABSTRACT: We demonstrate a vanadium redox flow battery with a peak power density of 557 mW cm−2 at a state of charge of 60%. This power density, the highest reported to date, was obtained with a zero-gap flow field cell architecture and non-wetproofed carbon paper electrodes. The electrodes were comprised of stacked sheets of carbon paper and optimized through systematic variation of the total electrode thickness. We anticipate significant reductions in the ultimate system cost of redox flow battery systems based on this design.
    Journal of Power Sources 05/2012; 206:450–453. DOI:10.1016/j.jpowsour.2011.12.026 · 6.22 Impact Factor
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    L J Zheng · A K Srouji · A Turhan · M M Mench
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    ABSTRACT: A comprehensive 2D+1 computational model has been developed to explore the operation of a polymer electrolyte fuel cell (PEFC) with a porous flow field, also called open metallic element (OME), in the ultra-high current density regime (>2A/cm(2)). The computational model has been validated to a greater extent than previously published multi-phase models, including in-situ experimental measurement of performance, high frequency resistance (HFR) and net water drag coefficient under a wide range of input relative humidity (RH) conditions. The combined experimental and modeling investigation found that, with the OME used as the flow field, gas phase transport of oxygen is not the limiting factor, even in the ultra-high current regime. The use of OME results in significant performance improvement compared to the conventional land-channel architecture at high current. Instead of oxygen transport limitation, however, anode dry-out limits performance, as confirmed by net water drag data from both experiment and model. With the OME architecture, diffusion flow is the dominant transport mechanism of water from the catalyst layer to the flow field, compared to capillary action and convection. Results also highlight the utility of experimentally-determined anode dry-out limits for validating multi-phase models.
    Journal of The Electrochemical Society 01/2012; 159(7). DOI:10.1149/2.048207jes · 3.27 Impact Factor
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    M P Manahan · M M Mench
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    ABSTRACT: The purpose of this work is to explore engineered interfacial and structural architecture in fuel cell diffusionmedia (DM). Perforations were introduced via lasers on samples of virgin DM that contained hydrophobic content. Depending on laser choice, some laser-cut samples displayed a "heat affected zone" (HAZ) at the catalyst layer | microporous layer interface, characterized by a region surrounding each perforation where hydrophobic content was removed. At 50% inlet relative humidity, DM with homogeneously dispersed 100-mu m perforations and a HAZ displayed a 25% power density increase compared to virgin DM. Analyzing the oxygen concentration dependence in the double-Tafel region showed transport resistances were dominated by oxygen at moderate current values. Electrochemical impedance spectroscopy (EIS) and neutron radiography results indicated charge-and mass-transport impedances and liquid water redistribution play an important role, depending on the operating current density. Results suggested two mechanisms for the increased performance of the 100-mu m DM with HAZ: i) liquid water storage and through-plane water redistribution led to rehydration of the catalyst layer and membrane, and ii) in-plane water redistribution led to improved oxygen transport through the DM. The results of this study shed light on the importance of interfacial and structural architecture of fuel cell DM.
    Journal of The Electrochemical Society 01/2012; 159(7). DOI:10.1149/2.084207jes · 3.27 Impact Factor
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    ABSTRACT: The Penn State chapter of the International Association for Hydrogen Energy supplied a team of 12 members to enter the 1st IAHE Hydrogen Design Competition. Our design team decided to build a portable fuel cell. The design objective was to limit the cell size to 6 cm × 6 cm × 2 cm, and the goal was to achieve maximum power over 1 h of operation. The type of fuel cell we chose was a proton exchange membrane (PEM) fuel cell, using hydrogen and oxygen as the fuel and oxidizer, respectively. The final design converged to a cell stack containing 6 bipolar/end plates, i.e. 5 cells, each measuring 6 cm × 6 cm × 1.975 cm, each with an active area of approximately 25 cm2. The total open circuit voltage was approximately 4.75 V, indicating an average 0.95 V per cell. With an active area of 25 cm2, the maximum power observed during operation was approximately 1.7 W cm−2. The maximum sustained power over 1 h averaged 1.15 W cm−2. The total cost of the project totaled $2245.
    Fuel and Energy Abstracts 10/2011; 36(21):13875-13879. DOI:10.1016/j.ijhydene.2011.04.214
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    ABSTRACT: Journal of Power Sources j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j p o w s o u r a b s t r a c t In this study, cathode-side, bi-layered diffusion media (DM) samples with micro-porous layer were per-forated with 300 m laser-cut holes (covering 15% of the surface area in a homogenous pattern) using a ytterbium fiber laser to investigate the effect of structural changes on the gas and water transport. Under reduced humidity conditions (50% inlet relative humidity on the anode and cathode), the perforated DM were observed to increase the potential by an average of 6% for current densities ranging from 0.2 to 1.4 A cm −2 . However, the perforated DM showed reduced performance for current densities greater than 1.4 A cm −2 and at all currents under high-humidity conditions. Neutron radiography experiments were also performed to understand the changes in liquid water retention characteristics of DM due to the laser perforations. Significant water accumulation and water redistribution were observed in the perforated DM, which helps explain the observed performance behavior. The results indicate that the perforations act as water pooling and possible channeling locations, which significantly alter the water condensation, storage, and transport scheme within the fuel cell. These observations suggest that proper tailoring of fuel cell DM possesses significant potential to enable fuel cell operations with reduce liquid overhead and high performance.
    Journal of Power Sources 07/2011; 196(13):5573-5582. DOI:10.1016/j.jpowsour.2011.01.014 · 6.22 Impact Factor
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    ABSTRACT: In this study, the effect of a controlled temperature gradient on water transport across a single fuel cell was quantitatively investigated using high-resolution neutron imaging. The direction of liquid water transport under isothermal and non-isothermal conditions was observed in both hydrophilic and hydrophobic diffusion media (DM). The change in distribution of liquid saturation with time revealed two different mechanisms of water transport; capillary driven flow and phase-change induced (PCI) flow, in which a water vapor concentration gradient is created by condensation at a colder location. This concentration gradient drives diffusion flow toward the colder location. A maximum liquid saturation plateau of ca. 30% was shown for all conditions tested, indicating a critical transition between pendular and funicular modes of liquid water storage was captured. Based on this, it is suggested that PCI-flow may be the main mode of liquid transport below this critical transition threshold, above which, capillary flow dominates. As expected, both average cell temperature and the magnitude of temperature gradient were shown to significantly affect the rate of condensation within the DM. Experimental results were compared with water saturation distribution model predictions from literature and show reasonable qualitative agreement. Finally, it was concluded that current available models significantly over predict vapor phase diffusive transport in saturated fuel cell media using a Bruggeman type model.
    05/2011; 158(6):B717-B726. DOI:10.1149/1.3577597

Publication Stats

2k Citations
178.86 Total Impact Points


  • 2011–2014
    • The University of Tennessee Medical Center at Knoxville
      Knoxville, Tennessee, United States
  • 2013
    • Oak Ridge National Laboratory
      • Energy and Transportation Science Division
      Oak Ridge, Florida, United States
  • 2003–2010
    • Pennsylvania State University
      • • Department of Mechanical and Nuclear Engineering
      • • Center for Electrochemical Engine
      University Park, Maryland, United States
  • 2008
    • William Penn University
      Worcester, Massachusetts, United States