Exchange Membrane Fuel Cell Performance Research Articles

Accelerated Testing of Polymer Electrolyte Membranes in Fuel Cells Containing Pt/C and PtCo/C Catalysts

The major source of membrane chemical degradation during proton exchange membrane fuel cell operation is from attack of radicals, which form when hydrogen and oxygen react on platinum. It is hypothesized that the higher durability of PtCo/C electrodes will decrease platinum deposition in the membrane and, therefore, increase membrane durability. After testing catalyst coated membranes (CCMs) containing either Pt/C or PtCo/C under open circuit voltage, it was observed that using PtCo/C rather than Pt/C resulted in lower CCM degradation in terms of voltage decay, fluoride emission, and performance loss before and after testing. Transmission electron microscopy images showed that platinum with particle sizes of 10 to 35 nm were dispersed throughout the membrane of the CCM containing PtCo/C, while the CCM containing Pt/C resulted in formation of a 2.5 micron wide platinum band 2.3 microns from the cathode with particle sizes of 15 to 85 nm. The increased degradation observed for the cell containing Pt/C compared to the cell containing PtCo/C is attributed to the formation of the Pt band in the cell containing Pt/C. Reactant crossover is stoichiometrically favorable for OH radical generation at the location of the Pt band, resulting in localized radical attack of the polymeric membrane.

PEM Fuel Cell Modeling and Pressure Investigation

For investigation of a proton exchange membrane fuel cell anode and cathode pressure effect on cell performance, a quasi two-dimensional, isothermal model is developed. The main solution domain is divided into two individual regions (channel and proton exchange membrane), subsequently by using two-one-dimensional models; each of these regions is modeled. The method is based on analytical methods combined with numerical techniques. For validation of modeling, an experimental setup was developed. Comparing the results with the experimental set-up has shown good agreement and acceptable accuracy of the method. Analytical results revealed that 5 bar pressure for anode and cathode sides have the best proton exchange membrane fuel cells performance.

3D Steady Model and Simulation for a Proton Exchange Membrane Fuel Cell Performance

3D Steady Model and Simulation for a Proton Exchange Membrane Fuel Cell Performance

Effect of Dispersion Solvent in Catalyst Ink on Proton Exchange Membrane Fuel Cell Performance

Effect of Dispersion Solvent in Catalyst Ink on Proton Exchange Membrane Fuel Cell Performance

Chloride contamination effects on proton exchange membrane fuel cell performance and durability

Chlorine is a major fuel contaminant when by-product hydrogen from the chlor-alkali industry is used as the fuel for proton exchange membrane (PEM) fuel cells. Understanding the effects of chlorine contamination on fuel cell performance and durability is essential to address fuel cell applications for the automotive and stationary markets. This paper reports our findings of chloride contamination effects on PEM fuel cell performance and durability, as our first step in understanding the effects of chlorine contamination.Fuel cell contamination tests were conducted by injecting ppm levels of contaminant into the fuel cell from either the fuel stream or the air stream. In situ and ex situ diagnosis were performed to investigate the contamination mechanisms. The results show that cell voltage during chloride contamination is characterized by an initial sudden drop followed by a plateau, regardless of which side the contaminant is introduced into the fuel cell. The drop in cell performance is predominantly due to increased cathode charge transfer resistance as a result of electrochemical catalyst surface area (ECSA) loss attributable to the blocking of active sites by Cl− and enhanced Pt dissolution.

Model and simulation of proton exchange membrane fuel cell performance at different porosity of diffusion layer

The proton exchange membrane fuel cell is an example of clean energy. Recently, a three-dimensional, steady-state non-isotherm mathematical model for proton exchange membrane fuel cell was developed for further exploration. This 3D model simultaneously takes into account the mass, momentum, energy, species, charge conservation equation as well as combines electrochemistry reaction inside the fuel cell. The simulation results reveals that it is easy to improve the fuel cell performance for higher porosity in the diffusion layer by speeding up the gas diffusion, reducing the concentration grads of gas, depressing the ridge board domino effect and falling current density grads.

In situ metal ion contamination and the effects on proton exchange membrane fuel cell performance

Automotive fuel cell technology has made considerable progress, and hydrogen fuel cell vehicles are regarded as a possible long-term solution to reduce carbon dioxide emissions, reduce fossil fuel dependency and increase energy efficiency. Even though great strides have been made, durability is still an issue. One key challenge is controlling MEA contamination. Metal ion contamination within the membrane and the effects on fuel cell performance were investigated. Given the possible benefits of using stainless steel or aluminum for balance-of-plant components or bipolar plates, cations of Al, Fe, Ni and Cr were studied. Membranes were immersed in metal sulfide solutions of varying concentration and then assembled into fuel cell MEAs tested in situ. The ranking of the four transition metals tested in terms of the greatest reduction in fuel cell performance was: Al 3+ ≫ Fe 2+ > Ni 2+, Cr 3+. For iron-contaminated membranes, no change in cell performance was detected until the membrane conductivity loss was greater than approximately 15%.

The effects of pinholes on proton exchange membrane fuel cell performance

Pinholes in the membrane electrode assembly (MEA) of a fuel cell can lead to premature fuel cell failure. The main causes for pinhole formation are contaminant particles, non-uniform stress distribution, and membrane corrosion. In this paper fuel cell performance is compared before and after piercing the MEA with a pin to introduce a pinhole. Experiments revealed that under some operation conditions, the presence of a pinhole did not immediately impact performance. This implies that fuel cell engineers might overlook pinhole damage in its initial stages. However, durability testing shows that the performance of a fuel cell with a pinhole declines faster than that of a fuel cell with an intact MEA. During open circuit voltage measurement, a substantial voltage drop is observed for the fuel cell with a pinhole in the MEA. Simulation results point to the formation of a hot spot in the cathode catalyst layer of the fuel cell at the site of the pinhole. The temperature of the hotspot is 4∼5 K higher than the surrounding area, which is not so high as to impair performance. This explains the steady operation of the fuel cell over a 40-hour run cycle. This study identifies increasing anode pressure as a method for pinhole detection in fuel cell stacks. Copyright © 2010 John Wiley & Sons, Ltd.

Membrane electrode assembly with Pt/SiO 2/C anode catalyst for proton exchange membrane fuel cell operation under low humidity conditions

In this work, a novel self-humidifying membrane electrode assembly (MEA) with Pt/SiO 2/C as anode catalyst was developed to improve the performance of proton exchange membrane fuel cell (PEMFC) operating at low humidity conditions. The characteristics of the composite catalysts were investigated by XRD, TEM and water uptake measurement. The optimal performance of the MEA was obtained with the 10 wt.% of silica in the composite catalyst by single cell tests under both high and low humidity conditions. The low humidity performance of the novel self-humidifying MEA was evaluated in a H 2/air PEMFC at ambient pressure under different relative humidity (RH) and cell temperature conditions. The results show that the MEA performance was hardly changed even if the RHs of both the anode and cathode decreased from 100% to 28%. However, the low humidity performance of the MEA was quite susceptible to the cell temperature, which decreased steeply as the cell temperature increased. At a cell temperature of 50 °C, the MEA shows good stability for low humidity operating: the current density remained at 0.65 A cm −2 at a usual work voltage of 0.6 V without any degradation after 120 h operation under 28% RH for both the anode and cathode.

Experimental study of commercial size proton exchange membrane fuel cell performance

Commercial sized (16 × 16 cm 2 active surface area) proton exchange membrane (PEM) fuel cells with serpentine flow chambers are fabricated. The GORE-TEX® PRIMEA 5621 was used with a 35-μm-thick PEM with an anode catalyst layer with 0.45 mg cm −2 Pt and cathode catalyst layer with 0.6 mg cm −2 Pt and Ru or GORE-TEX® PRIMEA 57 was used with an 18-μm-thick PEM with an anode catalyst layer at 0.2 mg cm −2 Pt and cathode catalyst layer at 0.4 mg cm −2 of Pt and Ru. At the specified cell and humidification temperatures, the thin PRIMEA 57 membrane yields better cell performance than the thick PRIMEA 5621 membrane, since hydration of the former is more easily maintained with the limited amount of produced water. Sufficient humidification at both the cathode and anode sides is essential to achieve high cell performance with a thick membrane, like the PRIMEA 5621. The optimal cell temperature to produce the best cell performance with PRIMEA 5621 is close to the humidification temperature. For PRIMEA 57, however, optimal cell temperature exceeds the humidification temperature.

Acoustic emission: Towards a real-time diagnosis technique for Proton Exchange Membrane Fuel Cell operation

This paper deals with one of the needs for PEMFC to be economically reliable: diagnosis tool for water management. This issue is actually a key parameter for both performance and durability improvement. Acoustic emission (AE) technique was employed to survey PEM single cell under various operating conditions. AE events coming from different sources have thus been identified, classified and finally ascribed to different phenomena induced by MEA water uptake and/or biphasic flow in the gas channel thanks to a statistical post-treatment of the acoustic data. Results, although qualitative, seems trusty enough to unravel hidden correlations between AE hits and physicochemical phenomena taking place during the cell operation and open up the way for an innovative and non-invasive online diagnosis tool.

Proton Exchange Membrane Fuel Cell Operating at 150°C with Ionic Liquid as Electrolyte

not Available.

Nitrogen Front Evolution in Purged Polymer Electrolyte Membrane Fuel Cell with Dead-Ended Anode

In this paper, we model and experimentally verify the evolution of liquid water and nitrogen fronts along the length of the anode channel in a proton exchange membrane fuel cell operating with a dead-ended anode that is fed by dry hydrogen. The accumulation of inert nitrogen and liquid water in the anode causes a voltage drop, which is recoverable by purging the anode. Experiments were designed to clarify the effect of blanketing, water plugging of the channels, and flooding of the gas diffusion layer. The observation of each phenomenon is facilitated by simultaneous gas chromatography measurements on samples extracted from the anode channel to measure the nitrogen content and neutron imaging to measure the liquid water distribution. A model of the accumulation is presented, which describes the dynamic evolution of a blanketing front in the anode channel leading to the development of a hydrogen starved region. The prediction of the voltage drop between purge cycles during nonwater plugging channel conditions is shown. The model is capable of describing both the two-sloped behavior of the voltage decay and the time at which the steeper slope begins by capturing the effect of concentration loss and the area of the starved region along the anode channel.

The impact of channel assembled angle on proton exchange membrane fuel cell performance

A three-dimensional, two-phase, multi-component model is used to investigate the effects of channel assembled angle on the performance of proton exchange membrane (PEM) fuel cell, including distribution of current density, membrane water content and local temperature. The flow-fields are assembled by single serpentine channels in anode and cathode with intersection angles of 0°, 90°, 180° and 270°, respectively. At high inlet humidity condition each flow-field has its owned strengths. Flow-fields with channel assembled angles of 0°, 90° and 270° show most uniform membrane water content, current density and local temperature distributions, respectively. However, at low inlet humidity condition, flow-field with channel assembled angle of 90° represents highest performance and uniformities in all aspects. Flow-field design for PEM fuel cell should take into account the effects of channel assembled angle on cell performance.

Temperature effect on the recovery of SO2-Poisoned GC/Nano-Pt electrode towards oxygen reduction

The SO2 poisoning of Pt nanoparticle (n-Pt) modified glassy carbon (GC/n-Pt) electrode and the recovery of its activity for the oxygen reduction reaction (ORR) were studied using cyclic voltammetry at ambient (25 °C) and elevated (70 °C) temperatures. Recovery of the GC/n-Pt electrode by cycling the potential within the ORR range (1.0 to 0.2 V (standard hydrogen electrode)) in 0.1 M H2SO4 was not effective at 25 °C, but at 70 °C the onset potential of the ORR was almost the same as that at the fresh GC/n-Pt electrode. For the two different temperatures used here, the recovery on cycling the potential between 0.4 and 1.7 V was efficient. However, the number of cycles and the amount of charge required for the recovery at 70 °C were the smallest, which is of great interest for the proton exchange membrane fuel cell performance. The recovery using such a wide potential range at 70 °C resulted in an enhancement of the electrocatalytic activity of the GC/n-Pt electrode over a non-poisoned (bare) GC/n-Pt electrode.

Influence of Formic Acid Impurity on Proton Exchange Membrane Fuel Cell Performance

The effect of trace amounts of formic acid (HCOOH) in hydrogen fuel on proton exchange membrane fuel cell (PEMFC) performance is reported. Long-term stability tests (100 h), periodic cyclic voltammetry scans, and electrochemical impedance spectroscopy analyses are used to evaluate and characterize the effects of this impurity on fuel cell performance. The results show that trace amounts of HCOOH cause degradation in fuel cell performance and significantly contaminate the electrodes. Furthermore, full recovery from the contamination could not be achieved by applying pure hydrogen to the anode while operating the fuel cell. However, this degradation may also be caused by the coarsening or dissolution of Pt, in addition to any permanent effects of HCOOH contamination. Mechanisms of contamination of the electrodes and performance degradation of the PEMFC are also postulated.

Effects of the cell thermal behavior and water phase change on a proton exchange membrane fuel cell performance

A two-dimensional, non-isothermal, electrochemical-transport using a fully coupled numerical model is developed for a proton exchange membrane fuel cell to investigate simultaneous water, heat transport phenomena and their effects on cell performance. The multiphase mixture formulation for the two-phase transport process is used, and developed model is treated as a single domain. This process is leading to a single set of conservation equations consisting of continuity, momentum, species, potential and energy for all regions of cell. The result indicates that flooding of porous cathode reduces the rate of oxygen transport to the cathode catalyst layer and causes an increase in cathode polarization. Also, flooding could effect current density distribution, where a slight abrupt change occurs in the slope of the local current density curve. The amount and location of condensation in the GDL cathode is directly related to the cell temperature, where the temperature difference predicted by this model is about 3.7 °C at 0.6 V. The maximum temperature occurs near the inlet and at interface between membrane/catalyst layers at cathode side where major heat generation takes place. The results are validated with experimental data available that are in good agreement.

Influence of Formic Acid Impurity on Proton Exchange Membrane Fuel Cell Performance

The effect of trace amounts of formic acid (HCOOH) on proton exchange membrane fuel cell (PEMFC) performance is reported. Experimental approaches including long term stability test, cyclic voltammetry (CV) scans and electrochemical impedance spectroscopy (EIS) were used to evaluate and characterize the contamination. The results show that trace amounts of HCOOH can cause degradation in fuel cell performance and significantly contaminate the electrodes. Furthermore, fully recovery from the contamination could not be achieved only by reverting to pure hydrogen while operating the fuel cell. Mechanisms of contamination of the electrodes and performance degradation of the PEMFC are also postulated.

Investigation of the Corrosion Stability of Stainless Steels under Simulated Low and High Temperature Proton Exchange Membrane Fuel Cell Operating Conditions

Stainless steels for low and high temperature proton exchange membrane fuel cell present several advantages over graphitic materials. The fabrication of bipolar plates from these kinds of alloys could reduce weight of the stack and provide high mechanical stability. Test results show that bipolar plates fabricated from standard V2A or V4A steel can withstand the corrosive conditions in a low-temperature (50 {degree sign}C) proton exchange membrane fuel cell. For water cooled applications with an operating temperature around 80 {degree sign}C and thus resulting heavily corrosive conditions, two high-alloyed steel specimens have proven to be suitable. Further analyses show variations in corrosion resistance after pre-treating steel samples with e.g. physicochemical surface treatments, electro-polishing, thermal annealing and corrosion protective coating solution. The high temperature PEMFC test condition with 85% phosphoric acid and 160 {degree sign}C operation temperature leads to visible corrosion traces on all specimens except one.

Model prediction of effects of operating parameters on proton exchange membrane fuel cell performance

The performance of a proton exchange membrane (PEM) fuel cell is greatly affected by the operating parameters. Appropriate operating parameters are necessary for PEM fuel cells to maintain stable performance. A three-dimensional multi-phase fuel cell model (FCM) is developed to predict the effects of operating parameters (e.g. operating pressure, fuel cell temperature, relative humidity of reactant gases, and air stoichiometric ratio) on the performance of PEM fuel cells. The model presented in this paper is a typical nine-layer FCM that consists of current collectors, flow channels, gas diffusion layers, catalysts layers at the anode and the cathode as well as the membrane. A commercial Computational Fluid Dynamics (CFD) software package Fluent is used to solve this predictive model through SIMPLE algorithm and the modeling results are illustrated via polarization curves including I–V and I–P curves. The results indicate that the cell performance can be enhanced by increasing operating pressure and operating temperature. The anode humidification has more significant influences on the cell performance than the cathode humidification, and the best performance occurs at moderate air relative humidity while the hydrogen is fully humidified. In addition, the cell performance proves to be improved with the increase of air stoichiometric ratio. Based on these conclusions, several suggestions for engineering practice are also provided.