High-Temperature Proton Exchange Membrane Fuel Research Articles

Ten-fold reduction from the state-of-the-art platinum loading of electrodes prepared by electrospraying for high temperature proton exchange membrane fuel cells

The electrospraying deposition technique was used to prepare electrodes with a Pt loading of only 0.1 mgPt cm−2 and make membrane electrode assemblies (MEAs) for High Temperature-Proton Exchange Membrane Fuel Cells (HT-PEMFCs) based in H3PO4-doped polybenzimidazole membranes. An MEA prepared from binderless electrodes yielded a maximum performance of 420 mW cm−2 (i.e. a cathode specific power of 4.2 kW gPt−1) when tested with H2/Air at ambient pressure, that is, to the best of our knowledge, the highest performance ever reported at such a low Pt loading in HT-PEMFCs. The durability of this MEA was not affected by both, the absence of binder or the low Pt loading of the catalytic layer, since it worked continuously for >3000 h at 0.2 A cm−2 with a performance loss of 4% and a voltage decay of 5 μV h−1 in the last 1500 h.

Synergistic Behavior of Phosphonated and Sulfonated Groups on Proton Conductivity and Their Performance for High-Temperature Proton Exchange Membrane Fuel Cells (PEMFCs)

Some new polybenzimidazoles (PBIs) containing different acidic groups (−SO3H and −PO3H2) as proton donors and amphoteric groups (imidazole and −PO3H2) as proton transmitters were synthesized. The proton conductivity was 0.015 S·cm–1 for PBI1 and 0.075 S·cm–1 for PBI2 at ambient temperatures in water. At 140 °C and RH = 30%, the proton conductivity equaled 0.126 S·cm–1 for PBI2 and 0.003 S·cm–1 for Nafion. Moreover, PBI2 showed high proton conductivity under anhydrous conditions at 140 °C. It exhibited a porous morphology due to its sulfonated hydrophilic side chains. Theoretical studies showed that hydrogen bonding (HB) interactions of side chains and main chain groups leads to the formation of pores in the polymer structure. The presence of pores and hydrophilic groups in polymer structure increases water uptake and the durability of water molecules at high temperatures. The formation of a great HB network between acidic and amphoteric groups helps proton transport under anhydrous conditions.

Effect of Methylimidazole Groups on the Performance of Poly(phenylene oxide) Based Membrane for High-Temperature Proton Exchange Membrane Fuel Cells

A series of phosphoric acid (PA) doped imidazolium poly(phenylene oxide) (PPO) membranes with different methylimidazole (MeIM) contents were prepared to tailor the performance of solid-state membranes. First, brominated poly(phenylene oxide) (BPPO) was synthesized by methyl bromination. Then BPPO was reacted with MeIM and doped with PA. The process was confirmed by Fourier transform infrared spectroscopy and 13C NMR. The PA absorption ability of the imidazolium poly(phenylene oxide) (PPO-MeIM) membranes changed with increasing MeIM content. PPO-MeIM membrane showed the best proton conductivity of 6.79 × 10–2 S cm–1 at 0% relative humidity, the highest mechanical strength of 4.8 MPa at the molar ratio of 4:10 (M-3#) at 30 °C, and high power density of 260 mW cm–2 without additional humidification at 160 °C. Results indicated that incorporation of an appropriate amount of MeIM groups can achieve the best proton conduction performance and mechanical properties.

Effect of Rectangular Ribs in the Flow Channels of HTPEM Fuel Cell by a Three-dimensional Model

Abstract This paper employs a three-dimensional model to study the cell performance of HTPEM (high temperature proton exchange membrane) fuel cells using rectangular ribs with various numbers transversely inserted at the axis in the anode and cathode channels, and determines the higher net cell power. The results show that the best net cell power occurs as the number of rectangular ribs is five, and the net cell power for five rectangular ribs is higher than that for without rib by 6.6%.

Evaluation of the Durability of a Metal-Organic Framework Catalyst in High-Temperature Proton Exchange Membrane Fuel Cells (HT-PEMFCs)

A non-pgm Metal Organic Framework (MOF) catalyst was evaluated for durability in the high-temperature environment associated with HT-PEMFCs under various conditions. Due to the higher PGM loading typically required for these systems, it is an ideal candidate for research regarding non-PGM catalysts. However, a common issue regarding non-PGM materials is their lack of durability in the low temperature humidified environment of a PEMFC, and until these issues are resolved, it will continue to provide a hindrance towards mass commercialization. Prior work had demonstrated the high performance of this particular catalyst[1], initially in RDE and low temperature fuel cells, and now in HT-PEMFCs. Membrane Electrode Assemblies (MEAs) were tested at 200˚C using a commercial polybenzimidazole (PBI) membrane, and were evaluated under several durability criteria, including constant voltage testing at various potentials (for demonstration of prolonged use), temperature cycling (to mimic startup/shutdown) and corrosion testing to evaluate losses in these primarily carbon-based materials. Early indications demonstrate a highly stable catalyst, as after nearly 40 hours of non-continuous chronoamperometric testing, the fuel cell demonstrated negligible performance losses at 650mV in air at 2.5bar total pressure. Acknowledgment: The authors gratefully acknowledge the financial support from the Department of Energy-Energy Efficiency and Renewable Energy, Fuel Cell Technology Office under an Incubator grant (DE-EE0006965). Use of the Stanford Synchrotron Radiation Light source, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. Use of Beamline 2-2 at SSRL was partially supported by the National Synchrotron Light Source II, Brookhaven National Laboratory, under U.S. Department of Energy Contract No. DE-SC0012704. Use of the beamline 9-BM in Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. MRCAT operations are supported by the Department of Energy and the MRCAT member institutions. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

A Mesoporous Structure SnP2O7/Graphite Oxide Composite as Proton Conducting Electrolyte for High-Temperature Proton Exchange Membrane Fuel Cells

A Mesoporous Structure SnP2O7/Graphite Oxide Composite as Proton Conducting Electrolyte for High-Temperature Proton Exchange Membrane Fuel Cells

Short Communication:In-situ Monitoring of Internal Temperature, Flow Rate and Pressure in the High-temperature Proton Exchange Membrane Fuel Cell Stack using Flexible Integrated Micro Sensor

Short Communication:In-situ Monitoring of Internal Temperature, Flow Rate and Pressure in the High-temperature Proton Exchange Membrane Fuel Cell Stack using Flexible Integrated Micro Sensor

Determination of the optimal operating temperature range for high temperature PEM fuel cell considering its performance, CO tolerance and degradation

The objective of this study is to propose guidelines for the operating temperature range of High-Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC) considering the overall performance, CO tolerance and durability. To study the effect of temperature on HT-PEMFC performance, polarization curves of the cell operating on respective hydrogen and hydrogen/CO mixture were measured at 5 different temperatures. The electrochemical impedance spectroscopy (EIS) was used to characterize the internal resistances and the results provided the electrochemical analyses and explanations of the temperature effect on the HT-PEMFC. In addition, the stability tests (100h) were also conducted, which were useful for trade-off study between performance requirement and lifespan of the cell. Results showed that the temperature effect on the cell performance and CO tolerance were less obvious in high temperature range (above 180°C) compared to the low temperature range (below 160°C). However, the degradation of cell performance is faster in the high temperature range. Analysis of experimental results revealed that the optimal operating temperature window is between 160 and 180°C by compromising among the cell performance, CO tolerance and durability, and where the low temperature end of the range is preferred depending on the feeding fuel.

Electrochemical Characterization of a High-Temperature Proton Exchange Membrane Fuel Cell Using Doped-Poly Benzimidazole as Solid Polymer Electrolyte

A high-temperature proton exchange membrane (PEM) fuel cell using H3PO4-doped poly benzimidazole (PBI) as solid polymer electrolyte has been developed and tested. The influences of operating temperature (between 130 and 170 °C), operating pressure (between 0 and 2 bar), and air flow rate on the performances of the fuel cell have been measured. A maximum power density of ca. 200 mW/cm2 has been measured. The existence of an optimum air flow rate (expressed in oxygen stoichiometric ratio) has been put into evidence. It allows an increase of the fuel cell voltage from 250 mV up to ca. 400 mV at 0.4 A/cm2.

Ion Dynamics and Mechanical Properties of Sulfonated Polybenzimidazole Membranes for High-Temperature Proton Exchange Membrane Fuel Cells

Polybenzimidazole (PBI)-based membranes are one of the systems of choice for polymer electrolyte fuel cells. Monomer sulphonation is one of the strategies suggested to improve proton transport in these membranes. We report a NMR and dynamic mechanical study aiming to investigate the effect of the sulphonation on the proton dynamics and the mechanical properties of the membranes. The analyses of 1H self-diffusion coefficients and 1H and 31P spectra versus temperature show that sulphonation causes the formation of interchain cross-links, which involve phosphoric acid molecules and the sulfonic groups. This, in turn, reduces the proton mobility and, consequently, the ionic conductivity. The increase of the membrane stiffness with sulphonation is confirmed by dynamic mechanical analysis through the behavior of the storage modulus.

Investigation on Catalyst Layers’ Structure Parameters on the Performance of High-Temperature Proton Exchange Membrane Fuel Cells

A two-dimensional steady state numerical model for high temperature polymer exchange membrane fuel cells based on Nafion212/SiO2composite membrane was developed. Finite element method was used to solve electrochemical kinetics coupled with flow, multi-component transport, charge balance and energy conservation. The model-predicted fuel cell polarization curve was compared with the published experimental result and a good agreement was found. The effects of the structure parameters of the catalyst layer including Pt/Carbon ratio and Pt loading on the performance of high temperature polymer exchange membrane fuel cells were evaluated.

Influence of the Sintering of Electrocatalysts and Decrease of Proton Conductivity on the Current-Voltage Performance in the High-Temperature Proton Exchange Membrane Fuel Cells (HT-PEMFC)

The influence of the sintering of electrocatalysts and decrease of the proton conductivity on the current-voltage performance in the HT-PEMFC was theoretically evaluated under the non-humid conditions at 150 °C, 170 °C and 190 °C. Decreasing rate of the proton conductivity was evaluated based on the tortuosity of the proton pass. The more the phosphoric acid was evaporated with a rise in temperature, the proton path found to become more tortuous and the proton conductivity was accordingly estimated to be decreased. A theoretical breakdown of the voltage drops indicated that the sintering of the electrocatalyst influenced on the voltage drop in earlier several hundreds of hours. The following voltage drop in the latter stage was caused mainly due to the decrease in the proton conductivity.

Evaluating Perfluorinated Acid Electrolytes for High-Temperature Proton Exchange Membrane Fuel Cell

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) based on phosphoric acid doped polybenzimidazole (H3PO4/PBI) membrane operate at elevated temperatures between 150 ºC and 180 ºC. The HT-PEMFC stacks have much simpler water and thermal management than lower-temperature PEM fuel cells and can operate on reformat gas. These advantages make this type of fuel cells an interesting candidate for auxiliary and stationary power units. At this moment, however, no commercial HT-PEMFCs have been developed to meet the reliability and cost requirements.One of the main reasons that limit the wide application of HT-PEMFCs is the sluggish oxygen reduction reaction (ORR) rate in concentrated phosphoric acid. Despite good physical and chemical properties, phosphoric acid is a rather poor fuel cell electrolyte. The slow ORR kinetics in concentrated phosphoric acid is still not completely understood, and it is believed to be related to strong adsorption of phosphoric acid species on the surface of the platinum catalyst.Fluorinated acids as alternative electrolytes might hold the key to overcoming this obstacle. They seem to adsorb less strongly on platinum compared with phosphoric acid, which may increase the ORR rate and lead to high-performance fuel cells. In addition, these novel acids are ideal model systems to study the influence of adsorbates on ORR.Appleby and Baker [1] were among the first who proposed trifluoromethane sulfonic acid (CF3SO3H) as an alternative electrolyte for phosphoric acid fuel cells. Later, Yeager and his co-workers adopted the idea and conducted a more extensive research on fluorinated acids such as monofluorophosphoric acid [FPO(OH)2] and trifluoromethane sulfonic acid. The quest for novel electrolyte compounds that have the physical and chemical properties to meet the HT-PEMFC requirements remains challenging. An ideal candidate material should be both electrochemically and thermally stable, and it should have a very low vapour pressure over the operating temperature range of HT-PEMFCs. Recently, a number of perfluoroalkyl- phosphonic and phosphinic acids with different chain length have been successfully synthesized. These compounds might have the desired properties to serve as electrolytes for HT-PEMFCs. Besides their higher O2solubility they show significant advantages over phosphoric acid, such as a high protonic conductivity under unhydrous conditions [2]. Furthermore, these strong acids tend not to have specific adsorption on the platinum surface.Here, we report cyclic voltammetry (CV) and rotating disc electrode (RDE) experiments with small amounts of phosphoric acid and novel perfluorinated electrolyte candidates added into the perchloric acid electrolyte. Noticeable differences in the voltammograms (Fig. 1) and significant impact on the RDE kinetic current (Fig. 2) were observed. For a more thorough analysis of the adsorption mechanism, electrochemical impedance spectroscopy (EIS) measurements were carried out. Evaluation of the charge transfer resistance for the ORR on platinum was found to be in good agreement with the RDE measurements.Additionally, preliminary experiments were performed to assess the effectiveness of such alternative electrolytes for practical fuel cell applications. Perfluorinated acids were added into the catalyst layer of a HT-PEMFC. First results on the influence on membrane electrode assembly (MEA) performance will be presented.

Influence of the Sintering of Electrocatalysts and Decrease of Proton Conductivity on the Current-Voltage Performance in the High-Temperature Proton Exchange Membrane Fuel Cells (HT-PEMFC)

The relevance of the sintering of electrocatalysts and voltage drops of HT-PEMFC was theoretically evaluated under the non-humid conditions at 150 °C, 170 °C and 190 °C. The degree of agglomeration of electrocatalysts over time simulated by three-dimensional kinetic Monte Carlo method was compared and quantitatively agreed with experimentally measured Transmission Electron Microscopy (TEM) results. Agglomeration of electrocatalysts leads to the loss of the electrochemically active surface area. It was found to be occurred more severe as temperature increased. Decreasing rate of the proton conductivity was calculated based on the tortuosity of the proton pass. The more the phosphoric acid was evaporated, the more tortuous the proton path became. A theoretical breakdown of the voltage drops indicated that the deterioration of electrocatalysts impacted on the earlier several hundreds of hours. The decrease in the voltage at the latter stage was due to mainly the decrease in the proton conductivity.

Effects of CO on Performance of HT-PEM Fuel Cells

High temperature proton exchange membrane (HT-PEM) fuel cell is considered as one of the most probable fuel cells to be large-scale applied due to characteristics of high efficiency, friendly to environment, low fuel requirement, ease water and heat management, and so on. However, carbon monoxide (CO) content in fuel plays an important role in the performance of HT-PEM fuel cells. Volt-ampere characteristics and AC impedance of HT-PEM fuel cell are tested experimentally in this paper, and effects of CO in fuel on its performance are analyzed. The experimental results show that CO in fuel increases remarkably the Faraday resistance of HT-PEM fuel cell and decreases the electrochemical reaction at anode; the more CO content in fuel is, the less HT-PEM fuel cell performance is; with the increasing cell temperature, the electrochemical reaction on the surface of catalyst at anode is improved and the poisonous effects on the HT-PEM fuel cell are alleviated.

Design and Experimental Characterization of a High-Temperature Proton Exchange Membrane Fuel Cell Stack

Proton exchange membrane (PEM) fuel cells based on polybenzimidazole (PBI) polymers and phosphoric acid can be operated at temperature between 120 °C and 180 °C. Reactant humidification is not required and CO content up to 1% in the fuel can be tolerated, only marginally affecting performance. This is what makes high-temperature PEM (HTPEM) fuel cells very attractive, as low quality reformed hydrogen can be used and water management problems are avoided. From an experimental point of view, the major research effort up to now was dedicated to the development and study of high-temperature membranes, especially to development of acid-doped PBI type membranes. Some studies were dedicated to the experimental analysis of single cells and only very few to the development and characterization of high-temperature stacks. This work aims to provide more experimental data regarding high-temperature fuel cell stacks, operated with hydrogen but also with different types of reformates. The main design features and the performance curves obtained with a three-cell air-cooled stack are presented. The stack was tested on a broad temperature range, between 120 and 180 °C, with pure hydrogen and gas mixtures containing up to 2% of CO, simulating the output of a typical methanol reformer. With pure hydrogen, at 180 °C, the considered stack is able to deliver electrical power of 31 W at 1.8 V. With a mixture containing 2% of carbon monoxide, in the same conditions, the performance drops to 24 W. The tests demonstrated that the performance loss caused by operation with reformates, can be partially compensated by a higher stack temperature.

Modeling and parametric study of a 1 kW e HT-PEMFC-based residential micro-CHP system

A detailed thermodynamic, kinetic and geometric model of a micro-CHP (Combined-Heat-and-Power) residential system based on High Temperature-Proton Exchange Membrane Fuel Cell (HT-PEMFC) technology is developed, implemented and validated. HT-PEMFC technology is investigated as a possible candidate for fuel cell-based residential micro-CHP systems, since it can operate at higher temperature than Nafion-based fuel cells, and therefore can reach higher cogeneration efficiencies. The proposed system can provide electric power, hot water, and space heating for a typical Danish single-family household. A complete fuel processing subsystem, with all necessary balance-of-plant components, is modeled and coupled to the fuel cell stack subsystem. The micro-CHP system’s synthesis/design and operational pattern is analyzed by means of a parametric study. The parametric study is conducted to determine the most viable system/component design based on maximizing total system efficiency, without violating the requirements of the system. Four decision variables (steam-to-carbon ratio, fuel cell operating temperature, combustor temperature and hydrogen stoichiometry) were parameterized within feasible limits to provide insight on their effect on the overall performance of the proposed system under study and also to provide input on more efficient design in the future. The system is designed to provide maximum loads of 1 kW e and 2 kW th. A sensitivity analysis is applied to investigate the influence of the most important parameters on the simulated performance of the system.

Modeling and off-design performance of a 1kWe HT-PEMFC (high temperature-proton exchange membrane fuel cell)-based residential micro-CHP (combined-heat-and-power) system for Danish single-family households

A novel proposal for the modeling and operation of a micro-CHP (combined-heat-and-power) residential system based on HT-PEMFC (High Temperature-Proton Exchange Membrane Fuel Cell) technology is described and analyzed to investigate its commercialization prospects. An HT-PEMFC operates at elevated temperatures, as compared to Nafion-based PEMFCs and therefore can be a significant candidate for cogeneration residential systems. The proposed system can provide electric power, hot water, and space heating for a typical Danish single-family household. A complete fuel processing subsystem, with all necessary BOP (balance-of-plant) components, is modeled and coupled to the fuel cell stack subsystem. The micro-CHP system is simulated in LabVIEW™ environment to provide the ability of Data Acquisition of actual components and thereby more realistic design in the future. A part-load study has been conducted to indicate performance characteristics at off-design conditions. The system is sized to provide realistic dimensioning of the actual system.

Porous Organic-Inorganic Hybrid Electrolytes for High-Temperature Proton Exchange Membrane Fuel Cells

A family of porous silica-based organic-inorganic hybrid electrolytes containing surface propanesulfonic acid groups or polystyrenesulfonic acid (PSS) chains for high-temperature proton exchange membrane fuel cells (PEMFCs) is described. Porous silica-propanesulfonic acid (porous silica-PS) has higher proton conductivity than the primary porous silica, but still has limited operating temperature and low water uptake at . Porous silica-polystyrenesulfonic acid (porous silica-PSS) has high proton conductivity, large water uptake, and improved operating temperature, which are influenced by the proton density on the inner surface of nanopores. A maximum conductivity of is achieved at a relative humidity of 40% and a temperature of for porous silica-PSS with a surface proton density of . The porous silica-PSS-based fuel cell has good cell performance at .