Temperature Proton Exchange Membrane Fuel Research Articles

Enhancement of high temperature PEMFC stability using catalysts based on Pt supported on SiC based materials

With the aim of overcome the carbon supports of high temperature Proton Exchange Membrane Fuel cells (HT-PEMFC) electrodes, two novel non-carbonaceous support based on SiC have been assessed, SiC and SiCTiC. 40%wt. Pt was successfully deposited on them and they were physicochemical and electrochemically characterized. Both catalysts on SiC based materials showed a very high electrochemical stability in the half cell experiments in comparison with Pt on carbon support, showing a lower degradation rate of the electrochemical surface area (ECSA). Membrane Electrode Assemblies (MEAs) were prepared with the different catalysts and tested in a single cell (25cm2) operated at 160°C. The Pt/SiCTiC showed a good performance and the highest stability in the fuel cell tests carried under the same operation conditions.

From hydrogen production by water electrolysis to its utilization in a PEM fuel cell or in a SO fuel cell: Some considerations on the energy efficiencies

Ultra-pure hydrogen to feed a low temperature Proton Exchange Membrane Fuel Cell (PEMFC) or a high temperature Solid Oxide Fuel Cell (SOFC) can be produced by water electrolysis, either in a Proton Exchange Membrane Electrolysis Cell (PEMEC) working at low temperatures (25–110 °C) or in a Solid Oxide Electrolysis Cell (SOEC) working at high temperatures (600–950 °C). Both processes will be presented and discussed comparatively in terms of energy efficiencies, taking into account the working conditions at a low (70–80 °C) or a high (800 °C) temperature and at a given current density, conditions which are far from the thermodynamic equilibrium (no current flowing). Conversely to what is often written in the literature, the electrical energy efficiency of a SOEC never exceeds 100% and is comparable to that of a PEMEC, reaching in both cases 60–70% depending on the working conditions. In addition the electrical efficiency of a hydrogen/oxygen fuel cell working at a low temperature (PEMFC) or high temperature (SOFC) will be calculated allowing us to evaluate the round-trip energy efficiency of a hydrogen redox battery, such as a Unitized Regenerative Fuel Cell (URFC) for storage of intermittent energy. Some experimental examples of URFC working at low (PEM) or high (SOC) temperatures from recent publications will be presented and their energy efficiency will be estimated according to our theoretical calculations.

Heterogeneous Electrocatalyst of Palladium-Cobalt-Phosphorus on Carbon Support for Oxygen Reduction Reaction in High Temperature Proton Exchange Membrane Fuel Cells.

Palladium-cobalt-phosphorus (PdCoP) catalysts supported on carbon (Ketjen Black) were investigated as a cathode catalyst for oxygen reduction reaction (ORR) in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The PdCoP catalyst was synthesized via a modified polyol process in teflon-sealed reactor by microwave-heating. From X-ray diffraction and transmission electron microscopic analysis, the PdCoP catalyst exhibits a face-centered cubic structure, similar to palladium (Pd), which is attributed to form a good solid solution of Co atoms and P atoms in the Pd lattice. The PdCoP nanoparticles with average diameter of 2.3 nm were uniformly distributed on the carbon support. The electrochemical surface area (ECSA) and ORR activity of PdP, PdCo and PdCoP catalysts were measured using a rotating disk electrode technique with cyclic voltammetry and the linear sweep method. The PdCoP catalysts showed the highest performances for ECSA and ORR, which might be attributed both to formation of small nanoparticle by phosphorus atom and to change in lattice constant of Pd by cobalt atom. Furthermore, The HT-PEMFCs single cell performance employing PdCoP catalyst exhibited an enhanced cell performance compared to a single cell using the PdP and PdCo catalysts. This result indicates the importance of electric and geometric control of Pd alloy nanoparticles that can improve the catalytic activity. This synergistic combination of Co and P with Pd could provide the direction of development of non-Pt catalyst for fuel cell system.

Electrospinning a versatile tool for designing hybrid proton conductive membrane

The development of efficient hybrid membranes for high temperature Proton Exchange Membrane Fuel Cell (PEMFC) is currently under investigation. Here, we show that the electrospinning process combined with the sol-gel chemistry conduces to membranes with protonic conductivity similar to Nafion, at high temperature under the relative humidity of 90%, and with anisotropic mechanical properties due to the presence of long-range anisotropic object. The electrospun membranes’ morphology is also highly dependent on the sol-gel chemistry (with/without additives) as well as the processing parameters including relative humidity, applied electrical field, temperature, rotating electrode's speed… Our hybrid fibers are based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)/ SO3H-silica networks that combines the ability to mimic the nano structural phase separation observed in hydrated Nafion with major feature, that is, array of orientated ionic nano channels intermingled within a locally aligned polymer, where proton can easily diffuse in this tubular nanostructure.

Use of Hybrid Cathodes to Reduce Platinum Content in High Temperature Proton Exchange Membrane Fuel Cells (HT-PEMFCs)

An investigation into the development and use of hybrid cathodes in high temperature proton exchange membrane fuel cells was undertaken. Previously, non-pgm materials had been developed for use as oxygen reduction catalysts in proton exchange membrane fuel cells[1, 2]. Compared to platinum, long term durability of these non-pgm materials at the elevated temperatures associated with high temperature fuel cells is negatively impacted by the low active site density. In this work, these non-pgm materials are combined with low platinum loadings in order to take advantage of the high activity of the non-pgms as well as the high active site density of platinum. This reduction of platinum content allows for a drastic reduction in the price of membrane electrode assemblies (MEAs). Additionally, these non-pgm materials have shown very high tolerance towards phosphate poisoning (Figure 1) when compared to platinum[3]. Hybrid cathodes were fabricated and used in conjunction with proprietary membranes (TPS Membrane, Advent Technologies) and operated between 160°C and 180°C in order to evaluate performance and stability. 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.

(Invited) Modeling and Control of Pemfcs with Dead-Ended Anodes

Nitrogen, oxygen and water crossover and their accumulation in the anode channels of low temperature Proton Exchange Membrane Fuel Cells present system level challenges for the design and operation of devices with high hydrogen utilization. The low flow rates enable operation under self-humidified anode conditions further reducing the system weight, cost, and complexity which is especially important for small portable applications. However, accumulated inert gasses and liquid water need to be purged before severe starvation conditions lead to carbon corrosion, inevitably wasting some Hydrogen. Frequent purging wastes fuel and dries the membrane leading to physical degradation and membrane delamination observed in post mortem Scanning Electron Microscopy images. Model based control methods provide an automated way to schedule the anode purges and study the tradeoff between degradation and fuel efficiency over the life of a fuel cell stack [1]. In addition the models can be used for design purposes such as optimizing the anode channel dimensions to balance the tradeoff between power density and interval between purges. The transport of gas species in the anode and cathode channels can be predicted by partial differential equations, specifically the 1-D the multi-component Stefan-Maxwell equation along the length of the channel. The distribution of membrane hydration level and temperature must also be considered as they impact the crossover rate. The model accurately predict the nitrogen accumulation and resulting recoverable drop in terminal voltage over time between purges when operating with a Dead Ended Anode (DEA). The model has been validated by simultaneous Neutron Imaging (NI) and Gas Chromatography (GC) sampling from within the anode channel [4]. Neutron imaging provides a unique measurement of the liquid water distribution within the cell and can be performed on relevant materials and channel designs without the need for modified hardware with different thermal properties such as transparent plates for optical imaging. The two dimensional images provide information about both the membrane electrode assembly water content, and channel liquid water [5]. This allows us to validate model predictions of the two phase (liquid water) transition point along the length of the channels. Dead Ended Anode (DEA) operation represents the extreme case of operation with high hydrogen utilization. There are several practical advantages to studying this limiting behavior of the system. Foremost is the direct measurement of membrane permeation rates since the only sources of nitrogen and oxygen in the anode channel is crossover. The introduction of oxygen into the anode gas stream from membrane crossover is the primary mechanism for cathode carbon corrosion. The oxygen present in a hydrogen depleted region creates a voltage reversal and hence large cathode potential in the adjacent region of the cell similar to the one observed during startup conditions when the air is pushed out of the channels by hydrogen. A quaternary system for the anode channels using the Stefan-Maxwell framework was augmented with a model of carbon corrosion [3]. The resulting model of cathode active site loss predicts the slow non-recoverable voltage drop over 1000 hours of operation. The modeled corrosion rate matched the decrease in cathode catalyst layer thickness observed in post mortem SEM images [2]. Finally the augmented model has been used to study the optimum purge scheduling considering both corrosion and fuel efficiency [1]. The physical channel dimensions provide a rough estimate of feasible target purge duration (volume) and interval between purges. The minimum purge duration pushes the nitrogen blanketed region to the end of the channel, fully recovering the terminal voltage, whereas the maximum duration completely clears the channel (anything beyond this needlessly wastes fuel). The analysis and methodologies presented herein can be used for the design and control of fuel cell systems operating with high hydrogen utilization to prolong stack life and achieve high efficiency. [1] J. Chen, J. Siegel, A. Stefanopoulou, and J. Waldecker, IJHE, 38, (2013). [2] T. Matsuura, J. Chen, J. Siegel, and A. Stefanopoulou, IJHE, 38 (2013). [3] J. Chen, J. B. Siegel, T. Matsuura, and A. G. Stefanopoulou, J. Electrochem. Soc., 158, 9, (2011). [4] J. B. Siegel, S. V. Bohac, A. G. Stefanopoulou, and S. Yesilyurt, J. Electrochem. Soc., 157, 7 (2010). [5] J. B. Siegel, D. A. McKay, A. G. Stefanopoulou, D. S. Hussey, and D. L. Jacobson, J. Electrochem. Soc. 155, 11 (2008). Figure 1

Refuse-derived Fuel Gasification for Hydrogen Production in High Temperature Proton Exchange Membrane Fuel Cell Base CHP System

Environmental challenges and energy sustainability remain relevant for meaningful growth and development. Economic growth has been coupled with increasing energy demand across the globe. Hydrocarbons from fossil fuels dominate other available fuel sources for energy production. The world is not unfamiliar with significant contributions of environmental degradations and social implications. Renewable energy sources (hydro, wind, tidal, solar, geothermal, and biomass) are potential alternative energy sources. Municipal solid wastes potentials possess the capacity to generate hydrogen-rich syngas. Enrichment of energy density of municipal solid wastes enhances the renewable energy source generation. After the pre-treatment of municipal solid wastes and its densification to produce refuse-derived fuel, biomass refuse-derived fuel gasification was modelled in Aspen Plus model environment. The study of effects of equivalence ratio, temperatures range, catalysts, gasifying agents, and choice of carrier gas were considered. This study was carried out to know which of the factors enhance high yield of H2/CO syngas production ratio. Influence of high temperatures, equivalence ratio and catalysts dictate H2/CO molar ratio while others are subjected to the composition analyses of refused-derived fuel. The rich hydrogen produced can be integrated with high temperature proton exchange membrane fuel cell based CHP system. The study proposes refused-derived fuel gasification towards rich hydrogen production, eliminates waste treatment and disposal challenges.

Energy System and Thermoeconomic Analysis of Combined Heat and Power High Temperature Proton Exchange Membrane Fuel Cell Systems for Light Commercial Buildings

The United States Department of Energy’s Pacific Northwest National Laboratory is teaming with industry to deploy and independently monitor 5-kilowatt-electric (kWe) combined heat and power (CHP) fuel cell systems (FCSs) in light commercial buildings. Results of an independent evaluation of manufacturer-stated engineering, economic, and environmental performance of these CHP FCSs are presented here. An important contribution of this paper is the precise definition and development of these essential terms for quantifying distributed CHP generator energy use within buildings: (1) electricity and heat utilization, (2) electrical and heat recovery efficiencies, (3) in-use electrical and heat recovery efficiencies, (4) percentage usage of electricity, and (5) percent usage of recoverable heat. Key additional parameters evaluated include the average cost of the CHP FCSs per unit of power and per unit of energy, the change in greenhouse gas (GHG) and air pollution emissions with a switch from conventional power plants and furnaces to CHP FCSs, the change in GHG mitigation costs from the switch, and the change in human health costs from air pollution. CHP FCS heat utilization is expected to be under 100% at several installation sites; for six sites, during periods of minimum heating demand, the in-use CHP FCS heat recovery (HR) efficiency based on the higher heating value of natural gas is expected to be only 24.4%. From the power perspective, the average per-unit cost (PUC) of electrical power is estimated to span $15–19,000/kWe (depending on site-specific installation, fuel, and other costs), while the average PUC of electrical and HR power is $7,000–9,000/kW. Regarding energy, the average PUC of electrical energy is $0.38–$0.46/kilowatt-hour-electric, while the average PUC of electrical and HR energy is $0.18–$0.23/kWh. GHG emissions were estimated to decrease by one-third after replacing a conventional system with a CHP FCS. GHG mitigation costs were also proportional to changes in GHG emissions. Estimated human health costs from air pollution emissions decreased by a factor of 1000 with changing to CHP FCS. Reported for the first time here is the derivation of the PUCs of power and energy for a CHP device from both standard and management accounting (MA) perspectives. Results show that the average PUC of combined electrical and HR power is equal to the average PUC of electric power applying an MA approach, and also equal to the average PUC of HR power applying an MA approach. Similar relations hold for the average PUC of energy. Results presented here demonstrate the value of using the equations herein for economic analyses of CHP systems to represent the average PUC of electrical power, HR power, or both, and for energy.

Understanding on Electrochemical Structure of Low Temperature Proton Exchange Membrane Fuel Cells

Membrane electrode assembly (MEA) is the heart of a PEM fuel cell. In the catalyst layer, the electrochemical reactions only happen on the catalyst, which has simultaneous access to proton, electron and gas. Therefore, it is also called three-phase boundary (TPB). The larger and more stable TPB, the better performance of the cell will be. Different from fundamental material studies, catalyst performance was evaluated based on the electrode structure point of view. Interaction between catalyst or catalyst support with Nafion ionomer was systematically investigated through an adsorption isotherm study[i], [ii]. Various adsorption strengths were observed depending on the surface properties of the absorbent. The structure of the resulting catalyst-ionomer-electrode (CIE) and the corresponding degradation pattern due to accelerated stress test were monitored with X-ray photoelectron spectroscopy[iii]. Based on our earlier studies[iv], the polymer phase can directly influence the other two phases in the electrode. Degradation of the polymer / corruption of the interphase structure in the catalyst layer can be the bottle neck of the overall challenge. Corresponding strategy for the improvement is proposed. [i] Carbon, 71 (2014) 218-228. [ii] J. Phy. Chem. C, 118 (2014) 10814–10823. [iii] J. Power Sources, 274 (2015) 1217-1223. [iv] ACS Appl. Mater. Interfaces 6 (2014) 16565−16576.

Improving of Micro Porous Layer based on Advanced Carbon Materials for High Temperature Proton Exchange Membrane Fuel Cell Electrodes

AbstractThis work reports the study of four different carbon materials for their application as carbon material in microporous layers for high temperature proton exchange membrane fuel cells electrodes. The microporous layers were prepared with carbon black (a commercial one, Vulcan XC72), two different carbon nanofibers, CNF, (Ribbon and Platelet structure) and carbon nanospheres, all of them prepared in our lab. The microporous layers were characterized by XRD. The hydrophobicity, electrical conductivity, and permeability to different gases were also evaluated. The stability is an important issue to be overcome in the field of proton exchange membrane fuel cells. Thus, accelerated thermal and electrochemical degradation tests in phosphoric acid media were carried out to evaluate the stability of the different advanced materials tested under the same conditions. From all the performed essays, the carbon nanospheres were the best nano‐carbon materials because of the lower degradation degree shown by the microporous layer prepared with them and the good conductivity and permeability achieved, whereas CNF with a Platelet structure showed a low electrochemical stability due to their greater edge plane exposure which favors their corrosion.

“Distributed hybrid” MH–CGH2 system for hydrogen storage and its supply to LT PEMFC power modules

This paper describes the layout and presents the results of the testing of a novel prototype “distributed hybrid” hydrogen storage and supply system that has the potential to be used for Low Temperature Proton Exchange Membrane Fuel Cell (LT-PEMFC) applications. The system consists of individual Metal Hydride (MH) and Compressed Gas (CGH2) tanks with common gas manifold, and a thermal management system where heat exchanger of the liquid heated-cooled MH tank is integrated with the cooling system of the LT-PEMFC BoP. The MH tank is filled with a medium-stability AB2-type MH material (H2 equilibrium pressure of about 10bar at room temperature). This innovative solution allows for (i) an increase in hydrogen storage capacity of the whole gas storage system and the reduction of H2 charge pressure; (ii) shorter charging times in the refuelling mode and smoother peaks of H2 consumption during its supply to the fuel cell stack; (iii) the use of standard parts with simple layout and lower costs; and (iv) adding flexibility in the layout and placement of the components of the hydrogen storage and supply system.

Choice of the Ionomer for Phosphoric Acid-Doped High Temperature Proton Exchange Membrane Fuel Cells (PEMFC)

Recent progress has been made on PEMFC operating from 100oC to 200oC under ambient pressure. This strategy is recognized as a promising solution to the current limitation of low temperature (below 100oC) technique. The advantages of operation at such elevated temperature are: 1) improved kinetics of cathode and anode reaction; 2) improved tolerance of anode fuel contaminants; 3) no humidification of fuel needed and better life time in sub-zero temperature; 4) improved gas diffusion, solubility and permeability; 5) simplified cooling system and increase of power density [1-3].However, many challenges for materials come with the advantages. For example, carbon support corrosion is accelerated, especially for phosphoric acid-doped membrane fuel cells. Catalyst sintering and dissolution also happen along with the carbon corrosion [3]. For >150oC temperature operation, Nafion membrane suffer from dehydration and loss of proton conductivity. PBI-based membranes, together with other sulfonated polyaromatic electrolytes, are typically used because of the high mechanical strength at high temperature and retain of phosphoric acid in the polymer chain network for proton transport [3]. Long-time durability has also been proved form PBI-based membranes [3].Although we may have the right membrane to work with, the role of ionomer played in the catalyst layer (CL) and its compatibility with the membrane cannot be neglected [3]. In Nafion-based membrane fuel cells, the ionomer serves as a proton conductor forming a triple-phase boundary [5], whereas in phosphoric acid-doped membrane fuel cells, the ionomer is a binder that helps maintaining the phosphoric acid in the CL [6]. In addition, the interfacial resistance between the CL and proton exchange membrane (PEM) is found to be dependent on the choice of ionomer [3]. For phosphoric acid-doped PBI-based PEMFC, different types of ionomer have been reported, such as Nafion, polyvinylidene difluoride (PVDF), PBI and a combination of PBI and PVDF [6,7]. Studies on the PBI content in the CL have shown that the ionomer is able to penetrate to the primary pores of carbon and the mean pore size increase slightly with the increase of ionomer content. However, an optimal content of around 3 wt% [6] and 10-20 wt% [7] is independently concluded from the two studies.In this study, we attempt to investigate the effect of ionomer type and content on the pore structure, oxygen and air diffusivity and overall cell performance. We employed a one-step dry CL deposition method, reactive spray deposition technology (RSDT), to fabricate catalyst coated membrane (CCM), in which a thin-film CL was directly deposited onto the PEM through a flame-initiated mechanism. RSDT not only has more precise control over the electrode microstructure and component-level dispersion, but also eliminates several traditional manufacturing steps than ink-based deposition process [8]. An Air quench was incorporated into the RSDT process that allows for the introduction of carbon and ionomer at lower temperatures than the primary flame zone, which prevents thermal damage during deposition.The membranes under study included a Celtec-P PBI-based membrane and a pyridine and polyaromatic ether membrane. Nafion, PVDF and PBI were selected as the binder. Catalyst layers with platinum loading of 0.3 mg/cm2 and electrode thickness of ~15 µm were produced; see Figure 1. Transmission electron microscopy and energy dispersive X-ray spectroscopy were used to investigate the catalyst particles and the ionomer distribution. Pore size distribution was obtained through nitrogen adsorption. Single-cell test was performed on a 25 cm2CCM at 160oC at ambient pressure. Gas transport property during the fuel cell test was investigated by electrochemical impendence spectroscopy. Figure 1. a)CCM cross section structure prepared by RSDT with PVDF as binder; b) Pore size distributions for CCM with varying Nafion/Carbon weight ratio.

One-Step Deposition of Catalyst Layers for High Temperature Proton Exchange Membrane Fuel Cells (PEMFC)

Catalyst-coated membranes (CCMs) for use in high temperature proton exchange membrane fuel cells (PEMFC) were successfully fabricated by a one-step jet-flame direct deposition process using reactive spray deposition technology (RSDT). The as-deposited catalyst layer (CL) was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and electrochemical measurements. Pt nanoparticles averaging 2.6 nm in diameter formed a good dispersion with a Pt content of 47.5 wt% on the carbon. The Pt/C catalyst had a specific activity and a mass activity of 277 μA/cmPt2 and 0.155 A/mgPt, respectively. Polybenzimidazole (PBI) was employed as the membrane, and the membrane electrode assemblies (MEAs) were tested in temperatures ranging from 140°C to 160°C. Power densities of 375 mW/cm2 in oxygen and 135 mW/cm2 in air were achieved with a total Pt loading of 0.8 mg/cm2.

Microscopic Monitoring of Local Temperature in the High Temperature Proton Exchange Membrane Fuel Cell Stack

Microscopic Monitoring of Local Temperature in the High Temperature Proton Exchange Membrane Fuel Cell Stack

One Step Direct Deposition of Durable Cathodes for High Temperature Proton Exchange Membrane Fuel Cells (PEMFC)

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Pre-Heat and Start-Up Process of High Temperature Proton Exchange Membrane Fuel Cell

High temperature proton exchange membrane fuel cell (HT-PEMFC) advances the applications of fuel cells in automobile applications, and smooth start-up is one of the critical topics in researches. This work utilizes four pre-heat fluid mediums, i.e. water, silicone oil, liquid paraffin and air, to examine the pre-heat and start-up performance of single HT-PEMFC. Experimental temperature data at 10 different locations on upper side of bipolar plates matches well with that of simulation. The results show preheating in liquid phase meets the requirements of start-up, but leads to instability in the system. So liquid cannot be employed for pre-heat. On the contrary, preheating by gas phase will achieve good start-up performance, and may be used for hybrid electric vehicle (HEV).

The 3rd CARISMA International Conference on Medium and High Temperature Proton Exchange Membrane Fuel Cells

The 3rd CARISMA International Conference on Medium and High Temperature Proton Exchange Membrane Fuel Cells

Catalyst Degradation in High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

AbstractDegradation of carbon supported platinum catalysts is a major failure mode for the long term durability of high temperature proton exchange membrane fuel cells based on phosphoric acid doped polybenzimidazole membranes. With Vulcan carbon black as a reference, thermally treated carbon black and multi‐walled carbon nanotubes were used as supports for electrode catalysts and evaluated in accelerated durability tests under potential cycling at 150 °C. Measurements of open circuit voltage, area specific resistance and hydrogen permeation through the membrane were carried out, indicating little contribution of the membrane degradation to the performance losses during the potential cycling tests. As the major mechanism of the fuel cell performance degradation, the electrochemical active area of the cathodic catalysts showed a steady decrease in the cyclic voltammetric measurements, which was also confirmed by the post TEM and XRD analysis. A strong dependence of the fuel cell performance degradation on the catalyst supports was observed. Graphitization of the carbon blacks improved the stability and catalyst durability though at the expense of a significant decrease in the specific surface area. Multi‐walled carbon nanotubes as catalyst supports showed further significant improvement in the catalyst and fuel cell durability.

Performance Investigation of Membrane Electrode Assemblies for High Temperature Proton Exchange Membrane Fuel Cell

Different types of ABPBI (poly(2,5-benzimidazole)) membranes and polymer binders were evaluated to investigate the performance of MEAs for high temperature proton exchange membrane fuel cell (HT-PEMFC). The properties of the prepared MEAs were evaluated and analyzed by polarization curve, electrochemistry impedance spectroscopy (EIS), cyclic voltammetry (CV) and durability test. The results showed that MEA with modified ABPBI membrane (AM) has satisfactory performance and durability for fuel cell application. Compare to conventional PBI or Nafion binders, polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF) are more attractive as binders in the catalyst layer (CL) of gas diffusion electrode (GDE) for HT-PEMFC.

Thermal and water management of low temperature Proton Exchange Membrane Fuel Cell in fork-lift truck power system

A general zero-dimensional Proton Exchange Membrane Fuel Cell (PEMFC) model has been developed for forklift truck application. The balance of plant (BOP) comprises of a compressor, an air humidifier, a set of heat exchangers and a recirculation pump. Water and thermal management of the fuel cell stack and BOP has been investigated in this study. The results show that humidification of the inlet air is of great importance. By decreasing the relative humidity of inlet air from 95% to 25%, the voltage can drop by 29%. In addition, elevated stack temperature can lead to a higher average cell voltage when membrane is fully hydrated otherwise it causes a drastic voltage drop in the stack. Furthermore, by substituting liquid water with water–ethylene glycol mixture of 50%, the mass flow of coolant increases by about 32–33% in the inner loop and 60–65% in the outer loop for all ranges of current. The system can then be started up at about −25°C with negligible change in the efficiency.