Air-breathing Proton Exchange Membrane Fuel Cell Research Articles

Numerical Study on Effect of Flow Field Configuration on Air-Breathing Proton Exchange Membrane Fuel Stacks

Air-breathing proton exchange membrane fuel cells (PEMFCs) show enormous potential in small and portable applications because of their brief construction time without the need for gas supply, humidification and cooling devices. In the current work, a 3D multiphase model of single air-breathing PEMFCs is developed by considering the contact resistance between the gas diffusion layer and bipolar plate and the anisotropic thermal conduction and electric conductive in the through-plane and in-plane directions. The 3D model presents good grid independence and agreement with the experimental polarization curve. The single PEMFC with the best open area ratio of 55% achieves the maximum peak power density of 179.3 mW cm−2. For the fuel cell stack with 10 single fuel cells, the application of the anode window flow field is beneficial to improve the stack peak power density compared to the anode serpentine flow field. The developed model is capable of providing assistance in designing high-performance air-breathing PEMFC stacks.

Optimization of hydrophobic additives content in microporous layer for air breathing PEMFC

This study explored the ideal polytetrafluoroethylene (PTFE) content in the microporous layer (MPL) for proton exchange membrane fuel cells (PEMFCs) operating under specific conditions: room temperature, ambient pressure, and no-external humidification. The physical properties of MPL were evaluated through FE-SEM and contact angle measurements, and to understand how these properties affect the performance of MPL under unique operating conditions only dependent on internally generated water, the maximum power density at various PTFE contents was compared and electrochemically investigated. Both 5% and 20% PTFE contents exhibited superior performance, and the optimal PTFE content for passive-type cells was determined through performance and durability evaluations. These findings are expected to enhance fuel cell technology's suitability as a compact, portable power source and offer valuable operational insights.

Portable proton exchange membrane fuel cell using polyoxometalates as multi-functional hydrogen carrier

Proton exchange membrane fuel cell (PEMFC) is an ideal energy-conversion technology for portable, motile as well as stationary applications. However, the use as a portable power source is still hindered by the stringent requirements for hydrogen storage. Herein, we propose a PEMFC system using hydrogenable polyoxometalate (POM) solution as hydrogen carrier that enables the whole system to work under atmospheric temperature and pressure. A proof-of-concept air-breathing PEMFC is constructed and three typical POMs are tested, the corresponding results demonstrate good cell performance and stability. Another impressive result shows that the hydrogen carrier, POMs, can be hydrogenated by multiple hydrogen sources such as H2, H2O and NaBH4 through both electrochemical and chemical ways. The newly designed system obtained a peak power density of 51 mW cm−2, making the real-world application of portable PEMFC possible.

Natural wood derived robust carbon sheets with perpendicular channels as gas diffusion layers in air-breathing proton exchange membrane fuel cells (PEMFCs)

Herein, a novel natural wood derived macroporous carbon sheet with three-dimension inter-connected perpendicular-channels was engineered as gas diffusion layers (w-GDLs) for air-breathing proton exchange membrane fuel cells (PEMFCs). Beneficial to the unique accessible perpendicular channels and the presence of a microporous layer, the current density reached 0.139 A/cm2 (at 0.6 V) and the maximum power density elevated up to 0.102 W/cm2 (at 0.43 V), which are comparable to the best results reported for the air-breathing PEMFCs with high Pt loadings. Furthermore, it exhibited excellent durability during preliminary constant discharge operation, demonstrating the feasibility of this w-GDL for practical applications.

Design, simulation and experimental characterization of a high-power density fuel cell

This research proposes a novel design of a millimeter-sized air-breathing proton exchange membrane fuel cell (AB-PEMFC). The producing method of the air-breathing PEMFC consisted of the sequential deposition of the elements in layers: 1) endplate of a flat polymer, 2) fuel flow channel with gas diffusion layers (GDL), 3) silicone seal with embedded micro Pt (platinum) wires, 4) membrane electrode assembly (MEA) with high platinum load, 5) GDL with micro Pt wires. Performance tests were done using an AB-PEMFC and the stack of two mono cells under different conditions. The results obtained by the computational fluid dynamics (CFD) allowed analyzing the current collector (CC) position. The performance results show 110 W L−1 for the cell power density and 2200 W kg−1 for the specific power density.

Durability of Alternative Metal Oxide Supports for Application at a Proton-Exchange Membrane Fuel Cell Cathode—Comparison of Antimony- and Niobium-Doped Tin Oxide

In this study, the resistance to corrosion of niobium-doped tin dioxide (Nb-doped SnO2, NTO) and antimony-doped tin oxide (Sb-doped SnO2, ATO) supports has been probed for proton-exchange membrane fuel cell (PEMFC) application. To achieve this goal, ATO or NTO supports with loose-tube (fiber-in-tube) morphology were synthesized using electrospinning and decorated with platinum (Pt) nanoparticles. These cathode catalysts were submitted to two different electrochemical tests, an accelerated stress test following the EU Harmonised Test Protocols for PEMFC in a single cell configuration and an 850 h test in real air-breathing PEMFC systems. In both cases, the dissolution of the doping element was measured either by inductively coupled plasma mass spectrometry (ICP–MS) performed on the exhaust water or by energy dispersive X-ray spectrometry (X-EDS) analysis on ultramicrotomed membrane electrode assembly (MEA), and correlated to the performance losses upon ageing. It appears that the NTO-based support leads to lower performances than the ATO-based one, mainly owing to the low electronic conductivity of NTO. However, in the case of ATO, dissolution of the Sb doping element is non-negligible and represents a major issue from a stability point-of-view.

Flexible and Lightweight Fuel Cell with High Specific Power Density.

Flexible devices have been attracting great attention recently due to their numerous advantages. But the energy densities of current energy sources are still not high enough to support flexible devices for a satisfactory length of time. Although proton exchange membrane fuel cells (PEMFCs) do have a high-energy density, traditional PEMFCs are usually too heavy, rigid, and bulky to be used in flexible devices. In this research, we successfully invented a light and flexible air-breathing PEMFC by using a new design of PEMFC and a flexible composite electrode. The flexible air-breathing PEMFC with 1 × 1 cm2 working area can be as light as 0.065 g and as thin as 0.22 mm. This new PEMFC exhibits an amazing specific volume power density as high as 5190 W L-1, which is much higher than traditional (air-breathing) PEMFCs. Also outstanding is that the flexible PEMFC retains 89.1% of its original performance after being bent 600 times, and it retains its original performance after being dropped five times from a height of 30 m. Moreover, the research has demonstrated that when stacked, the flexible PEMFCs are also useful in mobile applications such as mobile phones. Therefore, our research shows that PEMFCs can be made light, flexible, and suitable for applications in flexible devices. These innovative flexible PEMFCs may also notably advance the progress in the PEMFC field, because flexible PEMFCs can achieve high specific power density with small size, small volume, low weight, and much lower cost; they are also much easier to mass produce.

Construction of a high-performance air-breathing cathode using platinum catalyst supported by carbon black and carbon nanotubes

It is well recognized that pore structure and the hydrophilicity/hydrophobicity balance are key factors for the cathodes of air-breathing proton exchange membrane fuel cells (AB-PEMFCs). In this work, we attempted to adjust the pore structure and hydrophilicity of an air-breathing cathode by using two types of catalysts, Pt/C and Pt/CNT, to prepare the catalyst layer for the air-breathing cathode instead of using a single catalyst. An MEA with the dual-catalyst cathode exhibited significantly improved single-cell performance, which was affected by the ratio of Pt/C to Pt/CNT. Our optimized MEA, which had a ratio of 54:46 in the cathode catalyst layer, achieved a current density of up to 290 mA cm−2 at 0.6 V, which was 14% higher than that of a MEA without Pt/CNT. The Pt/CNT in the catalyst layer played the key role in the overall performance of the AB-PEMFC. We propose that the CNT improved charge transfer and enabled better electrical conductivity than carbon black. In addition, the tubular structure of Pt/CNT made the catalyst layer more porous and permeable to gas. Furthermore, the addition of Pt/CNT may have changed the cathode's hydrophilicity/hydrophobicity balance, giving the cathode better water balance and consequently yielding better performance.

Optimum design of the carbon composite bipolar plate (BP) for the open cathode of an air breathing PEMFC

The proton exchange membrane fuel cells (PEMFCs) are a promising source of portable power due to its high energy density, low emissions and wide power range. However, PEMFCs have some limitations for portable applications because of the supplementary power consumption and the mass increase by balance of plants, such as the fuel pump, air compressor and humidifier.In this study, a light mass PEMFC system was developed using carbon composite bipolar plates (BPs) and an air breathing stack design with open cathode channel configurations to reduce the mass of the stack. However, under the high compaction pressure, the failure occurred in the carbon composite BPs for the open cathode.To enhance the durability of the BP against the compaction pressure, the finite element analysis, the compressive test and the fracture toughness test were performed. The maximum compaction pressure on the BP was calculated by applying the maximum strain failure criterion to the composite BP. Then, the optimum thickness and stacking sequence of the open cathode bipolar plate were determined by considering the mass and the maximum compaction pressure.

Design strategy for reducing manufacturing and assembly complexity of air-breathing Proton Exchange Membrane Fuel Cells (PEMFC)

Conventional flat plate Proton Exchange Membrane fuel cell (PEMFC) designs have been under investigation for the last five decades with the majority of the research being conducted in fluid dynamics of the reactants, membrane chemistry, thermal characteristics, stacking, and electrical properties. By rigidly adhering to design characteristics and material choices (graphite flow plates and metal end plates), conventional fuel cell designs have become bulky, fastener intense designs that have a high degree of manufacturing and assembly complexity. The department of energy has recognized the need for economical and efficient manufacturing practices to further the market penetration and end user adoption of fuel cells. Therefore this paper analyzes air-breathing PEMFC's from the perspective of reducing manufacturing complexity, assembly complexity, and costs. Areas of complexity like the flow plates, end plates, sealing methods have been reassessed and this paper proposes alternatives to component functions, and the commonly employed materials along with an alternate assembly strategy. Prototypes built using the new design strategy achieved about 90% reduction in weight and number of components while enjoying an 80% reduction in costs. The new prototypes also possess a superior form factor, along with a 10-fold increase in power density as compared to conventional designs.

Performance evaluation of an air-breathing high-temperature proton exchange membrane fuel cell

The air-breathing proton exchange membrane fuel cell (PEMFC) is of great interest in mobile power sources because of its simple system design and low parasitic power consumption. Different from previous low-temperature air-breathing PEMFCs, a high-temperature PEMFC with a phosphoric acid doped polybenzimidazole (PBI) membrane as the polymer electrolyte is designed and investigated under air-breathing conditions. The preliminary results show that a peak power density of 220.5mWcm−2 at 200°C can be achieved without employing any water managements, which is comparable to those with conventional Nafion® membranes operated at low temperatures. In addition, it is found that with the present cell design, the limiting current density arising from the oxygen transfer limitation is around 700mAcm−2 even at 200°C. The short-term durability test at 200mAcm−2 and 180°C reveals that all the cells exhibit a gradual decrease in the voltage along with a rise in the internal resistance. The degradation rate of continuous operation is around 58.32μVh−1, which is much smaller than those of start/stop cycling operations.

Effect of cathode flow field configuration on air-breathing proton exchange membrane fuel cell

Air-breathing proton exchange membrane fuel cells (AB-PEMFCs) have been known to reduce the cost, complexity, noise, volume, and weight of fuel cells and can enhance their reliability. However, AB-PEMFCs still have some crucial issues such as the depletion of local oxygen concentration adjacent to the cathode in the absence of convection and hydrogen starvation at the anode side caused by the improper mass and water management in the dead-end mode. To manage mass and water efficiently, the effect of the opening ratio of the cathode opening geometry was investigated by considering the effects of the reaction area and contact resistance. When the opening ratio of the air flow field increased, the cell performance improved. However, at the high opening ratio of 72%, even though the voltage did not drop as quickly at high current densities as that at a low opening ratio, the cell performance was lower than that at the low opening ratio. And the slit-type fuel cells showed better performance by comparing the performances of the slit and square types of the cathode opening geometry. By introducing mesoscale channels on the flow field surface of the cathode, the formation of water droplets on the gas diffusion layer was minimized considerably.

Development of active breathing micro PEM fuel cell

Air-breathing proton exchange membrane fuel cells (AB-PEMFCs) can reduce the cost, complexity, noise, volume, and weight of fuel cells and can enhance their reliability. However, such cells are still typically characterized by low output power densities. In this study, to overcome the inherent weaknesses of low power density and oxygen concentration without mobility loss, we have adopted a microscale synthetic jet air breather (a crucial balance-of-plant device), which supplies air to the cathode side of the flow field of a planar AB-PEMFC. A synthetic jet air breather consists of a PZT diaphragm actuator, small cylindrical cavity, inlet and outlet channels, and a pump body. The flow rate of the fabricated synthetic jet air breather is more than 400 cc/min at 550 Hz with a power consumption of less than 0.3 W. An AB-PEMFC equipped with a microscale-synthetic jet air breather shows higher performance and stability, obtaining a maximum power density of 188 mW/cm2 at 400 mA/cm2.

A passive method of water management for an air-breathing proton exchange membrane fuel cell

Water management in an AB-PEMFC (air-breathing proton exchange membrane fuel cell) poses a big challenge due to its passive operation. The issue is addressed in a passive way by designing the fuel cell with low thermal conductivity materials. Use of low thermal conductivity materials for cell fabrication led to higher cell temperatures. The liquid water formation was delayed to high current densities due to increase in saturation pressure and higher buoyancy induced flow. Peak power density was increased by 36% and the limiting current density was increased by 37.5% when the cell was redesigned with low thermal conductivity materials. Fabricating the cells with low thermal conductivity materials can be very effective method of water management for air-breathing single PEM (proton exchange membrane) fuel cells and stacks of low capacity.

Effects of atmospheric aerosol on the performance of environmentally sustainable passive air-breathing PEM fuel cells

Abstract The effects of different airborne particulate contaminants (oxalic acid, soot, ammonium sulfate, and sodium chloride) and the gaseous air impurity NOx on the performance of a passive air-breathing proton exchange membrane fuel cell (AB-PEMFC) were investigated by introducing the pollutants into the oxidant air fed to a small AB-PEMFC module. All contamination data were corrected for variations in air temperature and relative humidity. While 10 ppmv NOx degraded fuel cell performance by 22% within 4 h and showed partial recovery of 70% within another 11 h, the effects of the aerosol particles were considerably less severe. Only oxalic acid and ammonium sulfate exhibited significant performance degradation with upper limits of 24% 1000 h−1 and 3% 1000 h−1, respectively. Sodium chloride as well as soot particles did not cause any significant performance decline. Because diffusion is the main transport mechanism for aerosol particles into a passive AB-PEMFC, only a minor fraction of the total particle mass can actually deposit inside these fuel cells resulting in rather low effects even under very high aerosol loadings. Therefore, aerosol related effects seem negligible under ambient conditions.

A New Complex Design for Air-Breathing Polymer Electrolyte Membrane Fuel Cells Aided by Rapid Prototyping

One of the most difficult issues to fabricate a fuel cell with a complex design is the manufacturing method. To solve this difficulty, the authors applied an innovative method of fuel cell fabrication, i.e., rapid prototyping technology. The rapid prototyping technology can both fabricate the complex design and shorten the fabrication time. In this paper, the authors used a 3D software (CATIA) on the fuel cell design and utilized the rapid prototyping to accelerate the prototype development of complex stack designs and to verify the practicability of the new fabrication for fuel cells. The honeycomb shape methanol reservoir and cathode structure design of a direct methanol fuel cell (DMFC) and the complex flow distributor design of a monopolar air-breathing proton exchange membrane fuel cell (PEMFC) stack, which were almost impossibly manufactured by traditional manufacturing, were made in this study. The performance of the traditional air-pumping DMFC and that of an air-breathing DMFC were compared in this study. The feasibility of a complex pseudobipolar design DMFC stack was also verified. For the miniature air-breathing PEMFC made by rapid prototyping with ABS material, its performance is close to the state-of-the-art compared to previous published literatures (Hsieh et al. 2006, “Study of Operational Parameters on the Performance of Micro PEMFCs With Different Flow Fields,” Energy Convers. Manage., 47, pp. 1868–1878; Schmitz, A., Wagner, S., Hahn, R., Uzun, H., and Hebling, C., 2004, “Stability of Planar PEMFC in Printed Circuit Board Technology,” J. Power Sources, 127, pp. 197–205; Hottinen, T., Mikkola, M., and Lund, P., 2004, “Evaluation of Planar Free-Breathing Polymer Electrolyte Membrane Fuel Cell Design,” J. Power Sources, 129, pp. 68–72). A new solution to manufacture complex fuel cell design, rapid prototyping, has been first applied to the fabrication of complicated flow channels in ABS materials and directly used in both DMFC and PEMFC in this paper. Its feasibility was verified and its promising performance was also proved.

Performance enhancement of air-breathing proton exchange membrane fuel cell through utilization of an effective self-humidifying platinum–carbon catalyst

One issue with air-breathing proton exchange membrane fuel cells (AB-PEMFCs) is that the reactants are not externally humidified, and thus the membrane or the catalyst layers might dry out due to electro-osmotic drag, diffusion and evaporation at the opening cathode. This results in a drop in internal ionic conductivity and thus in cell performance. Here, the preparation and characterization of self-humidifying carbon-supported Pt catalyst using citric acid modified carbon black (CA-CB) as the catalyst support are reported. Pt/CA-CB is highly hydrophilic due to the functional groups attached on the carbon support, which endows the ability to retain water in the membrane electrolyte assembly (MEA) and thereby help to improve the performance of AB-PEMFCs. A maximum power density of 204 mW cm −2 can be achieved in an air-breathing PEMFC stack using Pt/CA-CB, a thick polymer membrane (NRE212) and a circular opening cathode. A 23.4% enhancement in the output power density is obtained by using Pt/CA-CB in place of a commercial catalyst when oblique slit cathodes are employed. This self-humidifying catalyst is particularly suitable for portable PEMFC applications.

Innovative Design of an Air-Breathing Proton Exchange Membrane Fuel Cell With a Piezoelectric Device

This paper presents a three-dimensional transitional model to describe an innovative design for an air-breathing proton exchange membrane fuel cell (AB-PEMFC) with a microdiaphragm actuated by a piezoelectric device. This newly designed gas pump with a piezoelectric actuation structure is utilized as an air-flow channel in a proton exchange membrane fuel cell (PEMFC) system called PZT-PEMFC. When the actuator moves in the outward direction to increase the cathode channel volume, the air is sucked into the chamber: inward movement decreases channel volume and thereby compresses air into the catalyst layer and enhances the chemical reaction. The air-standard PZT-PEMFC cycle coupling with fuel∕air ratio is proposed to describe an air-breathing PZT-PEMFC. The model is able to simulate its major phenomena and performance in different fuel∕air ratio and PZT frequency. The results show that the PZT actuation leads to a more stable current output, more drained water, stronger suction, and overcome concentration losses at a proper PZT frequency.

The formation of water droplets in an air-breathing PEMFC

Air-Breathing Proton Exchange Membrane Fuel Cells (AB-PEMFC) have the potential to supersede lithium-ion batteries in portable electronics. However, their water management issue has yet to be resolved to ensure optimum cell performance and safe system operation. In this paper, the formation of water droplets and their aggregation in the cathode flow channels of an operating AB-PEMFC is investigated by direct visualisation under various operating conditions. The developed optical set-up enables observation of droplet formation on the surface of the membrane from the top and side view of the channels simultaneously. The two orthogonal views reveal that during formation the receding and advancing droplet contact angles are almost identical with values that increase, in a similar trend to the droplet height, with increasing droplet diameter. Water films were able to develop and maintain direct contact with the side wall of the channels even under the effect of gravitational force. The aggregation of water droplets in the channels was strongly influenced by the change in the air and hydrogen stoichiometry conditions. However, these operating parameters appear to have no significant effect on the water extraction from the channels contrary to load and temperature, where temperature has proved to be the most effective water removal mechanism with minimum reduction in the current density of AB-PEMFC.

Prediction of Deformation and Hygro-Thermal Stresses Distribution in Ambient Air-Breathing PEM Fuel Cells using Three-Dimensional CFD Model

The need for improved lifetime of air-breathing proton exchange membrane (PEM) fuel cells for portable applications necessitates that the failure mechanisms be clearly understood and life prediction models be developed, so that new designs can be introduced to improve long-term performance. A three-dimensional, multi-phase, non-isothermal computational fluid dynamics (CFD) model of an ambient air-breathing proton exchange membrane fuel cell has been developed and used to investigate the displacement, deformation, and stresses inside the whole cell, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the fuel cell during operation has been studied and investigated under real cell operating conditions. A unique feature of the present model is to incorporate the effect of mechanical, hygro and thermal stresses into actual three-dimensional fuel cell model. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. The nonuniform distribution of stresses can also contribute to delaminating between the gas diffusion layers and the current collectors, especially in the cathode side. These stresses may explain the occurrence of cracks and pinholes in the fuel cells components under steady-state loading during regular cell operation, especially in the high loading conditions. The paper ends with some recent patents and developments in the field.