Conventional Proton Exchange Membrane Fuel Cell Research Articles

Multi-criteria assessment of an auxiliary energy system for desalination plant based on PEMFC-ORC combined heat and power

A novel auxiliary energy system for desalination plant based on proton exchange membrane fuel cell (PEMFC)-organic Rankine cycle (ORC) combined heat and power is proposed in this paper. A thermodynamic model of the system is established, and a dynamic net present value (NPV) calculation method under the context of time-of-day tariff is designed. The system output power, economic and environmental evaluation indicators under steady-state and dynamic operation are optimized using NSGA-III and TOPSIS. The parameters sensitivity analysis shows increasing the ORC system saturation pressure and the auxiliary equipment efficiency is beneficial to increase output power and reduce indirect CO2 mass specific emission (MSE). However, excessive pressure and efficiency will lead to a significant decrease in NPV. Under steady-state optimization, the electrical power of the system is increased by 20.1 % compared to the conventional PEMFC system. And when the proposed system operates dynamically, the single-day power generation is 1620 kWh, which is 9.31 % higher than the PEMFC system. The single-day heated seawater production is 110.1 tons and the MSE is 0.105 kg/kWh. The NPV decreases significantly, but the system can pay for itself over its lifetime. Therefore, the proposed system has thermodynamic and economic performance advantages over the conventional PEMFC system.

Self-Water-Removal and Voltage Behavior Improvement of Dead-Ended Proton Exchange Membrane Fuel Cell Stack at Steady-State and Dynamic Conditions

The proton exchange membrane fuel cell (PEMFC) demonstrates high commercial competitiveness due to its advantages: low operating temperature, high power/mass ratio, fast response, no emission, and low noise. Thermal and water management remains a challenging issue for ensuring the fuel cell’s performance at steady-state and dynamic conditions. The cathode moisture condensation uses a semiconductor cooler to effectively remove excess water from the PEMFCs and reduce the probability of flooding of the stack. The stack’s voltage uniformity is an essential factor that affects the performance and lifetime of PEMFC. This paper investigates the dynamic response characteristics of the voltage uniformity of a PEMFC stack under cathode moisture condensation conditions. The results show that the condensation temperature at 10°C during the steady-state or transient operation of the PEMFC can effectively optimize the stack’s performance. Compared to conventional PEMFC, applying the cathode moisture condensation technology to the PEMFC stack increases the stack voltage by 6% and decreases the voltage uniformity by up to 30%. This self-water-removal technology effectively improves the voltage uniformity of the stack, which then increase the stack durability.

Improvement of thermal management of proton exchange membrane fuel cell stack used for portable devices by integrating the ultrathin vapor chamber

UVC (ultrathin vapor chamber) simultaneously has a high heat-conducting property, excellent temperature uniformity and simple structure. These advantages are very suitable for thermal management of the open-cathode PEMFC (proton exchange membrane fuel cell) stack. In this work, two-type UVCs with different appearances are integrated into a conventional PEMFC stack respectively. The effect of UVC on the output performance, thermal management and operating stability is investigated by the experiment combined with simulation. The results show that UVC can significantly increase the output voltage under high current density. In 35 A, the output voltage of the stack integrated the vertical UVC increases by 20.25% relative to the conventional stack. Thermal management is also improved by UVC. The highest temperature inside the stack decrease by 9 °C in 35 A, and the membrane temperature is decreased obviously. But it still exceeds the optimal operating temperature of open-cathode PEMFC stack due to the poor cooling type in the condensation side of UVC. UVC improves the operation stability of the stack and slows the deteriorative speed of output performance. This work hopes to attract more attention to the application of UVC on the thermal management of portable power sources used open-cathode PEMFC stack.

Experimental analysis of dynamic performance of air‐cooled PEMFC stack integrated ultrathin vapor chambers under New European Driving Cycle

Ultrathin vapor chamber (UVC) is very suitable for the thermal management of proton exchange membrane fuel cell (PEMFC) stack due to the simple structure, high heat conduction, and excellent temperature uniformity. For exploring the application of UVC on the thermal management of the PEMFC stack, a contrast experiment is performed between two PEMFC stacks (one named conventional PEMFC stack and the other named UVC-PEMFC stack) under the New European Driving Cycle mode with different purge periods. Experimental results show that UVC can significantly improve thermal management. It mainly behaves in two aspects: (a) UVC can effectively remove the waste heat. Under 60% load, the removed waste heat reaches 10.52% of Qgen, which generates a temperature difference of 12.5% between the two stacks. The maximum temperature is decreased from 58°C to 42.5°C under 0.645 A/cm2 and (b) UVC can also obviously improve the temperature uniformity. Under full load, the temperature uniformity of the UVC-PEMFC stack is 3.25 times lower than the conventional stack. The maximum temperature is decreased from 22°C to 3°C. The suitable working temperature and excellent temperature uniformity generate high efficiency, resulting in higher output power. For example, the output power of the UVC-PEMFC stack is 12.8% higher than the conventional PEMFC stack under 60% load. Unexpectedly, the long purge interval will reduce the dynamic response of the UVC-PEMFC stack under high current density. This investigation tries to provide an implication for a potential application of UVC on air-cooling PEMFC stack without changing its concise system.

Carbon nanotube sheet as a microporous layer for proton exchange membrane fuel cells

A multi-walled carbon nanotube (CNT) sheet was employed and investigated as a microporous layer (MPL) of proton exchange membrane fuel cell (PEMFC). The CNT sheet was synthesized via floating catalyst chemical vapor deposition method. The CNT sheet MPLs with the thickness of 15, 30, and 100 μm were prepared and compared with a commercial carbon-black MPL. As a result, it was found that the PEMFC with the 15-μm-thick CNT sheet MPL showed high electrochemical performance, and it outtopped the conventional PEMFC. The 15-μm-thick CNT sheet MPL increased the peak power density by 50.9% in air-supplied cathode and 20.9% in pure oxygen-supplied cathode compared to the conventional PEMFC. Through electrochemical impedance analyses, it was found that the CNT sheet MPL effectively decreased a charge transfer resistance, which is attributed to the improved reaction kinetics and mass transport through the MPL.

Research on the in-plane temperature distribution in a PEMFC stack integrated with flat-plate heat pipe under different startup strategies and inclination angles

Thermal behavior plays an important role in the application of a proton exchange membrane fuel cell (PEMFC) stack. Flat-plate heat pipe (FPHP) is proposed as an alternative cooling device in this study. Compared with conventional liquid-cooled PEMFC stack, PEMFC-FPHP stack needs less parasitic power for auxiliary system and provides a uniform temperature field. A PEMFC-FPHP stack was fabricated, assembled and tested. The experimental result shows that FPHP successfully delivers heat from the stack to surroundings. A more even in-plane temperature uniformity of cell unit is observed as load increases. The transient and stable in-plane temperature field of cell unit are influenced by startup strategy and gravity. In addition, direction of improvement for future work is given.

Graphene Oxide-Hydrogen Membrane Fuel Cell

Proton exchange membrane fuel cell (PEMFC) utilizes polymer electrolyte membrane, e.g., Nafion™, which is a perfluorosulfonic acid (PFSA) membrane with many disadvantages such as expensive, low mechanical strength, low chemical stability at high temperatures. Meanwhile, graphene oxide membrane (GOM) is an excellent proton conductor at room temperature under humidified conditions. However, graphene oxide membrane fuel cells (GOMFCs) exhibit low maximum power density compared to Nafion due to fuel gas crossover, membrane degradation and loss of surface functionalities. In this study, bilayer membrane consisting of GOM and hydrogen permeable metal thin film was investigated as electrolyte membrane for hydrogen membrane fuel cell (HMFC). In this fuel cell, the graphene oxide-hydrogen membrane (GOHM) simultaneously plays two roles, an anode catalyst and an electrolyte. A hydrogen permeable metal thin film of about 40 nm was deposited by DC magnetron sputtering at a suitable pressure and deposition time on a 12 µm-thick GOM using a Pd or Ni64Zr36 target to complete the bilayer GOHM electrolyte. The fuel cell performance of the GOHMFC using with Pt-free anode was compared with the GOHMFC with conventional Pt/C electrodes and conventional PEMFC.

Application of electrospinning for the fabrication of proton-exchange membrane fuel cell electrodes

Abstract Electrospun materials have been gaining great interest in the energy sector. Their tunability and robustness make them highly attractive, particularly for proton-exchange membrane fuel cell (PEMFC) electrodes. Conventional PEMFC electrodes, prepared by either spraying, painting, or slot-die coating, have not yet met the needs of large-scale PEMFC use. Electrospinning of fibrous materials has already shown great promise as an alternative methodology for electrode fabrication. Electrospinning has been used in fuel cell electrodes through two primary means: (1) segmented carbon or inorganic fibers to serve as precious metal catalyst support, and (2) high aspect ratio polymer/particle fibers to serve directly as the electrode. The use of electrospun fibrous electrodes has led to improved PEMFC durability and increased power output at low catalyst loadings, both of which are of paramount importance to large-scale commercialization of PEMFC electric vehicles.

Indirect fuel cell based on a redox-flow battery with a new structure to avoid cross-contamination toward the non-use of noble metals

An indirect fuel cell system is constructed. The system is composed of a redox flow battery (RFB) to extract electrical energy and two chemical reactors (anolyte and catholyte regenerators). A quinone as a redox mediator is reduced by a mixture of hydrogen and carbon monoxide in the anolyte regenerator, whereas a polyoxometalate as another redox mediator is oxidized in the catholyte regenerator, followed by a steady-state power generation at the RFB using the two redox mediators as active materials. This system demonstrates how to reduce the amount of platinum required in a proton-exchange membrane fuel cell (PEMFC), especially when using a fuel other than pure hydrogen. The RFB in our system contains two gas-diffusion electrodes (GDEs) with a platinum electrocatalyst to insert a “pure hydrogen gas phase” between the anolyte and catholyte to avoid cross-contamination. These two GDEs participate in the hydrogen evolution reaction and hydrogen oxidation reaction, respectively, and require only a small amount of platinum. In addition, the catalysts used in the anolyte regenerator are rhodium complexes. However, these catalysts are in a dissolved state (molecular catalysts) with micromolar-order concentrations, and very little noble metal is used. A carbonaceous catalyst without platinum is used in the catholyte regenerator. This eliminates the need for a noble metal for the oxygen reduction reaction, which is the main reason why platinum is used in a large amount in a conventional PEMFC. Steady-state operations of the anode side, the cathode side, and the total system are demonstrated in this work. Although a small amount of noble metal is still required at this stage, this work may contribute to the complete elimination of noble metals from a PEMFC.

Dynamic contact angle effects on gas-liquid behaviors in the cathode of proton exchange membrane fuel cell with stirred tank reactor design

ABSTRACTLiquid water management is still a critical issue in the improvement of proton exchange membrane fuel cell (PEMFC) performance. In this work, for the first time, the liquid water behavior and transport inside the cathode of a PEMFC with a stirred tank reactor (STR) design, rather than the conventional PEMFC flow channel design, are numerically studied. The dynamic contact angle (DCA) is applied to multiple wall boundaries in the numerical model through a user-defined-function (UDF) code, i.e., STR-DCA model. Another numerical model with the static contact angle (SCA) and same operating conditions, i.e., STR-SCA model, is also developed for comparison. The volume of fluid (VOF) method is employed in the simulation to track the gas-liquid interface. The results show that the liquid water distribution and transport are significantly different between these two models, indicating the remarkable effects of DCA on the simulation results. It is also verified the capability of STR-PEMFC to reduce the liquid water flooding, showing the potential of this channel-less type fuel cell in the further development.

High performance and durability of order-structured cathode catalyst layer based on TiO2@PANI core-shell nanowire arrays

In this paper, an order-structured cathode catalyst layer consisting of Pt-TiO2@PANI core-shell nanowire arrays that in situ grown on commercial gas diffusion layer (GDL) are prepared and applied to membrane electrode assembly (MEA) of proton exchange membrane fuel cell (PEMFC). In order to prepare the TiO2@PANI core-shell nanowire arrays with suitable porosity and prominent conductivity, the morphologies of the TiO2 nanoarray and electrochemical polymerization process of aniline are schematically investigated. The MEA with order-structured cathode catalyst layer is assembled in the single cell to evaluate the electrochemical performance and durability of PEMFC. As a result, the PEMFC with order-structured cathode catalyst layer shows higher peak power density (773.54mWcm−2) than conventional PEMFC (699.30mWcm−2). Electrochemically active surface area (ECSA) and charge transfer impedance (Rct) are measured before and after accelerated degradation test (ADT), and the corresponding experimental results indicate the novel cathode structure exhibits a better stability with respect to conventional cathode. The enhanced electrochemical performance and durability toward PEMFC can be ascribed to the order-structured cathode nanoarray structure with high specific surface area increases the utilization of catalyst and reduces the tortuosity of transport pathways, and the synergistic effect between TiO2@PANI support and Pt nanoparticles promotes the high efficiency of electrochemical reaction and improves the stability of catalyst. This research provides a facile and controllable method to prepare order-structured membrane electrode with lower Pt loading for PEMFC in the future.

Carbon‐Nanotube‐Supported Bio‐Inspired Nickel Catalyst and Its Integration in Hybrid Hydrogen/Air Fuel Cells

AbstractA biomimetic nickel bis‐diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H2/2 H+ interconversion from pH 0 to 9, with catalytic preference for H2 oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio‐inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni‐based PEMFC reaches 14 mW cm−2, only six‐times‐less as compared to full‐Pt conventional PEMFC. The Pt‐free enzyme‐based fuel cell delivers ≈2 mW cm−2, a new efficiency record for a hydrogen biofuel cell with base metal catalysts.

Carbon-Nanotube-Supported Bio-Inspired Nickel Catalyst and Its Integration in Hybrid Hydrogen/Air Fuel Cells.

A biomimetic nickel bis-diphosphine complex incorporating the amino acid arginine in the outer coordination sphere was immobilized on modified carbon nanotubes (CNTs) through electrostatic interactions. The functionalized redox nanomaterial exhibits reversible electrocatalytic activity for the H2 /2 H+ interconversion from pH 0 to 9, with catalytic preference for H2 oxidation at all pH values. The high activity of the complex over a wide pH range allows us to integrate this bio-inspired nanomaterial either in an enzymatic fuel cell together with a multicopper oxidase at the cathode, or in a proton exchange membrane fuel cell (PEMFC) using Pt/C at the cathode. The Ni-based PEMFC reaches 14 mW cm-2 , only six-times-less as compared to full-Pt conventional PEMFC. The Pt-free enzyme-based fuel cell delivers ≈2 mW cm-2 , a new efficiency record for a hydrogen biofuel cell with base metal catalysts.

Thermal Analysis of Heat Transfer Enhancement and Fluid Flow for Low Concentration of Al2O3 Water - Ethylene Glycol Mixture Nanofluid in a Single PEMFC Cooling Plate

Numerical analysis of thermal enhancement for a single Proton Exchange Membrane Fuel Cell (PEMFC) cooling plate is presented in this paper. A low concentration of Al2O3 in Water - Ethylene Glycol mixtures was used as coolant in 220mm x 300mm cooling plate with 22 parallel mini channels of 1 x 5 x 100mm. This cooling plate mimicked conventional PEMFC cooling plate as it was made of carbon graphite. Large header was added to have an even velocity distribution across all Re number studied. The cooling plate was subjected to a constant heat flux of 100W that represented the artificial heat load of a single cell. Al2O3 nano particle volume % concentration of 0.1 and 0.5 vol was dispersed in 50:50 (water: Ethylene Glycol) mixtures. The effect of different flow rates to heat transfer enhancement and fluid flow in Re range of 30 to 150 were observed. The result showed that thermal performance has improved by 7.3 and 4.6% for 0.5 and 0.1 vol % Al2O3 consecutively in 50:50 (water:EG) as compared to base fluid of 50:50 (water:EG). It is shown that the higher vol % concentration of Al2O3 the better the heat transfer enhancement but at the expense of higher pumping power required as much as 0.04W due to increase in pressure drop. The positive thermal results implied that Al2O3 nanofluid is a potential candidate for future applications in PEM fuel cell thermal management

Gasket-integrated carbon/silicone elastomer composite bipolar plate for high-temperature PEMFC

The primary components of proton exchange membrane fuel cell (PEMFC) systems are bipolar plates, end plates, membrane electrode assemblies (MEAs), gas diffusion layers (GDLs), and gaskets. The PEMFC composed of many components induces sealing problem of the stack, which affects the fuel efficiency, reliability, and maintenance costs of the system. Conventional PEMFCs are sealed with numerous elastomeric gaskets to seal the stack, which increases the manufacturing and assembly costs.To reduce the assembly time and to increase the sealing reliability without the use of gaskets, a gasket-integrated carbon/silicone elastomer composite bipolar plate is developed. Silicone elastomer is employed rather than conventional glassy thermoset or thermoplastic polymers for the matrix of the composite bipolar plate, where the silicone elastomer works as gaskets due to its resilience. The mechanical and electrical properties of the developed carbon/silicone elastomer composite are investigated at both room temperature and operating temperature of high-temperature PEMFCs (HT-PEMFCs). The sealability of the gasket integrated composite bipolar plate is tested.

Hydrogen Production on an Ethanol Dehydrogenation Reactor Coupled to a Conventional PEMFC

On board hydrogen storage has become a key factor for the technical viability of fuel cell driven electric or hybrid vehicles. In this work we present results of a system which comprises an ethanol dehydrogenation catalytic unit coupled to a conventional proton exchange membrane fuel cell (PEMFC). Ethanol is first dehydrogenated over a Cu/ZrO2 catalyst bed, and then the gas effluent is trapped in a simple cold condenser enabling a gas current rich in H2 to feed a PEMFC. Chronoamperometry (at a cell potential of 700 mV) showed apparent stability of the cell performance at about 300 mA cm-2 (with H2 produced from ethanol reaction) whilst at 550 mA cm-2 with pure H2. Maximum cell power density of our integrated system achieved almost 70% of the performance of the cell powered with pure H2.

Hydrogen Production on an Ethanol Dehydrogenation Reactor Coupled to a Conventional PEMFC

On board hydrogen storage has become a key factor for the technical viability of fuel cell driven electric vehicles. As the volumetric energy density of hydrogen is very low, on board storage of hydrogen remains a challenge in terms of weight, volume, kinetics, safety, and cost. Hydrogen can be produced from the steam reforming of ethanol (SRE) in a single-reactor usually operated in the temperature range of 823–1073 K so to avoid coke formation and to obtain high hydrogen yield. However, above 823 K the reverse water-gas shift reaction becomes thermodynamically favored to form carbon monoxide due to the high selectivity for the formation of C–C bond cleavage products (methane and CO), against the steps of C–O bond cleavage product (ethylene). Such formation of CO should be avoided because the PEMFC (proton exchange membrane fuel cell) conventional anode can only tolerate less than 10 ppm of CO, when operating in a low-temperature range (353–393 K). On the other hand, copper-based catalysts have been successfully employed for the selective conversion of ethanol to ethyl acetate or acetaldehyde.The best results for selective conversion to ethyl acetate has been achieved with ZrO2-supported copper catalysts, even though it provides 2 electrons/ethanol molecule against 12 electrons from ethanol dehydrogenation. However CO-free hydrogen gas phase and liquid fine chemicals can be produced at temperatures as low as 523 K. In this work we present results of a system which comprises an ethanol dehydrogenation catalytic unit coupled to a conventional PEMFC. Ethanol is first dehydrogenated over a Cu/ZrO2 catalyst bed, and then the gas effluent is trapped in a simple cold condenser enabling a gas current rich in H2 to feed a PEMFC with Pt/C electrodes. Chromatography showed that the liquid effluent is formed essentially by ethyl acetate which has heat of combustion between ethanol and gasoline. Thus, in a hybrid propulsion system for vehicles, the electricity generated by the fuel cell may feed an electric motor, while ethyl acetate may be used as fuel of an internal combustion engine. Chronoamperometry (at a cell potential of 0.7 V) showed apparent stability of the cell performance at about 300 mA cm-2 (with H2 produced from ethanol dehydrogenation) whilst at 550 mA cm-2 with pure H2 (from a cylinder). Cyclic voltammetry of the anode and cathode after four hours of reaction showed ease recovery to the fuel cell start conditions. The unprecedented and challenging development combines on line hydrogen production with a liquid renewable feedstock (ethanol) which employs low cost copper-based catalyst. Based on electrochemical experiments, the integrated system proved to be feasible, and so may play an important role to the progress of hybrid ethanol-hydrogen fuel cell vehicles.

Effect of wettability on water removal from the gas diffusion layer surface in a novel proton exchange membrane fuel cell flow channel

Effective water removal from the proton exchange membrane fuel cell (PEMFC) surface exposed to the flow channel is critical to the operation and water management in PEMFCs. In this study, the water removal process is investigated numerically for a novel flow channel formed by inserting a hydrophilic needle in the conventional PEMFC flow channel, and the effect of the surface wettability of the membrane electrode assembly (MEA) and the inserted needle on the water removal process is studied. The results show that the liquid water can be more effectively removed from the MEA surface for larger MEA surface contact angles and smaller needle surface contact angles. The pressure drop for the flow in the channel is also examined and it is seen to be indicative of the liquid water flow and transport in the flow channel, suggesting that pressure drop is a useful parameter for the investigation of water transport and dynamics in the flow channel.

Low-Cost, High-Efficiency Non-PGM Cathode Catalysts Using MOFs as Precursors

Oxygen reduction reaction (ORR) represents the most important electrochemical process in a proton exchange membrane fuel cell (PEMFC). An effective catalyst with improved active site design and support architecture could reduce the kinetic barrier, lower the electrochemical overpotential, and enhance the mass transfer as well as energy conversion efficiency. Conventional PEMFC cathode catalysts contain the platinum group metals (PGMs) which contributes significant fraction of the overall stack cost. We report herein our recent progress in developing low-cost, high-efficiency non-PGM catalysts for fuel cell using metal-organic framework (MOF) based compounds as the precursors. New approaches to prepare the catalysts with high surface area and active site density are demonstrated, supported by detailed characterization studies.

The Effects of the PEM Fuel Cell Performance with the Waved Flow Channels

The objective of this study is to use a new style of waved flow channel instead of the plane surface channel in the proton exchange membrane fuel cell (PEMFC). The velocity, concentration, and electrical performance with the waved flow channel in PEMFC are investigated by numerical simulations. The results show that the waved channel arises when the transport benefits through the porous layer and improves the performance of the PEMFC. This is because the waved flow channel enhances the forced convection and causes the more reactant gas flow into the gas diffusion layer (GDL). The performance which was compared to a conventional straight gas flow channel increases significantly with the small gap size when it is smaller than 0.5 in the waved flow channel. The performance is decreased at the high and low velocities as the force convection mechanism is weakened and the reactant gas supply is insufficient. The pressure drop is increased as the gap size becomes smaller, and the wave number decreases. (gap size)δ> 0.3 has a reasonable pressure drop. Consequently, compared to a conventional PEMFC, the waved flow channel improves approximately 30% of power density.