Cell Proton Exchange Membrane Research Articles

Mitigation of Performance Degradation of PEM Water Electrolyzers by Power Distribution Control of Fluctuating Renewable Energy

Introduction Hydrogen production by water electrolysis using renewable energy such as wind and solar power generation (i.e., green hydrogen production) has attracted considerable attention as a key technology towards decarbonization. Proton exchange membrane (PEM) water electrolyzers are often used in combination with renewable energy source since they show fast response to input power fluctuation. However, lifetime of PEM electrolyzer needs to be improved for reducing hydrogen production cost. Recently we reported a durability analysis of PEM electrolyzers under wind power voltage fluctuations, where the reversible and irreversible voltage losses were analyzed in terms of gas bubble transport and catalyst degradation [1]. We also developed a novel control strategy called the power distribution control (PDC) that controls the power converters so that the input fluctuating power is decomposed to several fluctuating patterns that less degrade the electrolyzers than the input pattern [2]. The purpose of this study is to validate the effect of the PDC on mitigation of performance degradation of PEM electrolyzers under wind power fluctuations. Experimental method A membrane electrode assembly (MEA) with an active area of 1 cm2 was prepared using Nafion 117 membrane, IrO2 anode catalyst and Pt/KB cathode catalyst. The catalyst loading for anode and cathode was 0.5 mg IrO2/cm2 and 0.3 mg Pt/cm2, respectively. A PEM water electrolysis cell was prepared by assembling the MEA into a cell holder. The cell temperature was kept at 80°C during the durability test.Figure 1a) and 1b) show a schematic system diagram for performing the PDC and the two voltage fluctuation patterns (A and B) used for the durability test, respectively. As in our previous study [1], actual 24-h voltage fluctuation of wind power turbine was used as the primary data. The pattern A was prepared from the primary data by (i) scaling down the maximum voltage by 1/100 and setting the minimum voltage higher than the standard potential of water electrolysis and (ii) accelerating the time scale by 5 times. The pattern B was prepared by applying the PDC, that is, converting the pattern A into an alternative sequence of a high-operating rate pattern and a low-operating rate pattern as described in Ref. [2]. Here we set the average voltage of the high-operating rate pattern (~2.4 V) and the low-operating rate pattern (~1.7 V) as the same value with the voltage of the pattern A (~2.05 V) for each time, ensuring that we model the situation in which the input fluctuating power is distributed between two series of electrolyzers as shown in Fig. 1a). We performed 240-h durability tests and analyzed performance degradation of the PEM cell for the pattern A and B, respectively. Results and Discussion Figure 2 summarizes the performance degradation of the PEM cell during the 240-h durability test. The cell current density at the cell voltage of 2.1 V showed a steep decrease during the initial ~30 h for both pattern A and B. For 30 – 240 h, the current density continuously decreased for the pattern A (−0.68 mAcm-2/h), while no distinguishable decrease was observed for the pattern B (+0.06 mAcm-2/h). Therefore we successfully demonstrated that performance degradation of the PEM electrolyzers can be effectively suppressed by the PDC when using actual wind power voltage fluctuation as the input power.To further investigate the performance degradation behavior, the increase in overpotential components of the PEM cell was analyzed. Figure 2b) shows the comparison of overpotential components before and after the 240-h test. For the pattern A, the diffusion overpotential (E diff) showed a significant increase after the test for the current density higher than 1.0 mAcm-2. In contrast, for the pattern B, increase in E diff was suppressed and confirmed only for > 1.4 Acm-2. Increase in the activation overpotential (E act) was small compared to increase in E diff for both pattern A and B. Furthermore, we confirmed that the performance degradation confirmed in this study was reversible, that is, the current density was almost recovered within 24-h rest time after the test. These results are consistent with our previous study [1] in that the reversible degradation is related to gas bubble transport, that is, the increase in E diff. Therefore it was shown that the PDC suppresses reversible degradation, which is important for mitigating irreversible degradation during long-term operation. Our results demonstrate that PDC is a promising technique for improving lifetime of PEM electrolyzers operating under fluctuating renewable energy.

Electrochemical Oxidation of Ethanol and Methanol at Rh@Pt Catalysts at 80 °C in Proton Exchange Membrane (PEM) Cells

Efficient oxidation of ethanol to carbon dioxide is crucial for the development of sustainable electrochemical generation of power and hydrogen from bioethanol. However, high anode overpotentials and partial oxidation to acetaldehyde and acetic acid result in low efficiencies and waste management issues. Bimetallic Rh-Pt catalysts have shown enhanced activities and CO2 production in aqueous electrolytes, but not in proton exchange membrane (PEM) cells. In this work Rh@Pt core–shell catalysts, prepared from commercial carbon-supported Rh, have been evaluated in both aqueous H2SO4 and PEM cells. Cyclic voltammetry of aqueous methanol and ethanol has shown that the catalytic activity of the Pt shell is increased by the compressive strain induced by the Rh core, and that there is also a significant bifunctional effect at low Pt coverages. In PEM cells, these effects also increase selectivity for cleavage of the C–C bond of ethanol to produce CO2, which will enhance the efficiencies of ethanol fuel and electrolysis cells for producing power and hydrogen, respectively. Deposition of 0.5 monolayers of Pt onto the Rh core produced the highest CO2 yields at the lowest anode overpotentials, while higher coverages of Pt increased performances and CO2 yields at higher potentials.

Performance evaluation and economic analysis of integrated solid oxide electrolyzer cell and proton exchange membrane fuel cell for power generation

In order to generate clean electricity from thermal energy, a hybrid electrochemical system is conceptually developed by coupling the proton exchange membrane fuel cell (PEMFC) and solid oxide electrolyzer cell (SOEC). For evaluating the proposed hybrid system, firstly, the two subsystems are modeled numerically and then they are merged into an integrated SOEC-PEMFC system. Moreover, the SOEC-PEMFC is analytically modeled for further evaluation. The effects of important operational parameters are examined. The outcomes show that when the SOEC operating temperature increases from 823 to 1273 K, the efficiency increases from 18.7 % to 38 % and the net output power improves about 36 % while cost per unit of power of hybrid system decreases about 80 %. Furthermore, by increasing the PEMFC operating temperature from 323 to 348 K, the system net output power and efficiency increase about 16.7 % and 10 %, respectively, whilst the cost per unit of electricity decreases about 19 %. In addition by increasing operating pressure of system, the net output power and efficiency are also improved. The proposed system has maximum output power density of 3.9 kW.m−2 and maximum efficiency of 38 %. In addition, the SOEC-PEMFC system is compared with the previously studied proton exchange membrane electrolyzer cell-proton exchange membrane fuel cell (PEMEC-PEMFC) system. In comparison with the previous PEMEC-PEMFC system, the present system's cost per unit of power and efficiency are about 16 % and 17 % higher, respectively; while the output power density is about double that of the PEMEC-PEMFC system. Generally, because hydrogen-powered systems offer reliable operation from an economic and energetic perspective, the SOEC-PEMFC system represents a promising technological solution to the clean energy demands.

Promotion of Sulfur Vacancies and Mn Substitution in Few-Layered Molybdenum Disulfide Towards Superior Hydrogen Evolution in Acid

The superior features of hydrogen as an energy source with high energy density (120 MJ kg-1) and zero CO2 emission, makes it a strong candidate for replacing fossil fuels. Recently the European Commission has pledged to invest €470 billion in renewable hydrogen technologies by 2050, with a significant portion of this investment expected to be allocated for the deployment of renewable hydrogen electrolyzers by 2030. Water electrolysis via Proton Exchange Membrane (PEM) with Pt/Pd-based noble metals as a cathode, is currently the most effective method for hydrogen production, but alternatives are highly needed due to the scarcity and the higher cost of these metals. One of the promising classes of electrocatalysts for hydrogen evolution reaction (HER) is transition metal dichalcogenides (TMDs), and among them molybdenum disulfide (MoS2) has shown promising properties as an electrocatalyst for hydrogen production. MoS2 has different phases of 1T, 2H, and 3R with 2H-MoS2 being the most promising electrocatalyst for hydrogen production due to its semiconductive behavior and long-term stability. However, the poor conductivity, large band gap and no active basal plane towards HER limits the applications of 2H-MoS2 for water electrolysis in PEM cells. Strategies such as introduction of defects, S-vacancies, edge engineering and doping can result in enhanced HER activity of 2H-MoS2. Incorporating different transition metals (Ni, Co, Mn, Fe) into MoS2 lattice can increase the number of active sites and improve charge transfer during the electrocatalytic reaction. Based on Density Functional Theory (DFT) studies, insertion of Mn into MoS2 layer can decrease the bandgap to zero, resulting in large number of available electronic states around the Fermi level. In this work we introduce Mn doped MoS2 produced via a cost-effective microwave-assisted solid-state approach to explore the potential of few-layered MoS2, doped with different levels of manganese (5%, 10% and 15% at.) for HER in acidic media. The electrocatalytic activity towards HER reveals that 10% at. Mn incorporation into MoS2 lattice, reduces the overpotential (η10) from 210 mV for pristine MoS2 to 148 mV for 10%Mn-MoS2, respectively. In addition, Tafel slope analysis has confirmed a faster kinetics of 10%Mn-MoS2 (53 mV dec-1) compared to MoS2 (75 mV dec-1) revealing the Volmer–Heyrovsky mechanism as the rate determining step (rds). Further characterization by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and DFT studies show that Mn substitution promotes the creation of sulfur vacancies, which in turn enhances the catalytic activity towards HER. Additionally, the 10% Mn-doped MoS2 demonstrates remarkable activity in a single-cell PEM electrolyzer with long-term durability. This study highlights the potential of Mn doped MoS2 as an efficient, low-cost electrocatalyst for hydrogen production, with implications for the development of a sustainable hydrogen economy. Figure 1

Supported-Ir Catalysts: The Impact of the Supports' Chemical Composition on the Oxygen Evolution Reaction

In water electrolyzer cells, the anode electrode is one of the most important components, where the oxygen evolution reaction (OER) takes place. In this process, the water molecules split into oxygen ions, protons, and electrons, and the oxygen gas is produced on the anode surface [1]. The most suitable materials that catalyze OER are ruthenium, iridium, and their oxides, but their cost and scarcity require reduction and enhancement of their utilization [2]. One morphological strategy consists of the dispersion of the active nanoparticles in supportive nanoparticles made of less expensive materials to increase their mass activity. In addition, due to the high potential reached during operating conditions for water splitting, supportive materials have to possess a high corrosion resistance. Titanium oxides are good candidates because of their high thermal and chemical stability, low cost, and commercial availability [3]. But their poor electric conductivity (∼10−6 S cm−1) makes the design of an active and stable catalyst a complex task. In this work, Ir nanoparticles have been synthesized on the surface of several Ti-based nanoparticles and a complete analysis of their physicochemical properties have been carried out ( Fig. 1a-b ). In addition, electrochemical behaviour has been tested ex-situ in a half cell by the rotating disk electrode technique and after, the catalysts have been deposited in a polymer membrane for testing in-situ in a single cell proton exchange membrane water electrolyzer. The results show a successful performance of the supported Ir/TiO2 nanoparticles comparable to the pure Ir black nanoparticles but with an active metal loading five times lower. Differently, even though TiC showed excellent electrical conductivity during the ex-situ characterization, Ir/TiC nanoparticles had a poor activity after just one day of performance in the WE due to the complete oxidation of the TiC into TiO2 ( Fig. 1c-d ). Finally, Ir/TiB2 showed a balanced result in terms of activity and stability, showing promising properties as a catalyst for PEM-WE. Sadhasivam T., Ho-Young J. Chapter 3 - Nanostructured bifunctional electrocatalyst support materials for unitized regenerative fuel cells// Nanostructured, Functional, and Flexible Materials for Energy Conversion and Storage Systems- 2020.- 69-103. Antolini E. Iridium as Catalyst and Cocatalyst for Oxygen Evolution /Reduction in Acidic Polymer Electrolyte Membrane Electrolyzers and Fuel Cells // ACS Catal. - 2014.- 4, N 5.- P. 1426-1440. Van Pham C., Bühler M. IrO2 coated TiO2 core-shell microparticles advance performance of low loading proton exchange membrane water electrolyzers// Applied Catalysis B: Environmental-2020.- P 269.- P. 118762. Figure 1. TEM image of Ir/TIO2 (a), EDX mapping of Ir/TiO2(b), linear sweep voltammetry of catalysts (c), the current density at given potential 1.80 V (d). Figure 1

Investigating the Suitability of Printed Circuit Components for Fuel Cells

Flexible electrochemical energy sources using non-traditional cell materials and topologies have attracted growing attention because they offer unique design opportunities that are still being explored. They also offer potential advantages such as conformability, high power density, high specific power, and low cost through the adoption of electronics manufacturing techniques. This study examines the feasibility of using flexible printed circuits boards (PCBs) as the anode and cathode current collectors (CCs) of single cell Proton Exchange Membrane Fuel Cell (PEMFCs). In this work, we determine the best anode and cathode interfaces at which to embed flexible CCs to obtain the highest power, as illustrated in Figure 1. The flexible anode and cathode CCs are embedded A) inside the PEM|Catalyst Layer (CL) interface, B) between the CL|Micro Porous Layer (MPL) interface and C) between the Gas Diffusion Layer (GDL)| Flow field (FF) interface. The performance of the single cell PEMFC with the embedded flexible anode and cathode CCs at the different interfaces described in Figure 1 is investigated by using I-V polarization curves, electrochemical impedance spectroscopy (EIS), and thermal imaging. The performance of the cells tested with the embedded flexible CCs is compared to the performance of a standard cell. This study also investigates the effect of varying the anode and cathode CC geometry (square shape vs. circular) and opening ratio (20%, 30%, 40%, 50% and 60%) on the cell performance. Figure 1

Performance recovery of proton exchange membrane electrolyzer degraded by metal cations contamination

Hydrogen production from renewable electricity offers an eco-friendly alternative to fossil fuels. Proton exchange membrane (PEM) electrolysis is a well-known method for this purpose. Studies have primarily focused on reducing costs of noble catalysts, improving efficiency, managing system degradation, and addressing membrane thinning caused by contaminated cations. However, techniques for PEM recovery post-degradation are still under development. This study investigated the effects of cations on PEM cells using artificial soft water, and analyzed two recovery methods to restore cell performance. Our findings indicate a significant rise in cell operating voltage and a decrease hydrogen production over 8 h of operation with soft water. After introducing both recovery methods, the initial operating value was reinstated in both cases. Only nitric acid treatment, however, achieved hydrogen production levels comparable to those of ultrapure water.

LMI-based Model Predictive Control Design for Supply Manifold Pressure Improvement of Proton Exchange Membrane Fuel Cell realized through Additive Manufacturing

The fuel cell is one of the renewable energy sources and proton exchange membrane (PEM) is the most common and widely used type. With the aim of increasing efficiency, this article first presents a developed PEM fuel cell with additive manufacturing (AM) process. Then, the nonlinear dynamic model describing the behaviour of the AM-based PEM cell is described, and considering the general working class, a new control method for adjusting the pressure of the supply manifold is presented. The planned control method is a combination of model predictive and LMI approaches and in addition to guaranteeing the stability of the closed loop system, it is able to adjust the pressure of the supply manifold and guarantee the optimal operation of the PEM system developed by the additive manufacturing process. The results of simulation and comparison in the MATLAB environment show the efficiency of the proposed control method in meeting the control objectives and improving the transient and permanent response.

Three-Dimensional CFD Simulation of a Proton Exchange Membrane Electrolysis Cell

The energy shift towards carbon-free solutions is creating an ever-growing engineering interest in electrolytic cells, i.e., devices to produce hydrogen from water-splitting reactions. Among the available technologies, Proton Exchange Membrane (PEM) electrolysis is the most promising candidate for coping with the intermittency of renewable energy sources, thanks to the short transient period granted by the solid thin electrolyte. The well-known principle of PEM electrolysers is still unsupported by advanced engineering practices, such as the use of multidimensional simulations able to elucidate the interacting fluid dynamics, electrochemistry, and heat transport. A methodology for PEM electrolysis simulation is therefore needed. In this study, a model for the multidimensional simulation of PEM electrolysers is presented and validated against a recent literature case. The study analyses the impact of temperature and gas phase distribution on the cell performance, providing valuable insights into the understanding of the physical phenomena occurring inside the cell at the basis of the formation rate of hydrogen and oxygen. The simulations regard two temperature levels (333 K and 353 K) and the complete polarization curve is numerically predicted, allowing the analysis of the overpotentials break-up and the multi-phase flow in the PEM cell. An in-house developed model for macro-homogeneous catalyst layers is applied to PEM electrolysis, allowing independent analysis of overpotentials, investigation into their dependency on temperature and analysis of the cathodic gas–liquid stratification. The study validates a comprehensive multi-dimensional model for PEM electrolysis, relevantly proposing a methodology for the ever-growing urgency for engineering optimization of such devices.

Performance evaluation of high-efficiency SOFC-PEMFC hybrid system fueled by liquid ammonia

The liquid ammonia-fueled SOFC-PEMFC (solid oxide fuel cell-proton exchange membrane fuel cell) hybrid system is studied, and the influence of three factors on the energy efficiency of the system is analyzed. The results show that when the SOFC fuel utilization rate gradually increases, the maximum power of the hybrid system is 1277.85 kW, the total electrical efficiency of the system can reach 62.55%, the combined cooling and power (CCP) efficiency is the highest 69.25%, and the thermoelectric efficiency is gradually increased to 93.19%. When the SOFC operating temperature gradually increases, the electrical efficiency of the hybrid system is the highest 62.72%, the CCP efficiency is 69.41%, and the thermoelectric efficiency is basically maintained at about 90%. When the SOFC operating pressure gradually increases, the total power of the system is up to 1352.19 kW, the electrical efficiency and CCP efficiency of the system are about 60%, and the thermoelectric efficiency of the system is basically maintained between 88% and 95%.

A Novel High Temperature Fuel Cell Proton Exchange Membrane with Nanoscale Phase Separation Structure Based on Crosslinked Polybenzimidazole with Poly(vinylbenzyl chloride)

A semi-aromatic polybenzimidazole (DPBI) is synthesized via polycondensation of decanedioic acid (DCDA) and 3,3-diaminobenzidine (DAB) in a mixed phosphorus pentoxide/methanesulfonic acid (PPMA) solvent. Ascribing to in-situ macromolecular crosslinker of ploly((vinylbenzyl chloride) (PVBC), a robust crosslinked DPBI membrane (DPBI-xPVBC, x refers to the weight percentage of PVBC in the membrane) can be obtained. Comprehensive properties of the DPBI and DPBI-xPVBC membranes are investigated, including chemical structure, antioxidant stability, mechanical strength, PA uptake and electrochemical performances. Compared with pristine DPBI membrane, the PA doped DPBI-xPVBC membranes exhibit excellent antioxidative stability, high proton conductivity and enhanced mechanical strength. The PA doped DPBI-10PVBC membrane shows a proton conductivity of 49 mS cm-1 at 160 °C without humidification. Particularly, it reveals an enhanced H2/O2 single cell performance with the maximum peak power density of 405 mW cm-2, which is 29% higher than that of pristine DPBI membrane (314 mW cm-2). In addition, the cell is very stable in 50 h, indicating the in-situ crosslinked DPBI with a macromolecular crosslinker of PVBC is an efficient way to improve the overall performance of HT-PEMs for high performance HT-PEMFCs.

A review on modeling of proton exchange membrane fuel cell

Fuel cells are electrochemical devices that convert chemical energy into electrical energy. Among various fuel cells proton exchange membrane fuel cell (PEMFC) is considered one of the most promising candidates for the next generation power sources because of its high-power densities, zero-emission, and low operation temperature. In recent years, modeling has received enormous attention and interest in understanding and studying the PEMFC phenomena. This article reviews recent progress in PEMFC modeling. Empirical/semi-empirical, analytical, and mechanistic models, zero-to-three dimensional models, and multiphase flow models, such as multiphase mixture, multi-fluid, and VOF models, are different types of PEMFC modeling approaches, respectively, in terms of parametric, dimensional and two or three-phase flow. The present study enlightens the importance of combining different modeling strategies and parameter identification in PEMFC modeling to achieve precise models to reduce the time and cost of experiments.

Decision support on membrane electrode assembly (MEA) production and factory concepts

Hydrogen production by the electrolysis of water using renewable energy is a key component of the energy transition toward carbon dioxide emission reduction. Therefore, electrolyzers are in increased demand and have to meet higher technical requirements. The most important component of an electrolyzer is the type of cell. The proton-exchange membrane (PEM) cell is the one that offers the most promise. Cell components and their materials are subject to volatile development conditions. In particular, various production technologies come to mind for producing assembled cells the so-called membrane electrode assembly (MEA). Currently, only small quantities are produced. To meet demand, production must be scaled up quickly. Nevertheless, high requirements are placed on the quality of the cells, since high-priced raw materials are used for PEM cells. Therefore, this paper presents a data-driven approach to assessing the appropriate production technology. First, general and specific requirements of a cell production scale-up are derived. Later, characteristics of suitable cell production technologies are extracted. By using a digital factory model, suitable for shop floor data, the basis for the conception and validation of possible production concepts is laid.

Role of H3O· Radical in the Degradation of Fuel Cell Proton-Exchange Membranes.

Membrane durability in proton-exchange membrane fuel cells (PEMFCs) is one of the major obstacles limiting its applications, especially in heavy-duty vehicles. Membrane degradation reactions are thought to be attacks by radicals such as hydroxyl (HO•) or hydrogen atom (H•) generated during fuel cell operation. For the H• case, computational modeling results have suggested that the reaction between H• and the sulfonic group should be the dominant degradation pathway. However, experimental work implies that the tertiary fluorine (t-F) attack is the dominant H• reaction pathway, apparently contradicting the theoretical prediction. Based on previous experimental evidence on isotopic substitution, we postulate that the hydronium radical (H3O•) might be present in PEMFCs. Our ab initio modeling indicates that this radical can be stabilized by the sulfonic anion on the polymer side chain. With the assistance of explicit water, the polymer side chain can undergo a conformational change, leading to a greatly reduced barrier for the t-F degradation reaction. Thus, our H3O• hypothesis is able to explain not only the previous isotopic substitution experiment but also why the t-F degradation reaction is a highly plausible H• degradation mechanism for proton-exchange membranes. To our knowledge, this is the first suggestion that H3O• radicals could be present in electrochemical devices with both experimental and theoretical support.

Constructing High-Density Hydrogen Bonding Networks via Introducing the Bipyridine Group for High-Performance Fuel Cell Proton Exchange Membranes

Constructing high-density hydrogen bonding networks is crucial to improve the proton conductivity of proton exchange membranes (PEMs) and the single-cell output power of high-temperature fuel cells (HTFCs). In this work, a series of benzimidazole polymers containing a pyridine group in the backbone are successfully synthesized via copolymerization. The high-density hydrogen network is constructed via blending the polyether polybenzimidazole (OPBI) with the bipyridine polybenzimidazole copolymer, and the 1,3,5-triglycidyl isocyanurate that contains nitrogen atoms and hydroxyl groups is used as a cross-linking agent. As a result, the proton conductivity and the output power density of the single cell are significantly enhanced by the high-density hydrogen bonding network. The single-cell performance of 693 mW cm–2 is achieved in the cross-linked OPBI/copolymer blend membranes containing pyridine group under a saturated phosphoric acid (PA) adsorption (284%). Even under the low PA uptake (178%), the proton conductivity (0.050 S cm–1) is 2.1 times that of the OPBI membrane (0.024 S cm–1), and the output power density of the single-cell performance (501 mW cm–2) is 1.4 times that of the OPBI membrane (358 mW cm–2). The results demonstrate that introducing nitrogen sites into polybenzimidazole cross-linked membranes is an effective strategy for preparing high-performance fuel cell PEMs.

Electrolysis of Ethanol and Methanol at PtRu@Pt Catalysts

Electrolysis of ethanol in a proton exchange membrane (PEM) cell is an attractive method for generating hydrogen from renewable resources. However, the most active anode catalysts, such as PtRu, produce acetic acid as the main product, which makes the process very inefficient. Core–shell nanoparticles can improve efficiency by providing more selective cleavage of the C–C bond at a Pt shell. Here, the influence of the amount of Pt deposited onto a commercial PtRu/C catalyst has been investigated for electrochemical oxidation of ethanol and methanol, in aqueous H2SO4 at ambient temperature and in a PEM electrolysis cell at 80 °C. It is shown that addition of a Pt shell improves voltammetric activity markedly for both methanol and ethanol oxidation, while half-wave potentials in the PEM cell are shifted to higher potentials as the Pt coverage is increased. However, limiting currents for ethanol oxidation in the PEM cell are increased, and it is shown that the distribution of products shifts strongly towards CO2, which provides more efficient production of hydrogen.

Constructing High-Density Hydrogen Bonding Networks Via Introducing the Bipyridine Group for High-Performance Fuel Cell Proton Exchange Membranes

Constructing High-Density Hydrogen Bonding Networks Via Introducing the Bipyridine Group for High-Performance Fuel Cell Proton Exchange Membranes

A Cooling design for an end cell in fuel-cell stack using forced air flow in metal foam: Modelling and Experiment

The effect of temperature on an end-cell plate in a proton exchange membrane (PEM) fuel cell stack is presented in this paper. Numerical analysis and experimental work investigated the impact of a heat exchanger filled with metal foam on the end-cell plate used for cooling a PEM stack. One side of the edge plate was subjected to constant heat flux (1.55 W/cm2) while the other side was insulated. A metal foam with a pore density of 40 and having a porosity of 60% was analysed. The model was simulated in ANSYS R3-CFD, and the thermal problem was solved using the local thermal non-equilibrium (LTNE) to investigate the heat transfer between the fluid and solid phases. The thermal solution studied the effect of metal foam heat exchangers at different airflow velocities between 0.2 and 1.5 m/s on end-cell plate’s temperature. The results showed heat transfer enhancement in plate temperature, proving that the use of the LTNE assumption illustrated the difference between the end-cell plate and fluid flow temperatures. The effect of inlet air velocity on the plate temperature was also examined. An experimental model of a commercial PEM stack was constructed out of aluminium. This model was tested at the same conditions as those employed in the numerical solution. The heat generated by a fuel cell was simulated by a surface heater providing the same heat flux as the actual PEM cell. The numerical and experimental results for the end-cell plate for both at flow direction and different inlet velocities were assessed. There was a good agreement between the numerical and experimental results.

Кроссовер в метанольном топливном элементе с модифицированной графеном мембраной

The possibility of modifying the nafion direct alcohol fuel cell proton-exchange membrane by monolayer graphene by hot pressing has been demonstrated. It is shown that this modification can reduce the permeability of the membrane on methanol while maintaining a high proton conductivity membrane, but with the long operation of the membrane without additional protection of the barrier layer formed in this way, it is detached. With a Nafion/graphene/Nafion membrane, the formed graphene layer is sufficiently protected to reduce the methanol crossover and increase the power of the single methanol fuel cell by 2 times.

(Invited) Development of Durable and Low Cost Membrane Humidifiers for Fuel Cell Systems

In order to operate effectively, currently commercialized fuel cell proton exchange membranes require sufficient hydration to ensure good proton transport. Hydration also ensures that membrane in the fuel cell stack will have a longer operational lifetime. In order to ensure adequate hydration in the stack, most liquid-cooled PEM fuel cell systems use external humidification. Without external humidification, the fuel cell must be operated at a lower operating temperature to ensure that the stack will not dry out. Operating the stack at lower temperature requires that the coolant loop in the system must reject a greater amount of heat, necessitating a large radiator, which increase system volume. Furthermore, operating at lower fuel cell stack temperatures leads to a significant trade-off in terms of stack power output and acceptable environmental operating ranges.Membrane humidifiers are an efficient form of external humidification that transport humidity through a membrane from the cathode exhaust to the incoming cathode supply air stream. In these humidifiers, membranes with a dense selective layer are used to transport water vapour without allowing oxygen and nitrogen to diffuse through the membrane. Since the membrane humidifier is coupled to the stack cathode exhaust and supply, in order to maintain its function, the membrane humidifier must not leak air or else reactant oxygen will bypass the stack through the humidifier. The humidifier must maintain a high level of water vapour transport and low air leakage over the lifetime of the device.In this presentation we present our work developing low-cost selective membranes for fuel cell humidification. These membranes are functional over a wide temperature range (-30 to +110°C) and have high water vapour permeance. They are resistant to contamination, relative humidity cycling, freeze-thaw cycling, oxidation, hydrolysis, and acidic conditions that are present in the cathode exhaust.This presentation will also discuss the incorporation of these flat-sheet membranes in to heat and mass exchangers (membrane humidifier cartridges). These cartridges are compact with a high membrane-to-volume ratio, high water vapour transport, and have low pressure loss. The membrane humidifiers are robust to a wide range of operating conditions. Furthermore, the design of these cartridges allows the humidifier to be manufactured at a low cost in high manufacturing volumes.Finally, this presentation will discuss membrane-based heat and mass exchanger performance at different operating conditions. A performance model will be presented which summarizes humidifier performance as a function of membrane properties, exchanger design and architecture, and fuel cell operating conditions.