PEMFC Single Cell Research Articles

On the smallness conditions for a PEMFC single cell problem

On the smallness conditions for a PEMFC single cell problem

Evaluation of the Performance and Mechanical Stability of PEMFC Single Cell Considering Vibration Characteristics in the Construction Equipment Working Environment

As the global demand for eco-friendly power sources increases, the adoption of hydrogen fuel cells as a sustainable and environmentally friendly alternative is gradually expanding in the construction equipment sector. Fuel cell technology has already gained significant attention with successful applications in various mobility sectors, including cars, buses, railways, and trucks. However, research in areas requiring extreme environmental conditions, such as construction equipment, is relatively scarce. Construction equipment often operates under high vibration and harsh climatic conditions, necessitating studies on fuel cell performance evaluation in similar environments. Previous studies have shown that applying vibration to hydrogen fuel cells can directly affect their performance, but research targeting construction equipment is very limited. Since vibration is an inevitable aspect of construction sites, research on this topic is essential for the practical application of hydrogen construction equipment. Based on this background, this study aimed to obtain basic data for the development of hydrogen fuel cells for construction equipment that can maintain stable performance even in a vibrational environment, by understanding the performance degradation and structural stability changes of fuel cells under vibration conditions. The fuel cells used in this study were 5 cm × 5 cm PEMFC single cells, and vibration tests were conducted in vertical, longitudinal, and lateral directions using a laboratory-scale shaker. The PEMFC single cells were kept in an operating (ON) state during the experiments, and vibrations that could occur in construction equipment were applied. The performance changes of the fuel cells according to vibration intensity and frequency were measured using constant current analysis, current-voltage (I-V) curves, and impedance analysis methods. Constant current analysis was used to evaluate the voltage stability of the single cell, I-V curves for assessing electrochemical efficiency and optimal operating conditions, and impedance analysis for evaluating electrical properties in electrodes and electrolytes.

Single Cell Regeneration Investigations on Ruthenium Poisoned Cathode Electrocatalysts for PEMFC

PEMFCs operating with reformate gases (a mixture of H2, CO2, and CO) are a promising alternative for CO2-neutral and environmentally friendly maritime transportation. [1] However, even trace amounts of CO in the hydrogen feed rapidly deactivate the platinum (Pt) electrocatalysts, leading to a high anode overpotential. [2] Pt-ruthenium (Ru) alloy nanoparticles (NPs) supported on carbon (PtRu/C) are among the most widely used anode electrocatalyst materials due to their high CO tolerance during the hydrogen oxidation reaction (HOR). [2, 3] Nevertheless, the PtRu/C anode catalysts suffer from the Ruz+ dissolution followed by crossover through the membrane and re-deposition onto the Pt/C cathode catalyst surface during the long-time PEMFC operation. [3] These phenomena are the main degradation processes in PEMFCs operated with reformate gas. Even at a Ru coverage of the Pt/C cathode catalyst surface of less than 20 %, there is an 8-fold decrease in the kinetics of the oxygen reduction reaction (ORR). [4, 5] Hence, the development of electrochemical regeneration procedures to mitigate or remove Ru-poisoning of the cathode catalyst surface on cell level is essential to extend the lifetime of PEMFCs, e.g. for maritime applications. [6]Based on our previous work in a three-electrode setup [6], we transferred a selective set of regeneration protocols for Ru-poisoned ORR catalysts using a fully automatic single-cell PEMFC test station. Therefore, catalyst coated membranes (CCMs) with a 12 cm2 geometric surface area were prepared by using two commercial Pt-Ru/C catalysts with different atomic ratios on the cathode side, maintaining the Pt loading of 0.2 - 0.3 mgPt cm-2 geo, while the anode electrode layer contained Pt/C with around 0.1 mgPt cm-2 geo. The anode side was exposed to successive H2/air fronts with different residence times as part of a regeneration strategy of the cathode electrode. The effect of the H2/air front and their residence time were investigated through electrochemical characterization methods, such as polarization curves, Tafel slope, ECSA, HFR, and impedance spectroscopy. Electrochemical performance results were correlated with PEMFC operating conditions (H2/air front, residence times) and structural data to evaluate changes in particle size, structure, and chemical composition of two different Pt-Ru/C catalysts using several techniques like cross-section scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), and microscopic X-ray fluorescence spectroscopy (µ-XRF).Our work evaluated different electrochemical recovery protocols of Ru-poisoned ORR catalyst materials to identify the most promising set of parameters for their re-activation procedure and therefore improve the lifetime of PEMFCs.

Understanding heat and charge transfer in a low temperature PEM Single Cell: a simulation tool development

This work is a study of coupled charges and heat transfers phenomena on a low temperature PEMFC single cell. A one-dimensional steady state model was developed to compute current and temperature distributions in a PEMFC single cell whatever the operating conditions. The work comprises of three parts: Firstly, a literature survey was conducted to describe the principle of a PEMFC and the fundamental operations. A state of the art of the previous modeling works on the PEMFC was also presented in this part. Secondly, the developed model using the basic relations to describe heat and charges transfer phenomena occurring in the single PEM cell was presented. Finally, a simple simulation tool called FCvb was performed and optimized using Visual Basic Excel and referring to the previous relations in the developed model. To finalize this study, a conclusion and perspectives were presented in the last part of this work.

Preparation of Membrane Electrode Assemblies Using Waste Tire Derived Carbon Supported Platinum Catalyst

Carbon supported Pt catalyst materials were synthesized from waste tire derived carbon by two different methods (microwave and refluxing). Catalysts and carbons were physically (XRD, N2 sorption analysis, TGA) and electrochemically characterized (RDE, CV, PEMFC single cell measurements). The RDE measurements were performed in 0.1 M HClO4 solution. For PEMFC single cell measurements, membrane-electrode assembly systems (MEAs) were prepared from catalyst materials by using different methods of coating the cathode layer and additional treatments. Catalysts were sprayed onto the membrane or GDL. In addition, MEAs were prepared where the catalyst was pipetted into GDL in several drops. Some of the MEAs were additionally treated with extra layer of Nafion and hot-pressed. The highest power density (0.42 W cm−2) was achieved with the MEA where the Pt catalyst synthesized via refluxing method was coated on the GDL with multiple drops and additional treatments were applied.

Synergistic Utilization of a CeO2-Anchored Bifunctionalized Metal–Organic Framework in a Polymer Nanocomposite toward Achieving High Power Density and Durability of PEMFC

The free radicals produced during the long-term operation of fuel cells can accelerate the chemical degradation of the proton exchange membrane (PEM). In the present work, the widely used free radical scavenger CeO2 was anchored on amino-functionalized metal–organic frameworks, and flexible alkyl sulfonic acid side chains were tethered onto the surface of inorganic nanoparticles. The prepared CeO2-anchored bifunctionalized metal–organic framework (CeO2-MNCS) was used as a promising synergistic filler to modify the Nafion matrix for addressing the detrimental effect of pristine CeO2 on the performance and durability of PEMs, including decreased proton conductivity and the migration problem of CeO2. The obtained hybrid membranes exhibited a high proton conductivity up to 0.239 S cm–1, enabling them to achieve a high power density of 591.47 mW cm–2 in a H2/air PEMFC single cell, almost 1.59 times higher than that of recast Nafion. After 115 h of acceleration testing, the OCV decay ratio of the hybrid membrane was decreased to 0.54 mV h–1, which was significantly lower than that of recast Nafion (2.18 mV h–1). The hybrid membrane still maintained high power density, low hydrogen crossover, and unabated catalytic activity of the catalyst layer after the durability test. This study provides an effective one-stone-two-birds strategy to develop highly durable PEMs by immobilizing CeO2 without sacrificing proton conductivity, allowing for the realization of improvement on the performance and sustained durability of PEMFC simultaneously.

Investigation of degradation mechanisms in PEM fuel cells caused by low-temperature cycles

Environmental influences, especially temperatures below the freezing point, can affect the performance and long-term stability of PEMFCs. Within the scope of this research, a completely new test procedure was developed to characterize PEMFC single cells with respect to their long-term stability at temperature cycles between 80 °C and −10 °C. Using this procedure, the behavior of PEMFC single cells (active surface area of 43.6 cm2) with different cathode-ionomer-to-carbon (I/C) weight ratios (0.5/1.0/1.5) was evaluated. The generated in-situ measurement data clearly demonstrate that the performance of each PEMFC single cell changes individually as a function of the cathode I/C-ratio during the 120 stress cycles. While the MEA with an I/C ratio of 0.5 showed a power loss of ~1.49%, the MEAs with an I/C ratio of 1.0 and 1.5 showed a power loss of about ~7.75% and ~24.7%, respectively. The subsequent post-mortem ex-situ analyses clearly showed how the test procedure and the different I/C-ratios affected the changes in the catalyst layers (CL). The destructive mechanisms responsible for the changes can be divided into two categories: One part was driven by rapid enthalpy change leading to mechanical failure, and the other part, which led to the reduction of cathode CL thickness, was driven by rapid potential changes and potential shifts (overpotentials). This reduction in cathode CL thickness ultimately leads to an accumulation and excessive load of ionomer in the direction of GDL, resulting in a reduction in pore size, a shift in the core reaction area, and high O2 transport resistance.

Online Measurements of Hydrogen Impurities in PEMFC Single Cells and Short Stacks

Impurities can easily contaminate pure hydrogen at various points in the supply chain. The maximum allowed impurity concentrations in hydrogen, sold for automotive PEMFC use, are regulated by the ISO 14687 standard. Imposing too strict limits on hydrogen quality increases the cost of hydrogen unnecessarily but too lax limits risk the performance and durability of PEFMCs. It is therefore imperative that the specified limits are based on rigorous and realistic studies of impurity behaviour in fuel cells. As part of the European Union funded projects HYDRAITE and MetroHyVe2, NPL is investigating the impact of fuel impurities on the performance and durability of fuel cells. The overall aim is to develop new testing standards and provide more reliable information to ISO committees for the continuous revision of fuel quality standards.Impurity studies are being carried out primarily on commercial short stacks tested with a hydrogen recirculation loop and a dead-end anode. This operation mode is typical in real systems as it gives a very high fuel utilisation, however it also causes fuel impurities to concentrate well above their inlet level. Standard fuel cell testing is coupled with online measurements of the concentration of a range of contaminants inside the anode recirculation loop. For example, a Gas Chromatograph with a methanizer and flame ionising detector (GC-methanizer-FID) is used to provide information on CO2, CO, and CH4; while Selected Ion Flow Tube - Mass Spectrometry (SIFT-MS) is used to analyse isotopically labelled impurities and probe the concentrations of other species as a function of time.Our results will first show the power and limitations of using online gas analysis with isotopically labelled impurities to monitor processes related to CO poisoning in single cells. We will then demonstrate that certain hydrocarbon impurities have little impact on stack performance despite being stringently regulated. Finally, we will present information on rates of O2 and CO2 crossover, drawing conclusions relevant for setting the next iteration of hydrogen fuel standards. This work provides vital underpinning metrological support for the development of more robust business cases for large scale deployment of hydrogen in automotive applications.

Bipolar plate design and fabrication using graphite reinforced composite laminate for proton exchange membrane fuel cells

A bipolar plate is designed to have high electric conductivity, low corrosion and good mechanical strength characteristics. The two most common materials adopted for bipolar plates are carbon and metal. The carbon bipolar plate has good electric conductivity and corrosion resistance but brittle. The metal bipolar plate has good mechanical strength, acceptable electrical conductivity but worse corrosion resistance. The main objective of this paper is to design and fabricate graphite composite laminate based PEMFC bipolar plate. A thermoset type phenolic resin is adopted as the matrix with a plain weave type woven graphite fiber cloth adopted as the composite laminate reinforcement. In the fabrication process, thermoset phenol-formaldehyde resin is first printed onto the plain-weave woven carbon fiber cloth and the waiting until air-dry as prepregs. Several layers of prepregs were then stacked into a mold and heated. The resin contained in the prepregs melted and cured into a composite laminate. The carbonization process is further conducted to increase the electric conductivity. The flow channels are carved and the bipolar plate is completely fabricated. The developed bipolar plates are assembled into a single cell PEMFC and tested. The composite bipolar plate performance with or without carbonization are also studied. The back side bipolar plate electric conductivity would also significantly affect the cell performance. Therefore, increasing the back side conductivity could increase the cell performance.

ZIF derived PtNiCo/NC cathode catalyst for proton exchange membrane fuel cell

High performance cathode catalysts with minimum platinum amount for the electrocatalyzed oxygen reduction reaction (ORR) in PEMFCs remain as a significant challenge for commercial application. Zeolitic Imidazolate Framework (ZIF) based catalyst can provide void 3D framework of N-doped nano-porous carbon for promising ORR activity. Here we report a bimetallic pyrolyzed NiCo-ZIF supported fine Pt/Pt alloy electrocatalyst for ORR. After pyrolysis, nano-porous carbon is obtained with well dispersed Pt/Pt alloy nanoparticles (˜ 3 nm). This catalyst shows superior performance and stability in acidic medium against the commercial catalyst comprising of Pt/C. In a single cell PEMFC, high peak power density value of 1067 mW. cm−2 is attained at 70 °C by using low platinum amount of 0.12 mg cm-2 on cathode. The enhanced activity and durability is credited to the synergistic impact of N-doped nano-porous carbon originated from NiCo-ZIF and the defect rich carbon support to anchor Pt/Pt alloy nanoparticles.

Investigation on the Impact of Carbon Porosity in the Microporous Layer of PEM Fuel Cells

In recent years, the PEMFC has seen tremendous progress in terms of reliability, durability and performance. The cathode performance in particular, greatly influences the overall performance. Issues such as water management remains a huge issue that must be addressed particularly in cases under high current density operating conditions as the occurrence of flooding is prevalent. The microporous layer (MPL) is pivotal in improving water management in PEMFCs. The layer which generally consists of carbon particles and a hydrophobic agent, functions as an intermediate layer between the catalyst layer and the more porous substrate layer. In MPL research, different types of carbon particles (BLACKPEARLS, XC-72R, acetylene black, graphite, etc.) have been compared and key relationships between the carbon porosity and overall PEMFC performance have been reported. However, it is difficult to delineate the impact of porosity from parameters such as particle size and agglomeration packing which are intrinsic to each type of carbon. This study focuses on the application of porous carbons that have been systematically modified in terms of porosity in the MPL to establish a clearer comparison. The first approach involves the modification of the porosity of carbon black to different degrees through physical activation. Carbon black particles were activated under CO2 ­for different durations to induce different levels of porosity. In the second approach, colloid-imprinted carbons (CIC) were synthesized with various pore sizes and used to study the impact of pore size in carbons on overall MPL performance in PEMFCs. Both approaches utilize the same type of carbon material but with varying porosities. The wettability of the carbon materials will also be studied as it also impacts the interaction between water and the carbon surface. To fabricate the MPL, the carbon was made into a slurry before being applied on a carbon fiber paper followed by sintering. The newly fabricated gas diffusion layer (GDL) was incorporated in a membrane electrode assembly (MEA) before being tested in a single cell PEMFC. The Pt loadings on the anode and cathode were 0.04 mgPt/cm2 and 0.4 mgPt/cm2 respectively. Polarization tests were used to study the electrochemical properties of the GDL during operation. Bulk powder samples were also characterized using N2 sorption, x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD) and transmission electron microscopy (TEM). The wettability and through-plane resistance of the fabricated GDLs were also examined. This study attempts to elucidate the impact of the porosity of carbons in the MPL on the mass transport losses in PEMFC. By establishing a further understanding on the effect of carbon porosity, improved microporous layer designs through material selection and design can be achieved leading to greater PEMFC operational robustness. Synthesis and characterization results of the porous carbon samples and the fabricated GDL along with their electrochemical results will be presented.

Implementation of DEIS for reliable fault monitoring and detection in PEMFC single cells and stacks

Dynamic Electrochemical Impedance Spectroscopy (DEIS) was presented as novel method for diagnostic and monitoring of PEMFC stack and single cells operation. Impedance characteristics were obtained simultaneously with current - voltage characteristics for stack and each individual cell. Impedance measurements were performed in galvanodynamic mode. It allowed to compare performance of each cell and identification of faulty cell operation for activation, ohmic and mass transfer losses regions. The biggest difference in impedance value between healthy and faulty cell was registered for mass transfer losses region. The authors discussed the statistical selection of an equivalent circuit based on the course of χ2 value in the function of current.

PEM FC Single Cell Based on a 3-D Printed Plastic Housing and Experimental Validation with the Mathematical Model

This paper presents the design, modelling, and testing of a PEM single fuel cell based on the use of 3D printing. The design of the housings was made of SolidWorks, while MATLAB/SIMULINK were used to model performance. The fabricated cell performed satisfactorily with no leaks of gas, showing that the 3D printing method can be used in the additive manufacturing of fuel cells thus leading to significant cost savings.

A Class of High Performance Electrocatalysts for Oxygen Reduction Reaction of Fuel Cells, using Iodine Doped Graphene

Low cost, sustainable and high performance electrocatalysts for oxygen reduction reaction (ORR) which can replace/reduce rare metals base catalysts are highly desirable for the effective commercial development of fuel cells. In this paper, we report a class of low cost electrocatalyst with highly performance for ORR, obtained by graphene doping with iodine precursor. It can be one of the most promising alternatives to Pt-based catalysts to date. Iodine doped graphene based materials were prepared by nucleophilic substitution and characterized by different techniques, including Scanning Electron Microscopy SEM, wavelength dispersive X-ray fluorescence WDXRF, that revealed the structure and morphology. The iodinated graphene was sprayed on gas diffusion layer (GDL) and tested in a single cell PEMFC. The electrochemical performances of fuel cell with/without iodinated graphene under typical experimental conditions were evaluated, namely current-voltage polarization and cyclic voltammetry curves, electrochemical impedance spectroscopy (EIS).

Design of Mg-Cu alloys for fast hydrogen production, and its application to PEM fuel cell

Mg-Cu alloys are designed for fast hydrogen generation by precipitating an electrochemically noble phase (Mg2Cu) at the grain boundaries. The noble precipitates accelerate the hydrolysis kinetics of the alloy by synergetic action of galvanic and intergranular corrosion. The Mg-3Cu alloy exhibits a hydrogen generation rate of 5.23 ml min−1 g−1, which is 307 times faster than that of pure Mg (0.017 ml min−1 g−1). Furthermore, the effects of annealing of the alloy on the hydrogen generation rate and the feasibility of the production of power via hydrolysis of Mg-3Cu alloy are also confirmed. The annealing of the alloy reduces the hydrogen generation rate through the decrease of precipitates, and 10 g of Mg-3Cu alloy can produce power of 7.25 W for 37 min by operation of a single cell PEMFC.

Effect of the Nafion content in the MPL on the catalytic activity of the Pt/C-Nafion electrode prepared by pulsed electrophoresis deposition

The aim of this work is to study the effect of Nafion content in the microporous layer (MPL) on the electrophoretically deposited Pt/C-Nafion electrode performance. First, the MPLs are prepared with different Nafion ionomer contents (5, 10, 20, 30 and 40 wt%) on the carbon paper substrates. Next, Pt/C-Nafion electrodes are prepared by pulsed electrophoresis deposition (pulsed EPD) from a Pt colloidal solution as a plating bath. The catalytic activities of the prepared Pt/C-Nafion electrodes are evaluated using the cyclic voltammetry (CV) technique for hydrogen oxidation reaction (HOR). Also, a PEMFC single cell test is carried out using the Pt/C-Nafion electrodes prepared with the pulsed EPD method as a cathode. The mass-specific power density for the Pt/C-30wt% Nafion electrode is 1578.8mWmgPt−1, which is higher than the rest of the Pt/C-Nafion electrodes. The Nafion content in the cathode MPL should affect the performance of the PEMFC, especially at a high current density.

Electrochemical Performance of Thin-Film Pt3y Electrodes in PEMFC

In current polymer electrolyte fuel cells (PEMFC), high amounts of platinum catalysts is required due to the sluggish kinetics of the oxygen reduction reaction (ORR). As such it is important to find ways to increase the activity of the ORR catalyst. Previous studies have shown that alloying platinum with yttrium results in a catalyst which is more than six times as active as sole Pt in half cell rotating disk electrode measurements [1]. The model electrodes in this study are prepared by sputtering a well-defined layer of alloy catalyst onto a gas diffusion layer (GDL). In this manner the composition and thickness of the film can be controlled. These electrodes are studied with single cell PEMFC measurements to characterize the materials, similar to previous work done with these types of electrodes [2]. Using these methods the electrochemical surface area (ECSA), ORR activity, and stability are evaluated. The effects of different MEA preparations will also be investigated. Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis as well and X-ray photoelectron spectroscopy (XPS) are used to characterize the structure of the alloy catalyst as well as the bulk and surface compositions, i.e. platinum to yttrium ratio. This characterization is performed on both as-prepared samples and electrodes after being used in the PEMFC. The main focus is to determine the role of yttrium in platinum thin-film platinum electrodes, and if the excellent activity in half cell experiments will also be seen in real PEMFC measurements.

Research on the performance differences between a standard PEMFC single cell and transparent PEMFC single cells using optimized transparent flow field unit–Part II: Performance comparison and explanation

Three transparent single cells, i.e., a cathode transparent single cell, an anode transparent single cell and an overall transparent single cell are tested and compared with a standard single cell. Results show the standard single cell presents the best performance and the overall transparent single cell shows the worst performance. This is because a large contact resistance exists between the gas diffusion layer and the graphite pierced flow field plate of a transparent single cell due to the deformation of the transparent flow field unit, which is caused by the bolt preload. Based on the testing data, four deformation process models are proposed to reveal how the structure differences affect the performance differences between the standard single cell and the transparent single cells.

Research on the performance differences between a standard PEMFC single cell and transparent PEMFC single cells using optimized transparent flow field unit–Part I: Design optimization of a transparent flow field unit

In this article, the optimization design steps of a transparent flow field unit, which is composed of a graphite pierced plate and a hollow transparent end plate, are introduced. Four graphite end plates of different gas channel depths (i.e., 0.6 mm, 1.1 mm, 2 mm and 2.5 mm) are firstly designed. Four standard single cells are assembled, which employ the four graphite end plates. I–V curves and Electrochemical Impedance Spectra (EIS) of these four standard single cells are then tested. Results show that the standard single cell with a gas channel depth of 2 mm presents the best performance when the current density is within 1200 mAcm−2. This is because the total resistance of this single cell always shows a minimum value. According to the analysis of the gas channel depth and considering trying to choose a larger thickness in order to avoid being broken during assembling a transparent single cell, 2 mm thick is determined to be the suitable thickness of the graphite pierced plate. Furthermore, a hollow transparent end plate is designed, i.e., a polycarbonate frame of 25 mm thick is assembled between two polycarbonate sheets of 6 mm thick to form a hollow transparent end plate. Glycerol, which is firstly heated to a temperature three degrees higher than the cell temperature, is pumped into the glycerol cavity of the hollow transparent end plate. No fog is formed on the inner surface of the hollow transparent end plate when the new design is employed in a transparent single cell.

Impact of Cell Compression on Resistance, Mass Transport, and Ultimate PEMFC Performance

The gas diffusion layer (GDL) plays multiple roles in the performance of a PEMFC: it provides pathways for fuel transport to and water away from the catalyst layer via the tortuous void/pore structure and it ensures a good electronic contact between the catalyst layer and the current collector of the PEMFC stack. A balancing act in cell assembly must be struck for the GDL to simultaneously offer the best transport pathways and electronic contact; different PEMFC operating conditions can require different assembly in terms of compression. To gain a better understanding of this balancing act and to optimize the performance of the PEMFC, we systematically varied the compression of a single cell PEMFC and evaluated it under different operating conditions to extract the impact on contact resistance and mass transport. Scanning electron microscopy of the GDL and catalyst layers post mortem reveal changes in the overall pore/void structure and provide further clues on the implications of compression on performance.