Fuel Cell Manufacturing Research Articles

High performance biomass-derived catalysts for the oxygen reduction reaction with excellent methanol tolerance

The discovery of low cost and efficient catalytic materials for the oxygen reduction reaction (ORR) is of paramount importance for industrial-scale fuel cell manufacture. In this work, a convenient and straightforward approach was designed and applied to produce iron and nitrogen co-doped biomass carbon/graphene composite (Fe–N/CB-RGO) by using soybean dregs combined with graphene oxide (GO). The results show that the optimized Fe–N/CB-RGO (1) sample has high catalytic activity and stability for ORR, the onset potential of Fe–N/CB-RGO (1) is 0.02 V vs. Hg/HgO, which is merely 50 mV negative-shifted comparison with commercial Pt/C. The composition optimized Fe–N/CB-RGO (1) catalyst showed excellent methanol tolerance, with the presence of methanol surprisingly improving ORR performance. This unique catalytic performance of the Fe–N/CB-RGO (1) catalyst is attributed to electron transfer synergies arising from close interfacial contact between the biomass-derived carbon and graphene.

A Thermodynamic Analysis of an Air-Cooled Proton Exchange Membrane Fuel Cell Operated in Different Climate Regions

A fundamental thermodynamic analysis of an air-cooled fuel cell, where the reactant air stream is also the coolant stream, is presented. The adiabatic cell temperature of such a fuel cell is calculated in a similar way as the adiabatic flame temperature in a combustion process. Diagrams that show the dependency of the cathode outlet temperature, the stoichiometric flow ratio and the operating cell voltage are developed. These diagrams can help fuel cell manufacturers to identify a suitable blower and a suitable operating regime for their fuel cell stacks. It is found that for standard conditions, reasonable cell temperatures are obtained for cathode stoichiometric flow ratios of ξ = 50 and higher, which is in very good agreement with manufacturer’s recommendations. Under very cold ambient conditions, the suggested stoichiometric flow ratio is only in the range of ξ = 20 in order to obtain a useful fuel cell operating temperature. The outside relative humidity only plays a role at ambient temperatures above 40 °C, and the predicted stoichiometric flow ratios should be above ξ = 70 in this region. From a thermodynamic perspective, it is suggested that the adiabatic outlet temperature is a suitable definition of the fuel cell operating temperature.

Vinylidene chloride- and styrene-based sulphonate-containing copolymers

Bare polyvinyl chloride (PVC) and polyvinylidene chloride are not commercially used due to their high softening point (185–200 o С ) and the absence of a suitable solvent for obtaining coatings (films) from their solutions. Therefore, vinyl chloride and vinylidene chloride are mainly applied in the production of copolymers having a lower pour point and better solubility as compared to homopolymers. Polymer materials based on copolymers of vinyl chloride and vinylidene chloride are widely used in a number of industrial applications. Recent research has been focused on monomer rafting onto a vinyl chloride and vinylidene chloride copolymer base by the formation of free radicals as a result of the transfer reaction of a chlorine atom to an initiating agent followed by sulphonation. Membranes obtained from solutions of grafted copolymers possess high proton conductivity values resulting in their perspective application for fuel cell manufacture. In order to obtain such membranes, it is necessary to carry out studies on the synthesis of vinylidene chloride copolymers and the substitution of chlorine atoms with sulphonic acid groups in these copolymers. In the framework of this work, vinylidene chloride and styrene copolymers were obtained by radical copolymerisation. The substitution of chlorine atoms by sulphonic acid groups in the synthesised copolymer was studied. The composition and structure of the copolymers were characterised using elemental analysis and IR spectroscopy data. The co-polymerisation values indicate a greater reactivity of styrene in comparison with vinylidene chloride. The interaction of a vinylidene chloride copolymer and styrene with sodium sulphide is accompanied by dehydrochlorination of vinylidene chloride units. The spatial modified copolymer structures are generated by double bonds formed as a result of elimination in a macromolecule.

Hollow PtFe Alloy Nanoparticles Derived from Pt-Fe3 O4 Dimers through a Silica-Protection Reduction Strategy as Efficient Oxygen Reduction Electrocatalysts.

The development of efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) is critical for the large-scale production of fuel cells. Platinum (Pt) nanoparticle catalysts show excellent performance for ORR, though the high cost of Pt is a limiting factor that directly impacts fuel cell production costs. Alloying Pt with other transition metals is an effective strategy to reduce Pt utilization whilst maintaining good ORR performance. In this work, novel hollow PtFe alloy catalysts were successfully synthesized by high-temperature pyrolysis of SiO2 -coated Pt-Fe3 O4 nanoparticle dimers supported on carbon at 900 °C, followed by SiO2 shell removal and partial dealloying of the PtFe nanoparticles formed using HF. The obtained hollow PtFe nanoparticle catalysts (denoted herein as PtFe-900) showed a 2.3-fold enhancement in ORR mass activity compared to PtFe nanoparticles synthesized without SiO2 protection, and a remarkable 7.8-fold enhancement relative to a commercial Pt/C catalyst. Further, after 10 000 potential cycles, the ORR mass activity of PtFe-900 remained very high (90.9 % of the initial mass activity). The outstanding ORR performance of PtFe-900 can be attributed to the modification of Pt lattice and electronic structure by alloying with Fe at high temperature under the protection of the SiO2 coating. This work guides the development of improved, highly dispersed Pt-based alloy nanoparticle catalysts for ORR and fuel cell applications.

Enhancing Activity, Charge Transport, Power Production, and Stability of Commercial Solid Oxide Fuel Cells with Yttria-Stabilized Zirconia Nanoparticles

Interconnected networks of 10–30 nm yttria-stabilized zirconia (YSZ) nanoparticles dramatically enhance both the electrocatalytic activity and bulk charge transport of commercial lanthanum strontium manganite (LSM)-YSZ solid oxide fuel cell (SOFC) cathodes. The improvement in both electrode functions increases the maximum power density of the commercial SOFC by 90%. In comparison, modifying cathodes with lanthanum strontium cobalt ferrite (LSCF) and praseodymium barium cobaltite (PBC) nanoparticles, highly active catalysts with mixed ionic-electronic conductivity (MIEC), only enhances electrocatalytic activity. The combination of dual enhanced electrode functions with nanoYSZ results in a maximum power density that is 50% and 11% higher than LSCF and PBC, respectively. Finally, the performance stability over time is highest for nanoYSZ modified cells.

Autonomous planning tool for changeable assembly systems

Car manufacturers are expected to start series production of fuel cell vehicles within the next years. Simultaneously, other industries are pushing towards the utilization of fuel cells. Fuel cell manufacturers need to scale up production at the right time and react to changing product requirements with the ideal level and point of changeability. This complex task requires methods and tools for decision support. The authors present SkaliA, an autonomous planning tool, which generates guidelines for the efficient use of change enablers specific to an assembly system. The planning tool is demonstrated on the example of an assembly system for high pressure valves used in fuel cell applications.

Development of a Novel Technological Readiness Assessment Tool for Fuel Cell Technology

Technology Readiness Level and Manufacturing Readiness Level evaluation methodologies have been applied for a long time by the aerospace and defense industries to systematically determine the state of readiness for their products and processes. These tools have been proven to be extremely valuable not only in assessing the stages of product development, but also in providing requirements and guidance for continuing pursuit towards final products. This paper describes the creation of a novel and unique technology readiness level methodology tool that applies specifically to fuel cell technologies. This evaluation tool used modified criteria from the above-mentioned readiness level tools and adapted them to reflect the aspects of fuel cell technology. The biggest challenge in developing the readiness evaluation tool was due to the fact that there are several different fuel cell types and many different applications. In this complex matrix of drastically different conditions and diverse components, a general evaluation tool was developed first. Subsequently, specific versions of the tool will be developed to reflect the fuel cell types and applications. The Fuel Cell Technology Readiness Level (FCTRL) methodology is developed for those skilled in the art of fuel cells, engineers, and other professionals who need to evaluate fuel cell technologies for integration into existing systems and applications, as well as for anyone interested in fuel cells and renewable energy systems in general. The tool can also be very effective for use by investors planning to fund a fuel cell projects or government panels in charge of assigning research funds. The FCTRL evaluation tool comprises seven levels and a varying number of specific criteria within each level. The application of the tool is relatively simple in the form of a checklist. The technology is assumed to progress to a higher level once all criteria in the lower level are met. An example of the application is presented for a general case of fuel cell technology and places the most advanced fuel cell product in the correct level of readiness. The FCTRL is expected to make a significant impact on understanding fuel cell technology and its role in the energy systems poised to replace conventional energy technologies.

Preparation and Analysis of Ni–Co Catalyst Use for Electricity Production and COD Reduction in Microbial Fuel Cells

Microbial fuel cells (MFCs) are devices than can contribute to the development of new technologies using renewable energy sources or waste products for energy production. Moreover, MFCs can realize wastewater pre-treatment, e.g., reduction of the chemical oxygen demand (COD). This research covered preparation and analysis of a catalyst and measurements of changes in the concentration of COD in the MFC with a Ni–Co cathode. Analysis of the catalyst included measurements of the electroless potential of Ni–Co electrodes oxidized for 1–10 h, and the influence of anodic charge on the catalytic activity of the Ni–Co alloy (for four alloys: 15, 25, 50, and 75% concentration of Co). For the Ni–Co alloy containing 15% of Co oxidized for 8 h, after the third anodic charge the best catalytic parameters was obtained. During the MFC operation, it was noted that the COD reduction time (to 90% efficiency) was similar to the reduction time during wastewater aeration. However, the characteristic of the aeration curve was preferred to the curve obtained during the MFC operation. The electricity measurements during the MFC operation showed that power equal to 7.19 mW was obtained (at a current density of 0.47 mA·cm−2).

Accelerating Fuel Cell Development with Additive Manufacturing Technologies: State of the Art, Opportunities and Challenges

AbstractIn recent years, the use of additive manufacturing (AM) has been demonstrated in the fabrication of components in polymer electrolyte membrane fuel cell, solid oxide fuel cell (SOFC), microbial fuel cell (MFC) and laminar flow‐based fuel cell (LFFC). Various AM technologies have been successfully demonstrated in fuel cell manufacturing include material extrusion, powder bed fusion, vat photopolymerization and binder jetting. One of the unique advantages of AM is the ability to handle sophisticated design with features ranging from macro to micro scales, which are inaccessible by conventional manufacturing technologies. Well‐designed complex 3D structures were reported to have the potential for increasing the performance of fuel cells. Therefore, AM presents itself as a promising fabrication method to promote the development of fuel cells. Besides, AM also showed its specialty in time‐saving, flexibility, and on‐demand manufacturability in the fabrication of fuel cell components. In spite of the prospects of AM in fuel cells, more studies and researches are required to overcome challenges, such as availability of material, manufacturing quality, and the costs. This review focuses on the advantages and applications of additive manufacturing that enable improvement in fuel cell performance. The critical challenges and directions for future development are also highlighted.

Bridging the Gap between Automated Manufacturing of Fuel Cell Components and Robotic Assembly of Fuel Cell Stacks

Recently demonstrated robotic assembling technologies for fuel cell stacks used fuel cell components manually pre-arranged in stacks (presenters). Identifying the original orientation of fuel cell components and loading them in presenters for a subsequent automated assembly process is a difficult, repetitive work cycle which if done manually, deceives the advantages offered by either the automated fabrication technologies for fuel cell components or by the robotic assembly processes. We present for the first time a robotic technology which enables the integration of automated fabrication processes for fuel cell components with a robotic assembly process of fuel cell stacks into a fully automated fuel cell manufacturing line. This task uses a Yaskawa Motoman SDA5F dual arm robot with integrated machine vision system. The process is used to identify and grasp randomly placed, slightly asymmetric fuel cell components, to reorient them all in the same position and stack them in presenters in preparation for a subsequent robotic assembly process. The process was demonstrated as part of a larger endeavor of bringing to readiness advanced manufacturing technologies for alternative energy systems, and responds the high priority needs identified by the U.S. Department of Energy for fuel cells manufacturing research and development.

Characterization of Thermal and Electronic Conductivities of Catalyst Layers of Polymer Electrolyte Membrane Fuel Cells

AbstractThis work proposes new and accurate systematic methodologies for ex situ measurements of through‐plane thermal and in‐plane electronic conductivities of catalyst layers (CLs) of polymer electrolyte membrane fuel cells (PEMFC). The developed methods are based on measurements of different thicknesses/lengths of a CL on different substrates. Suitability of the proposed methods is confirmed through a set of microstructural properties measurements on a typical CL design to ensure the measured CLs would be representative of CLs in a real fuel cell product. Conductivity measurements of two CL designs with different compositions and microstructures confirm capability of the developed procedures to track structural changes in CLs. The present characterization platform is not limited to CLs and may be used for other composite porous materials with similar structures.

Overpotential Analysis of Low Loading Pt/C Electrodes at Low Humidity Conditions

In 2014, the transportation sector accounted for 35.3% of all greenhouse gas emissions in the State of Connecticut [1]. A significant amount of greenhouse gases emitted can be primarily attributed to the use of fossil fuels in passenger vehicles and other light-duty trucks. In an effort to reduce the amount of transportation-related emissions, there is a need to produce low- and zero-emission vehicles, such as fuel cell vehicles. Compared to vehicles with traditional internal combustion engines which emit greenhouse gases, fuel cell vehicles only emit water vapor. Through research and development of fuel cell and electrolyzer technologies, fuel cell vehicles have the potential to significantly reduce the greenhouse gas emissions related to the transportation sector. In order to improve the viability of fuel cell vehicles, fuel cell performance must be optimized at low relative humidity conditions while keeping production costs low. One such method for improving the fuel cell performance at low relative humidity is examined by changing the ionomer used in the fuel cell electrodes. Research has been shown that reducing the ionomer side chain length as well as reducing the ionomer equivalent weight may be beneficial to low humidity operation [2]. While low humidity operation is important, fuel cell production costs must also be kept to a minimum in order to offer these zero-emission vehicles to a broader market. The primary method that will be used in this work to reduce the cost of fuel cell production is Reactive Spray Deposition Technology (RSDT). RSDT is a one-step flame-based process which can directly spray a Pt/C electrode onto a membrane using without additional drying steps. Previous work by Yu et al examined the use of RSDT to create low Pt loading electrodes for fuel cell applications [3]. With the cost-effective RSDT method chosen for the development of the fuel cells, the RSDT-produced catalyst coated membranes (CCMs) will be tested in 100% relative humidity conditions as a baseline as well as reduced humidity conditions used in fuel cell vehicle applications. While it is important to improve low humidity fuel cell performance, it is important to have a better understanding of how low humidity directly impacts the electrochemical mechanism. This work will analyze collected polarization and impedance data using a six-step overpotential analysis technique used by Yu et al [3, 4]. This overpotential analysis looks to separate the contributions of different polarization sources to have a better understanding of what is impacting the cell performance. This technique used at low humidity should allow us to have a better understanding about low humidity operation and how to improve fuel cell production by minimizing losses. The work presented will incorporate the RSDT process to make the change in ionomer with the target of improving and better understanding the performance of the fuel cells at low humidity conditions. Along with utilizing the six levels of overpotential analysis technique, we can determine how the changes to the ionomer and membrane as well as the carbon support all affect the polarization sources which will allow to better optimize the fuel cells moving and improve the future viability of fuel cell vehicles.

(Invited) Atomic Scale Models of PGM-Free ORR Electrocatalysts: Activity, Stability, and Experimental Signatures of Active Site Structures within the Electrocatalysis Consortium

The electrification of transportation will rely predominantly on electrochemical technologies including fuel cells and batteries. In 2016 the U.S. Department of Energy started the Electrocatalysis Consortium (ElectroCat) in order to increase U.S. competitiveness in fuel cell manufacturing. The main focus of the consortium has been how to replace rare, expensive, and non-domestically mined platinum group metals (PGMs) used as electrocatalysts in fuel cell cathodes to improve efficiency of the oxygen reduction reaction (ORR). At predicted production scale, these PGM components will be one of the dominant cost drivers for fuel cell vehicle membrane electrode assemblies and, unlike other components, will not benefit from economies of scale during mass production. Currently the most promising PGM-free ORR electrocatalysts are based on heat treated M-N-C structures (M = Mn, Fe, Co). Great strides have been made over the previous decade in improving ORR activity, 4 electron pathway selectivity, and durability of these PGM-free materials but further improvements are required to meet the application needs of these materials. Thermal treatments in the range of 800-1100 °C have been shown to produce the most ORR active PGM-free materials but these temperatures lead to highly heterogeneous structures. This heterogeneity makes it difficult to identify the atomic scale structures responsible for facilitating ORR activity (the so-called active site conundrum) and also complicates the study of their associated ORR reaction pathways and degradation mechanisms. One approach within ElectroCat to address these knowledge gaps and to improve synthesis through a targeted, rational approach is the application of computational quantum chemistry. In this approach, an inverse problem to the active site conundrum is addressed. Instead of trying to identify “what is the active site”, the approach is to build a library of plausible atomic scale structures based on theoretical and experimental input and to understand the activity, durability, and experimental signatures of each site, enabling a comparison between the structures within the library. These comparisons can address fundamental questions about active sites and guide in the interpretation of experimental data aiding in the identification and behavior of particular atomic scale structures under specific environmental conditions. The developed approaches rely heavily on high performance computing (HPC) and density functional theory (DFT) to provide input about atomic scale interactions. By studying the binding of ORR intermediates to given library member structures and application of thermochemical models, activity descriptors can be obtained as well as relative energies of proposed reaction pathways. Additionally, kinetics of bond breaking associated with proposed degradation pathways can be identified, giving proposed durability descriptors for given active site structures. Both of these approaches have provided valuable insight into the roles of transition metal species and local carbon environment for material activity and durability. Theoretical approaches can also aid in interpretation of experimental data. Quantification of the number of active sites is more complicated in PGM-free materials vs. their PGM counterparts and experimental approaches are still being developed in order to better decouple active site density and active site turn over frequency. Study of active site interaction with probe molecules, those that can be controllably added and removed from (ideally) only ORR active sites enabling site counting, can also be determined via theoretical approaches, shedding light on binding specificity and thus the veracity of proposed approaches. For Fe-bearing materials, a host of Fe-specific spectroscopies have been developed which enable direct study of this subset of proposed active site structures. These include Mössbauer spectroscopy, nuclear resonance vibrational spectroscopy (NRVS), and x-ray adsorption spectroscopy (XAS). One major drawback to these approaches is a lack of well characterized standard structures that enable assigning given peaks to particular components of the material. By producing libraries of atomic scale structures and their experimental signatures, trends in experiments can be identified. This is valuable to determine the impact of synthesis conditions on produced materials and predominance of structures produced. Also, it has been predicted that certain ligands may evolve spontaneously on these structures under certain conditions. By studying structures with various ligands and probe molecules, trends can be identified which help in determining not just predominant Fe-structures from spectroscopy but also what ligands evolve under what conditions in-situ. Combined, theoretical input for ORR activity, active site durability, and experimental interpretation will be discussed.

Carbon-Based Air-Cathodes for Hydrogen Peroxide Production in Microbial Fuel Cells

Harnessing the chemical energy in wastewater while treating it is a key goal of new treatment technologies. Microbial fuel cells (MFC), a type of microbial electrochemical technology, could be one potential treatment technology with this goal. MFCs can help recover the chemical energy in wastewater organics directly in the form of electricity or as valuable chemicals such as hydrogen peroxide (H2O2). In MFC, anode-respiring bacteria (ARB) oxidize organic matter and respire electrons to an anode. At the cathode, the electrons combine with oxygen to result in the oxygen reduction reaction (ORR), which can proceed by the 4-e- reduction pathway on precious metal catalysts (e.g. platinum) to produce water, or via the 2-e- pathway on carbon catalysts to produce H2O2. The cathode catalyst may likely be a key factor affecting the efficiency of the reduction reaction, especially in relation to producing H2O2. In this study, we examine the production efficiency of H2O2 using three different carbon-based catalysts: 1) Vulcan carbon, 2) graphene oxide, and 3) MXene (Ti3C2). To prepare the cathodes, 1.5 mg/cm2 of carbon-based ink was coated on CeTech carbon cloth with a carbon-containing hydrophobic microporous layer. Three different graphene oxide powders were produced using modified Hummers method from pure graphite powder with mesh sizes of: 1) -325 (GO-325), and 2) +200 (GO+200), and (3) graphene nanoplatelets. MXene was produced by exfoliating Ti3AlC2 in hydrofluoric acid. The prepared cathodes were then placed inside an electrochemical cell with the gas diffusion layer (GDL) open to air and the coated catalyst layer facing the electrolyte solution inside the cathode chamber. The anode (plain carbon cloth) and the cathode chambers were separated with a Chemours Nafion cation-exchange membrane. For each experiment, the anode and the cathode chambers were filled with 100mM of phosphate buffer solution to serve as the electrolyte. An Ag/AgCl reference electrode was used to measure/control anode and cathode potentials. The cathode chamber electrolyte was recirculated at a rate of 25 mL/min to allow well-mixed conditions. A constant current density of 1 mA/cm2 was applied using chronopotentiometry (CP), and the anode and cathode potentials were measured over time. The H2O2 concentration in the cathode solution was measured every half an hour for a total of four hours using Titanium(IV) oxysulfate-sulfuric acid solution as the reagent. The cathodic Coulombic efficiency (CCE) for H2O2 production ([CH2O2actual/ CH2O2theoretical]*100%) was then determined for each sampling time point. Results show that adding a carbon catalyst layer to the CeTech carbon cloth increases the initial CCE from 20% to 50%. After an hour of operation, CCE dropped from 50% to 23% and 14% for Vulcan carbon and GO-325 mesh, respectively. Whereas, the CCE remained mostly stable for MXene and GO+200 during the entire four hours of operation. Here, no H2O2 was produced with GO- nanoplatelets as the carbon catalyst layer. We are currently analyzing our data to correlate catalyst selection with H2O2 degradation due to local pH changes, and electrochemical decomposition of H2O2 on the cathode surface. To better understand the morphology of the catalyst layer, scanning electron microscopy (SEM) and a laboratory X-ray CT system will also be conducted. Results from these characterization studies will also be presented. Figure 1

Influence of Coating Method on Performance of Roll-to-Roll Coated PEM Fuel Cell Catalyst Layers

Industrial production of polymer electrolyte membrane fuel cell (PEMFC) electrodes will rely on continuous roll-to-roll (R2R) coating methods to meet the rates needed for mass production.1–5 R2R production commonly uses solution coating methods to coat liquids onto a moving substrate at linear speeds over 100 m/min.6 There are many coating methods, which have different coating physics and require different ink formulations. For PEMFC catalyst layers these differences may result in different morphologies and performance. As production of fuel cell vehicles and power systems increases there is a need to understand the process science of fuel cell manufacturing. Here we present the results of a study comparing fuel cell catalyst layers coated using two R2R coating methods: slot-die and gravure, shown in Figure 1. These two methods were selected because the physics of applying the liquid to the substrate is very different between the two cases. Also, they have different viscosity and wet-film thickness ranges, which may make one method better suited to certain materials or catalyst loadings. In slot die coating, the pre-metered liquid is fed through the cavity of a metal die and extruded onto the substrate, as shown in Figure 1a. In gravure coating, an engraved metal roller is used to transfer the liquid from a pan to the substrate (Figure 1b). In both of these methods the coated liquid film then consolidates into the final dry film. These methods are quite different than common lab-scale coating methods like ultrasonic spraying or hand painting where ink is repeatedly applied to the same area to build up the thickness of the catalyst layers. Pt/C catalysts layers were coated directly onto carbon-fiber gas diffusion media to create gas diffusion electrodes (GDEs), without the use of a decal transfer process. These GDEs were assembled into membrane electrode assemblies (MEAs) by hot pressing to Nafion membranes. In situ performance and other electrochemical diagnostics were used to determine the influence of coating method on catalyst layer electrochemical properties. Electron microscopy was utilized to understand the influence of coating method on electrode morphology and its influence on electrochemical properties. We also explored the influence of solvent ratio to understand the potential coupling between ink formulation and coating methodology. Through this work we demonstrate R2R-coated GDEs with performance equal to ultrasonic spray-coated GDEs and a 200x increase in production rate. This demonstrates that R2R coating methods are suitable for mass-production of high-performance fuel cells. It also lays a foundation for further process science studies. (1) Mauger, S. A.; Neyerlin, K. C.; Yang-Neyerlin, A. C.; More, K. L.; Ulsh, M. Gravure Coating for Roll-to-Roll Manufacturing of Proton-Exchange-Membrane Fuel Cell Catalyst Layer. J Electrochem Soc 2018, 165 (11), F1012–F1018. https://doi.org/10.1149/2.0091813jes. (2) Bodner, M.; García, H. R.; Steenberg, T.; Terkelsen, C.; Alfaro, S. M.; Avcioglu, G. S.; Vassiliev, A.; Primdahl, S.; Hjuler, H. A. Enabling Industrial Production of Electrodes by Use of Slot-Die Coating for HT-PEM Fuel Cells. Int. J. Hydrog. Energy 2019. https://doi.org/10.1016/j.ijhydene.2018.11.091. (3) Steenberg, T.; Hjuler, H. A.; Terkelsen, C.; Sánchez, M. T. R.; Cleemann, L. N.; Krebs, F. C. Roll-to-Roll Coated PBI Membranes for High Temperature PEM Fuel Cells. Energy Environ. Sci. 2012, 5 (3), 6076–6080. https://doi.org/10.1039/c2ee02936g. (4) Ding, X.; Didari, S.; Fuller, T. F.; Harris, T. A. A New Fabrication Technique to Manufacture an MEA Using Direct Coating of Nafion® onto Catalyzed GDL. In 218th ECS Meeting; ECS, 2010; pp 255–265. https://doi.org/10.1149/1.3484523. (5) Ding, X.; Didari, S.; Fuller, T. F.; Harris, T. A. L. Membrane Electrode Assembly Fabrication Process for Directly Coating Catalyzed Gas Diffusion Layers. J. Electrochem. Soc. 2012, 159 (6), B746. https://doi.org/10.1149/2.103206jes. (6) Ding, X.; Liu, J.; Harris, T. A. L. A Review of the Operating Limits in Slot Die Coating Processes. AIChE J. 2016, 62 (7), 2508–2524. https://doi.org/10.1002/aic.15268. Figure 1

Additive Manufacturing of Advanced Solid Oxide Fuel Cells – a Review

Fuel cells are appealing energy generation gadgets due to their high performance, advanced electricity density, low emissions and quiet operation. Among exceptional types of fuel cells, solid oxide fuel cells (SOFC) provide greater flexibility due to the fact that they can run on a diffusion of fuels and are tolerant to impurities within the realistic fuels. Additive manufacturing (AM) strategies allow the fabrication of complicated parts with the desired composition, microstructure and properties directly from the computer-aided design (CAD) models. Additive production era to SOFC will allow extra complex and advanced cell and stack designs to be manufactural, regardless of steel-supported or ceramic-supported structure. Fabrication of whole monolithic fuel cell stacks in fewer or even a single step without successive assembly require a brilliant approach. This paper attempts to review the latest applications of additive manufacturing tactics in SOFC development and production, binder jetting, spraying, extrusion, lithography-primarily based, and laser sintering.

Advancements on scaling-up simulation of Proton Exchange Membrane Fuel Cells impedance through Buckingham Pi theorem

This article addresses a generalized scaling-up technique applied to proton exchange membrane fuel cells. Such a methodology allows simulating the impedance related to a full stack from that of a single cell or short stack, combining experimental data with physical reasoning and phenomenological modelling. The use of such technique can reduce electrochemical impedance spectroscopy testing costs, with a significant impact on fuel cell manufacturing and performance assessment processes. The procedure described in this paper relies on a former approach, already presented by the authors, which has been improved with respect to two main aspects. Firstly, non-dimensional parameters are computed, by referring to the Buckingham Pi theorem, through a generalized physical model. Secondly, single cell or short stack internal states (i.e., water content and limiting current) are evaluated through significant information gained from impedance measurements and inverse modelling. Stack impedance simulation is performed through proper internal states distribution assumptions. To prove the consistency and robustness of the proposed technique, experimental data taken from the literature and the European funded project HEALTH-CODE are used, with stack impedance accurately reproduced by means of only a single cell spectrum.

Polarization Analysis of Durable Low Loading Pt/C Electrodes Produced By Reactive Spray Deposition Technology for Low Humidity Conditions

In 2016, the transportation sector accounted for 28% of greenhouse gas emissions in the United States, according to the United States Environmental Protection Agency [1]. One way in which the transportation industry is looking to reduce the greenhouse gas emissions is in the production of fuel cell vehicles. Compared to vehicles with traditional internal combustion engines which emit greenhouse gases, fuel cell vehicles only emit water vapor. Through research and development of fuel cell and electrolyzer technologies, fuel cell vehicles have the potential to significantly reduce the greenhouse gas emissions related to the transportation sector. In order to improve the viability of fuel cell vehicles, research must be done to reduce the cost of the fuel cell production, optimize the fuel cell to operate at low humidity conditions, and improve the durability of the catalyst. The primary method that will be used in this work to reduce the cost of fuel cell production is Reactive Spray Deposition Technology (RSDT). RSDT is a one-step flame-based process which can directly spray a Pt/C electrode onto a membrane using without additional drying steps. Previous work by Yu et al examined the use of RSDT to create low Pt loading electrodes for fuel cell applications [2]. With the cost-effect RSDT method chosen for the development of the fuel cells, the RSDT-produced catalyst coated membranes (CCMs) will be tested in 100% relative humidity conditions as a baseline as well as reduced humidity conditions used in fuel cell vehicle applications. To improve the fuel cell performance at lower humidity, we will look to make changes to the membrane and ionomer which can allow for improved conductivity at the desired operating conditions. Additionally, we will look to improve on the catalyst durability by adjusting the carbon support used in the Pt/C electrodes. Rather than using Ketjen black supports, a change to a more graphitized carbon will be used which will look to improve the stability and durability to improve the lifespan of the fuel cells used in this application. The work presented will use the RSDT process to make the change in ionomer and carbon support to improve the performance of the fuel cell at low humidity conditions as well as improving the catalyst durability. We will also utilize the six-step analysis technique used by Yu et al to examine how these changes affect the contributions from the different polarization sources [2, 3]. By analyzing the polarization sources, we can determine how the changes to the ionomer and membrane as well as the carbon support all affect the polarization sources which will allow to better optimize the fuel cells moving and improve the future viability of fuel cell vehicles.

Thermodynamic modelling and intelligent control of fuel cell anode purge

Dead-ended anode Polymer Electrolyte Membrane Fuel Cell (PEMFC) is promising in small-scale power generation applications due to its simple structure, high reliability, and low price. However, it necessitates the anode purge to remove the impurities accumulated in the anode channel, making the system operation suffer from the sudden anode pressure drop during the purge. In most cases, a widely used solution of many fuel cell manufacturers is to open up the anode inlet valve regularly to recover the fuel cell terminal voltage. Although simple, the performance would degrade in case of the operation condition change. To this end, this paper proposes a modified Iterative Learning Control (ILC) strategy, which can repeatedly improve the control performance by learning from the previous actions. A mathematical model is developed to analyse the variations of the voltage and the anode pressure, by taking into account the membrane water transfer and the nitrogen permeation. The purge action is triggered when the single-cell terminal voltage drops by 0.1 V. The dynamics of the anode pressure is investigated under different openings of the purge valve. The simulation results have demonstrated the efficacy of the modified ILC strategy for anode pressure regulation in mitigating the periodic purge influence and the model uncertainty.

Generalized scaling-up approach based on Buckingham theorem for Polymer Electrolyte Membrane Fuel Cells impedance simulation

The present paper describes a generalized scaling-up methodology applied to Polymer Electrolyte Membrane Fuel Cells. The use of proper scaling-up algorithms can reduce testing costs within fuel cell manufacturing process by evaluating full stack performance (i.e., impedance behavior) from a single cell/short stack measurement. The algorithm here described relies on a former approach developed by the authors and consists in a generalized methodology combining information measured on single cell and simple physical models (e.g., charge transfer resistance expressed through Tafel equation). A robust technique for the identification of cell reference operational state, such as membrane hydration, from non-scaled data is also introduced. Connection between charge transfer resistance and limiting current is established through diffusion losses modelling. Single cell internal states are estimated by means of inverse models function of numerical intercepts of measured cell spectrum. Stack impedance estimation is then performed through stack internal states assumptions. To prove the consistency and robustness of the proposed methodology, literature data used to design and test the former algorithm version are here considered for algorithm testing and verification.