bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer Electrolyte Membrane Fuel Cell Characterisation Based on Current Distribution Measurements
Authors: Chevalier Stephane , Olivier Jean-Christophe , Josset Christophe , Auvity Bruno 
Published: February 2020

Polymer Electrolyte Membrane (PEM) fuel cells are considered as promising clean sources for automotive applications. A key challenge to reduce the cost of this technology is to increase the power density by operating PEM fuel cells at high current densities. Part of the research are focused in developing and designing new materials for this technology such as advanced catalyst layers (CL), new gas diffusion layers (GDL) structure, or innovative cell assembly conditions (clamping pressure, channel design…)[1]. To assess the performance of new materials, in situ characterisation techniques are required. Electrochemical impedance spectroscopy (EIS) is one of the most used technique to characterise the material impact onto the fuel cell mass/charge transfer, ohmic resistance and mass transport. However, due to the large number of parameters which has to be identified, inaccuracy in the identification process may arise leading to incorrect fuel cell material properties characterisation [2].
In authors’ recent work [3], it was shown that current density distributions can be used as a useful information to characterise fuel cell material properties. Thus, in this communication we will present a segmented cell designed and built to measure current density distribution along the channel while allowing optical access inside the channel to visualise the presence of liquid water. A range of fuel cell GDLs is characterised in situ in this cell for a range of operating conditions. The effective diffusivity of the GDLs is directly obtained from the current density distribution without any knowledge of the other fuel cell parameter (membrane ohmic resistance or CL kinetics). The values of effective diffusivity obtained using our methodology are compared to the ones obtained through EIS measurements, and their respective accuracy will be discussed. In addition, examples on the use of this characterisation cell to assess the performance of channel designs and fuel cell assembly conditions will be given. The results presented in this communication will introduce a novel fuel cell characterisation methodology which can strongly improve the development of more efficient fuel cell systems.

References

[1] T. Yoshida, K. Kojima, Toyota MIRAI Fuel Cell Vehicle and Progress Toward a Future Hydrogen Society, Interface Mag. 24 (2015) 45–49.
[2] S. Chevalier, D. Trichet, B. Auvity, J.C. Olivier, C. Josset, M. Machmoum, Multiphysics DC and AC models of a PEMFC for the detection of degraded cell parameters, Int. J. Hydrogen Energy. 38 (2013) 11609–11618.
[3] S. Chevalier, C. Josset, B. Auvity, Analytical solutions and dimensional analysis of pseudo 2D current density distribution model in PEM fuel cells, Renew. Energy. 125 (2018) 738–746.
Investigating Factors That Influence Conditioning Time of PEFCs
Authors: Rockward Tommy , Spears Andre , Garzon Fernando H , Martinez Ulises 
Published: February 2020

The conditioning time required for PEFCs to reach either peak performance or system power requirement will have a definite impact on overall system cost. During the past decade, FC research and development has focused its efforts on overcoming several technical barriers (targets) that could compromise the viability of the technology. Performance, cost, and durability are three of the barriers in which a large portion of the efforts were placed. Consequently, this attention led to substantial improvements in the FC materials and components helping meet and or surpass technical targets. While these scientific advances were instrumental in the emergence of pilot Fuel Cell Electric Vehicles; it becomes critical that the conditioning time be minimal in order to produce affordable Fuel Cell systems for large scale production. We will present results on factors that influence the PEFC conditioning time.
The various aspects that can affect the conditioning time include:

MEA manufacturing processing conditions (pressing / drying conditions)

Electrode Morphology/Engineering (Ionomer/carbon ratio, catalyst and catalyst support materials, membrane (composition, thickness, radical scavenger additives),

Conditioning methodology (potential cycling versus steady state)

Operating conditions (Temp, relative humidity)
The Impact of Compression on PEM Fuel Cell Performance at High Power
Authors: Swider-Lyons Karen , Garsany Yannick , Netwall Christopher J. , Atkinson Robert W. , Gould Benjamin D. , Sassin Megan B. 
Published: February 2020

The compression of PEM fuel cells has a significant impact on performance, particularly at high current densities where the ohmic contribution of mass transport and contact losses are major contributors. Compression, or more accurately the compressive stress on the fuel cell membrane electrode assembly (MEA), affects the mass transport of gases and water through the gas diffusion media (GDM). The transport of gases and water in turn affects the kinetics of the cells.
This talk will review our work toward better understanding how the compressive stress affects fuel cell performance. We observe that a break-in compression cycle decreases the contact or ohmic resistance between the GDM and metal bipolar plates when forming a high performance fuel cell stack, as the cycling appears to improve the interface between the porous GDM and roughness of the metal surface [1]. In a following effort to make laboratory-scale high performance MEAs, we observed that the compressive stress on the MEA was largely absorbed by the GDM, and the resulting porous structure of the compressed GDM had a large effect on overall performance at >0.2 A cm-2 due to the influence on both ohmic losses and transport effects [2]. We therefore recommended attention to compression of the MEA/GDM as a major influence in the performance of high performance fuel cells [3]. While a compression near 14% is recommended for paper-type GDM in laboratory cells that use rigid gaskets as compression stops [2,3], we see that much greater compression is desirable for fuel cells in “open air” configurations, for which the air is very dry [4]. Three-dimensional imaging of paper- and felt-type GDM with computed tomography shows a clear correlation between how the porosity of the GDM vs compression affects fuel cell performance, and that higher compressive stress is advantageous for fuel cells with felt-type GDM [5].
References

C. Netwall, B. D. Gould, J. A. Rodgers, N. J. Nasello, K. Swider-Lyons, J. Power Sources, 227, 137 (2013).

M. B. Sassin, Y. Garsany, B.D.Gould, K. Swider-Lyons, J. Electrochem. Soc., 163, F808 (2016).

M. B. Sassin, Y. Garsany, B.D. Gould, K. Swider-Lyons, Anal. Chem., 89(1), 511 (2017).

R. W. Atkinson III ,M. W. Hazard, J. A. Rodgers, R. O. Stroman, B. D. Gould, ECS Trans., 75(
14), 531 (2016).

R. W. Atkinson III, Y. Garsany, B. D. Gould, K. E. Swider-Lyons, I. V Zenyuk, ACS Appl. Energy Mater.,
1(1),
191 (2018).

Acknowledgements
We are grateful to the Office of Naval Research for their longstanding support of this research.
Kinetic Analysis of Oxygen Transport Phenomena through Ionomer Thin Film on Pt Surface in PEFC
Authors: Kurihara Yuya , Mabuchi Takuya , Tokumasu Takashi 
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are expected as power sources because of their low emissions and high efficiencies. However, it is required to improve the power density at lower Pt loading to develop high power systems at a lower cost. It is known that the losses of the power density are caused by activation losses, ohmic losses, and mass transport losses, and that the mass transport losses are dominant at high current density. Moreover, it is suggested that one of the causes of the mass transport losses is the shortage of oxygen in the cathode side of PEFC. In the cathodic catalyst layer, there are Pt catalysts on supported carbon microparticles, and those particles are covered with ionomer thin films. The film has two properties for the water-generating reactions in the cathodic catalyst layer: the proton conductivity and the oxygen permeability. These two properties depend on the film thickness and water content in the film, however, as one of the problems, the dependence of the oxygen permeability on water content is required to be clarified.
In our previous research, we analyzed the oxygen transport properties—i.e., solubility, diffusivity, and permeability—in an ionomer thin film on a Pt surface based on the solution-diffusion theory using molecular dynamics (MD) simulations. As a result, the oxygen permeability decreased with increasing water content. The local oxygen permeability in each region was obtained, and it was found that the oxygen permeability in the ionomer/Pt interface is the lowest for all water contents. Moreover, compared with the oxygen diffusivity, the oxygen solubility has a larger contribution to the water content dependence of oxygen permeability. Then, the oxygen permeability of the film was obtained from the local oxygen permeability in each region of the film; however, the total permeability was not in good agreement with that estimated using the oxygen flux and the pressure differential. It is suggested as the causes that the local equilibrium condition at each boundary of the region is not satisfied in the non-equilibrium system for the oxygen permeation through the film.
In this study, therefore, without an assumption of the local equilibrium condition, a new theory was constructed to describe the oxygen transport phenomena in the film using the chemical potential distribution of oxygen in the system. In this theory, it is assumed that the oxygen flux is generated by the spatial gradient of the chemical potential in the thickness direction of the film. Based on the theory, the oxygen transport resistances in the film are discussed using the oxygen mobilities obtained by MD simulations. Moreover, since oxygen pathways in the film are found to be important to estimate the chemical potential distribution of oxygen, the structure of the film is also analyzed. Then, the relationship between the film structure and the oxygen transport properties is investigated.
Fuel Cell Testing of Intermetallic Catalysts
Authors: Spendelow Jacob S , Pan Yung-Tin , Kim Yu Seung , Li Junrui , Sun Shouheng , Cullen David A. , More Karren L. 
Published: February 2020

Oxygen reduction catalysts based on alloys of Pt with base metals such as Fe, Co, and Ni have demonstrated high performance in ex situ aqueous studies and in situ fuel cell studies, but excessive rates of base metal leaching continue to hinder deployment of these catalysts. Recently, ordered intermetallic structures have been demonstrated to be less susceptible to base metal leaching. Results so far indicate that the degree of ordering is a critical parameter in determining intermetallic catalyst activity and durability, with fully-ordered face-centered tetragonal (fct) FePt catalysts exhibiting substantially improved activity and durability compared to partially ordered phases [1]. These tests have been confirmed with good durability in the fuel cell environment [2].
Several factors can affect base metal stability, including chemical nature of the base metal, degree of ordering, particle size, and Pt skin formation. By carefully tuning these parameters, extremely high durability can be achieved (Fig. 1 Top), with diffraction data demonstrating that high degrees of ordering can be maintained even after the DOE accelerated stress test (30,000 trapezoidal cycles between 0.6 and 0.95 V with 0.5 s rise time) (Fig. 1 Bottom). Ongoing work seeks to focus on optimizing the surface structure of fct-FePt and fct-CoPt intermetallic nanoparticle catalysts such that a synergistic effect between the surface and core can be established, i.e., a stable Pt surface that protects the fct-core that is thin enough to benefit from the geometric and electronic effects from the core.
Fig. 1 Top. Fuel cell polarization behavior of fct-CoPt/C before and after the 30,000 cycle AST. H2/air, 100%/20% RH, 80°C, 150 kPaabs, 0.1 mgPt/cm2.
Fig. 1 Bottom. X-ray diffraction of fct-CoPt/C before and after the 30,000 cycle AST.
References

Q. Li et al., "New Approach to Fully Ordered fct-FePt Nanoparticles for Much Enhanced Electrocatalysis in Acid," Nano Lett. 2015, 15, 2468−2473.

J. Li et al., “Fe Stabilization by Intermetallic L10-FePt and Pt Catalysis Enhancement in L10-FePt/Pt Nanoparticles for Efficient Oxygen Reduction Reaction in Fuel Cells,” JACS 2018, 140, 2926−2932.

Acknowledgements
This research is supported by the Fuel Cell Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy.

Figure 1
Formation of Metal-Nitrogen Sites in Atomically-Dispersed Catalysts Observed By in Situ Microscopy
Authors: Cullen David A. , More Karren L. , Myers Deborah J , Wu Gang , Litster Shawn , Xu Hui , Chung Hoon T , Zelenay Piotr 
Published: February 2020

Platinum group metal-free (PGM-free) catalysts are under intense development for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells. Recent research efforts have focused on catalysts derived from metal organic frameworks doped with transition metals such as Fe, Ni, Co, and Mn. High temperature pyrolysis is a key synthesis step in the formation of the active catalyst, and aims to produce porous, mesographtic carbons with a high density of single transition metal atoms bound to nitrogen.
In this work, correlated in situ characterization techniques have been employed to explore the mechanisms that influence catalytic activity and provide guidance for synthesis protocols. The coordination of advanced synctrotron and electron microscopy methods provide new insight into the atomic-level transformations which occur during pyrolysis.
Micro-electro-mechanical system (MEMS)-based heating devices were utilized to directly observe transformations occurring at the atomic scale as the temperature was ramped to 1100oC within the electron microscope. It was observed that significant amounts of the transition metal and nitrogen were lost as the pyrolysis temperature increased from 900-1100oC, which could limit the active site density. However, rotating disk electrode measurements indicate that pyrolysis temperatures beyond 900oC appear to be required to maximize mass activity. As shown in Figure 1, low voltage scanning transmission electron microscopy observations indicated that the degree of carbon graphitization increased as the temperature was elevated 1100oC and nitrogen-bound transition metal sites were also more readily observed within the graphene lattice by electron energy loss spectroscopy. Consequently, approaches are being explored to maintain higher Fe and N content while also generating highly graphitized domains.
Beyond active site density, the microporosity of the support can also play a key role in the performance of the catalyst. Ongoing in situ studies will also aim to explore the mechanisms of microporosity formation within the MOF support and its subsequent influence on fuel cell performance.
Research sponsored by the Fuel Cell Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, as part of the ElectroCat Consortium, which is part of the Energy Materials Network. Microscopy performed as part of a user project at ORNL’s Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility.

Figure 1
Electrocatalyst Performance for Selective Methanol Formation in Methane Electrolyzer
Authors: Fornaciari Julie , Primc Darinka , Weber Adam Z. , Bell Alexis T. 
Published: February 2020

Methane’s abundance and low cost makes it an optimal raw material for chemical precursors and other energy dense fuels. Traditional methods of converting methane to methanol require large amounts of energy through thermal catalysis and high capital costs. However, electrochemical oxidation of methane is a cleaner and cheaper way to produce methanol, and a systematic study of an electrochemical cell could help assure selectivity over undesired products.
Electrochemical oxidation of methane is an underdeveloped field, but electrochemical cells have been employed with high selectivity towards methanol.[1,2] Promising transition state metal-oxide catalysts have shown activity towards the selectivity of methanol over other by products, such as carbon dioxide, carbon monoxide, formic acid, formaldehyde.[2, 3] Further investigation of single site metal oxide catalysts is required to improve conversion and activity, but system optimization is also required. Reports of electrolyzer and fuel cell systems show varying assemblies, ranging from various solid and liquid electrolytes, temperatures, pressures, and current densities. [1-3] Few reports have been consistent on the operating current density and potential windows of such systems. Little work has been done on understanding how various components for these systems and understanding the phenomena of creating methanol in this partial oxidation pathway.
In this study, we explore the activity, selectivity, efficiency of transition metal oxide catalyst in operation in an electrolyzer. The electrolyzer used was tested under a variety of relative humidity, operating temperatures, current densities, and membrane electrode assemblies. Through electrochemical and conductivity measurements, and gas phase analysis of the effluent, a better understanding of the partial electrochemical oxidation of methane to methanol is elucidated. The results of this study provide a systematic approach to this challenging problem and provide insights on new catalyst and electrochemistry pathways.

References:

Tomita, A., et. al., Direct Oxidation of Methane to Methanol at Low Temperature and Pressure in an Electrochemical Fuel Cell. Angewandte Chemie International Edition, 2008. 47: p. 1462–1464.

Lee, B., et. al., Direct oxidation of methane to methanol over proton conductor/metal mixed catalysts, Journal of Catalysis, 271(2): p. 195-200.

Rocha, R.S., et. al., Electrosynthesis of methanol from methane: The role of V2O5 in the reaction selectivity for methanol of a TiO2/RuO2/V2O5 gas diffusion electrode. Electrochimica Acta, 2013. 87: p. 606-610.
Smooth and Fiber-Shaped Co Coatings Decorated with Pt Crystallites As the Anode Catalysts for Direct Borohydride-Hydrogen Peroxide Fuel Cells
Authors: Balčiūnaitė Aldona , Zabielaitė Aušrinė , Sukackienė Zita , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus 
Published: February 2020

In the present work, the smooth and fiber-shaped Co coatings decorated with Pt crystallites were investigated as the anode material in direct borohydride-hydrogen peroxide fuel cells (DBHPFCs). The Co sublayers, which have different structures, e.g. smooth and fiber-shaped, were used as a substrate for the depositing of Pt crystallites. The Co layer having smooth structure was deposited on the Cu surface (denoted as Cosmooth/Cu) via electroless deposition using morpholine borane as a reducing agent. Co layers, which have a fiber-shaped structure and the thickness of ~3 mm, were electroplated on the Cu surface (denoted as Cofiber/Cu) from the electrolyte containing CoSO4, NaOH and N-(2-Hydroxyethyl) ethylenediamine. The Pt crystallites were deposited on the Cosmooth/Cu and Cofiber/Cu electrodes by their immersion into a Pt(IV)-containing solution at a temperature of 25oC for different time periods. It has been determined that the Pt loadings were in the range from 10 to 14 µgPt cm–2 and 5 to 29 µgPt cm–2 in the PtCosmooth/Cu and PtCofiber/Cu catalysts, respectively.
The activity of the prepared PtCosmooth/Cu and PtCofiber/Cu catalysts for borohydride oxidation reaction (BOR) was evaluated using cyclic voltammetry and chronoamperometry. The performance of a DBHPFC operating with 1 M NaBH4 + 4 M NaOH as fuel and 5 M H2O2 + 1.5 M HCl as an oxidant, while employing Pt as the cathode catalyst and PtCosmooth/Cu and PtCofiber/Cu catalysts with different Pt loadings as the anodes were investigated.
It has been determined that the prepаred PtCosmooth/Cu and PtCofiber/Cu cаtаlysts hаve а higher аctivity аnd а better stаbility for the oxidаtion of BH4
- compаred to those of Cosmooth/Cu аnd Cofiber/Cu. The аssembled direct borohydride-hydrogen peroxide fuel cell with PtCosmooth/Cu and PtCofiber/Cu cаtаlysts as the anodes exhibited аn open circuit voltаge of cа. 1.9 V.

Acknowledgment

This research was funded by a grant (No. M-ERA.NET-1/2016) from the Research Council of Lithuania.
Electrolytic Solution of Anion Exchange Membrane Electrolyzer
Authors: Ito Hiroshi , Kawaguchi Natsuki , Someya Satoshi , Munakata Tetsuo 
Published: February 2020

In the promotion of the use of renewable energy, the role of hydrogen (H2) as the energy carrier is a key for buffering the fluctuating and/or intermittent power from renewable energy sources. As the hydrogen production device from renewable energy, a water electrolyzer is the simplest and most realistic. Among several options, PEM water electrolysis is suitable for intermittent power input, and also capable of operation at higher current density (> 3 A cm-2). However, a major drawback of PEM electrolysis is its high capital cost per power input compared to conventional alkaline electrolysis. The acidic environment of PEM limits the type of material that can be used for cell components (i.e., bipolar plates and current collectors) to titanium (Ti) and that of the catalyst to platinum-group metals (PGMs). The use of these precious materials is a major reason for the high stack cost of a PEM electrolyzer. When a membrane performing under alkaline (basic) conditions is applied to the electrolyte, the material restriction for the cell components can be relaxed. In particular, the material Ti of the bipolar plates can replaced by a cheaper material such as stainless steel, which would significantly reduce the stack cost, because the cost share of Ti-bipolar plates is significant in the total stack cost of PEM electrolyzer. An alternative material for the electrolyte is an anion exchange membrane (AEM) that has high internal pH. When such an AEM is applied as the electrolyzer based on the same structure as the PEM electrolyzer, a low-capital-cost device is possible and still retain the advantages of PEM electrolysis.
In this study, in order to confirm the potential of AEM electrolysis under mild alkaline conditions (pH ≤ 12), the effect of species and concentration of electrolytic solution on the performance of AEM electrolysis was experimentally examined, where DI water, KOH (10mM), and K2CO3 of different concentrations (0.1, 1, and 10 wt. %) were applied for the electrolytic solution. In the cell, Pt/C was used as the cathode catalyst and CuCoOx as the anode catalyst. Furthermore, to examine the effect of structure of anode current collector (i.e., gas diffusion layer; GDL) on the performance, either nickel (Ni)-foam or Ni-felt was applied to the cell. In addition to current-voltage (i-V) characteristics, the Faraday (current) efficiency and hydrogen cross-permeation was also evaluated based on the experimental data.