bluuebunny/crossref_metadata_2025 huggingface dataset:
High Tap Density MgO Doping Composite Composition 0.5Li2MnO3-0.5LiNi0.5Mn0.5O2 Cathode Material
Authors: Kumar Arun , Tomar Maharaj
Published: February 2020

Introduction

Last decade Lithium-rich layered and spinal base oxide materials have been studied as a promising cathode material for using in the next generation high energy lithium-ion batteries for intensively pursued for electric and hybrid electric vehicle applications. Commercial lithium ion cells are currently made largely with the layered LiCoO2 cathode. However, only 50% of the theoretical capacity of LiCoO 2 can be utilized in practical cells due to the chemical and structural instabilities at deep charge as well as safety concerns. One of these layer materials composite , xLi2MnO3-(1-x)LiNi0.5Mn0.5O2 (0<x<1) has been widely studied since Thackeray et al. discovered it when they were researching the LiMnO2 layered material.1 This material shows capacities larger than 280 mAhg-1 and operating voltages larger than 4.5 V making it one of the cheapest high energy density material for Li-ion batteries. However, many challenges must be overcome in order to realize its commerciality, for example its poor capability and its voltage degradation during cycling.2

In this study, we are doping MgO with composite cathode. The effect of doping not only will provide stability in the composite structure in the lithiation and delithiation process, also improve electrochemical properties..

Experimental

0.5Li2MnO3-0.5LiNi0.5Mn0.5O2 has been synthesized using carbonate based co-precipitation method.

The structural and morphological features have been studied by powder X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Figure 1 shows the XRD patterns of as-synthesized LNMO powder. Results show the complete two phases formation of composite material corresponding to the two group space of R3m (LiNi0.5Mn0.5O2) and C2/m (Li2MnO3). This patterns were compare with JCPDS database, #84-1634 for Li2MnO3 and #09-0063 for LiNi0.5Mn0.5O2, which have been well indexed on the basis of LiNiO2 structure.1

SEM measurements show highly dense particle agglomerations, particle size lies to 0.5-2 μm, while agglomerations around 10-20 μm. Smaller particles are strongly related with a good electrochemical behavior.

Electrochemical properties will be study using cyclic Voltammetry, Charge-Discharge Curves, and Electrochemical Impedance spectroscopy (EIS). These measurements are still in progress.

Figure 1. XRD patterns of as prepared LNMO powder. Inset shows the small picks between 20-30 degrees related to the monoclinic Li2MnO3 structure,

References

[1] Haijin Yu et al., J.
Phys. Chem. Lett.,
4, 1269 (2013)

[2] Gurpreet Singh et al., J. Electrochem. Soc.,
159 (4), A3 (2012)
The Promise of Aqueous Chemistry Semi-Solid Flow Cells (SSFCs)
Authors: Davies Greg , Steingart Daniel A.
Published: February 2020

For large scale energy storage and long distance transport applications it is necessary to decouple the power output and capacity of the energy storage device to reduce costs to viable levels. Traditional flow batteries offer this power/capacity decoupling, however, amongst other challenges, the typical energy densities are significantly lower than those available from standard closed cell battery designs.

More recently there has been interest in a new type of flow battery, the semi-solid flow cell (SSFC). This type of cell combines the advantages of both flowing and solid battery concepts: the ability to decouple power output and capacity while still maintaining good energy densities. Suggested SSFC electrochemistries to this point have been mostly based on Li-ion technology. We will present research based on an aqueous SSFC chemistry, which has the potential to be safer and cheaper than Li-ion technologies. The important features of the system, and the promise of this technology for future large scale energy storage or transport applications will be considered.
Solid-State Electrochemical Heat Engine
Authors: Williams Mark C. , Richards George , Gemmen Randall
Published: February 2020

This paper explores the potential of using solid-state electrochemical heat engines operating on reversible redox reactions to continually harvest waste heat from available thermal energy from natural and man-made sources. These systems are electrolyers/fuel cells that operate on thermal energy. These systems utilize and control the electrochemical potential of molecules undergoing redox reactions in a manner to produce electrical energy from thermal energy. The electrochemical potential of these redox pairs is a function of composition, temperature and pressure. EHE’s in this paper exploit the change in basic thermodynamic properties with temperature. Each EHE is not only an energy storage device, but an energy producer using no fuel other than waste thermal energy. The EHE technology can be deployed using fuel cell/electrolyser combinations.
High-Efficiency Electrochemical System for Harvesting Low-Grade Heat Energy
Authors: Lee Seok Woo , Yang Yuan , Lee Huym-Wook , Chen Gang , Cui Yi
Published: February 2020

Tremendous thermal energy exists in low-grade heat sources (<100 °C), so high-efficiency and low-cost thermal energy harvesting system is highly demanded to utilize them. Current technologies, such as thermoelectric device, still have a low efficiency to satisfy commercial application. As an alternative choice, thermogalvanic cell, the electrochemical counterpart of thermoelectric device has benefit of higher electrochemical Seebeck coefficient low thermal conductivity, and material abundance. However, its efficiency is incomparable to thermoelectric system due to the low ionic conductivity. Another approach to utilize the high electrochemical Seeback coefficient is the thermally regenerative electrochemical cycle (TREC) aimed for harvesting high temperature thermal energy (>500 °C) half a century ago. In this approach, the electrochemical cell is discharged at T1 and recharged at a different temperature T2. The electrochemical Seeback effect induces lower charging voltage at T2 than the discharging voltage at T1, and thus net electricity is generated as the difference between the discharged and charged energy. This thermal-cycle-like design could lead high efficiency by decoupling electrical conduction and thermal conduction. However, large polarization of electrode materials of TREC has suppressed low temperature thermal energy (<100 °C). Here we demonstrate a new effective TREC to utilize low-grade heat by employing proper materials. The demonstrated system achieved very high efficiency at low temperature range. We believe that the demonstrated system is anticipated to be a good alternative choice of low cost and high efficiency thermal energy harvesting system from various low heat sources such as heat engine system, solar thermal, geothermal, and body heat.
Fibrous Mixed Conducting Cathode with Embedded Ionic Conducting Particles: Facile Synthesis and Their Electrochemical Properties for Solid Oxide Fuel Cells
Authors: Choi Jinyi , Lee Hunhyeong , Lee Sewook , Shin Dongwook
Published: February 2020

We propose the MIEC (Sm0.5Sr0.5CoO3−δ or La0.6Sr0.4Co0.2Fe0.8O3−δ) fiber with embedded ionic conducting particles (Sm0.2Ce0.8O1.9 or BaCe0.7Zr0.2Y0.1O3−δ) instead of simple external composite method. This structure is devised to strengthen the advantages of fibrous cathode; (i) suppress grain growth of the MIEC matrix by dispersed ionic conducting particles, (ii) relieve residual thermal stress within the fibers, (iii) maintain the overall porosity without filling the network pores, and (iv) simplify the composite processing compare to other process such as infiltration. The ionic conducting nanoparticles were embedded in the MIEC fiber matrix as the composite cathode for SOFCs application by electrospinning method. We compared the electrochemical performance of the fiber composite with the conventional composite cathode. As a result, we could conclude that the structural excellence of the fibrous composite cathode, i.e. promoting the charge transfer reactions by building continuous paths and maximizing the TPB sites in virtue of the dispersed ionic conducting particles within the MIEC fiber matrix. The single cell with the fiber composite cathode shows much higher performances; its maximum power densities are about 1,400 and 380.5 mW∙cm−
2 at 700 and 600 oC respectively, accounting for 63.1 % and 75.8 % improvements as compared to the cell with the powder composite cathode operating at the same temperatures. The performance improvement of the fiber composite cathode far surpasses that of the powder composite cathode, which is ascribed to the microstructural contribution originating from fibrous structure.
Coking Study in Anode Materials for SOFCs: Physicochemical Properties and Behavior of Mo-Containing Perovskites in CO and CH4 Fuels
Authors: Zheng Kun , Świerczek Konrad , Carcases Nahum Maso , Norby T.
Published: February 2020

Recent research trend on Solid Oxide Fuel Cells is aimed at utilizing non-hydrogen fuels [1-4]. When SOFC is running on syngas, methane and/or other hydrocarbons, on the typical Ni-YSZ anode carbon deposition occurs, which consequently significantly decreases SOFC cell performance, due to a decrease of the triple phase boundary catalytic sites, which are blocked by coking [1, 2]. Among candidate anode material for usage with such fuels, A2MMoO6-δ(A: Sr, Ba; M: 3d metals) ordered perovskites seem to be particularly interesting [3, 4]. However, the coking mechanism in such compounds is still under intensive research, due to a fact that carbon deposition process is affected with many factors, such as operation temperature, water content, etc. [1, 2].

In this study, B-site modified double perovskites with Sr2Fe1.5-xMnxMo0.5O6 formula were investigated as candidate anode materials for SOFCs operating with syngas and/or methane, in terms of their crystal structure, oxygen nonstoichiometry, chemical stability, their electrochemical properties, and carbon deposition tolerance in CO and/or CH4 gases. The coking effect on the electrical conductivity and SOFC performance was studied at different temperatures. Deposited carbon morphology, as well as degradation of microstructure of the materials were investigated by SEM. It was found that carbon deposition is significantly dependent on the operation temperature and annealing time. Elucidation of the coking mechanism on Sr2Fe1.5-xMnxMo0.5O6-based anodes is given.

Acknowledgments

The project was funded by the National Science Centre Poland (NCN) on the basis of the decision number DEC-2011/03/N/ST5/04785.

One of the authors (K. Zheng) acknowledges financial support from the National Science Centre Poland (NCN) under the ETIUDA doctoral scholarship on the basis of the decision number DEC-2013/08/T/ST5/00100.

References

1. X. Ge, S. Chan, Q. Liu, Q. Sun, Adv. Energy Mater. 2 (2012) 1156-1181.

2. T. Chen, W. Wang, H. Miao, T. Li, C. Xu, J. Power Sources 196 (2011) 2461-2468.

3. Y.H. Huang, R.I. Dass, Z.L. Xing, J.B. Goodenough, Science 312 (2006) 254-257.

4. K. Zheng, K. Świerczek, W. Zając, A. Klimkowicz, Solid State Ionics 257 (2014) 9-16.
Characterization of Ion Exchange Membrane Based on Hydrocarbon Based Polymer and Functional Additives
Authors: Nam Sang Yong , Kim DeukJu
Published: February 2020

A sol-gel method and an in situ method were used to synthesize organic-inorganic composite membranes based on poly(arylene ether sulfone) (SPAES), phosphotungstic acid (PWA) containing sulfonic acid and amine groups. HPA is generally water soluble and causing a deterioration of cell performance. To solve this problem, PWA particles were functionalized with various silane compounds to enhance proton conductivity and to possess insoluble property in water. This study compares the performance of polymer electrolyte membrane fuel cells with different preparation methods for the membrane and composite PWA-silica-SO3H particles. The optimum composition of PWA-silica-SO3H and effect of amine groups in SPAES composite membrane are determined on the basis of the mechanical properties, the behavior of water in the membrane, and the level of proton conductivity. The mechanical properties of the composite membrane prepared by sol-gel method were improved with the introduction of PWA-silica-SO3H particles. Also, the sol-gel composite membrane containing amine groups has higher levels of proton conductivity than the other composite membranes. An increase in the silica content of the PWA-silica sol-gel particles increases the ion conductivity because the inorganic component and the incorporation of PWA lead to a high concentration of functional.
Study on the Oxygen Bonding Energy to Pt by Valence Band DOS Measurement of Pt Nano-Particle Catalysts
Authors: Hidai Shoichi , Ishii Kenji , Matsumura Daiju , Niwa Hideharu , Miyawaki Jun , Aoki Tsutomu , Oshima Masaharu , Harada Yoshihisa
Published: February 2020

In order to improve the catalytic activity and durability of PEFC cathode Pt catalysts the particle size and ligand effects on the oxygen bonding energy of a Pt nano-particle catalyst were evaluated from the valence band DOS of Pt by using resonant inelastic X-ray scattering (RIXS). The RIXS measurement is suitable to probe changes of the valence band states by oxygen adsorption because it is element specific and compatible with ambient pressure. A hard X-ray whose photon energy is slightly lower than the Pt L
3 absorption edge was introduced on the sample to eliminate fluorescence component and subsequent emission by transition from the Pt valence states to the 2p core hole was detected as a function of energy transfer as shown in Fig. 1.

The RIXS spectra of Pt nano-particle catalysts measured by 11.563 keV excitation are shown in Fig. 2. The mean particle diameters are evaluated from TEM images to be from 1.6 to 3.9 nm. The main peaks in the region between 2 and 4 eV can be assigned as X-ray Raman peak which comes from the bonding between platinum and oxygen. The X-ray Raman peak position decreases with increasing mean particle diameter as shown in Fig. 2.

The energy transfer value of X-ray Raman peak position can be closely related to the oxygen bonding energy with Pt. Therefore Figure 2 suggests that the oxygen bonding energy to Pt decreases with the Pt particle size. Strong bonding between oxygen and Pt might reduce the catalytic activity and the durability of Pt nano-particles with diameters less than 3 nm. Alloying with transition metals also changes the bonding energy of oxygen to Pt. Based on these results, relationship between electronic structure and catalytic activity will be discussed.

Acknowledgement

This work was supported by New Energy and Industrial Technology Development Organization (NEDO). The RIXS experiments were approved by the Japan Atomic Energy Agency (JAEA) Proposal Review Committee (Proposal No. 2010B3575, 2011A3574 and 2013A3514).
PVA/Polyelectrolyte Bipolar Membranes for Fuel Cell Applications
Authors: Staser John A , Movil-Cabrera Omar , Frank Logan
Published: February 2020

In the last few years, direct borohydride/hydrogen peroxide fuel cells (DB/HPFC) have attracted considerable attention due to their potential use as air-independent power sources in undersea vehicles. In general, a DB/HPFC system can be built using either a cation exchange membrane (CEM) or an anion exchange membrane (AEM) as a polymer electrolyte. Unfortunately, to date, these systems exhibited low efficiency, mainly due to some problems related to the intrinsic properties of the polymer electrolyte themselves. Bipolar membranes are promising candidates to improve the efficiency of DB/HPFC systems, since these incorporate advantageous features of both AEM and CEM, and also mitigate the loss of fuel.

The present work focuses on the fabrication and characterization of a novel bipolar membrane for DB/HPFC applications. The first goal is to fabricate water-soluble PVA-based AEM and CEM with both high ionic conductivity and excellent mechanical stability. For this purpose, a variety of AEMs are prepared via polymer blending of PVA and poly(diallyldimethylammonium chloride) (PDDA) or poly(acrylamide-co-diallyldimethylammonium chloride) (PACoDDA). Similarly, CEMs are fabricated via polymer blending of PVA and acid polymer ((poly (styrene sulfonic acid) (PSSA) or poly (acrylic acid) (PAA)). Subsequently, the membranes are cross-linked using a chemical or physical method. The chemical cross-linking is performed at different concentrations of glutaraldehyde (GA), whereas the physical cross-linking is performed at different temperatures. The electrical, mechanical and morphological properties of these membranes are evaluated as a function of PVA content and cross-linking process conditions. Some of the material characterization techniques used in this study include, but are not limited to: Fourier transform infrared spectroscopy (FTIR), four-electrode impendence measurement, transmission electron microscopy (TEM), and tensile tests. Preliminary results indicate that PVA-PDDA and PVA-PSS membranes have excellent mechanical and alkaline stability. Also, the maximum OH− conductivity of 8.57E-3 S cm−1 was achieved for physically cross-linked PVA/PDDA membrane with a polymer composition of 70/30 as shown in Figure 1a. In the case of CEM, the high H+ conductivity of 1.77E-2 S cm−1 corresponds to the chemically cross-linked PVA-PSS membrane with a polymer composition of 70:30 (see Fig. 1b).

Figure 1. Ionic conductivity as a function of PVA content for (a) PVA/PDDA membranes and (b) PVA/PSS membranes.
MEA Pt/C Cathode Catalyst Degradation during Repeated Anode Gas Exchange Cycles: In-Situ XAFS, STEM-EDS and Electrochemical Analysis
Authors: Samjeské Gabor , Higashi Kotaro , Takao Shinobu , Nagamatsu Kenichi , Nagasawa Kensaku , Sekizawa Oki , Kaneko Takuma , Uruga Tomoya , Iwasawa Yasuhiro
Published: February 2020

The start-up and shut-down processes in polymer electrolyte fuel cell (PEFC) operations involve anode gas (fuel) mixing with air, which may diffuse into the Pt/C anode from either the anode gas outlet or the Pt/C cathode through the Nafion membrane. This causes a transient, short-lived anode-condition, in which a part of the anode catalyst layer is exposed to hydrogen while another is exposed to oxygen (air). The resulting mixed gas-condition leads to oxygen reduction reaction (ORR) at the oxygen-covered area of the anode, while hydrogen oxidation reaction takes place at the hydrogen-covered area of the anode, by the so called reverse current decay mechanism./1/

The electrolyte potential (potential of the Nafion layer) is drawn to negative values in the air-covered regions to facilitate the ORR on the anode, thus causing the potential difference between the Nafion layer and cathode catalyst layer on the corresponding areas of the cathode to increase up to 1.6 V. At the high potentials not only dissolution of Pt from the cathode catalyst but also oxidative corrosion of the carbon support take place.

We have measured the Pt/C cathode catalyst in PEFC during repeated fast anode-gas exchanges (AGEX) cycles by means of in-situ time-resolved XAFS, to study the structural and electronic transformations of Pt nanoparticles at the cathode caused by the AGEX cycles. The in situ XAFS and time-resolved XAFS techniques together with STEM-EDS provided new insights into the origin and mechanism for the Pt/C cathode catalyst degradation by the AGEX cycles.

/1/
Carl A. Reiser et al.; Electrochem. Solid-State Lett.; 2005 (6) A273
Cathode Design of Non PGM Catalysts for Anion Exchange Membrane Fuel Cells
Authors: Asazawa Koichiro , Nishino Eriko , Kishi Hirofumi , Miyake Junpei , Uchida Makoto , Miyatake Kenji , Watanabe Masahiro
Published: February 2020

An anion exchange membrane fuel cell (AEMFC) using hydrazine hydrate liquid fuel has been developed1 and the concept vehicle powered by Precious Metal free Liquid Feed Fuel Cell (PMfLFC) was exhibited at the 42nd and 43rd Tokyo Motor Show. For the improvement of the AEMFCs, technological breakthrough is necessary for anion exchange membranes. Especially, it is important to overcome the counteracting relationship of high ion conductance and low fuel permeability. And also, technology to control triple-phase interface formed by catalyst and ionomer is important to improve the performance. Our approach to develop the advanced AEMFC is using anion conductive quaternized aromatic multiblock copolymers, poly(arylene ether)s (QPEs)2 and control the interface and non platinum group metal (PGM) catalysts both for anode and cathode. Even for state-of-the-art proton exchange membrane fuel cell electrode that consists of Pt catalysts and perfluorinated ionomer, triple-phase interface has not been optimized and the catalyst utilization is still insufficient. This is also the case for non PGM catalyst and anion exchange ionomer. In this paper, for the preliminary study we focus on electrode design for cathode and evaluated pore size of non PGM catalyst and distribution of catalyst in the ionomer solution. The non PGM catalysts formed meso pores (10-100nm) with the mixture of carbon materials. There are two different types of pores, one is inside of the catalyst itself and the other one is outside pores between the catalysts. Mixture of non PGM catalyst and carbon materials are increased meso pores. Oxygen reduction reaction (ORR) activity of the non-PGM catalysts was evaluated in 1M KOH aq using rotating ring disk electrode (RRDE). The Fe-N-C non-PGM catalyst showed comparable ORR performance to platinum/carbon catalyst (TEV10V60E). The half wave potentials were 0.886V and 0.849V, respectively. MEA consists of the QPE membranes and ionomers were fabricated with non-PGM catalysts and subjected to performance evaluation. The MEA performance of direct hydrazine fuel cells will be shown and discussed in the meeting.

References

[1] K. Asazawa, H. Tanaka, U. Martinez, B. Halevi, A. Serov, K. Artyushkova, P. Atanassov, and B. Kiefer, Abstract #1610, Honolulu PRiME 2012

[2] M. Tanaka, K. Fukasawa, E. Nishino, S. Yamaguchi, K. Yamada, H. Tanaka, B. Bae, K. Miyatake, and M. Watanabe, J. Am. Chem. Soc. 2011, 133, 10646–10654
The Effect of Cathode Pressure Perturbations on the Voltage Stability of a Simulated Fuel Cell Stack
Authors: Burkholder Michael , Litster Shawn
Published: February 2020

During polymer electrolyte fuel cell (PEFC) operation, proper water management is necessary to optimize performance [1]. It is desirable to have enough water to fully hydrate the electrolyte membrane with no excess liquid water to interfere with the transport of oxygen to the cathode, causing power loss. However, the air flow rate and pressure drop used to remove liquid water from the cathode and maintain power can cause large parasitic power losses. Low cathode pressure drops that are parasitically inexpensive to maintain lead to voltage instability and loss [2], while high flow rates and pressure drops stabilize voltage at the cost of a higher parasitic load on the PEFC and lower system efficiency.

In this work, we perform experiments on a simulated fuel cell stack that consists of a constant hydraulic resistance bypass around the cathode, allowing air flow to the cathode to divert through the parallel bypass as the cathode's hydraulic resistance changes in the presence of liquid water. This bypass can be used to simulate a stack of unflooded cells in parallel with the experimental cell [2]. Downstream of the simulated stack we placed a solenoid valve followed by a pressure regulator to apply controlled pressure perturbations to the simulated stack. The perturbations consist of a short (< 1 second) reduction in backpressure followed by backpressure recovery. The PEFC cathode was also equipped with a differential pressure transducer to measure the pressure drop across the flow field. We formulated reduced order nonlinear statistics based on chaotic invariants (the Lyapunov exponent of the voltage return map, λ) to quantify the level of instability in the PEFC and implemented a computer program to monitor the PEFC stability in real time.

Using the simulated stack under galvanotstatic operation, we recorded the PEFC voltage, cathode differential pressure (ΔPc), and λ responses to varying magnitudes of pressure perturbations during operation in an unstable regime (low current density, low air flow rate). We found that the pressure perturbations stabilized the voltage, Fig. 1, while allowing for a reduced pressure drop. We then implemented a control scheme that monitors the Lyapunov exponent for values above a threshold and applies a corrective pressure perturbation when this occurs. As Fig. 2 shows, this control scheme recovered lost power, stabilized voltage, and reduced cathode pressure drop with minimal energetic expense.

References

[1] N. Yousfi-Steiner et al., Journal of Power Sources 183 (1) (2008) 260-274.

[2] J.P. Owejan et al., Journal of Power Sources 171 (2) (2007) 626-633.
Investigation of Performance and Durability of MEAs at Higher Temperature
Authors: Kitamura Masahiko , Minamida Yasuto , Zhao Xiaojing , Noda Zhiyun , Hayashi Akari , Sasaki Kazunari
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) recently attract more attention because fuel cell vehicles (FCVs) are commercially available from 2015. Even though the technology for the first generation FCVs has been mainly established, for the next generation FCVs, the operation at high temperature is desired in order to improve the power generation efficiency and durability. The target operating temperature is about 120 °C for FCVs. Since there are still technological problems for electrolyte membranes over 100 °C, almost no report is found about either performance or durability under such a condition at present. Here, the objective of our study is to extract the problems on the catalytic degradation at higher temperature. In this study, we have evaluated performance and durability of MEAs under higher temperature like 105 °C and low humidity such as RH57%.

MEAs were manufactured using a standard Pt/Ketjen black catalyst (TEC10E50E, TKK Corp.) and Nafion. Then, their IV characteristics were examined. Regarding to the durability evaluation, two protocols[1] recommended by Fuel Cell Commercialization of Japan (FCCJ), “load cycles” and “start-stop cycles”, were in use. Three different conditions of operation temperature and humidity (80 °C/RH100%, 105 °C/RH57%, and 80 °C/RH57%) were applied. Then, the effects of such conditions on both performance and durability of MEAs were evaluated.

On evaluation of IV performance in three different conditions before and after the load cycle durability tests, the operation at 105 °C greatly deteriorated the performance than at 80 °C. Also, by comparing two different humidity conditions at 80 °C, the lower humidity led to the smaller degradation. Moreover, the change in electrochemical surface area (ECSA) was examined at the same time, and then the retention of ECSA was lower under both higher temperature and higher humidity, likewise. In addition, SEM observations were performed to see the change in Pt particle size. As a result, Pt grain growth was confirmed after the load cycle durability tests. The average particle size became larger at both higher temperature and higher humidity. In other words, a similar trend to the deterioration of IV performance was obtained. Here, we believe that one possible reason why the deterioration was suppressed at lower humidity comes from the existence of less water relating to the diffusion of Pt ions. Similarly, the examination on the start-stop cycle durability tests will also be reported.

Reference

[1] A. Ohma et al., ECS Trans, 41 (2011) 755.
Tolerance of Impurities in Bio-Ethanol on Pd/C Catalyst Toward the Ethanol Oxidation Reaction in Alkaline Media
Authors: Chen Rongrong , Qi Jing
Published: February 2020

In the recent years, bio-ethanol could be produced massively from various sources and has attracted great interests as an alternative fuel source in low temperature fuel cells. However, the bio-ethanol may contain some impurities, such as lactic acid, acetic acid, glucose, glycerol, maltose, fructose and so on, to contaminate the catalysts in the fuel cells. The objective of this work is to investigate the effects of impurities in bio-ethanol on the performance of Pd/C catalyst for the ethanol electro-oxidation reaction (EOR) in alkaline media.

The electrocatalytic activities of Pd/C toward EOR with the addition of 0.01 M of various organic compounds were tested by cyclic voltammetry (CV). By comparing the EOR current at the corresponding potential, the presence of lactic acid and acetic acid was found to have little effects on the electrocatalytic activity of Pd/C toward EOR; however, the performance of Pd/C toward EOR get worse with the presence of glucose, glycerol, maltose, and fructose.

The quasi-steady state current for EOR on the Pd/C catalyst was also measured by chronoamperometry (CA) measurements. The EOR current of the Pd/C decayed slowly with time. The steady currents at 0.5 V for EOR on Pd/C catalyst exhibit the order of EOR » EOR+0.01 M lactic acid > EOR+0.01 M acetic acid > EOR+0.01 M glucose > EOR+0.01 M glycerol > EOR+0.01 M maltose » EOR+0.01 M fructose. This trend is consistent with the CV test results.

The tolerance of impurities in bio-ethanol on other catalysts toward the ethanol oxidation reaction in alkaline media will be also studied and discussed.
Performance of the High Temperature PEM Membrane Electrode Assembly
Authors: Kerr Robert , García Héctor R. , Romero Maria T. , Terkelsen Carina , Hjuler Hans A. , Steenberg Thomas
Published: February 2020

High temperature polymer electrolyte membrane (HT-PEM) fuel cells provide an attractive alternative to low temperature (LT) PEM fuel cells owing to several advantages that include a tolerance to carbon monoxide so that reformate may be used, simplified cooling systems and balance of plant, higher value waste heat and no need for humidification of reactants. PEMs derived from phosphoric acid-doped polybenzimidazoles (PBI) have so far generated the most interest for high temperature PEM fuel cell operation. However, in order to realize a commercially competitive product there are several challenges that remain regarding the performance, durability and cost – particularly the cost associated with the platinum-based electrodes.

This communication will provide details on some of the HT-PEM MEA performance targets most recently achieved by Danish Power Systems, namely;

MEA performances of >0.7 V cm-2 at 0.2 A cm-2 and >0.5 V at 0.8 A cm-2 using dry H2/Air.

MEA lifetime of 12000 h at 0.23 A cm-2 using dry H2/Air with a degradation rate of <10 µV h-1.

An integrated 5 kW stack/reformer system operating for 3000 h using methanol reformate as fuel.

The task of optimizing MEA performance is carried out using rotating disc electrode voltammetry and CO stripping/electrochemical surface area studies in order to improve electrode properties (porosity and phosphoric acid management). Investigations into MEA durability are conducted using post mortem analyses on MEAs tested under operating conditions. These studies are comprised of cross-sectional SEM imaging and X-ray diffraction to monitor catalyst layer/membrane degradation and catalyst particle growth, respectively. Studies using reformate have also led to promising results with an MEA performance of 0.58 V cm-2 at 0.385 A cm-2 with a degradation rate of 30 µV h-1 using wet H2 (30 mol%)/Air.

In addition to reaching performance benchmarks, a reduction in the standard deviation for MEA performance to <5% has been achieved through efforts aimed at improving the uniformity of the membrane and catalyst layer thicknesses.
Development of Next Generation Heavy Duty Bus Fuel Cells with Enhanced Durability
Authors: Kjeang Erik , Holdcroft Steven , Knights Shanna , Malek Kourosh , Djilali Ned , Eikerling Michael , Golnaraghi Farid , Wang Gary , Rajapakse Nimal , Wild Peter , Devaal Jake , Lauritzen Mike , Watson Mark , Rogers Erin
Published: February 2020

The large-scale commercialization of durable and cost-competitive Polymer Electrolyte Fuel Cell (PEFC) technology for automotive applications still faces significant challenges. Fuel cell manufacturers need to develop low cost materials and fabrication approaches that surpass current levels of performance and durability. With funding from Ballard Power Systems and Automotive Partnership Canada, the present three-year project is dedicated to research and product development of next generation PEFC stack technology for transit buses [1]. The central objective is to advance the fundamental understanding of membrane degradation mechanisms and failure modes under drive cycles and conditions that are typical of heavy duty vehicle operation, and to leverage this knowledge to develop enhanced durability solutions.

The project involves a cohesive research team from Ballard Power Systems, Simon Fraser University, and University of Victoria, with complementary and multi-disciplinary expertise in fuel cell science and technology, materials design and fabrication, multi-scale modeling, system design and engineering, as well as system controls and diagnostics. A comprehensive experimental-theoretical research approach is pursued that ranges from fundamental theory to empirical analysis, with close university-industry collaboration. For validation purposes, the research benefits from extensive real-time field data and field operated material samples extracted from the Whistler, British Columbia fuel cell bus fleet. The results obtained to date have enabled substantial improvements in membrane stability under bus conditions (based on laboratory testing) and enhanced the ability to accurately predict the fuel cell stack lifetime over several years of on-road transit service. This understanding will guide the development of the next generation of heavy duty fuel cell modules that reduce both capital cost and operating costs of fuel cell buses, making them commercially competitive with diesel hybrid buses on a lifecycle basis.

References: [1] http://www.apc-hdfc.ca/
Hydrogen Fuel Cells for Small Unmanned Air Vehicles
Authors: Swider-Lyons Karen , Stroman Richard O'Neil , Gould Benjamin D. , Rodgers Joseph A. , Mackrell Joseph , Schuette MIchael , Page Gregory
Published: February 2020

The Naval Research Laboratory has been researching the use of hydrogen fuel cells for propulsion of long-endurance unmanned air vehicles (UAVs) for military and civilian applications. The high electrical efficiency of polymer electrolyte fuel cells (PEFCs) in combination with the high energy content of hydrogen enable the long endurance flights. The systems also offer the numerous attractive attributes of electric power, including instant starting, ease of control, near-silent operation, rapid load response, and high quality electric power.

The progression of Ion Tiger flights will be discussed. Ion Tiger used a ~ 1 kg 550-W (0.75-horsepower) fuel cell system from Protonex Technology Corporation with 0.5 kg of compressed H2 in a 4-kg a carbon/aluminum pressure vessel to fly for 24 hours continuously in Nov 2009. The vehicle also carried a 5-lb payload. In April 2013, the Ion Tiger flew for 48-hours by using liquid hydrogen fuel in a new, NRL-developed, cryogenic fuel storage tank and delivery system. These 1-day and 2-day demonstrations prove that hydrogen fuel cells provides a clear path to long endurance electric flight: in comparison, the Ion Tiger would be able to fly for only 4 hours on the comparable amount of lithium batteries.

This talk will discuss the scientific challenges related to using PEFCs in UAVs. The most important criterion is weight, demanding a high power to weight fuel cell along with high efficiency to maximize the use of the on-board hydrogen. Therefore, high activity, efficient electrocatalysis is needed, along with components with few I2R losses. The system should ideally operate near 80 °C to minimize the need for heat rejection. We have also become cognizant of poisoning issues, specifically related to coolant leakage through carbon bipolar plates, and also issues related to airborne contaminants, such as SO2, and the NaCl in sea mist.

We are grateful for support from the Office of Naval Research.
Fuel Cells Current Capabilities and Challenges for the Military Applications
Authors: Chu Deryn , Jiang Rongzhong , Ren Xiaoming , Grew Kyle , McClure Joshua
Published: February 2020

During the last two decades, U. S. Army and Defense Advanced Research Project Agency (DARPA) have supported numerous fuel cells research and development projects. Many different types of fuel cell systems are successfully developed and demonstrated. This presentation focuses on the technical challenges of fuel cell systems for military applications and Lesson Learned and the Road Ahead.
Invited: Development of PFSA Ionomers for the Membrane and the Electrodes
Authors: Kinoshita Shinji , Tanuma Toshihiro , Yamada Kohta , Hommura Satoru , Watakabe Atsushi , Saito Susumu , Shimohira Tetsuji
Published: February 2020

Asahi Glass Company (AGC) has been developing the PFSA ionomers for the membrane and electrodes. Ionomers for the membrane are required to have high ion exchange capacity (IEC) but the water uptake should be below certain level to avoid excess dimensional changes during dry and wet operating condition cycles. Polymer electrolytes with high softening temperatures and high proton conductivity were prepared and tested in various conditions. For the cathode electrode, polymer electrolytes with high oxygen permeability were prepared with the assumption that the flux of oxygen can be the rate limiting step for the reaction. Oxygen permeability of polymer electrolytes was increased by decreasing their density. The performances of MEAs using high oxygen permeable ionomers in the cathode were tested and they showed improved performances compared to the MEA using conventional ionomers especially when the Pt loading was low. The ionomer was also used in the micro porous layers (MPLs) between the catalyst layers and the Gas diffusion substrate to create hydrophilic MPLs. The MEAs applying them were explored to achieve better performances at dry conditions as well as at wet conditions.
La2NiO4 Ceramic Electrodes for Hydrogen Peroxide Electroreduction
Authors: Santos Diogo M.F. , Sousa Nuno , Sljukic Biljana , Sequeira Cesar A.C. , Figueiredo Filipe M
Published: February 2020

Direct borohydride/peroxide fuel cells (DBPFCs) use sodium borohydride (NaBH4) as an anodic fuel and hydrogen peroxide (H2O2) as the oxidant. DBPFCs are superior to similar types of fuel cells in terms of their theoretical cell voltage and energy density. Additionally, the fact that both fuel and oxidant reactants are liquid at ambient temperature simplifies their storage, thermal management and internal processing [1]. For these reasons, DBPFCs can be promising alternatives as power sources for space, underwater, and specific terrestrial applications where oxygen is not available.

To develop the DBPFC, we are focused on finding low-cost, stable, durable, and efficient electrocatalytic materials for H2O2 reduction that can simultaneously inhibit its decomposition. H2O2 decomposition is known to proceed even on platinum, which is the most commonly used electrocatalyst. Recently, some perovskite-type oxides were found to have reasonable activity for H2O2 electroreduction in DBPFCs [2].

Here, La2NiO4 ceramic disks are prepared by mechanosynthesis and characterized by scanning electron microscopy and X-ray diffraction. The use of ceramic pellets as electrodes allows avoiding cross-contributions of carbon or nickel foam catalyst supports, thus preventing the influence of such effects in the evaluation of La2NiO4 activity.

Several electrochemical methods, namely cyclic voltammetry, chronoamperometry and chronopotentiometry, were used to investigate the electrodes activity for H2O2 reduction in alkaline media. These studies made possible determination of the reaction kinetic parameters as well as its coulombic efficiency. The effect of temperature on the calculated number of exchanged electrons and on the charge transfer coefficients was analyzed. Stability tests were also performed.

Then, a test laboratory DBPFC was assembled using a La2NiO4 cathode and main cell parameters (e.g., open circuit voltage, peak power density, cell voltage and current density at the peak) were evaluated for temperatures ranging from 25 to 65 ºC.

References

D.M.F. Santos, C.A.C. Sequeira, Sodium borohydride as a fuel for the future, Renew. Sustain. Energy Rev. 15 (2011) 3980.

D.M.F. Santos, T.F.B. Gomes, B. Sljukic, C.A.C. Sequeira, F.M.L. Figueiredo, Electrochemical study of perovskite cathodes for H2O2 reduction in direct borohydride fuel cells (in preparation).
The Role of Lipid-Membrane in the Direct Electrochemistry of Human Liver-Microsomal Films
Authors: Krishnan Sadagopan , Walgama Charuksha , Nerimetla Rajasekhara , Schildkraut Deniz , Elman James F
Published: February 2020

Cell membranes play a crucial role in molecule/ion transport, cell signaling, bioenergetics, interactions between biomolecules, and many other important biological processes. Due to these significant roles of lipid-membranes in life-processes, investigating the ion and charge-transport processes across them in vitro by designing biomimetic membranes has been an active research area. Lipid-membranes have been used widely to construct artificial photosynthetic systems and efficient electro- and photo-catalytic processes. Nevertheless, the potential of exploiting transport processes across lipid-bilayer membranes in developing robust modern biosensors, biocatalytic systems, and energy-conversion devices is challenging.

We provide here new insights on the direct electrochemical kinetics of micron-thick innate human liver-microsomal films containing embedded oxidoreductases and major drug metabolizing monooxygenase enzymes. Additional insights on the effect of electrode-materials in oxygen binding kinetics to the oxidoreductase reduced heme-proteins present within the HLM-film will also be presented. We were able to control the nominal HLM-film thickness by using different electrode-materials, and thus seem to have influenced the arrangement of redox proteins in the HLM-films. Our results suggest that one can directly use liver-microsomal films coated on appropriate electrodes for drug screening and biosensing applications without requiring purified monooxygenases and reductases, reconstituted assay systems, chemical/NADPH electron donors, and electrode modification procedures. Thus the cost and time of developing novel drug screening platform can be greatly minimized.

Acknowledgements. This work was supported by the Oklahoma State University.
The Protoelectric Potential Map (PPM): The Two-Dimensional Plot of Absolute Redox Potentials and Absolute pH Values
Authors: Radtke Valentin , Himmel Daniel , Pütz Katharina , Krossing Ingo
Published: February 2020

We recently introduced a unified Brønsted acidity scale on the basis of the chemical potential of the proton in any medium allowing the comparison of pH values of different media and a precise definition of superacidic media. For this purpose we defined the reference state of maximum acidity as the standard chemical potential µ
abs°(H+, g) of the proton in the gas phase (ideal H+ gas at 1 bar and 298.15 K), which is arbitrarily set to 0 kJ mol–1. The acidity and hence the chemical potential of the gaseous proton H+(g) is lowered by the interaction with any type of a medium, i.e. complexation of H+ in the gas phase, solution, or in the solid state. In this way the defined absolute pH value pHabs depends in a simple manner on the absolute potential of the proton in the media of interest. [1]

Analogously to the definition of the pHabs value we define an absolute redox potential (peabs) scale on the basis of the absolute chemical potential of the electron with the ideal electron gas at 1 bar and 298.15 K as reference state (µ

abs°(e–, g) = 0 kJ mol–1). This scale establishes the possibility of direct comparison of the reduction power (which we term “reducity”) of any redox system in any medium. [2]

Above all, both scales are combined to the Protoelectric Potential Map (PPM, peabs vs. pHabs, see fig.) as the Hydrogen Evolution Reaction (HER) correlates the pH scale to the redox scale. [2] The thermodynamics of any redox, acid-base or combined system in any medium can be represented and related to any other. For example, the pH-dependency of a redox system can be easily read off by the slope of the line representing the redox system in the whole pH range of the solvent under consideration. Thermodynamic stabilities of solvents can be clearly displayed and even predictions of reactions become possible at a glance, please compare with K. Pütz who presents that silver is a non-noble metal in the acidic IL HmimBr at this conference.

Figure: The Protoelectric Potential Map (PPM).

[1] a) D. Himmel, S.K. Goll, I. Leito, I. Krossing, Angew. Chem., Int. Ed. Engl.
2010, 49, 6885-6888; b) VIP-Paper: D. Himmel, S.K. Goll, I. Leito, I. Krossing, Chem. Eur. J.
2011, 17, 5808 – 5826.

[2] V. Radtke, D. Himmel, K. Pütz, S. Goll, I. Krossing, Chem. Eur. J.,
2014, DOI: 10.1002/chem.201302473
An Rrde Investigation of Manganese Dioxide Anodic Electrodeposition
Authors: Donne Scott W , Burns Robert C , Gibson Andrew J
Published: February 2020

Manganese dioxide is a prominent material in the literature surrounding metal oxide based electrochemical supercapacitors due to its low toxicity and cost, combined with its good pseudocapacitive behaviour [1]. It is important to understand how the deposition of MnO2 proceeds on different substrates and in different solution conditions when attempting to design thin films of MnO2for use in electrochemical capacitors.

In this presentation, evidence will be presented that shows MnO2 deposition from solutions containing MnSO4 proceeds by one mechanism on Pt, and another on MnO2. The preferred mechanism of growth varies with acidity. In relatively acidic solutions, 0.1 M H2SO4, an island growth regime is seen. In solutions of neutral pH, 0.1 M Na2SO4, behaviour corresponding to a very rapid spread of a thin coating is seen. In both cases, the deposition on Pt proceeds by a solution based [Mn(OH2)6]3+ disproportionation mechanism, whereas the deposition on MnO2proceeds by a solid state reaction through the Mn(III) species, MnOOH.

Shown in the figure below is an example of the kinetic current curves obtained from the disc of the RRDE. These curves show that as the potential is increased, the Pt surface is more rapidly covered by MnO2, with a smaller nucleation kinetic current seen, related to the smaller size of islands at coalescence. It can be seen that these curves decay to the same current value, related to the kinetically (chemical, not electrochemical) limited transition from MnOOH to MnO2.

[1] A. D. Cross, A. Morel, T. F. Hollenkamp, S.W. Donne, Journal of the Electrochemical Society,
158, A1160 – A 1165, 2011.