bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuum Approach for Modeling Mechanical Fatigue of Ionomer Membrane
Authors: Liu Wenqing , Qiu Diankai , Peng Linfa , Lai Xinmin
Published: December 2020

The mechanical degradation of the proton exchange membrane is one of the main aspects affecting the lifetime of proton exchange membrane fuel cell. In previous study, we have found a plastic deformation occurs after the temperature and water content are increased, and would be substantially enhanced by the gas pressure difference between the anode and cathode. We further concentrates on the stress/strain evolution in the membrane of fuel cells throughout the assembly and running processes. However, the polymer electrolyte membranes suffers complex hygrothermal loading in the running process and show unlinear visco-elastic–plastic behavior. Thus the membrane express a different fatigue behavior compared to traditional metal materials. We propose an approach suitable for modeling mechanical degradation in polymer electrolyte membranes based on a constitutive model of Nafion membrane considering the rate, temperature, and hydration dependent deformation response under cyclic loading. A finite element analysis was performed and the results were compared to experimental observations.
Titanium Niobium Oxide Anode-Based Lithium-Ion Batteries for 10 Minutes Fast-Charging Applications
Authors: Lyu Hailong , Li Jianlin , Sun Xiao-Guang , Dai Sheng
Published: December 2020

Lithium-ion batteries (LIBs) have attracted considerable attention as environment friendly power sources for portable electronic devices. Although graphite (LiC6: 372 mAh g-1) has been used as the anode material for Li-ion batteries, the search for high rate anode materials has been actively pursued to meet the fast-growing requirements of high-power Li-ion batteries. As a promising anode candidate, TiNb2O7 (TNO) anode material with a nanoporous nature was prepared by a facile sol-gel approach. To satisfy the requirements of practical application, the hundred-gram scale synthesis of carbon coated TNO (TNO@C) have been achieved with low-cost reactants. The full cells based on high loading TNO@C anode (>13 mg/cm2) and matched LiNi0.6Mn0.2Co0.2O2 (NMC622, D50=10µm, Targray) cathode were evaluated for the 10 mins fast-charging application, delivering a high energy density of 142.8 Wh/kg (357 Wh/L) and a good energy density retention over 80% after 500 cycles.
Enabling > 4C Fast Charging of Li-Ion Batteries with Graphite/Hard Carbon Hybrid Anodes to Overcome Energy/Power Density Tradeoffs
Authors: Chen Kuan-Hung , Goel Vishwas , Namkoong Min Ji , Wied Markus , Müller Simon , Wood Vanessa , Sakamoto Jeff , Thornton Katsuyo , Dasgupta Neil P.
Published: December 2020

Li-ion batteries with high energy density and fast-charge capability are required to realize the widespread use of electric vehicles. However, current graphite-anode-based Li-ion batteries are unable to achieve fast charging without adversely impacting battery performance. This is because when graphite anodes are subjected to fast charging conditions, large cell polarizations reduce the accessible capacity and induce Li plating on the anode surface. The formation of metallic Li on the graphite anode surface results in irreversible loss of Li inventory, leading to significant capacity fade. In contrast to graphite, hard carbon is known to exhibit enhanced power performance. However, the high redox potential, low first-cycle efficiency, and low material density have prevented the adoption of hard carbon in high-energy-density battery systems. Thus, there is a unmet need to develop Li-ion technology to achieve both high energy density and power performance.

In this work, we demonstrate hybrid anodes fabricated by mixing graphite and hard carbon to achieve fast-charging Li-ion batteries with high energy density, using industrially relevant multi-layer pouch cells (> 1Ah) and electrode loadings (3 mAh/cm2). Standard roll-to-roll slurry casting was performed to fabricate the hybrid anodes, demonstrating the compatibility with existing Li-ion manufacturing. By tuning the blend ratio of graphite and hard carbon, it is shown that the battery performance can be tailored to simultaneously achieve high energy density and power performance. As a result of the hybrid anode design, we demonstrate pouch cells with > 96% and > 93% capacity retention over 100 cycles of 4C and 6C fast-charge cycling respectively. Synchrotron tomography was employed to investigate the microstructure effects (porosity, tortuosity, and pore size) on the electrochemical performance. Electrochemical dynamic simulations were also performed to provide mechanistic insight into the origins of the improved fast-charging performance of the graphite/hard carbon hybrid anodes.
Bimetallic MOFs(Co/Mn)@Rice Husks for Electrode Materials
Authors: Kim Hyunuk , Sohail Muhammad , Rosillo-Lopez Martin , Foord John S , Han Seong Ok
Published: December 2020

Novel pseudocapacitive nanomaterials storing energy electrochemically through surface redox reactions have been extensively investigated as an electrode to increase both power and energy density. The pyrolysis of metal-organic frameworks (MOFs), assembled from metal ions and organic ligands, generates well dispersed metal oxides within the carbon with high surface area. Herein, we report the synthesis of CoMn2O4/Co/MnO @rice husks (RHs) by pyrolysis of two different-sized bimetallic Co/Mn-MOFs@RHs and their electrochemical performance. SEM and PXRD analysis showed that Mn(CH3CO2)2/Co(NO3)2-derived MOF-74 (1) has much smaller crystal size and grain size than those of MnCl2/Co(NO3)2-derived MOF-74 (2) although both have an identical phase. The different crystal sizes of 1 and 2 were rationalized by considering the nucleophilic reactivity of the counter anions to the metal cations. For instance, acetate during the crystallization of 1 has a higher nucleophilic reactivity than chloride during that of 2 in DMF, hence acetate is less readily solvated. Consequently, the smaller crystal size of 1 means a higher loading capacity inside the channels of the RHs compared to 2 since the larger crystal size of 2 can block the channels of the RHs and lead to lower loading capacities. The pyrolysis of 1@RH and 2@RH generates CoMn2O4/Co/MnO mixtures inside the RHs, which work as pseudocapacitive nanomaterials. Interestingly, the electrochemical performance of 1_C@RHs is superior to that of 2_C@RHs even though they have a similar surface area. The high capacitance of 1_C@RHs across all scan rates is attributed to the high loading amount of metal/metal oxide in RHs, high mesopore volume and good electrical contact. Furthermore, the smaller crystals size of 1 than that of 2 prevents the blockage of micrometer-scale channels of RHs, and increases the loading amount of 1 and the mesopore volume. Therefore, the crystal size control of MOFs in RHs is crucial to improve the electrochemical performance of pseudocapacitive nanomaterials. We believe that the impregnation of well-organized MOFs in biomass carbons could contribute the design of novel energy storage devices with high performance.
Ultra-High Capacitive Energy Storage Device Designed By Wooden Biomass Derived Lignin Based Hierarchically Porous Carbon
Authors: Choi Min Sung , Yeon JeongSeok , Park Ho Seok
Published: December 2020

On the field of carbon-based material, researches about biomass conversion have steadily investigated owing to their specific characteristics such as abundance, ease of handling and environmental-friendly. Here is an outline for a kind of biomass, lignin which in a main composition of lignocellulosic structure of lignum and also the second abundant aromatic biopolymer in nature. In this research, lignin was used as a carbon precursor to manufacture hierarchically porous carbonaceous material for energy storage. Hydrothermal carbonization and chemical activation were operated to convert the biomass precursor to object porous carbon which possessed high specific surface area over 2800 m2 g-1. The hierarchical pore structure of as-obtained material could support increasing electron percolation properties in the electrochemical performance test. Due to their high specific surface area and hierarchical porous architecture, the as-obtained porous carbon showed excellent ion and electron transport properties, which can be a benefit for high performance in supercapacitor application.
Development of Fast-Rechargeable Lithium Ion Batteries By Graphite Etched with Potassium Hydroxide
Authors: Kim Young-Min , Shim Jae-Hyun
Published: December 2020

Surface-modified graphite for application as an anode material in lithium ion batteries was obtained by etching with KOH under mild conditions without high-temperature annealing. The surface of the etched graphite is covered with many nano-sized pores that act as entrances for lithium ions during the charging process. As compared with pristine graphite and other references such as pitch-coated or etched graphite samples with annealing, our non-annealed etched graphite exhibits excellent electrochemical properties, particularly at fast charging rates of over 2.5 C. While avoidance of the trade-off between increase of irreversible capacity and good rate capability has previously been a main concern in highly porous carbonaceous materials, we show that the slightly larger surface area created by the etching does not induce a significant increase of irreversible capacity. This study shows that it is important to limit the size of pores to the nanometer scale for excellent battery performance, which is possible by etching under relatively mild conditions.
Uncovering the Relationship between Diameter and Height of Electrodeposited Lithium Protrusions in a Rigid Electrolyte
Authors: Ho Alec S. , Balsara Nitash P.
Published: December 2020

A promising approach for enabling rechargeable batteries with significantly higher energy densities than current lithium-ion batteries is by deploying lithium metal anodes. However, the growth of lithium protrusions during charging presents significant challenges. While solid electrolytes have the potential to solve this problem, protrusions grow in all electrolytes when the current density exceeds a critical value. Fundamentally understanding the formation is necessary to develop a rational approach for increasing the critical current density, but it is challenging due to the complex interplay between electrochemical and material properties. The diameters and heights of protrusions on lithium metal anodes stabilized by a rigid block copolymer electrolyte were measured in situ by synchrotron hard X-ray microtomography. The diameter of the shorting protrusions increased linearly with increasing electrolyte thickness. Further, a universal linear relationship between protrusion height and diameter of both shorting and non-shorting protrusions was observed. A model based on concentrated solution theory was used to establish the electrochemical and mechanical sources for our observations. Experiment and computation combine to give the counterintuitive result: the fastest-growing protrusions have the largest diameter.
Electrochemical Techniques to Detect and Quantify Li Plating after Fast Charge of Li-Ion Batteries
Authors: Konz Zachary M. , McShane Eric J. , McCloskey Bryan D.
Published: December 2020

Despite electric vehicles (EVs) gaining a small foothold in the light vehicle market, long charging times and battery safety have been key limitations in EV’s general acceptance. In commercial Li-ion batteries, fast charging is limited by the deposition of metallic lithium on graphite, or ‘Li plating’, which can cause capacity fade and catastrophic cell shorting. The ability to detect plating on-line in vehicles is critical to allow faster charging while maintaining safety standards. Analyzing the cell voltage relaxation after charge is a promising approach for in-situ Li detection. Plated Li can insert into the graphite at rest, which gives a dV/dt feature unique to plating. Our work shows that voltage relaxation can be used to detect small quantities of Li plating immediately after battery charging at any charge rate, including those relevant for fast charging.
Bilateral Growth of Monoclinic Tungsten Oxide and 2D Ti3C2Tx-MXene on 3D Free-Standing Multilayer Hollow Graphene Foam for Flexible All-Solid-State Pseudocapacitor
Authors: Patil Amar , Wang Jiajia , Kitiphatpiboon Nutthaphak , Yue Xiyan , Yoshida Akihiro , Abudula Abuliti , Guan Guoqing
Published: December 2020

To overcome the subordinate electrochemical performance of the pseudocapacitor, it is essential to design two-dimensional (2D) electroactive nanostructured material with enormous electroactive sites on the highly conductive current collector for enriching the rates of reversible charge transfer reactions. Herein, a scalable strategy was employed to prepare the electrodes by depositing pseudocapacitive materials on a three-dimensional (3D) free-standing highly conductive hollow multilayered graphene foam (HGF) synthesized through a template assisted-chemical vapor deposition (TA-CVD) method for the first time. The stable nanostructured monoclinic tungsten oxide (m-WO3) nanoparticles and 2D transition metal carbide (Ti3C2Tx-Mxene) sheets were bilaterally loaded on inner and outer sides of 3D HGF by a unipolar electrodeposition (UPED) method and a drop casting method, respectively. This free-standing electrode exhibited exceptional specific capacitance (Cs) of 487 F/g (439 mF/cm2) at 2 mA/cm2, outstanding rate performance and extraordinary cycling stability of 92.9 % over 5000 cycles owing to its significant metallic conductivity and reversible redox reactions of hydrophilic 2D Ti3C2Tx-Mxene. To assemble asymmetric pseudocapacitor, a MWCNT/RuO2 electrode with tiny RuO2 was also synthesized through a simple and inexpensive layer-by-layer (LBL) method. The obtained flexible asymmetric solid-state pseudocapacitor (FASC) illustrated 2-fold wider potential of 1.4 V in an acidic electrolyte when compared with Mxene based symmetric supercapacitor. This FASC displayed excellent Cs of 152.2 F/g at 5 mV/s, high energy density of 18 Wh/kg at 497 W/kg and an outstanding capacity retention of 93.3 % over 10000 GCD cycles with superb coulombic efficiencies of 99 ~ 100 %. In addition, the extraordinary demonstration performance of this FASC device by driving light emitting diodes (LEDs) and digital stopwatch signified its real-world applicability in electronic gadgets.
(Invited) Design of Electrospun Polyimide-Based Separators for Electrical Double-Layer Capacitors and Lithium-Ion Batteries
Authors: Hu Chi-Chang , Pai Jui-Yu , Hardwick Laurence J.
Published: December 2020

Separators are one of the very important components in the energy storage devices such as electrical double-layer capacitors (EDLCs) and Li-ion batteries (LIBs). The basic requirements for a suitable separator include high ionic transportation capability, good chemical stability, strong mechanical strength, and good thermo-dimensional stability. In order to reach the above requirements, in this work, we prepare the polyimide (PI) nanofibers with a controllable thickness via the electrospinning method. The introduction of Al2O3 nanoparticles significantly enhances the mechanical strength and ion conductivity of electrospun PI nanofibers. The as-prepared PI and PI@Al2O3 separators are tested for the EDLC and LIB applications. The functions of separators can be added onto the PI separators by a thin-film coating of functional polymers. We also evaluate the physical and electrochemical characteristics of these separators which are better than or compatible to the commercial separators.
(Invited) Carbon/Dichalcogenide Composites As Electrodes for Electrochemical Capacitors
Authors: Tobis Maciej , Foroutan Masoud , Frackowiak Elzbieta
Published: December 2020

Electrochemical capacitors (ECs) are considered to be the very promising energy storage systems because they possess a high power density as well as a long life span. However, contrarily to the batteries, the energy density of ECs is rather moderate. It is very well known that the energy stored in ECs is mostly dependent on the specific surface area of the electrode materials, i.e., microporosity, but conductivity also plays an important role. Energy can be greatly increased by the utilization of redox reactions from electrolyte and/or electrode materials. For this work, two dimensional transition metal dichalcogenides (2D-TMDs) have been applied as electrode material components. TMDs are layered materials of the MX2 type where M is a transition metal (Mo, Re, W, Co or V) and X is a chalcogen (S, Se or Te). In their structure, one layer of M atoms is sandwiched between two layers of X atoms. Different salts such as sodium molybdenate, ammonium perrhenate, cobalt nitrate with thiourea or L-cysteine as a sulfur source were used as TMD precursors. Taking into account moderate conductivity of dichalcogenides, various mesoporous carbon materials such as carbon nanotubes, reduced graphene oxide rGO, 3D-graphene hydrogel, carbon black have been used by us for composite preparation. In some cases functionalization of multiwalled carbon nanotubes has been performed to improve adhesion in the composite. The amount of carbon in the C/TMD composites varied from 5-30%. Hydrothermal method have been successfully used for carbon/TMD production. The composites were characterized with the various textural/structural methods: scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. After a detailed physico-chemical characterization, all composites served for electrode preparation. Mostly, 90wt% of active material, 5 wt% of conducting agent C65 and 5wt% of Teflon as binder were used as electrode components. Two-electrode and three-electrode configuration cells have been applied for capacitance measurements. Aqueous solutions (neutral and alkaline) served as electrolytes (1M lithium sulfate, 6M KOH). The capacitor voltage ranged from 1-2V. The electrochemical performance of EC cells were studied by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The capacitance values, coulombic and energetic efficiency were affected by composite structure, its specific surface area as well as its conductivity and composition. Typically for faradaic reactions, the lower regime, the lower energetic efficiency was observed. High capacitance values (100 F/g – 300F/g) have been reached for C/MoS2. Selected carbon/TMD composites have been used as a positive electrode whereas a negative electrode was composed only from carbon materials. In such a way, high energy electrochemical capacitor has been constructed and investigated.
(Invited) Designing Electrocatalysts for Controlling Selectivity of Oxygen Reduction Reaction
Authors: Joo Sang Hoon
Published: December 2020

The oxygen reduction reaction (ORR) is arguably one of the most important electrochemical reactions affecting the efficiency of energy conversion devices such as fuel cells [1] and metal-air batteries [2]. Oxygen (O2) can be reduced in two ORR pathways are possible: the four-electron (4 e–) pathway to generate water (H2O) by complete reduction and the two-electron (2 e–) pathway to hydrogen peroxide (H2O2) involving partial O2 reduction [3,4]. Although the 2 e– pathway ORR has been regarded as an adverse side reaction that impedes the efficient 4 e– pathway, it has recently garnered a surge of interest as a means of the electrochemical production of H2O2.

In this presentation, we present a catalyst design strategy for controlling catalytic selectivity of ORR. We have developed a general synthetic strategy that can produce atomically dispersed precious metal catalysts of Os, Ru, Rh, Ir, and Pt, which served as model catalysts for unravelling catalytic activity and selectivity trends for the ORR [5]. The atomically dispersed precious metal catalysts generally showed higher selectivity for H2O2 production, due to their isolated geometry, than their nanoparticle counterparts for the ORR. Among the atomically dispersed catalysts, the H2O2 selectivity was changed by the types of metals, with atomically dispersed Pt catalyst showing the highest selectivity. A combination of experimental results and density functional theory calculations revealed that the selectivity trend of atomically dispersed catalysts could be correlated to the binding energy difference between *OOH and *O species. In terms of 2 e− ORR activity, the atomically dispersed Rh catalyst showed the best activity. We also present our recent results on the design of carbon-based and non-precious metal catalysts for the selective 2 e– ORR for H2O2 production [6,7].

References

1. K. Debe, Nature 486, 43 (2012)

2. P. G. Bruce, S. A. Freunberger, L. J. Hardwick, J.-M. Tarascon, Nat. Mater. 11, 19 (2012).

3. A, Kulkarni, S. Siahrostami, A. Patel, J. K. Nørskov, Chem. Rev. 118, 2302 (2018).

4. H. Kim, Y.-T. Kim, S. H. Joo, Curr. Op. Electrochem. 21, 109 (2020).

5. H. Kim, D. Shin, J. Lee, D. S. Baek, T. J. Shin, Y.-T. Kim, H. Y. Jeong, J. H. Kwak, H. Kim, S. H. Joo, ACS Nano 14, 1990 (2020).

6. J. Sa, J. H. Kim, S. H. Joo, Angew. Chem. Int. Ed. 58, 1100 (2019).

7. M. Ko, L. T. M. Pham, Y. J. Sa, J. Woo, T. Nguyen, J. H. Kim, D. Oh, P. Sharma, J. Ryu, T. J. Shin, S. H. Joo, Y. H. Kim, J.-W. Jang, Nat. Commun. 10, 5123 (2019).
Strategies to Enhance the Activity and Durability of MEA for High Temperature PEMFC
Authors: Park Hyanjoo , Kim Hoyoung , Bang Hotea , Tran Dinh Son , Yeo Kyeongrim , Kim Soo Kil
Published: December 2020

High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) using phosphoric acid (PA)-doped polybenzimidazole (PBI) membrane have advantages of enhanced electrode kinetics, improved carbon monoxide (CO) tolerance, and simplified water management [1], while poisoning of the catalysts by phosphate adsorption to deactivate them remains as an issue [2]. In addition, the deliquescence of PA (absorption of moisture when exposed to the humid atmosphere) resulted in the un-even distribution of PA [3], therefore deterioration in the MEA performance.

To mitigate these issues, we have tried to optimize the structures of the commercial electrode and controlled the hydrophilicity of the electrode through additional deposition of very small amounts of Pt (anode) [4] or PtCu (cathode) using pulse electrodeposition. It was confirmed that the cell performance was improved by adjusting the hydrophilicity, improving the distribution of PA, and changing the formation of the triple phase boundary (TPB) of the catalyst layer. The performance loss due to the deliquescence of PA in the commercial PBI membrane when exposed to various humidity conditions was mitigated through an additional PA dosing method on the electrode [5].

Apart from the activity, the durability of the modified MEAs exhibited different aspects. Various MEAs were fabricated by selectively combining the results of the pulse electrodeposition and PA dosing, and the durability tests for the MEAs were performed with repeated cycles of turning on (180°C) and turning off (room temperature). 40 cycles of repeated temperature variation deactivated most of the MEAs regardless of the modifications, while the amounts of the deterioration were the functions of the modification methods. Interestingly, the performance deterioration was more obvious in the observation of the peak powers while the change in the cell potential at low current density region (200 mA/cm2) was not substantial, implying the deterioration was greatly related to the mass transport management. The different behaviors in the durability according to the modification methods along with the materials characterization using electrochemical and spectroscopic analyses will be introduced at the conference.

[1] I. I. Ponomarev, K. M. Skupov, A. V. Naumkin, V. G. Basu, O. M. Zhigalina, D. Y. Razorenov, I. I. Ponomarev, Y. A. Volkova, RSC Adv., 9 (2019) 257-267.

[2] S. Kaserer, K. M. Caldwell, D. E. Ramaker, C. Roth, J. Phys. Chem. C, 117 (2013) 6210-6217.

[3] S. Jahangiri, I. Aravi, L. I. Sanli, Y. Z. Menceloglu, E. Ozden-Yenigun, Polym. Advan. Technol., 29 (2018) 594-602.

[4] D.-K. Kim, H. Kim, H. Park, S. Oh, S. H. Ahn, H.-J. Kim, S.-K. Kim, J. Power Sources, 438 (2019) 227022-227030.

[5] H. Park, H. Kim, D.-K. Kim, W. J. Lee, I. Choi, H.-J. Kim S.-K. Kim, Int. J. Hydrogen Energy, (2019) DOI:10.1016/j.ijhydene.2020.03.039.
Toward a Fundamental Understanding of Strain Generation and Strain Tuning for ORR: DFT Insights
Authors: Zeng Zhenhua , Liu Guangdong , Deng Huiqiu , Greeley Jeffrey
Published: December 2020

The development of industrial electrocatalysts with improved ORR performance strongly relies on the fundamental understanding of governing principles of catalysis from fundamental research on well-defined model systems. One particularly successful strategy has been to tune surface strain and thereby modulate the surface electronic structure and energetics of reaction intermediates, leading to a fundamental understanding and identification of catalysts with improved activity. For the well-known example of the ORR on platinum, previous studies indicated that a 1% compressive strain could improve the activity by more than 300%.

While the concept of tailoring the reactivity of metal catalysts through surface strain has been discussed over two decades, fundamental challenges remain regarding both strain generation and strain tuning. In the present talk, we will share our recent progress on these topics, including [1] tunable intrinsic strain in two-dimensional transition metal electrocatalysts, [2] tunable intrinsic strain in stepped transition metal electrocatalysts, and [3] strain tuning of supported transition metal overlayers. We will demonstrate [1] how these fundamental understanding can be used to understand terrace-width dependent ORR activity of stepped Pt surfaces that have puzzled the community over a decase; and [2] how they pave the way toward developing both model electrocatalysts and industrial electrocatalysts with significantly improved performance toward the oxygen reduction reaction.

References

Wang, Z. Zeng, W. Gao, T. Maxson, D. Raciti, M. Giroux, X. Pan, C. Wang, J. Greeley,. Science
363, 870-874 (2019).

Zeng, J. Greeley, Nano Energy 29 (2016) 369.
Development of in situ A-SAXS and XAS Measurements of Pt Catalyst under Controlled Electrochemical Condition Using Channel Flow Electrode Cell
Authors: Watanabe Takeshi , Kawamoto Teppei , Suda Kohei , Pondchanok Chinapong , Hiraoka Yuji , Hirosawa Ichiro , Inukai Junji
Published: December 2020

Understanding of the structural and the chemical properties of Pt catalysts in polymer electrolyte fuel cells (PEFCs) is necessary to improve the activity for the durability of the catalysts. The small-angle X-ray scattering (SAXS) and the X-ray absorption spectroscopy (XAS) measurements are widely used to investigate these properties. Recently, we developed a measurement system of SAXS and fluorescence-yield (FY)XAS in the same observed area to investigate the structural and the chemical properties of low-concentrated catalysts. [1] As the results, the diameter size, distributions, and chemical state of catalysis were successfully characterized. Our measurement system also found to be easy to combine the electrochemical cell. In this study, we newly developed a channel flow cell to control the electrochemical conditions during SAXS and FYXAS measurement in the same observed area.

All experiments were carried out at SPring-8 BL19B2. Electrochemical measurements were conducted using a newly developed channel flow cell. Using the flow system, the electrolyte solution with a controlled temperature was continuously supplied to the cell during the in-situ measurements. A commercial Pt/carbon black catalyst(TEC10E50E, Tanaka Kikinzoku Kogyo) was used as the sample in this experiment. In situ SAXS and FYXAS measurement was conducted while holding the potential at 0.4 V, 1.0 V, and 1.5 V vs. the reversible hydrogen electrode (RHE). For the XAS measurements, the Pt LⅢ edge was used. The ionization chamber and a single-element Ge solid state detector were used to obtain the FYXAS spectra. For the SAXS measurements, the X-ray energy was set to 11.5 keV and 11.55 keV, which are below and near to the Pt LIII absorption edge, respectively. The scattered X-ray was detected using an area detector (PILATUS 2M).

As the result, we could estimate the diameter size, distributions, and chemical state of Pt catalysis under controlling the electrochemical conditions. We will discuss the degradation mechanism of the Pt nanoparticle catalyst from both SAXS and FYXAS data.

Takeshi Watanabe, et al., ECS 236th I01D-1593, (2019) Atlanta, USA.
Preparation of Unique Flower-like Pt-Ni Alloy Catalysts As the Cathode of a PEMFC By Electrodeposition Technique
Authors: Huang Jen-Hui , Yeh Tsung-Kuang , Wang Mei-Ya
Published: December 2020

The hydrogen economy can play an important role in the low-carbon economy, and fuel cells technology is an essential part of the hydrogen economy. The proton exchange membrane fuel cell (PEMFC) is one kind of electrochemical reaction device with the advantages of low temperature operation, high conversion efficiency and noiseless, which is expected to widely utilizes in public transportations.

The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in PEMFC. To enhance the ORR activity at the cathode, the unique flower-like platinum-nickel binary alloy catalysts were electrodeposited on the commercial carbon cloth by potentiostatic electrodeposition technique, the PtNi alloy effectively improved the oxygen adsorption and desorption paths on the surface. The PtNi alloy catalysts with shorter lattice distance and effects of high-index facets would increase the electrochemical surface area (ECSA) of the catalysts and power density of fuel cell. The samples of the pure platinum and commercial Pt/C catalyst were also prepared as comparison.

Morphology, particle size and elemental composition were characterized by SEM, XRD and ICP-MS. In addition, the electrochemical characteristics of the PtNi catalysts were investigated via cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analysis in 0.1 M perchloric acid solution with rotating disk electrode (RDE). In single cell test, the maximum peak power density of PEMFC with homemade PtNi alloy catalyst as the cathode reached 1031 mW/cm2, enhancing about 12% power density, compared to the commercial Pt/C.

Figure 1
Ternary Pt Alloy Catalysts and Carbon Modified Supports for Low Pt Loaded Fuel Cell Cathodes
Authors: Dionigi Fabio , Weber Carl Cesar , Pan Lujin , Parniere Alice , Blanchard Pierre-Yves , Cavaliere Sara , Jones Deborah J. , Strasser Peter
Published: December 2020

The sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode of proton exchange membrane fuel cells (PEMFCs) and the harsh environment pose challenges on the development of cheap, active and stable catalysts. As a consequence, Pt catalysts are the most utilized catalysts in commercial PEMFC stacks for automotive applications. While the progress in the recent years allowed a considerable decrease of Pt loadings (from 0.4-0.8 to ~0.1 mgPt cm-2), other challenges emerged at such and lower Pt loadings at high current densities.1

For example, octahedral PtNi nanoparticles have been reported to achieve extremely high mass activity in rotating disk electrode (RDE) experiments2 and the introduction of a third metal as surface dopant has been shown to have beneficial effects on the RDE performance.3 Despite these promising steps toward shape-stable PtNiX octahedral nanoparticles, the morphological stability and the performance in membrane electrode assembly (MEA)-based fuel cell measurements still need to be improved to match and surpass the state of the art Pt and dealloyed Pt-alloy catalysts.4

In this contribution we will show our recent efforts in improving the performance of PtNi based octahedral nanoparticle catalysts towards integration in low Pt loading cathodes for PEMFC. In particular, two strategies will be presented. First, Rh surface doping is introduced to improve the morphological stability. Second, new carbon modified supports by nitrogen plasma treatment have been investigated.

References

A. Kongkanand and M. F. Mathias, J Phys Chem Lett, 2016, 7, 1127-1137.

P. Strasser, Science, 2015, 349, 379-380.

X. Q. Huang, Z. P. Zhao, L. Cao, Y. Chen, E. B. Zhu, Z. Y. Lin, M. F. Li, A. M. Yan, A. Zettl, Y. M. Wang, X. F. Duan, T. Mueller and Y. Huang, Science, 2015, 348, 1230-1234.

F. Dionigi, C. C. Weber, M. Primbs, M. Gocyla, A. M. Bonastre, C. Spöri, H. Schmies, E. Hornberger, S. Kühl, J. Drnec, M. Heggen, J. Sharman, R. E. Dunin-Borkowski and P. Strasser, Nano Lett, 2019, 19, 6876-6885.

Acknowledgements

The GAIA project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 826097. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and Hydrogen Europe Research.

Figure 1. Mass activity from RDE measurements as a function of the electrochemically active surface area obtained by hydrogen under potential deposition, before (black) and after (red) stability tests. The blue arrow and the percentage indicate the loss after stability tests. Pt/Cv and Oh-PtNiMo/Cv data from ref.4.

Figure 1
Advanced Thermal Conductivity Characterization with Implications for Thermal Control Strategies during Fast Charging
Authors: Steinhardt Marco , Gillich Elisabeth Irene , Stiegler Maximilian , Jossen Andreas
Published: December 2020

Extreme fast charging lithium ion batteries require aggressive thermal management, which keeps the maximum cell temperature below abusive thresholds without derating the charging power. The importance of thermal management is further increased for many new cell designs with improved energy density which often brings along weaker thermal performance. For instance, reducing the volume fraction of electrochemically inactive materials like the current collectors reduces the thermal conductivity and increases the heat generation. Aggressive cooling is achieved by increasing the heat convection coefficients between the cell surface and the heat transfer medium. With high heat convection coefficients, the internal thermal conductivity of the electrode-separator-composite determines the maximum cell temperature. Consequently, the thermal conductivity needs to be characterized accurately for fast charging investigations, which includes dependencies on parameters like temperature or compression load at the cell surface. Therefore, this work presents thermal conductivity measurements at different cell temperatures and compression loads with their impact on fast charging.

The thermal conductivity of a large-format NMC-111 graphite cell with a flat-wound jelly roll and prismatic PHEV2 hardcase made of aluminum alloy is measured at temperatures between -10 and 50 °C and at external compression loads between 37 and 74 kPa. This compression range is defined by the manufacturer at the largest cell surfaces to counter swelling of the jelly roll. Based on the guarded heater principle, a precise thermal conductivity test bench is designed and validated by a stainless steel reference material. For deriving the thermal conductivity of the electrode-separator-composite from the full-cell measurements, the thermal conductivity of the hardcase has to be compensated. For this purpose, a fast and simple technique for measuring the thermal conductivity of the hardcase by using electrical resistance measurements and applying theories like the law of Wiedemann–Franz is introduced.

According to the measurement result, the thermal conductivity increases by 13.6% at 20 °C when the compression load rises from 37 to 74 kPa, which is mainly attributed to reduced thermal contact resistances between the cell layers. At constant compression and rising mean temperature, the thermal conductivity decreases by more than -1% per °C compared to the value at 20 °C. Both findings affect the cell internal temperature rise during aggressive cooling and therefore the power-derating events due to overheating. Based on these findings, implications for thermal control strategies during fast charging are discussed.

Figure: Thermal conductivity of NMC-G electrode-separator-composite in through-plane direction at different cell temperatures and compression loads at the two largest surfaces of a prismatic PHEV2 cell.

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Single-Step Bipolar Exfoliation of Black Phosphorus into Phosphorene for Capacitive Energy Storage Application
Authors: Rabiei Baboukani Amin , Khakpour Iman , Drozd Vadym , Allagui Anis , Wang Chunlei
Published: December 2020

Black phosphorus (BP) as a two-dimensional material has attracted attention for various applications from energy storage to biomedical devices due to its exceptional physical and chemical properties such as tunable bandgap and high charge carrier mobility. However, the key step therefore towards the application of BP is the preparation of few-layer phosphorene. Different methods have been evaluated to exfoliate BP such as mechanical, liquid and electrochemical exfoliation. Most of them are multi-step and time-consuming, and less attractive for practical applications. In this study, we propose a novel and straightforward two-in-one bipolar exfoliation technique to exfoliate BP into phosphorene nanosheets in DI water, which are then dragged electrophoretically to be deposited on a conductive substrate. The exfoliated-and-deposited BP nanosheets were characterized with different microscopic and spectroscopic techniques, revealing thin layers of phosphorene with orthorhombic crystal structure and lateral dimensions up to a few hundreds of nanometers. The electrochemical characterization of the phosphorene-modified positive feeding electrode showed a fractional-order capacitive behavior with high power density of 350 μW cm-2 at a constant current rate of 0.5 mA cm-2 and discharge energy of 22.8 nWh cm-2 recoverable with very high efficiency after 40000 of charge/discharge cycles. In this conference, detailed novel bipolar exfoliation and deposition of phosphorene nanosheets and its electrochemical characterization will be presented.
Porous Carbon Having Rod Shaped Structure from Tea Waste for High Performance Supercapacitor
Authors: Khan Abrar
Published: December 2020

The porous carbon derived for batteries and supercapacitor have increased research consideration because of low cost, easy to fabricate, and environmental friendly. In this study, we successfully synthesized the porous carbon with rod-like structure from tea using carbonization, followed by activated by KOH and KNO3 to produce having high porosity carbon with large surface area 1810 m2 g-
1. The electrochemical performance of porous carbon were characterized with 3-electrode system in 6 M KOH electrolyte and provide specific capacitance up to 365 F g-
1 at 1 A g-
1, and 232 F g-
1 at 100 A g-
1 with very little retention rate of 3.5% of its initial capacitance over 120,000 at 100 A g-
1.The Porous carbon use for symmetrical supercapacitor with 6 M KOH electrolyte supplies the highest energy density of 17.6 Wh kg-1 at 505 W kg-1 with only 3.5% decay rate of capacitance over 10,000 cycles at 20 A g-1.
Welcome Remarks - I01D: Polymer Electrolyte Fuel Cells & Electrolyzers 20 (PEFC&E 20) - Catalyst Activity/Durability for Hydrogen(-Reformate) Acidic Fuel Cells
Authors: Uchida Hiroyuki
Published: December 2020

Welcome to I01D: Polymer Electrolyte Fuel Cells & Electrolyzers 20 (PEFC&E 20) - Catalyst Activity/Durability for Hydrogen(-Reformate) Acidic Fuel Cells! Take a moment to listen to welcome remarks from the lead organizer, Hiroyuki Uchida.
Preparation of Anion Conducting Pore Filling Membranes for Direct Hydrazine Fuel Cells
Authors: Lim Seohee , Hwang Yoon-Ah , Park Jong-Hyeok , Park Jin Soo
Published: December 2020

Hydrazine fuel cells in an alkaline medium are a promising energy conversion technology due to the extraordinary properties of hydrazine as a hydrogen carrier. Alkaline electrolyte fuel cells allow the use of less expensive metals such as cobalt and nickel as an electrode catalyst. The devices consist of a pair of electrochemical reactions at electrodes and anion movement through electrolytes to complete full electrochemical cells. Anions move from cathode to anode or vice versa for electron exchanges. Pathway for ions is normally in an aqueous phase. Regardless, the introduction of any aqueous phase in energy conversion devices causes many problems during fabrication, operation, maintenance, and so on. Thus, much efforts have been devoted to develop quasi-solid electrolytes such as gel polymer, ion exchangeable polymers, impregnation of ions in porous matrix and so on. An approach to minimize areal resistance of film-type polymeric electrolytes is to make membrane thickness as thin as possible. In this study, pore filling membranes have been studied as a new type of electrolytes. Pore filling membranes are made by impregnating monomers into thin porous substrates, followed by heat or UV cured polymerization. Pore filling membranes with the thickness of 20-50 μm were prepared using porous substrates with hydrophilized surface. A technique to make the surface of pore filling membranes hydrophilic were developed so as to adsorb liquid hydrated hydrazine fuel in KOH supporting electrolyte. Characterization in terms of ion conductivity, ion exchange capacity, water uptake, dimensional stability, mechanical strength was carried out and discussed.

Acknowledgment

This research was supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science, ICT ＆ Future Planning(NRF-2018M1A2A2063866).
Study of Cathode Catalyst Layers for Anion Exchange Membrane Fuel Cells Using Fe-N-C Catalyst and a Novel Polymer Electrolyte
Authors: Otsuji Kanji , Yokota Naoki , Tryk Donald A. , Kakinuma Katsuyoshi , Miyatake Kenji , Uchida Makoto
Published: December 2020

In this work, we examined the cell performance of membrane-electrode assemblies (MEAs), for anion exchange membrane fuel cells (AEMFCs), using a non-noble metal catalyst and a novel polymer electrolyte. The chemical structure of quaternized poly(arylene perfluoroalkylene), i.e., QPAF-4 (ion exchange capacity: IEC = 2.1 meq g-1) developed in this laboratory1 is shown in Figure 1. Since this ionomer is soluble in lower alcohols such as methanol, it is also suitable for use as an electrode binder. The non-precious metal catalyst cell was loaded with 0.45 mg cm-2 Fe-N-C catalyst supplied by Pajarito Powder on the cathode and 0.45 mg cm-2 platinum catalyst on the anode, respectively. Pt loaded on carbon black (Pt/CB, TEC10E50E), supplied from TKK Japan, was used as the platinum electrocatalyst.

Figure 2 shows the results of current-voltage (I-V) measurements of the cell using the Fe-N-C catalyst under back pressures from 0 to 100 kPag (same pressure on both sides) at 60 oC, 100% RH; anode H2 (100 mL min-1); cathode O2 (100 mL min-1). The cell using the Fe-N-C catalyst showed hysteresis in the I-V curves between increasing and decreasing current. The degree of hysteresis decreased with increasing the back pressure. Figure 3 shows the results obtained when the back pressure of the anode was 100 kPag and the back pressure of the cathode was varied. The hysteresis decreased as the cathode back pressure increased. At the present stage, the loading amount of Fe-N-C catalyst, ionomer content, and porosity of the catalyst layer have not yet been optimized.

By increasing the back pressure, liquid water would be generated more easily which is advantageous since cathodic reaction in AEMFCs requires water. We found that supplying liquid water to the cathode lead to decrease of the hysteresis when using the QPAF-4 polymer and Fe-N-C catalyst as the cathode.

Acknowledgements

This project was partly supported by NEDO Japan through funds for the “Advanced Research Program for Energy and Environmental Technologies” and the Japan Society for the Promotion of Science (JSPS) and the Swiss National Science Foundation (SNSF) under the Joint Research Projects (JRPs) program.

Reference

Ono, T. Kimura, A. Takano, K. Asazawa, J. Miyake, J. Inukai, K. Miyatake, J. Mater. Chem. A, 5, 24804 (2017).

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A New Method for Producing Hydrogen Carrier Using Renewable Energy -Direct MCH–
Authors: Nagatsuka Tomomi , Takamura Toru , Misu Yoshitatsu , Miyoshi Kota , Matsuoka Koji , Sato Yasushi
Published: December 2020

New energy sources with lower environmental impact are the focus of increasing attention to enable the sustainable growth of human societies. There is an urgent need for technologies that enable conversion of renewable energy (RE) to a transportable energy carrier and recovery of that energy for later use. We have focused on organic hydrides, specifically the toluene (TOL) / methylcyclohexane (MCH) system, and have been working on a one-step process for producing MCH from TOL via electrochemical hydrogenation. We named this new method “Direct MCHTM”.

The equipment needed for Direct MCH is basically the same in structure as that already used for water electrolysis. An electrolyzer with a membrane-electrode-assembly (MEA), similar to those used for polymer electrolyte water electrolysis (PEWE), can be used. The cathode consists of a carbon-supported Pt-Ru alloy catalyst with a high specific surface area and a proton-conductive ionomer. The cathode shows good electron conductivity and high diffusivity of protons and TOL, and provides a three-dimensional network of active sites. On the cathode catalyst, TOL from the diffusion layer is converted directly to MCH via electrochemical hydrogenation by protons coming from the anode through the electrolyte membrane. (Fig. 1)

For process commercialization, it will be necessary to get the electrolysis voltage closer to the theoretical voltage and achieve current densities as high as those seen in alkaline water electrolysis. We also looked at how the toluene concentration affects Direct MCHTM. It has been shown that as electrolysis proceeds and the TOL concentration drops, the current density falls because it is a diffusion-limited reaction. But from the standpoint of transport efficiency, the MCH conversion rate needs to be 95% or higher, and the average current density during electrolysis to reach this rate should be comparable to that of water electrolysis, which is 0.4 A/cm2. By studying the catalyst compositions, we have made it so the percolating water through with the protons from the anode drains more easily from the cathode catalyst layer. Moreover, we obtained a cathode catalyst with high TOL diffusivity. (Fig. 2)

Finally, we conducted a demonstration of the Direct MCHTM process in Queensland, Australia that was powered only by renewable energy, using electricity generated by photovoltaic cells. Over four liters of MCH obtained via Direct MCHTM was brought to Japan, showing that it is possible to transport CO2-free energy from Australia to Japan. Then, so-called "green hydrogen" was generated via dehydrogenation of the MCH and used to run a miniature car equipped with a fuel cell.

Figure 1