bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Thermal Runaway Propagation Testing of Lithium-Ion Cells Using the Transportation Standard Protocol
Authors: Jeevarajan Judith A. , Azam Saad , Lopez Carlos , Kinyon S. E.
Published: February 2020

The thermal runaway of lithium-ion cells and batteries has been a significant concern to users and transporters of li-ion cells and batteries. The accidents in the aviation industry observed during the transportation of lithium based cells and batteries have sometimes resulted in catastrophic failures with loss of life. The ICAO and SAE have organized a team of experts to write a standard that would verify the safety of the packages transporting lithium based cells and batteries. The intent of the standard is to verify that if a single cell in the worst case location went into thermal runaway, whether the resulting event would produce excessive pressure change, smoke, fire or a volume of gases that would be combustible. This paper will present the data gathered from the tests carried out using a heater tape as the trigger method with the trigger cells located in various positions within the shipping package, with the cells at varying states of charge and with triggering the cells at various heating rates. This presentation will focus on the tests carried out on 18650 li-ion cells of the highest capacity available from one manufacturer.
Thermal Runaway Propagation within Lithium-Ion Battery Packs: Modes and Mechanisms
Authors: Jia Yikai , Xu Jun
Published: February 2020

Safety related incidents caused by failure of lithium-ion batteries (LIBs) are often reported in news in recent years. Thermal runaway (TR) and subsequent propagation, as one of the most critical failure modes, could cause catastrophic consequences in battery packs or modules of LIBs. In this study, the TR propagation behaviors and mechanisms within battery packs are determined through series of experiments. A theoretical calculation model is used to predict and discuss the TR propagation behaviors. During the experimental processes, the TR of a specific-location battery in battery packs of various sizes is triggered by mechanical loading. 0D thermal runaway is combined with electrical and thermal conduction models to build the TR model of packs. Three typical modes of TR propagation are abstracted from experimental results. The mechanisms of these modes are further discussed with the combination of the computational model. High overall temperature, overheating of local area, and uneven thermal contact within battery packs are the three main reasons for hazardous TR propagation. Moreover, ambient temperature, state of charge, and stacking form are three critical factors that determine possibility and speed of the propagation. Our results may provide theoretical insights into the fundamental understanding of TR propagation within battery packs. Further, we anticipate that those results contribute to development of an efficient and effective computational frame for the safety design of battery modules.
(Invited) A New Paradigm of Li-Ion Batteries for Both High Safety and High Specific Energy
Authors: Wang Chao-Yang
Published: February 2020

In this presentation I shall describe a new class of Li-ion batteries that possess high safety, high energy density, high power, and low degradation all simultaneously. The paradigm shift in battery design is enabled by highly stable active materials and electrolytes as well as a novel battery structure that activates high power on demand but retains high stability otherwise. Comprehensive test results show that the new battery is (1) safe even with NMC622 or 811/Graphite chemistry, (2) operates stably at elevated temperatures such as 60oC, thus eliminating cooling need, greatly simplifying battery management, and permitting its use next to engines in hybrid vehicles, or in extreme hot environments, or as solider power with high-temperature stability and operationality, (3) extends calendar life by 5 times, and (4) deliver high power at all ambient temperatures.
Modeling and Experimental Studies of Zn Dendrites Formation and Growth
Authors: Yurkiv Vitaliy , Foroozan Tara , Ramasubramanian Ajaykrishna , Paoli Roberto , Ragone Marco , Shahbazian-Yassar Reza , Mashayek Farzad
Published: February 2020

Li-ion batteries (LIBs) have shown the tremendous success over past decade for various application starting from portable electronics up to large grid storage solutions. There are many advantages of LIBs comparing to other rechargeable energy storage devises. However, safety concerns originated from the toxic/flammable electrolyte, high materials/manufacturing costs, and relatively low energy density hinders LIBs’ widespread applications. In this regard, metal-air batteries with a light metal (e.g., Li or Zn) as a negative electrode and a porous cathode are very favorable candidates. Among various metal-air batteries, the Zn-air battery is one of the most promising concepts due to Zn’s low cost, low equilibrium potential, abundance, environmental benignity, and long shelf-life.

In the present contribution, we combine modeling and experimental work to study Zn-metal electrodes under various conditions. Experimentally, a novel substrate is suggested to modify the electrodeposition morphology of Zn electrode and its behavior under different cycling conditions. The electrode is characterized using various electrochemical, microscopy and spectroscopy techniques. It is found that Zn dendrites formation can be controlled by a proper choice of current density and current collector material, thus allowing for stable and long-lasting operation. In order to understand the underlying mechanism of Zn dendrites formation and their suppression a phase-field model (PFM)1,2 is developed and applied. In addition, density functional theory (DFT) calculations are used to derive the appropriate parameters needed in the PFM. A detailed description of the relevant electrochemical and mechanical processes is incorporated into the PFM allowing to predict ion concentration field, electrical potential variation as well as elastic-plastic properties of the electrodeposited Zn. The results of the combined PFM and the DFT study show a significant local stress development indicating a direct correlation between the stress field and the origin of the undesired Zn dendrites initiation. In addition, the effects of the solid electrolyte interface (SEI) on Zn electrodeposition is studied.

Thus, the present combined multi-scale modeling methodology and experimental work allows a mechanistic interpretation of the origin of Zn dendrites formation, growth as well as their interdependence with interfacial mechano-electrochemical processes.

References:

[1] V. Yurkiv, T. Foroozan, A. Ramasubramanian, R. Shahbazian-Yassar, F. Mashayek, Electrochim. Acta. 265 (2018) 609 –619.

[2] M.R. Tonks, D. Gaston, P.C. Millett, D. Andrs, P. Talbot, Comput. Mater. Sci. 51 (2012) 20–29.
Durability and Reliability of Commercial Lithium-Ion Cells As a Function of Chemistry and Cycling Conditions
Authors: Preger Yuliya , Barkholtz Heather Marie , Fresquez Armando , Mier Frank Austin , Chalamala Babu R. , Ferreira Summer
Published: February 2020

Energy storage systems (ESS) utilizing Li-ion batteries are increasingly deployed to maintain a robust and resilient grid and facilitate the integration of renewable energy resources. For this application, ESS are expected to last for a decade or even longer. To ensure long-term system safety and reliability, batteries must be selected based on application specific requirements and performance characteristics. However, suitable cell selection is made difficult by the dearth of data comparing popular commercial chemistries under comparable operating conditions. To address this gap, we initiated a large-scale, multi-year aging study of commercial LiFePO4/LFP, LiNixCoyAl1-x-y­O2/NCA, and LiNi0.80Mn0.15Co0.05O2/NMC cells, varying the discharge rate, depth of discharge (DoD), and environment temperature. Though all cells were cycled within manufacturer specifications, the time to reach 80% capacity varied by thousands of hours among cells of different chemistries and cycling conditions. Analysis of variance was performed to determine what variable levels or combinations of variables contribute most to degradation. Notable results included the resilience of LFP cells to full discharge (in contrast to the sensitivity of NCA and NMC cells), and the inverse temperature dependence of LFP and NMC cells. The source of differences in aging behavior was investigated through electrochemical impedance spectroscopy and differential capacity analysis. Efforts were made to identify markers of degradation that could be translated beyond high-precision lab equipment to field instrumentation. The next phase of this study involves monitoring the abuse response of aged cells to determine if the aging pathway influences the severity of the failure.

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2018-13934 A
(Invited) Spectroscopy of Nanocarbon Structures Synthesized in the One-Dimensional Core of Carbon Nanotubes
Authors: Wenseleers Wim , Martinati Miles , Cambré Sofie , Kuzmany Hans , Shi Lei , Rohringer Philip , Ayala Paola , Pichler Thomas
Published: February 2020

The hollow core and well-defined diameters of carbon nanotubes (CNTs) make them the ideal template for ordering one-dimensional (1D) arrays of molecules and for the controlled synthesis of 1D carbon nanostructures from suitable precursor molecules. For instance, we previously demonstrated that in this way dipolar dye molecules can be naturally aligned in an ideal head-to-tail arrangement to create assemblies with a giant total nonlinear optical response,[1] and that the optical properties of dye molecules encapsulated in SWCNTs can be strongly modulated by the SWCNT diameter, indicating very specific diameter-dependent stacking and interactions of the molecules.[2] By thermal conversion also well-defined carbon structures such as long 1D carbon chains (carbyne) or graphene nanoribbons can be synthesized inside the hollow core of CNTs. Here we show that the structure and properties of such 1D carbon chains are strongly modulated by the interaction with the host tube, which greatly modifies the chains’ bond-length alternation.[3] We also show how the band-gap and electronic spectrum of the encapsulated carbon structures can be measured in detail, even in heterogeneous mixtures, through extensive wavelength dependent resonance Raman (excitation) spectroscopy, disentangling the vibrational and electronic spectra of the different structures.

[1] S. Cambré, J. Campo et al., Nature Nanotechnol.
10, 248 (2015).

[2] S. van Bezouw, D. H. Arias et al., ACS Nano
12, 6881 (2018).

[3] L. Shi et al., Phys. Rev. Mater.
1, 075601 (2017).
(Invited) Thermo-Excitonic Properties of Semiconducting Single-Walled Carbon Nanotubes
Authors: Miyauchi Yuhei
Published: February 2020

Because of the large binding energy of one-dimensional excitons on the order of 0.5 eV, excitons are stable in semiconducting single-walled carbon nanotubes (SWNTs) even at high temperatures more than 1000 K. This unique exciton property, with the very high intrinsic thermal stability of the materials, enables thermal generation of excitons in semiconducting SWNTs; this results in thermal radiation with very narrow spectral bandwidth even at 1000-2000 K [1]. We will report our recent progress in the study on the thermal exciton radiation from SWNTs.

[1] T. Nishihara, A. Takakura, Y. Miyauchi, and K. Itami, Nat. Commun. 9, 3144 (2018).
Dual Storage Mechanism Induced High Capacity Cathode for Rechargeable Aluminium Ion Battery
Authors: Ajay Piriya Vijaya kumar Saroja , Ramaprabhu Sundara , M Kamaraja
Published: February 2020

Rechargeable energy storage devices have attained much interest in the society as it provides solution to energy crisis. The excessive use of lithium due to ever increasing demand of lithium ion battery in stationary energy storage and portable electronic devices coupled with restricted availability, urges to move towards alternative low cost energy storage device. Developing a new type of sustainable electrochemical energy storage device depends on the exploration of electrochemistry of other alkali metals. Looking for the low cost energy storage device, Al is the third most abundant element in the Earth’s crust and can be used as low cost energy storage device. Moreover, it can exchange three redox electrons per cations so that the energy density of the battery is high compared to lithium based storage system. But the lack of suitable cathode material is the major draw back of aluminium ion battery not reaching the level of commercialization. Carbon based materials like graphite and reduced graphene oxide have been probed as a cathode material where the charge storage occurs by the in intercalation of AlCl4
- anion into the graphite interlayer which limits the specific capacity in the range of 80 to 100 mAh g-1. Cathode materials, which can also intercalate trivalent aluminium ions, can enhance the specific capacity. This work aims to design a cathode material, which can react with both Al3+ and AlCl4
– ions. Sulfur, a cost effective material, embedded in distorted multiwalled carbon nanotubes (DCNT) provides a new concept of both intercalation of AlCl4
– ions in DCNT as well as conversion reaction of sulfur with trivalent aluminium ions. This design of cathode delivers a specific capacity of 500 mAh g-1 at a current density of 50 mA g-1 with a stable cycling of about 600 cycles and can lead to the development of high energy density rechargeable aluminium ion battery.
Biocorrosion Reduction of Pipeline Steel in Desulfovibrio
ferrophilus Culture in the Presence of Carboxymethyl Chitosan Grafted Poly(2-methyl-1-vinylimidazole)/Cerium Molybdate Nanocomposite
Authors: Eduok Ubong , Szpunar Jerzy
Published: February 2020

In oilfield water systems, the presence of sulfate reducing bacteria (SRB) has caused significant corrosion problems in recent times. On pipeline steel, SRB utilize extracellular electrons from iron oxidation for intracellular reduction of sulfate within the cytoplasm to produce energy, leading to microbiologically influenced corrosion (MIC). In this work, the effects of Desulfovibrio
ferrophilus (strain IS5) SRB cellular growth on steel (X70 pipeline steel) corrosion within an anaerobic culture and oilfield-produced water are investigated. SRB are cultured in media of varying concentrations of organic carbon source, using lactate and citrate extracts. To combat MIC, we have also inoculated the SRB culture with different concentrations of a newly synthesized carboxymethyl chitosan grafted poly(2-methyl-1-vinylimidazole)/cerium molybdate nanocomposite. Without this nanocomposite, bacterial growth increased within the culture duration, leading to MIC. MIC episodes are observed as severe anodic steel dissolution. SRB cell counts reduced with the level of carbon source reduction after incubation, but significant cellular survival was observed at extreme carbon starvation. The rate of MIC reduced more than 90 times in the presence of this hybrid nanocomposite under anaerobic conditions, and this has been attributed to the inhibition of SRB cellular growth. D.
ferrophilus biofilm growth on steel substrate was analyzed using confocal microscopy with appropriate fluorescent probes. From X-ray photoelectron spectroscopy evidence, the adhering biofilm/corrosion product aggregates on the metallic substrates were mostly ferrous oxides/sulphides. Extensive biocorrosion studies were conducted using electrochemical techniques. Linear polarization resistance and electrochemical impedance spectrometry data confirmed the trend in surface pitting patterns. Our experimental results demonstrate the efficacy of this new chitosan/poly(2-methyl-1-vinylimidazole)/cerium molybdate nanocomposite as a biocide. Without this nanocomposite, the energy needed for cellular survival was harnessed by a combination of extracellular iron oxidation and sulfate reduction even with insufficient carbon source within the media.
(Invited) Challenges for the Electrochemical/Electroless Metallization of Additive Manufactured Polymer Parts
Authors: Dietz Andreas
Published: February 2020

Additive manufacturing is a well-known technology for manufacturing components with complex geometries. Materials for this process are mainly metals, but also ceramics and polymers. Many components that are produced in large series are still produced today using traditional manufacturing methods such as turning or milling. This also limits their design. In the case of small series or individual parts, additive processes are being used more and more frequently, for which there are no such restrictions. In these cases, the design of these components can be optimally adapted to the required function. Another advantage is often a considerable weight saving.

A major disadvantage of this process is often the insufficient surface quality, which can lead to problems when using the component.

Particularly with polymer components, galvanic metallization can create additional advantages, e.g. mechanical reinforcement, electrical conductivity or the prevention of outgassing.

However, components manufactured by different AM processes have different surface structures depending on the manufacturing process. For example, powder bed-based processes (SLM - Selective Laser Melting) provide a very rough surface. Filament-based methods (FDM - Fused Deposition Modeling), on the other hand, produce a very smooth surface when viewed microscopically, and a very rough surface when viewed macroscopically (half wave profile).

For the electroless and electrochemical metallization of polymer components, this can lead to a major problem with the adhesion of the metal layer to the polymer. In addition, AM-manufactured components are geometrically very complex, so Faraday shielding must be taken into account in galvanic metallization.

The lecture discusses the basics and latest findings on galvanic metallization of plastic components with special consideration of AM-manufactured components and Cr(VI)-free pre-treatment.

Figure 1
Direct Synthesis of Pt Catalyst on Multi-Walled Carbon Nanotubes
Authors: Drexler Matthew , Alamgir Faisal M.
Published: February 2020

If metal catalysts could be grown directly on their support, the resulting bonds between them may be stronger than those formed by drop casting nanoparticles as they would form by more than mere physical contact. Surface limited redox replacement (SLRR) is a process that has been used to grow epitaxial metal films on metal substrates in a layer-by-layer process, allowing for better adhesion to the substrate and the tuning of electrochemical properties through strain and ligand effects. The possibility for adapting this process to carbon-based substrates like those found in fuel cells is explored through the used of multi-walled carbon nanotubes. SEM and TEM images showed that the catalysts mostly grew in the form of nanoparticles, almost entirely coating the nanotubes by the 20th iteration. However, surface area measured via CV showed a self-limiting behavior to the growth of surface area after the 10th iteration despite the increase in nanoparticle density observed in SEM. The behavior in ORR also showed a limiting behavior, with the onset potential increasing to .6 V (vs. Ag/AgCl) by iteration 8, then remaining in the vicinity of that value with subsequent iterations.
Electrodeposition and Kinetic-Controlled Phase Separation in Ag-Pd Alloy Films
Authors: Sun Yunkai , Zangari Giovanni
Published: February 2020

Ag-Pd alloy films have been applied as decorative finishing, electrical contacts and electrocatalysis. In this work, we investigate the mechanism of Ag-Pd electrodeposition from simple nitric acid solutions. Electrochemical characterization of this alloy system showed that at intermediate applied potentials, phase separation was observed at the micron scale, while in the underpotential region of Ag and the limiting current region for Ag and Pd, we achieved uniform deposits. The main features of these deposits can be summarized in the following three growth stages:

At underpotential region with respect to Ag/Ag+, the Ag-Pd films grow via underpotential codeposition (UPCD), in close agreement to thermodynamic predictions, with a slow deposition kinetics.

At intermediate applied potentials, phase separation occurs due to local concentration gradients generated by mass transfer limitation for Ag, and a large nucleation barrier for Pd. This resulted in large composition difference between a Pd-rich phase (~80 %at,Pd) and an Ag-rich phase (~25 %at,Pd). Film formation involves two stages: (1) formation of Ag-rich phase, followed by (2) nucleation and growth of Pd-rich phase, which could be fitted using the Scharifker-Hills model. The large nucleation overpotential and sluggish reduction kinetics of Pd suggest a 3D diffusion field for individual Pd nucleus, resulting in the depletion of Pd2+ at the interface.

Under mass transfer limitation, the growth is uniform and the composition corresponds to the prediction based on the ion diffusivities and the constitution of the solution. Using the ratio of the mass-transfer coefficient of Ag and Pd, specific composition of Ag-Pd film could be achieved in the limiting current region of Ag-Pd electrodeposition by varying the ratio of Ag+ and Pd2+ in the deposition bath.

Figure: (a) classification of deposition potential regions based on initial cathodic scans of the solutions, and (b) comparison between experimental compositional results and the thermodynamic model calculated with concentration of 1 mM Ag+, Activity of AgPd alloy is derived from CALPHAD data by Ghosh et al.

Figure 1
Correlating Catalyst Ink Rheology with Fuel Cell Performance and Durability
Authors: Yang Fan , Spinetta Magali , Zhong Sichen , Xu Hui
Published: February 2020

In polymer electrolyte membrane (PEM) fuel cells, catalyst ink formulation and mixing processes are closely related to catalyst layer coating quality, thus affect the fuel cell performance. Therefore, it would be important to understand these complex solvent-catalyst-ionomer interactions to control the ink properties for coating requirements and performance targets. Ink rheological characterization and particle size distribution (PSD) analysis are two powerful tools that can help to extract valuable information of the catalyst ink. This information can be used to optimize electrode morphology and structure to maximize fuel cell performance. In addition, it can also be used to monitor the ink quality and consistency from batch to batch, and from small lab scale to subsequent scale-up as well.

To establish the correlation between the ink property and MEA performance, the electrode made of catalyst inks with various rheology have been tested for fuel cell performance and durability. The catalyst inks are varied by ionomer, solvent, catalyst, mixing approach and time. The selection of a variety of non-aqueous solvents for catalyst ink preparation will also be investigated as the solvents impact the catalyst particle morphology and structure, and thus electrode performance.

This work will provide a comprehensive understanding of interactions among Pt, carbon, ionomer and their impact on the electrode structure and fuel cell performance. The attained information can be used for better fuel cell electrode design.

Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-SC0012049.
Pressure-Induced Control of Core-Shell Nanoparticles for Oxygen Reduction Reaction
Authors: Park Hyun-Uk , Jang Jeongyun , Seo Min Ho , Choi YongMan , Yim Sung-Dae , Park Seok-Hee , Park Gu-Gon
Published: February 2020

Precious metal-based active metals are mainly used as electrocatalysts for ORR (Oxygen Reduction Reaction), and cost and durability are major research and development issues in fuel cell applications. In order to obtain high performance in electrocatalysts, composition, dispersion, structure and particle size have been studied as key parameters. A number of researchers have been reporting enhanced ORR performance by alloying approaches. Platinum-based alloy nanoparticles are typically prepared through a heat treatment process, which can result in significant levels of specific activity and mass activity improvements. However, the high temperature of the alloying process leads to size growth of the nanoparticles, resulting in a reduction in active area. In order to prevent growth of nanoparticle size during heat treatment, various approaches have been reported such as forming a protective layer by using physical barriers using inorganic and organic materials [1-3]. However, in this case, post-treatment or additional process is required to remove the protective layer, which limits the mass production.

In this work, we propose a method to easily control the size of the core-shell nanoparticles by controlling the pressure of the inert gas during the heat treatment process. As synthesized M@Pt/C (M = Co, Fe, etc.) catalysts were conducted heat treatment with varied pressure control (1, 40, 80 bar) under inert atmosphere. The average size of the metal nanoparticles was distributed in the range of about 3 to 5 nm, and the particle size was clearly reduced in inverse proportion to the pressure. By scanning transmission electron microscopy (STEM) analysis, we also confirmed that the catalysts show clear M core-Pt shell structure. Theoretical calculations show the correlation between the size of metal nanoparticles and external pressure. Herein, we introduce a novel particle size control method (Pressure-induced particle size control). Furthermore, we believe that our unique synthetic approach can be a promising way to obtain intermetallic structure NPs with controlled particle size.

References

1. L. Guo, W.-J. Jiang, Y. Zhang, J.-S. Hu, Z.-D. Wei and L.-J. Wan, ACS Catal.,
5, 2903-2909 (2015).

2. N. Cheng, M. N. Banis, J. Liu, A. Riese, X. Li, R. Li, S. Ye, S. Knights and X. Sun, Adv. Mater., 27, 277-281 (2015).

3. D. Y. Chung, S. W. Jun, G. Yoon, S. G. Kwon, D. Y. Shin, P. Seo, J. M. Yoo, H. Shin, Y. H. Chung, H. Kim, B. S. Mun, K. S. Lee, N. S. Lee, S. J. Yoo, D. H. Lim, K. Kang, Y. E. Sung and T. Hyeon, J. Am. Chem. Soc., 137, 15478-15485 (2015).

Figure 1
In-Situ XAFS Study to Monitor the Degradation of an Fe/N/C Cathode Catalyst in PEMFC
Authors: Nabae Yuta , Nagata Shinsuke , Kusaba Keizo , Aoki Tsutomu , Yuan Qiuyi , Takao Naoki , Itoh Takanori , Arao Masazumi , Imai Hideto , Higashi Kotaro , Sakata Tomohiro , Uruga Tomoya , Iwasawa Yasuhiro
Published: February 2020

Understanding the degradation mechanism of Fe/N/C cathode catalysts in proton exchange membrane fuel cells (PEMFCs) is extremely important. In this study, an Fe/N/C catalyst prepared from polyimide nano-particles were placed in an in-situ cell for X-ray absorption spectroscopy, and its Fe K-edge adsorption spectra were recorded during a continuous operation of the fuel cell.

The Fe/N/C catalyst used in this study was prepared by pyrolyzing Fe-containing polyimide nano-particles, which were synthesized by the precipitation polymerization of Pyromellitic dianhydride and 1,3,5-tris(4-aminophenyl)benzene. The Fe content after the preparation procedure was 0.6 wt%. This catalyst was used to fabricate a membrane and electrode assembly (MEA) with a Pt/C anode and a Nafion 212 membrane. This MEA was installed in a test cell for in-situ X-ray adsorption fine structure (XAFS) measurements, and operated at 0.5 V and 80°C for 8 h monitoring its Fe K-edge adsorption spectra.

Fig. 1 shows the changes in the spectra during the fuel cell operation. The valence of the Fe specie at the initial stage was 3+. The spectra gradually changed during the fuel cell operation, suggesting that the dissolution of the Fe species from the active sites. This change could be relevant to the degradation of the cathode catalyst.

Acknowledgements

This study is financially supported by NEDO. The in-situ XAFS study was carried out at BL36XU in SPring-8 (No. 2016B7907, 2018A7840 and 2018B7907).

Figure 1
Role of Protons on Activity and Selectivity of Fe-N-C Electroctatalysts for Oxygen Reduction Reaction
Authors: Chen Yechuan , Asset Tristan , Matanovic Ivana , Artyushkova Kateryna , Atanassov Plamen
Published: February 2020

As one of the most promising candidates to replace Pt-based electrocatalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC), iron-nitrogen-carbon (Fe-N-C) materials have attracted tremendous research interests in recent years. Different from platinum-group-metal (PGM) catalysts, Fe-N-C have several categories of active sites: Fe-Nx has 4-electron pathway; pyrrolic-N and hydrogenated pyridinic-N can partially reduce oxygen into peroxide; pyridinic-N can reduce peroxide into water. Due to this complicated environment and numerous synthesis approaches from various precursors, the electrocatalysis mechanism of Fe-N-C still needs intensive investigation. Here we report the proton independence/dependence of rate-determining step (RDS) for a specific Fe-N-C catalyst via kinetic isotope effect (KIE), in addition to the activity inhibition of proton-involved N active sites via two molecular inhibitors. It is found that Fe-N-C can behave proton independent RDS like conventional Pt electrocatalyst in kinetic-controlled region, but it undergoes proton-coupled electron transfer in mass transport-controlled region, probably attributed to N active sites. It is also discovered that two molecules, tris(hydroxymethyl)aminomethane and etidronic acid, can inhibit and transform two categories of N active sites respectively: tris can effectively poison Fe-Nx active sites and pyridinic-N, resulting in obvious increase of peroxide yielding and drop of half-wave potential; etridonic acid can readily inhibit pyrrolic-N as well as hydrogenated pyridinic-N but no damage to Fe-Nx active sites, leading to decrease of peroxide yielding and no change of half-wave potentials. These results elucidate that Fe-N-C catalysts could, in principle, compete with Pt-based ORR catalysts through careful optimization of structure and morphology.

Figure 1
Electrochemical Characterization Methods of Fe-Based Oxygen Reduction Reaction Electrocatalysts for Polymer Electrolyte Fuel Cells
Authors: Park Jaehyung , Ferrandon Magali , Myers Deborah J. , Chung Hoon T , Komini Babu Siddharth , Zelenay Piotr
Published: February 2020

Transition metal-nitrogen-carbon (TM-N-C) materials are now regarded as the most promising class of platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) catalysts for polymer electrolyte fuel cells catalysts [1]. An Fe catalyst with atomically-dispersed FeNx sites imbedded in a graphene matrix (Fe-N-C), derived from an iron-doped zeolitic imidazolate framework (ZIF), has recently been shown to have outstanding ORR activity and to be a relatively durable PGM-free catalyst [2,3]. This presentation will describe methods to quantify the amount and relative adsorption energies (i.e., desorption temperatures) of nitric oxide (NO), a molecular surface probe, adsorbed on different surface sites on Fe-N-C catalysts. Catalyst powder samples are electrochemically reduced and oxidized using an electrochemical cell specially designed for easy retrieval of the powder after electrochemical treatment. Using a commercial temperature-programmed reactor (TPR), as-prepared and electrochemically-reduced catalyst samples are exposed to gas-phase NO followed by temperature-programmed desorption (TPD) with mass spectrometric detection of NO and thermal conductivity detection of all desorbed species. The TPD results quantify the amount and relative adsorption energies (i.e., desorption temperatures) of NO adsorbed on different surface sites on the Fe-N C catalyst. In addition, following NO exposure, the powders are also transferred to the above-mentioned electrochemical cell or incorporated into a catalyst-ionomer ink and deposited onto a rotating disk electrode (RDE) tip for electrochemical stripping of the adsorbed NO and for ORR activity and selectivity measurements. The potentials and stripping charges and desorption peak temperatures and areas for both the as-prepared and electrochemically-reduced forms of the catalyst are compared and used to provide insight into the active site identity and density of the Fe-N-C catalysts.

References

S.T. Thompson, A.R. Wilson, P. Zelenay, D.J. Myers, K.L. More, K.C. Neyerlin, and D. Papageorgopoulos, Solid State Ionics, 319 (2018) 68-76.

H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao, Gang Wu, J. Am. Chem. Soc., 139 (2017) 14143-14149.

H. T. Chung, D. A. Cullen, X. Yin, S. Komini Babu, K. L. More, D. J. Myers, P. Zelenay, 234th Electrochemical Society Meeting Abstract 1540, Oct 4 2018, Cancun, Mexico.

This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office under the auspices of the Electrocatalysis Consortium (ElectroCat). Argonne National Laboratory is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.
Highly Reversal Tolerant Anodes Using Ti4O7-Supported Platinum with a Very Small Amount of Water Splitting Catalyst
Authors: Ioroi Tsutomu , Yasuda Kazuaki
Published: February 2020

Gross fuel starvation (cell reversal) event are known to damage the anode of PEFC seriously due to exceptionally high anodic potential (> 2 V vs RHE) when the anode gas channel or manifolds are clogged with water or ice. This high potential is due to oxygen evolution and/or carbon corrosion reactions (OER & COR) at anode to generate protons, instead of hydrogen oxidation reaction. Especially, COR may lead to rapid destruction of the anode structure so that promotion of OER instead of COR would be better way to mitigate serious damages by the fuel starvation. Thus, reversal tolerant anode (RTA), which includes water splitting catalyst to promote OER is one of the solution from material side to mitigate these serious damages. So far, water splitting catalyst (iridium and/or ruthenium) mixed Pt/C has been proposed as RTA, however a significant amount of iridium is indispensable to mitigate the damages. Here we will present oxidation-resistant and electro-conductive titanium oxide (Ti4O7) supported Pt (Pt/Ti4O7) catalyst-based RTA with very small amount of Ir without compromising RTA properties. For example, MEAs using a conventional Pt/C RTA including 0.04 mgIr cm-2 showed significant voltage loss after severe cell reversal test (0.2 A cm-2 load @H2-starved anode for 7,200 seconds), however, almost no performance loss was observed for the Pt/Ti4O7 RTA including the same amount of Ir. Moreover this superior reversal tolerant property of Pt/Ti4O7 RTA was found to be kept at as low as 0.014 mgIr cm-2. Detailed data about electrochemical and post mortem analyses of the tested MEAs will be discussed at the Meeting.
Hydrogen Oxidation Reaction on Pt and Pt Alloys and the Role of Cations in Alkaline Media
Authors: Weber Daniel Jochen , Oezaslan Mehtap
Published: February 2020

Hydrogen oxidation/evolution reactions (HOR/HER) are the main key for the hydrogen economy in the

future. The control of an efficient hydrogen generation from water and of its reverse reaction, particularly

in fuel cells, is still insufficient. For instance, very low Pt loadings are required for the HOR in proton

exchange membrane fuel cells,1 whereas the HOR kinetics change tremendously in alkaline media and

become at least two order of magnitudes slower.2 To design catalyst materials with improved HOR/HER

performance in alkaline conditions, a deeper understanding about the reaction mechanism and kinetics is

needed. This includes to uncover the significant role of cations during the HOR in alkaline media.3

Firstly, we have studied the effect of monovalent cations on the HOR kinetics on polycrystalline and nanosized

platinum in different alkaline solutions (MOH, M = K+, Na+, Li+). Depending on the cations, we

observed a significant change of the HOR activity and activation energy for the Pt. More precisely, the

HOR activity of Pt increases in the order of K+ < Na+ < Li+, respectively, while the activation energy

simultaneously decreases in the same order. We suggest that the catalytic properties of the Pt are strongly

influenced by non-covalent interactions of the hydrated cations with the adsorbed hydrogen by the hydrogen

bond formation. In the second part, various Pt-Co alloys were investigated for the HOR/HER in alkaline

media using rotating disc electrode set up. Our results show that the HOR/HER performance can be tuned

by variation of atomic Pt & Co arrangements like core-shell, segregation and alloy nanoparticles. We

developed a multi-dimensional matrix to clarify the relationship between structural parameters and catalytic

HOR activities for the Pt-Co nanoparticles.

The combination of both works allows to provide a deeper understanding about the mechanism and kinetics

of the HOR/HER for Pt and Pt alloys in alkaline media.

References

1. H. A. Gasteiger, S. S. Kocha, B. Sompalli and F. T. Wagner, Applied Catalysis B: Environmental,

56(1-2), 9–35 (2005).

2. J. Durst, A. Siebel, C. Simon, F. Hasché, J. Herranz and H. A. Gasteiger, Energy Environ. Sci., 7(7),

2255–2260 (2014).

3. D. J. Weber, M. Janssen and M. Oezaslan, Journal of the Electrochemical Society, 166(2), F66-F73

(2019).
Synthesis and Characterization of Electrocatalysts for the Hydrogen Evolution and Hydrogen Oxidation Reactions in Alkaline Environment
Authors: Williams Stefan T. D. , Goenaga Gabriel A. , Elgammal Ramez A. , Zawodzinski Thomas A.
Published: February 2020

The development of catalysts for the electrochemical processes of hydrogen systems (e.g. fuel cells and electrolyzer systems) continues to be a significant area of research for renewable energy technologies. One significant challenge has been the development of hydrogen catalysts that can be utilized in alkaline environments as the kinetics of hydrogen reactions decrease by two orders of magnitude in alkaline environments compared to acidic[1,2]. Chemical vapor deposition (CVD) is a conventional tool used in the synthesis of such catalysts[3,4]. This presentation discusses the extending work being done using a variant CVD process known as “Poor Man’s” CVD (PMCVD), to further its impact in electrochemical catalyst application[5]. PMCVD is utilizes an inexpensive vacuum oven to sublime commercially available metal-organic precursors; lowering synthesis cost while providing increased control of particle size and distribution. This work describes the work done to assess the PMCVD mechanisms as well as its use to develop catalysts for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in alkaline environments.

Preliminary studies have shown that PMCVD can develop catalysts with highly dispersed nanoparticles on various supports. As depicted in Figure 1, PMCVD synthesized Pt/C and PtRu/C catalysts have shown to have improved kinetics over commercial developed catalysts exhibiting approximately a 40% and 45% increase in average exchange current densities respectively when compared to Tanaka Kikinzoku catalysts of the same loading. An extended function of the PMVCD process is the ability to synthesize alloyed catalysts in a single deposition process. By understanding the parametric effects of temperature and pressure on the deposition process with respect to particle size and distribution, we can optimize the PMCVD process to develop highly active catalysts that can be used in alkaline hydrogen systems.

[1] Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energ. Environ. Sci. 7, 2255–2260 (2014).

[2]Sheng, W. et al. Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes. . Electrochem. Soc. 2010 volume 157, issue 11, B1529-B1536

[3] Garcia, Vargas, et al. “Chemical Vapor Deposition of Iridium, platinum, Rhodium, and Palladium.” Materials Transactions, Vol. 44, No. 9 (2003) pp. 1717-1728

[4] Serp, Philppe, et. al. “Chemical Vapor Deposition Methods for the Controlled Preparation of Supported Catalytic Materials.” Chem. Rev. 2002, 102, 3085−3128

[5] Papandrew, A. et al. Advanced Electrodes for Solid Acid Fuel Cells by Platinum Deposition on CsH2PO4. Chem. Mater. 2011, 23, 7, 1659-1667

Figure 1
Towards High-Performancepgm-Free ORR Electrocatalysts: Interplay between Theory and Experiment
Authors: Chen Zhongfang
Published: February 2020

Fuel cells are clean and sustainable energy conversion devices for power generation, and platinum and other platinum-group-metal (PGM) have been long known as the most effective catalystsfor the oxygen reduction reaction (ORR) in fuel cells. However, the scarcity and high costof the PGM-based ORR catalysts are main obstacles forcommercialization of the fuel cell technology. Therefore, searching high-performance PGM-free ORR catalysts has been a key scientific issue in the development of fuel cells.

In this talk, we will present our recent progress on computational design of ORR catalysts based on two-dimensional nanomaterials, especially single-atom catalysts and metal-free catalysts. Notably our designed nanocatalysts can be experimentally realized by standard procedures, as evidenced by our recent collaborations with experimental peers. We are calling for more interplays between theory and experiment, which will greatly facilitate the catalyst discovery and innovation.
(Invited) Chemical and Structural Factors Affecting the Hydrated Morphology of Anion Exchange Membranes
Authors: Paddison Stephen J.
Published: February 2020

The hydrated morphology of ion containing polymers is a critically important property affecting ion and water transport. Anion exchange membranes (AEMs) are increasingly of interest as the electrolyte in energy and conversion devices due, in part, to their suitability with non-noble metal catalysts. However, the rather low chemical stability under alkali conditions and only meager ionic conductivity present difficulties in their application. A promising strategy to enhance the conductivity of these materials may be through tailoring of the phase segregation of the polymer. Recently, AEMs based on the triblock copolymer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS), and functionalized with various cationic groups have shown satisfactory chemical stability.

We are continuing an extensive investigation to understand how various molecular features (degree of functionalization, placement of alkyl spacer(s) on the side chain, choice of the cationic group, and the associated anion) determine the hydrated morphology of functionalized SEBS ionomers. With this goal we are utilizing dissipative dynamics (DPD) simulations, a meso-scale technique, to probe relatively large time and length scales and thereby elucidate the morphology of the polymer systems. The optimized structure and the interaction parameters used in these DPD simulations were calculated using a recently developed methodology employing DFT based electronic structure calculations. The morphology was determined over a broad range of hydration and our results underscore the complexity of the effects of these parameters.
(Invited) Kinetic Parameters in Anion-Exchange Membrane Fuel Cells
Authors: Carlson Annika Elisabet , Grimler Henrik , Ekström Henrik , Lagergren Carina , Lindbergh Göran , Wreland Lindström Rakel
Published: February 2020

Anion-exchange membrane fuel cells (AEMFC) are promising mainly due to the possibility to use none-PGM catalysts in the alkaline media [1]. However, before elaborating with alternative catalysts a better understanding is needed on which electrode is limiting and what the limitations are for the reference Pt/C catalyst. In fact, the rate constants for the ORR and HOR are not determined in the in the fuel cell [2]. On top of this the influence of water on the kinetics and water transport in and between the electrodes is debated [3]. In this study we have measured the influence of partial pressure in both a symmetrical H2/H2cell a H2/O2cell. Experimental I-V and impedance data has been modelled by two separate physic-based models. The experimental results show that the hydrogen reaction has two separate time-constants in the impedance spectra for the symmetrical cell, indicating a two-step reaction at the anode (see Figure below). From the O2/H2cell the ORR is found to be the limiting reaction at low currents densities, while the HOR has a greater impact at high currents densities. From the model, a limiting current is observed at the anode. The level of humidity is likely not determining the direct catalytic reaction kinetics but may affect indirectly through its impact on ionomer conductivity and swelling.

Fig. Nyqvist plots of H2/H2symmetrical cell at OCP at different H2mixtures in Ar at 50°C, 95% RH, 125 ml/min. MEA: 0.4 mg/cm2Pt/C, AS4 ionomer and A201 Tokuyama membrane [4].

[1] D. R. Dekel. Journal of Power Sources, 375:158–169, 2018.

[2] E. S. Davydova, S. Mukerjee, F. Jaouen, D. R. Dekel, ACS Catal. 8 , 665-6690, 2018.

[3] B. Eriksson, H. Grimler, A. Carlson, H. Ekström, R. Wreland Lindström, G. Lindbergh, C. Lagergren, Int. J. Hydrognen Energy 44, 4930-4939, 2019.

[4] A. CarlsonShapturenka, B. Eriksson, G. Lindbergh, C. Lagergren, R. Wreland Lindström, Electrochimica Acta 277 (2018) 151-160
Durability-Limiting Factor of Anion Exchange Membrane Fuel Cells
Authors: Leonard Daniel Philip , Maurya Sandip , Lee Albert S , Li Dongguo , Kim Yu Seung
Published: February 2020

Anion exchange membrane fuel cells (AEMFCs) hold the promise of low-cost energy conversion. However, one of the most significant challenges in the development of AEMFCs has been their limited durability, ca. < 1,000 h, when compared to proton exchange membrane fuel cells (PEMFC). The most common explanations for loss in fuel cell performance (AEM degradation, (bi)carbonation, water management, and catalyst aggregation) do not fully explain the irreversible performance degradation that limits the durability of AEMFCs.

In our study, we set out to identify the source or causes of that performance loss in AEMFCs. To mitigate known sources of degradation, we applied fully humidified conditions and periodically replenished the cell with a dilute NaOH solution. To resolve the current density dependence of cell degradation we conducted several extended duration experiments at different current densities and observed the lifetimes of those cells. Finally, we conducted a rotating disk electrode (RDE) and 1H NMR spectroscopic experiments to identify the durability-limiting factor.

We found that when controlling for the known mechanism of performance loss significant and accelerating performance degradation was present. This pointed to a previously unreported means of performance loss. Lower current densities (higher operating potential) resulted in decreased cell lifetime. These tests led to the electrode rather than membrane degradation as the source for performance loss. Our studies with RDE and 1H NMR experiments identified the generation of phenolic compounds that accumulate at the cathode throughout fuel cell operation. Once produced, the phenolic groups remain tethered to the ionomer, and cannot be removed by replenishment of the cell with a caustic solution. While quick recovery of cell performance occurs after caustic treatment continued to fuel cell operation inevitably leads to more phenol group formation that consumes quaternary ammonium counter ions. Eventually, these compounds reach a critical concentration that results in cell failure. The proposed mechanism is consistent with the degradation behaviors during our long-term test. Finally, we will discuss the mitigation strategy of the observed AEMFC degradation.