bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Harsh Environments Treatment and Detection: Piezocatalysis and Wireless Triboelectric Vibration Sensor
Authors: Wu Jyh-Ming
Published: February 2020

The rapid growth of materials and science technology yields miniaturized and stretchable electronics, with a various revolutionary technology on multifunctional devices. However, without the self-powered function, it is difficult to make the sensor to be deployed in harsh environments. Thus, considering the sustainable operation for most of the internet of things (IoT) devices, which have become challenges, especially for the inconvenience of having to replace batteries in devices such as environmental monitoring for high temperature and high humidity regions, deep ocean areas, the implanted biomedical sensor, and the complexly industry-treatment system. Moreover, one of the major problems is the emission of all sorts of organic compounds in water, such as textile dyeing, industrial food waste, printing industries, which cause severe health issue and environmental contamination. Such problems become more difficult when there is no obvious solution and strategies. In this work, we will report the piezocatalysis could deliver the powerful technologies for decomposing the waste water while the wireless self-powered triboelectric sensor is successful developed for operating in an underwater environment at various temperatures through the enzymatically treated process.
(Invited) Large Photoluminescence Enhancement of Monolayer Molybdenum Disulfide Via Molecular Treatment
Authors: Kiriya Daisuke
Published: February 2020

Molecular interaction is an essential process in various fields such as chemistry, biology and materials science. The interaction of molecules includes: 1) the local electron transfer process, 2) local chemical bonding and 3) assembling to form a structure. All three occur essentially from each molecule’s “recognition” ability. We are trying to extend the molecular interaction system onto inorganic electronic materials to harness the highest-performance of inorganic systems. In this presentation, I will present our recent results of molecular interaction on a semiconducting 2D material, transition metal dichalcogenides (TMDCs).1,2,3

TMDCs are constructed by stacking atomically-thin layers (thickness ~0.7 nm) with van der Waals interaction, and they are expected to generate tiny optoelectronic devices due to their thin nature. Since monolayer TMDC has a direct bandgap, it is a good platform for realizing atomically thin optoelectronic devices. However, an issue is their low luminescence brightness. For example, a representative TMDC, MoS­2, shows photoluminescence (PL) quantum yield of ~1% or less. In this presentation, I will show our recent results of improving the brightness of monolayer MoS2 dramatically (more than 100 times enhancement from the original) via molecular treatments. One method is using a superacid (bis(trifluoromethane)sulfonimide; TFSI) molecule.3 The superacid molecular treatment onto a monolayer MoS2 changes the PL quantum yield of MoS2 from 1% to near-unity. I will discuss the PL enhancement factor in the TFSI treatment on MoS2. The second method is using a redox-active molecule, fluoranil. The fluoranil molecule can reduce the electron concentration of monolayer MoS2, resulting in enhancement of the PL intensity.4 Furthermore, we found that the solvent used for the fluoranil treatment is critical to obtain bright monolayer MoS2. Solvent molecules would screen the charges on fluoranil molecules, as a result, which stabilizes the electron transfer-interaction between fluoranil and MoS2.

Keywords: Superacid, redox-active molecules, Transition metal dichalcogenides, Photoluminescence, Transistors

References:

1D. Kiriya et al., J. Am. Chem. Soc. 2014, 136, 7853.

2H. Ichimiya, et al., ACS NANO, 2018, 12, 10123.

3M. Amani*, D.H. Lien*, D. Kiriya*
et al., Science, 2015, 350, 1065. (* equal contribution)

4H. Ichimiya, et al. Appl. Phys. Express, 2019, in press.
(Invited) Cross-Reactive Graphene and Metal Oxide Sensors for Gas Discrimination
Authors: Li Qiliang , Shi Chen , Ioannou Dimitris
Published: February 2020

Discriminating similar molecules remains a very challenging problem for semiconductor gas sensors. Here, we report a method to achieve precise gas discrimination of similar chemical vapors (mesitylene, o-xylene, and toluene) by using cross-reactive arrays consisting of metal oxide semiconductor and graphene sensors. It is difficult to identify these three chemicals as they have very similar responses to these sensors. Through a cross-reactive Principal Component Analysis (PCA) of the sensor response features, however, the discrimination accuracy improved from about 70% with a single gas sensor to almost 100% with the cross-reactive sensor array. Such a precise discrimination and the low-cost planar process make this approach a very attractive candidate for smart gas sensing and for future Internet of Things (IoT) applications.
Numerical Study of Mass Transport and Electrochemical Kinetics inside Porous Structure Layers of PEMFC Using Direct Simulation Approach
Authors: Satjaritanun Pongsarun , Shimpalee Sirivatch , Weidner John W. , Hirano Shinichi , Zenyuk Iryna V.
Published: February 2020

The enhancement of the mass transports in porous layers of a polymer electrolyte fuel cells (PEFCs) is essential for developing material and design system to improve the PEFC performance and durability. The oxygen transport resistance is a large fraction of the mass-transport overpotential at the cathode. Condensed water in the flow field and porous layers reduces oxygen transport to the oxygen reduction reaction (ORR) region. Experimental investigation of locally saturated porous media in the operating cell is difficult. The Computational Fluid Dynamics (CFD) is mathematical modeling tool, which can be considered the incorporation of theory and experimentation in the field of kinetics, heat, and mass transport of the PEFCs. The purpose of this work is to use direct modeling-based, Lattice Boltzmann Method (LBM) within the detailed structure of porous layers to understand the kinetics and multi-scalar/multi-physics transports in a polymer electrolyte fuel cells (PEFCs). The model geometries consist of gas diffusion layer (GDL), micro porous layer (MPL), and Catalyst layer (CL), as shown in Fig. 1. The studies include the understanding of water evolution, water saturation, breakthrough pressure, heat transfer, species transport, and electrochemical kinetics inside porous layers under different conditions and situations that could occur in fuel cells.

This work will show the enhancement of direct CFD simulation with LBM (CFD-LBM) approach [1-4], which incorporates with detailed structure of porous and catalyst layers from both micro- and nano- X-ray CT. This approach will consist of the kinetic model in the catalyst layer, which will involve coupling electrochemical kinetic to investigate the electrical potentials, electrical current, electron transfer, and exchange current in the catalyst layers, as shown in Fig. 2. The output of this work will be used for the optimization of catalyst layer thickness, with durability and water management improvement, for novel porous materials, particularly in the catalyst layer.

References:

P. Satjaritanun, S. Hirano, A. D. Shum, I. V. Zenyuk, A. Z. Weber, J. W. Weidner, and S. Shimpalee, Journal of the Electrochemical Society, 165 (13), (2018) F1115-F1126.

P. Satjaritanun, J.W. Weidner, S. Hirano, Z. Lu, Y. Khunatorn, S. Ogawa, S.E. Litster, A.D. Shum, I.V. Zenyuk, S. Shimpalee, Journal of the Electrochemical Society, 164 (11), (2017) E3359-E3371.

S. Shimpalee, S. Hirano, M. DeBolt, V. Lilavivat, J.W.Weidner, Y. Khunatorn, Journal of the Electrochemical Society, 164(11), (2017) E3073-E3080.

S. Shimpalee, V. Lilavivat, H. Xu, J. R. Rowlett, C. Mittelsteadt, and J. W. Van Zee, Journal of the Electrochemical Society, 165 (11), (2018) F1019-F1026.

Figure 1
Comparative Investigation of Polyphenylene Sulfide Polymer-Graphite Bipolar Plates for Fuel Cell Application
Authors: Dushina Anastasia , Satola Barbara , Dyck Alexander , Wagner Peter
Published: February 2020

Bipolar plates (BPPs) are one of the key components of the polymer electrolyte membrane fuel cell (PEM FC) which play an important role in the development of fuel cell application. They should fulfil many functions in a fuel cell stack such as feeding H2 and O2 gases through the flow field upon operation, heat transfer, physical separation of individual fuel cells in series, collection and transport of electrons from anode to cathode of adjacent cells [1]. Among the BPPs used in PEM FC the polyphenylene sulfide (PPS) polymer-graphite BPP has a good electrical conductivity, lower cost, higher flexibility and chemical stability, in comparison to metallic and graphite plates. However, some challenges such as higher thickness and weight in comparison to metallic bipolar plates are limiting their use in automotive application [1]. In addition, it was reported that corrosion of carbon is taking place under operation conditions of fuel cells [2].

Therefore, in this work two compression molded commercial polyphenylene sulfide (PPS) polymer-graphite composite bipolar plates BPP-20 and BPP-15 from two different manufacturers with amount of PPS binder equal to 20 and 15 %, respectively, were employed for an analytical comparative investigation using physical and electrochemical analysis. Chemical stability of BPPs was investigated after storage in phosphoric acid. Corrosion resistance and electrochemical aging of the BPPs were studied by using linear sweep voltammetry, cyclic voltammetry and electrochemical impedance spectroscopy in phosphoric acid. In order to characterize the difference in physical properties water contact angle measurement and through-plane electrical conductivity experiments were performed. The morphology of the BPPs surfaces was determined by scanning electron and confocal microscopy. The chemical composition was investigated by X-ray diffraction and energy dispersive X-ray spectroscopy, respectively. Comparison of BPPs revealed that the surface roughness and electrical conductivity is lower while acid uptake and hydrophilicity is higher for BPP with higher amount of PPS. Moreover, there was a trend of reduced corrosion rate for BPP with increased PPS content. These properties could be explained based on structure and electrical characteristics of the materials.

[1] S. S. Araya, F. Zhou, V. Liso, S. L. Sahlin, J. R. Vang, S. Thomas, X. Gao, C. Jeppesen, S. K. Kær, International Journal of Hydrogen Energy 2016, 41, 21310-21344.

[2] T. Engl, L. Gubler, T. J. Schmidt, Journal of the Electrochemical Society 2015, 162, F291-F297.

Figure 1
Bypassing the Jam: How GDLs with Engineered Water Highways Can Re-Enable Interdigitated Flow Fields for PEFCs
Authors: Manzi-Orezzoli Victoria , Siegwart Muriel , Schmidt Thomas J. , Boillat Pierre
Published: February 2020

The use of interdigitated flow fields in polymer electrolyte fuel cells (PEFCs) was originally proposed in the 90’s by Nguyen (1), and can lead to a significant reduction of mass transport losses due to the fact that oxygen is not transported by diffusion, but by convection under the flow field lands (2). However, the same authors reported a few years later (3) that this type of flow field introduces significant cell-to-cell flow distribution issues when placed in a stack arrangement. With the help of neutron imaging, several authors (4-6) have identified the accumulation of water at the end of the inlet channels and the related increase in pressure drop as a major contribution to this problem.

Here, we will present a novel solution to this problem on the basis of our previously developed gas diffusion layers featuring patterned wettability (7). Hydrophilic lines are used to create a bypass for water without altering the mechanical structure of the GDL – which would produce a bypass for gases in dry conditions. Experiments conducted on a 12 cm2 cell and with gas flow stoichiometries as low as 1.4 demonstrated an outstanding improvement in comparison with a standard, fully hydrophobized material. Besides the stable performance, the increase of pressure drop is moderate and nearly constant in comparison with the much larger and unpredictable pressure drop obtained with a conventional GDL. Neutron imaging confirmed that this difference is due to the water accumulation in the gas flow channels with a commercial material – which is fully avoided thanks to the hydrophilic highways in the patterned material (see Figure 1). The moderate and stable pressure drop of our proposed design is highly promising, as it will likely solve the cell-to-cell flow distribution issue in a stack configuration.

References

T. V. Nguyen, Journal of The Electrochemical Society, 143, L103 (1996).

K. Tajiri, J. Karani and U. N. Shrivastava, Journal of The Electrochemical Society, 165, F1385 (2018).

T. Van Nguyen and M. W. Knobbe, Journal of Power Sources, 114, 70 (2003).

N. J. Cooper, A. D. Santamaria, M. K. Becton and J. W. Park, Energy Conversion and Management, 136, 307 (2017).

D. Kramer, J. Zhang, R. Shimoi, E. Lehmann, A. Wokaun, K. Shinohara and G. G. Scherer, Electrochimica Acta, 50, 2603 (2005).

J. P. Owejan, T. A. Trabold, D. L. Jacobson, D. R. Baker, D. S. Hussey and M. Arif, International Journal of Heat and Mass Transfer, 49, 4721 (2006).

A. Forner-Cuenca, J. Biesdorf, L. Gubler, P. M. Kristiansen, T. J. Schmidt and P. Boillat, Advanced Materials, 27, 6317 (2015).

Figure 1
Degradation-Conscious Control for PEM Fuel Cell Systems
Authors: Goshtasbi Alireza , Ersal Tulga
Published: February 2020

Cost and durability remain the main roadblocks to widespread commercialization of polymer electrolyte membrane (PEM) fuel cell technology for automotive applications. Significant research efforts over the past decade have resulted in considerable improvements on both fronts. Most of this research has focused on developing new materials for enhanced durability. Nevertheless, as demonstrated by the commercialized Toyota Mirai, system-level strategies designed to effectively utilize the full potential of a given fuel cell stack also hold a great promise in realizing the durability targets. Additionally, such system-level approaches can reduce the overall cost, for example by downsizing or eliminating the humidifier. Despite their potential, these system-level mitigation strategies are not commonly pursued in the literature.

As a starting step towards developing a system-level strategy to mitigate membrane degradation, in this talk we present a degradation-conscious control algorithm that aims to meet the requested power demand while respecting the degradation constraints to ensure safe operation of the fuel cell. This is achieved using the model-predictive-control (MPC) framework [1]. In particular, we present a coarsely discretized version of a two-phase and non-isothermal model for transport phenomena in the through-the-membrane direction [2], [3]. We then show how the model can be simplified for the purpose of the control design. To ensure feasibility of real-time control law generation, we further simplify the model by linearizing it about the current operating point. Having derived the linear model, we show how we can construct a degradation-conscious controller that respects the bounds on the membrane hydration and its temperature using the MPC framework. Our preliminary results indicate that the approach can be used to control the state of the membrane in order to ensure its safe operation [4].

[1] J. B. Rawlings and D. Q. Mayne, Model predictive control: Theory and design. Nob Hill Pub. Madison, Wisconsin, 2009.

[2] A. Goshtasbi, B. L. Pence, and T. Ersal, “Computationally efficient pseudo-2D non-isothermal modeling of polymer electrolyte membrane fuel cells with two-phase phenomena,” J. Electrochem. Soc., vol. 163, no. 13, pp. F1412–F1432, 2016.

[3] A. Goshtasbi, B. L. Pence, and T. Ersal, “A real-time pseudo-2D bi-domain model of PEM fuel cells for automotive applications,” in ASME 2017 Dynamic Systems and Control Conference, 2017, p. V001T25A001-V001T25A001.

[4] A. Goshtasbi and T. Ersal, “LQ-MPC Design for Degradation-Conscious Control of PEM Fuel Cells,” in Proceedings of the 2019 American Control Conference, 2019.
Temperature Dependent Mechanical Behavior of Perfluorosolfonic Acid Membranes for Electrochemical Applications
Authors: Arthurs Claire , Kusoglu Ahmet
Published: February 2020

Perfluorosulfonic acid (PFSA) membranes are the prototypical solid-electrolyte used in electrochemical devices such as polymer-electrolyte membrane fuel cells (PEMFCs) and electrolyzers [1]. To be commercially viable, polymer-electrolyte membranes (PEMs) in PEMFCs and electrolyzers must perform over a long operational time in both dry and wet environments. The ionic conductivity of PFSA membranes can be optimized by changing thickness, material (ionomer chemistry), and pretreatment to increase the ionic conductivity, and reduce power losses, thus improving cell efficiency. However, any effort to improve the transport functionality tends to undermine the membrane’s mechanical stability. [2] Therefore, a key challenge in PEM design is to improve transport of ions without compromising mechanical integrity and characterize the factors influencing mechanical stability of these materials in controlled environments.

Most past studies on the mechanical properties of PFSA membranes investigated only tension [2], although there are some exceptions [3][4]. Compression testing, however, is critical for understanding membrane behavior in electrochemical devices. For example, in fuel cells, hydration-related swelling of a constrained membrane generates partially reversed cyclic stresses, whereas in electrolyzers, PEMS undergo static compression as high as 40 MPa. Cyclic stresses combined with a harsh chemical environment make the PEMs susceptible to failure such as pinhole formation as well as crack initiation and propagation. High static stresses make creep response a great concern. To investigate how temperature and hydration state affect the membrane’s mechanical behavior and properties under compression in-situ, a compression setup with temperature control was used. PFSA membranes of varying chemistry, equivalent weight, thickness (from 50 to 200 µm), and thermal pretreatments were tested. Our results show that the mechanical behavior of PFSA membranes is different under compression than tension. Uniaxial compression and creep tests indicate that the PFSA membranes exhibit time-dependent nonlinear response over long periods of time. This work demonstrates the importance of studying the mechanical properties of these membranes under compression, which is more relevant for the various stress-states the membrane undergoes during operation.

Odgaard, M., Advanced Fluoride-Based Materials for Energy Conversion, in Advanced Fluoride-Based Materials for Energy Conversion. 2015, Elsevier. p. 325-374.

Kusoglu, A. and A.Z. Weber, New Insights into Perfluorinated Sulfonic-Acid Ionomers. Chemical Reviews, 2017. 117(3): p. 987-1104.

Kusoglu, A., et al., Effect of compression on PFSA-ionomer morphology and predicted conductivity changes. Journal of Membrane Science, 2012. 421(0): p. 283-291.

Kusoglu, A., et al., Role of Mechanical Factors in Controlling the Structure–Function Relationship of PFSA Ionomers. Macromolecules, 2012. 45(18): p. 7467-7476.
Capturing Hydroxyl Radical Generated from Oxygen Reduction on Fe/N/C Catalyst By Fluorescence Detection
Authors: Chen Lina , Tian Na , Zhou Zhiyou , Sun Shigang
Published: February 2020

Low-cost ternary Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction (ORR) in fuel cells. However, poor stability of Fe/N/C catalyst severely hampers its applications. A widely accepted mechanism for the instability of Fe/N/C catalysts is the oxidative attack by reactive oxygen species, especially by aggressive •OH radical. The •OH is speculated mainly via the decomposition of H2O2 intermediate through Fenton’s reaction. However, there are few reports about direct detection, especially quantitatively analysis of •OH radical during ORR on pyrolyzed Fe/N/C catalysts. The exact mechanism for generating •OH is unclear yet.

In this study, we use coumarin as a fluorescent probe to detect •OH generated from ORR on Fe/N/C catalyst. During the Fe/N/C ORR non-fluorescent coumarin will react with the •OH to generate the intense fluorescent 7-hydroxyl coumarin. According to the fluorescent intensity of 7-hydroxyl coumarin, the •OH can be quantitatively analyzed. Meanwhile, this probe molecule is highly specific to •OH radical, and is insensitive to O2, H2O2 and electrochemical oxidation.

We tested the •OH produced by the ORR at different potentials, and investigated its correlation with H2O2 intermediate. As shown in Figure 1, with potential decreased from 0.70 to 0.60 V, the amount of •OH generated from the ORR process on Fe/N/C catalyst increased and then declined, reaching a maximum at 0.65 V. This variation of •OH amount is greatly different from that of H2O2, and the latter increased linearly with decreasing potentials. Our result indicates that •OH is not mainly generated by the H2O2 decomposition.

Figure 1
Dissociation Barrier Informatics on Heterogeneous Catalysts
Authors: Kang Joonhee , Lee Chan-Woo , Lee Jehyun , Kim Byung-Hyun , Yim Kanghoon
Published: February 2020

Over the last few decades, there are steady development in the understanding of electrocatalytic reactions on the heterogeneous catalysts for polymer electrolyte membrane fuel cells (PEMFC). Unfortunately, high performance catalysts for electrochemical systems are made by a huge amount of experimental trial and error process. First-principles density functional theory (DFT) calculations have begun to provide a rapidly screened database and a simple way to rationally design materials. These atomic-scale database are suitable for guiding of heterogeneous catalysts design. Despite this, high-throughput screening cannot adequately handle the kinetics such as reaction barrier. Database for transition state energies demands considerable time and computational costs, therefore the other concept is required. In this work, we attempt to mitigate time and computational expenses by using a relationship between the reaction energy and the activation barrier. Also, machine learning techniques are applied to predict the key parameter of the dissiciation reaction barrier.
Development of Porous Structured PtCu/C Catalyst Via Sputtering Method for Efficient Oxygen Reduction Reaction.
Authors: Lee Dong Wook , Jang Injoon , Jang Jue-Hyuk , Lee Kwan Young , Yoo Sung Jong
Published: February 2020

Polymer exchange membrane fuel cell (PEMFCs) is expected to be the promising candidate as the future clean energy sources. Especially, it is considered that the PEMFCs are suitable for applying to the transportation because of its various advantages such as high-power density, easy scale up and immediate response to change in the demand for power. However, due to the high cost of fuel cell system, it is difficult to commercialize of fuel cell automobiles. The system cost is usually depending on the usage of PGM catalyst in MEA. Herein, PtCu/C catalyst were synthesized by using sputtering method to reduce the amount of Pt which is occupying a large portion of the system cost. First, various ratio of PtCu nanoparticles were carried out onto the powder substrate by adjusting the sputter gun power. After then nanoparticles were transferred to carbon. Through the heat treatment and acid treatment, we can get mesoporous structured PtCu/C catalysts. This PtCu alloy catalyst shows similar or higher oxygen reduction reaction activity then that of commercial Pt/C even though the amount of Pt is much lower.
(Invited) Design of Catalyst Layer Structure for High Fuel Cell Performance
Authors: Lee Seon-Ho , Taning Ahmad Zulfikri , Woo Seunghee , Park Seok-Hee , Yim Sung-Dae
Published: February 2020

The low Pt electrode is an important research topic for the commercialization of polymer electrolyte fuel cell (PEFC). Platinum nanoparticles act as a catalyst for the fuel cell electrode and promote the oxygen reduction reaction (ORR). In this process, the surface properties and structure of adjacent carbon supports and ionomer binders greatly affect the Pt catalyst. Therefore, the performance of the Pt/C catalyst in the fuel cell electrode is determined not only by the intrinsic activity of the catalyst itself, but also by the interface structure between the ionomer binder and the Pt/C catalyst. It has been reported that the ORR activity of the Pt/C catalyst in the fuel cell electrode is affected by the Pt poisoning of the sulfonic acid group tethered to the Nafion backbone as well as the oxygen permeability of the ionomer binder [1]. The difference in pore characteristics of the carbon support affects the optimum ionomer content [2] and Pt utilizaton [3] in the electrode. The surface properties of the carbon support also affect ionomer distribution and ionomer thickness on the catalyst surface, thereby altering the activity of the catalyst [4]. In spite of recent studies, understanding of complicated physicochemical phenomena in the microstructure of electrode is still very limited.

In this talk, we will discuss the fuel cell performance characteristics based on several electrochemical analyses according to the microstructure control of the catalyst layer. Various functional groups were introduced on the surface of Pt/C catalyst by post treatment and the catalyst layer was prepared to observe the ionomer distribution and ion transport characteristics according to functional groups. In addition, a multilayer catalyst layer having different ionomer contents in the thickness direction of the catalyst layer was prepared using an ultrasonic spraying process, and changes in hydrogen ion transfer and oxygen diffusion transfer characteristics in these catalyst layers were observed in a fuel cell. Finally, the electrochemical properties of the catalyst layer made of the ionomer dispersed in the high-boiling organic solvent will be introduced.

1. V. Yarlagadda, M. K. Carpenter, T. E. Moylan, R. S. Kukreja, R. Koestner, W. Gu, L. Thompson, A. Kongkanand, ACS Energy Lett. 3 (2018) 618.

2. Y. Liu, C. Ji, W. Gu, J. Jorne, H. A. Gasteiger, J. Electrochem. Soc. 158(6) (2011) B614.

3. Y.-C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida, J. Power Sources 315 (2016) 179.

4. A. Orfanidi, P. Madkikar, H. A. El-Sayed, G. S. Harzer, T. Kratky, H. A. Gasteiger, J. Electrochem. Soc. 164 (2017) F418.
Understanding Stability of the Transition Metal Carbides and Nitrides By Combining Experimental and Computed Thermochemical Properties
Authors: Matanovic Ivana , Garzon Fernando H
Published: February 2020

Thermochemistry plays a key role in determining durability of the catalysts and catalytic supports, but is also critical in guiding the rational design of synthesis processes that lead to materials with advanced properties [1, 2]. In the last decade computations based on density functional theory have been used as an important tool in the calculation of thermodynamic properties, such as reaction enthalpies, free energies, and heat capacities. In this work we combine experimental thermochemical data available in the HSC Chemistry software and the data obtained using density functional theory calculations to study the stability of various transition metal carbides and nitrides in aqueous media as a function of pH, cell potential, and temperature.

Earth abundant transition metal carbides and nitrides have drawn considerable interest due to their low cost, unique chemical and physical properties, and high catalytic activity for variety of reactions, such as nitrogen electroreduction to ammonia, ammonia decomposition, alcohol electrooxidation, and biomass conversion. We will discuss the thermodynamics directed towards understanding oxidation of transition metal carbides and nitrides at different cell potentials, pH and temperatures. Namely, oxidation of the material will lead to the change in the geometric and electronic structure of the material, which can cause degradation and decrease in the catalytic activity. More specifically, transition metal carbides and nitrides based on molybdenum, iron, vanadium, and nickel will be considered to illustrate the importance of mapping out their stable phase as a function of pH, potential, and temperature. These diagrams can then be used to determine the stability of the materials in the aqueous media and guide the reaction conditions that will ensure highest durability for a targeted application.

[1] S. K. Nayak, A. D. Benavidez, I. Matanovic, and F. H. Garzon, Thermochemical analysis of Mo-C-H systems for synthesis of molybdenum carbides, Thermochim. Acta, 676, 27-32 (2019).

[2] S. K. Nayak, A. D. Benavidez, F. H. Garzon, Facile synthesis of high surface area molybdenum carbide nanoparticles, J. Am. Ceram. Soc., 00: 1– 7 (2018).
(Invited) Creating High-Performance Pt-Based ORR Catalysts through Surface Engineering
Authors: Huang Yu
Published: February 2020

Pt-based nanocatalysts have played important roles in PEMFC due to their high activity and chemical stability. Owing to the large surface to volume ratio at nanoscale slight changes in the surface structure of catalytic materials can have large impacts on the catalytic stability and activity. The composition, facet, and the topology of the top surface layers of a nanocatalyst eventually determine its performance in catalytic reactions. In this presentation, I will share our recent efforts on designing the surface compositions, structures and the overall morphology of noble metal catalysts to improve both catalytic activity and stability of nanocatalysts.
In Situ Characterization of Fe-N-C Electrocatalysts Synthesis By XPS and XRD
Authors: Chen Yechuan , Asset Tristan , Kodali Mounika , Artyushkova Kateryna , Atanassov Plamen
Published: February 2020

As one of the most promising candidates to replace Pt-based electrocatalyst for oxygen reduction reaction in fuel cell, Metal-Nitrogen-Carbon (M-N-C) catalysts, especially Iron-Nitrogen-Carbon (Fe-N-C) materials, have attracted massive research interests in recent years. Typically, there are three main categories of synthesis approaches for Fe-N-C electrocatalyst, based on what chemicals are used as iron and nitrogen precursors: macrocyclic iron complexes, metal-organic frameworks, and various heterocyclic compounds. Despite these different approaches, it is found that numerous purified preliminary Fe-N-C products need further heat treatment to achieve better electrocatalysis performance. However, the reason why heat treatment is efficient, as well as the best parameters such as atmosphere, time and temperature, are still unclear and require intensive characterization for elucidation.

Here, we report in situ XPS for the investigation how carbon environment and nitrogen moieties change, in addition to in situ XRD, on a specific atomic-dispersed Fe-N-C material (made from nicarbazin via sacrificial support method[1]) during high temperature heat treatment. Figure 1 shows the change of surface contents via XPS C 1s and N 1s under ultra-high vacuum. It is found by rising the temperature from room to 750 °C, the graphitic C with a characteristic peak around 284.5 eV decreases from ~50 atomic % to ~20 %, resulting in a more fragmented carbon structure, while sp3 carbon and nitrogen-carbon have an obvious increase. After flash heating to 950 °C (the typical point used in 2nd heat treatment for this electrocatalyst synthesis) and followed cooling back to 150 °C, there is no reversibility of graphitic carbon. For N 1s shown in Figure 1B, comparing initial 150 °C and final 150 °C after cooling, it is found that pyridinic-N content drops from ~20 atomic % to 15%, and pyrrolic-N decreases from ~40 % to 30 % respectively. Meanwhile, metallic/amine nitrogen increases from ~10% to ~15% while graphitic-N/N+ grows from ~7 % to 20 %, resulting in a more efficient Fe-Nx bonding and surface ionic conduction. In addition, in situ XRD shows that there is no obvious crystalline formed during high temperature treatment, indicating that there is no agglomeration of iron particles. These in situ XPS and XRD results elucidate that extra heat treatment of Fe-N-C electrocatalyst after preliminary synthesis and purification is an essential procedure and can improve the electrochemical performance efficiently.

[1] M. J. Workman, M. Dzara, C. Ngo, S. Pylypenko, A. Serov, S. McKinney, J. Gordon, P. Atanassov, K. Artyushkova, J. Power Sources
2017, 348, 30-39.

Figure 1
One-Pot Synthesis of Gram-Level Shape-Controlled Pt-Ni Catalysts with Enhanced Electrocatalytic Properties for PEMFC
Authors: Cai Xin , Lin Rui
Published: February 2020

Proton exchange membrane fuel cells (PEMFC) are one of the most effective ways to solve energy and environmental problems due to their high efficiency, environmental protection and stability. As the most efficient redox catalyst, Platinum (Pt) remains the first choice for PEMFC catalysts. However, the low reserves and high prices of platinum have made it difficult to reduce the cost of PEMFC and affect its commercial application. Therefore, improving the utilization and activity of Pt is still the focus of current research on fuel cell catalysts.

In recent years, the development of catalyst has been focused on the shape-controlled platinum alloy nanoparticles. It is reported that more highly active Pt-M (111) crystal faces can be exposed in the shape-controlled catalysts, which increases the activity of the catalyst and the utilization of Pt. However, these high performance catalysts were usually prepared by multistep synthesis method with difficult preparation and poor reproducibility, which also has a low yield in one-batch. Thus, a facile yet efficient synthesis strategy is necessary for enabling atomic-scale engineering and mass production of nanocatalysts for real world applications. Herein, we report a relatively effective and simple one-pot synthesis of novel shape-controlled Pt-Ni catalysts and its single production is around 0.5g. By controlling the reaction time, the catalysts with different morphology were prepared and their electrocatalytic properties were studied. The nanoframe catalyst possess the best ORR activity and durability. In this regard, this method can be a promising way for mass production of the high performance shape-controlled Pt-Ni alloy electrocatalyst.
Iron and Nitrogen Doped Carbide Derived Carbon and Composite Catalysts for Fuel Cell Cathodes
Authors: Ratso Sander , Sahraie Nastaran Ranjbar , Sougrati Moulay Tahar , Käärik Maike , Kook Mati , Saar Rando , Vlassov Sergei , Kisand Vambola , Paiste Päärn , Jia Qingying , Leis Jaan , Mukerjee Sanjeev , Jaouen Frederic , Tammeveski Kaido
Published: February 2020

Producing renewable energy is one of the most important electrochemical challenges in the 21st century. Currently the focus is mainly on enhancing the oxygen reduction reaction (ORR) on the cathode of the fuel cell and to utilize non-noble metal catalysts instead of the expensive and scarce Pt-based catalysts that are currently prevalent. Iron and nitrogen doped nanocarbons have emerged as a possible replacement. Here, we study a catalyst material synthesized from carbide-derived carbon (CDC, a carbon material made by removing the metal atoms from a carbide) and composites of CDC and carbon nanotubes (CNT). To dope this material, 1,10-phenanthroline and iron(II)acetate were used in a ball-milling and pyrolysis procedure.1,2 The composites were created by adding CNTs, dicyandiamide and additional iron(II)acetate before repeating the ball-milling and pyrolysis process. The surface morphology was examined by scanning electron microscopy (SEM), and elemental composition by X-ray photoelectron spectroscopy (XPS), porosity analysis was done by N2 adsorption/desorption and the bulk elemental composition was studied by inductively coupled plasma mass spectroscopy (ICP-MS). The speciation of iron was studied using 57Fe Mössbauer spectroscopy.

These CDC-based Fe-N-C catalysts show promising half-wave potential for ORR of 0.81 V vs RHE in 0.5 M H2SO4. For a same Fe content of 0.5 wt% in the catalyst precursor, the Fe-N-C catalyst derived from CDC-2 (derived from TiC) showed ca. 5 times higher activity at 0.8 V vs. RHE than that derived from CDC-1 (derived from B4C). The residual presence of boron in CDC-1 seems to be the main reason for the lower activity of CDC-1 derived catalysts, leading to the preferential formation of iron boride instead of ORR-active FeNxCy moieties. Higher Fe contents were investigated for CDC-2, but lead to unmodified activity, which is explained from Mössbauer spectroscopy measurements by the increasing formation of ORR-inactive Fe species at high Fe content. The addition of CNTs to create a core-shell composite with a CNT shell surrounding the CDC cores increased the stability of the catalyst in acidic media.

Figure 1
Heteroatom (N, P, B) Doped Hierarchical Porous Carbons from Coal Tar Pitch with High Specific Surface Area for Oxygen Reduction Reaction
Authors: Dong Fang , Qiao Jinli
Published: February 2020

Heteroatom (N, P, B) Doped Hierarchical Porous Carbons from Coal Tar Pitch with High Specific Surface Area for Oxygen Reduction Reaction

Fang Dong, Jinli Qiao*

College of Environmental Science and Engineering, Donghua University, 2999 Ren’min North Road, Shanghai 201620, China.

*qiaojl@dhu.edu.cn

In the past few decades, fuel cells, as a kind of clean and efficient energy sources, which is considered to be the most promising solution to the increasingly serious energy crisis of energy conversion equipment, has attracted significant attention.1 Oxygen reduction reaction (ORR) in fuel cells plays a decisive role in determination of performance, and electrocatalysts with high-performance ORR are essential for practical applications. Up to now, the platinum or its alloyed nanoparticles have been used to catalyze the sluggish ORR, however, their high cost as well as the limited natural abundance hinder the development and commercialization of the interrelated technologies.2 The development of new ORR catalysts free of noble metals is thus the next challenge for the long-term viability and sustainability of fuel cells. Due to the introduction of porous structure, porous carbon materials with high specific surface area, porous rich and aperture can be adjusted, which has the advantages of high chemical stability and good electrical conductivity, and this has been widely used in the aspects such as catalysis, adsorption and electrochemical energy storage.3 Recent years witnessed the dramatic interest in using nitrogen-doped porous carbon as one of the promising ORR catalysts. Besides N, other heteroatoms have also been introduced into carbon materials and they also show enhanced catalytic activity for ORR.4 In this work, we choose N, P and B as doped heteroatoms to fabricate the hierarchical porous carbons derived from coal tar pitch. The catalytic ORR activities of the heteroatom (N, P, B) doped hierarchical porous carbons from coal tar pitch are studied and the results show that heteroatom (N, P, B) doped with hierarchical porous carbon from coal tar pitch has high specific surface area and high catalytic activity for ORR.

References

1 M.L. Xiao, J.B. Zhu, L.G. Feng, C.P. Liu, W. Xing, Advanced Materials, 27, 2521 (2015).

2 M. Sahoo, S. Ramaprabhu, Energy, 119, 1075 (2017).

3 L. Osmieri, R. Escudero-Cid, A.H.A. Monteverde Videla, P. Ocón, S. Specchia, Applied Catalysis B: Environmental, 201, 253 (2017).

4 M.J. Wu, Q.W. Tang, F. Dong, Z.Y. Bai, L. Zhang, J.L. Qiao, Journal of Catalysis, 352 , 208 (2017).
(Invited) Ammonia Production Beyond Haber-Bosch Process
Authors: Zhu Liangzhu , Cadigan Chris , Duan Chuancheng , Sullivan Neal P , O'Hayre Ryan
Published: February 2020

Ammonia has been an important chemical precursor for agriculture and other applications for about a century. It is estimated that about 180 million tons of ammonia is produced annually, and over 90% of the ammonia is produced via the Haber-Bosch (HB) process. While the reaction for the Haber-Bosch process is simple (N2+3H2=2NH3), the actual production process is complicate. The first major step is the methane steam reforming process which provides the H2 source. This step consumes significant amount of energy and releases large amount of CO2. For the ammonia synthesis step, it typically requires high pressure such as up to 300 bar at around 400 to 500 oC. Therefore overall the HB process is very energy intensive. It is poorly suited to distributed/small-scale applications, and not suitable for fast ramping/turndown and thus not dispatchable. Thanks to the fast progress on capturing renewable energy such as solar, wind, tidal in recent years, small to medium scale clean energy becomes readily available. Meanwhile the regulations on the CO2 emission has become more and more rigorous and urgent, there seems higher demand to look for alternative and cleaner process on ammonia synthesis. This abstract will cover two parts: a brief review on current progress of ammonia production via non-Haber-Bosch process particularly using ionic conducting ceramic cells and current development and progress at the Colorado School of Mines using the state-of-the-art reversible protonic ceramic fuel cells on ammonia production and power generation.
(Invited) Development of Cathode Materials for All-Solid-State Batteries
Authors: Zeng Leiying
Published: February 2020

With the rapid development of all-solid-state battery technology, the research of all-solid-state battery has been developed in all directions. XTC New Energy Company has also done a lot of work in the development of cathode materials in order to meet the requirements of all solid state batteries. This paper introduces the design and development capability of XTC for material. In particular, the fabrication techniques of precursors and cathode materials are introduced, and the performance relationship between them is also studied. Based on these studies, we can design the morphology, structure and special treatment of the material to suite for the requirements of battery. so that the material has better pertinence and adaptability. At the same time, we have also demonstrated some materials that may be suitable for all-solid-state battery applications. We hope to have the opportunity to cooperate with major companies and research institutes to promote the development of all-solid-state battery.
(Invited) Current Status of Solid Oxide Fuel Cell Technology and Commercialization
Authors: Singhal Subhash C.
Published: February 2020

After almost four decades of research and development, considerable progress has now been made in the development and commercialization of solid oxide fuel cells (SOFCs) for clean and efficient power generation. The main advantages of SOFCs are low emissions, fuel flexibility, and high efficiency. The SOFC power generation systems are now sold commercially with units totaling over 500 MW installed or on order, for small residential units (~1 kWe), commercial and industrial systems (100-400 kW), and microgrids (several MW). The most important need to further accelerate commercialization of SOFC technology is to significantly reduce the overall cost of such systems while maintaining adequate performance and performance stability with time. This overview focuses on the designs, materials, processing, and performance of solid oxide fuel cells, and discusses the progress in the deployment of power generation systems built with various design solid oxide fuel cells and their operating experiences. Challenges in reducing cell and system costs are also summarized.

SOFCs can also be operated in reverse operating mode for hydrogen and syngas production through electrolysis of steam and mixtures of steam and carbon dioxide; interest in such solid oxide electrolysis has greatly increased during the last decade. Application of solid oxide cells for electrolysis is also discussed in this overview.
(Invited) Electrode Engineering of Solid-Oxide Electrochemical Cells at National Energy Technology Laboratory
Authors: Hackett Gregory A , Lee Shiwoo , Abernathy Harry , Kalapos Thomas , Na Beom-Tak , Muhoza Sixbert P , Duffy Jack , Gross Michael D , Brinkman Kyle S
Published: February 2020

The National Energy Technology Laboratory (NETL) Solid Oxide Fuel Cell (SOFC) Team performs fundamental SOFC technology evaluation, enhances existing SOFC technology, and develops advanced SOFC concepts in support of the U.S. Department of Energy SOFC Program. Program targets include a reduction in performance degradation to 0.2% per 1000 hours and a system cost of $900 per kilowatt. Research and development is essential to meet these targets. Research efforts are broadly focused on an investigation of cell and stack degradation, electrode engineering, grid integration challenges, and system analysis. The research approach is targeted to specifically address SOFC program technology development goals, especially regarding reducing stack costs, increasing cell efficiency, and increasing cell reliability and robustness. The goal of these efforts is to transfer technology that facilitates commercial acceptance of SOFC technology. This is accomplished through close collaboration with SOFC commercial developers, national laboratories, and academic institutions.

NETL system-level analysis has shown that a critical consideration for reducing the cost of SOFC technology is the enhancement of electrode performance and longevity through materials and microstructure engineering. Within this scope is the special consideration of cell production costs and operating temperature. Specifically, at NETL, nano-electrocatalyst infiltrations have been a successful operation by scaling up the patented technology to a commercially-relevant scale, partnering with industrial manufacturers. The effort has continued to the construction of a scaffold microstructure that is optimized for surface modification and the development of gel-derived high surface area electrodes. Electrode materials selection has been made through a computational approach that uses electronic structure and energetics in conjunction with thermodynamics and statistical physics, identifying multicomponent oxides with high oxygen reduction reaction activity and stability. Highly reliable electrical conductivity relaxation analysis confirmed the predicted electrode materials’ superior surface exchange property when compared to the state-of-the-art lanthanum strontium cobalt ferrite. The developed electrode engineering techniques have been applied for reversible solid-oxide cell operation as well as single mode solid-oxide cells to stabilize electrodes while maintaining improved performance and longevity.
(Invited) Understanding Lithium Sulfur Batteries at Different Scales
Authors: Xiao Jie , Lu Dongping , Liu Jun
Published: February 2020

With the recent advances of Li-S battery research, new knowledge has been gathered which greatly deepens the understanding of this electrochemical couple. However, a cell-level understanding of Li-S chemistry is rarely reported, although it is expected that the dynamic interactions among sulfur, lithium and electrolyte in the enlarged testing format may lead to quite different findings. Herein, this work discusses the fundamentals underneath a Li-S cell when transiting from a coin cell to a realistic high-energy pouch cell. New challenges and opportunities have been discovered which in turn provide feedback for the rational design of materials/electrode at relevant scales. The potential solutions to further balance the energy density and cycling life of Li-S pouch cells will also be dicussed.