bluuebunny/crossref_metadata_2025 huggingface dataset:
Cathode Catalyst Layer Design and Optimization for Portable Power Applications Using Non-Precious Metal Catalysts
Authors: Kishimoto Takeaki , Sato Tetsutaro , Kobayashi Yoshikazu , Narizuka Kumi , Banham Dustin , Zhou Yingjie , Marquez Emil , Bai Kyoung , Ye Siyu
Published: February 2020

In recent years, the inherent activity of M/N/C (M=Fe, Co, or Mn) non precious metal catalyst (NPMCs) has advanced to a stage where these catalysts can be considered as potential alternatives to Pt/Pt-alloy catalysts for certain applications(1-4), provided stability/durability can be improved(5). Due to these achievements, NPMCs have advanced beyond purely rotating disc electrode (RDE) studies, and are now ready to be thoroughly evaluated at the membrane electrode assembly (MEA) level. While previous work has looked at in-situ MEA evaluation of NPMCs, few of these studies have investigated maximizing performance through rational design of the cathode catalyst layer (CCL). However, recent work by Serov et al. (3) has highlighted the importance of CCL design parameters in maximizing the performance of NPMC-based CCLs.

The significant difference in CCL layer thickness of NPMC-based CCLs vs. conventional Pt/C CCLs means any optimization used for conventional Pt/C CCLs will likely not apply to these novel NPMC CCLs. This provides the research community with significant opportunity in this largely unexplored area.

In this work, we will present some of our recent findings on designing and optimizing NPMC-based CCLs for portable power and backup power applications. The NPMC used in this work is developed by Nisshinbo Holdings, and has demonstrated world-leading performance in laboratory scale (50 cm2) MEA testing. After a brief discussion on the synthesis of this NPMC, the results of optimizing the CCL design (e.g. ionomer type/content) will be shown. Performance data recently obtained under conditions relevant for portable power/backup power will be presented and compared against product requirements.

Acknowledgements

The authors thank Alan Young for many helpful discussions,

References

1. M. Lefèvre, E. Proietti, F. Jaouen and J.-P. Dodelet, Science, 324, 71 (2009).

2. F. J. Eric Proietti, Michel Lefèvre, Nicholas Larouche, Juan Tian, Juan Herranz, Jean-Pol Dodelet, Nature Communications, 2 (2011).

3. A. Serov, K. Artyushkova, E. Niangar, C. Wang, N. Dale, F. Jaouen, M.-T. Sougrati, Q. Jia, S. Mukerjee and P. Atanassov, Nano Energy, 16, 293 (2015).

4. A. Serov, M. H. Robson, B. Halevi, K. Artyushkova and P. Atanassov, Electrochemistry Communications, 22, 53 (2012).

5. D. Banham, S. Ye, K. Pei, J.-i. Ozaki, T. Kishimoto and Y. Imashiro, Journal of Power Sources, 285, 334 (2015).
Change in Surface Composition of La0.9Sr0.1Ga1-XMgxO3-
d Investigated with Low Energy Ion Scattering Analysis
Authors: Schraknepper Henning , Ishihara Tatsumi
Published: February 2020

In oxide based energy conversion devices, e.g. fuel and electrolyser (SOFCS and SOECS), predominantly materials crystallizing in the perovskites structure are employed as both, electrodes and electrolyte. Being exposed to realistic operation conditions, however, both components suffer from various degradation phenomena. Here surface segregation and interface diffusion are of pivotal practical importance, as both phenomena are known to deteriorate device performance. Up to now, surface segregation was mainly studied on perovskite oxide cathode and it was found that A site is always segregated surface, in particular, alkaline earth cation is easily segregated on the surface.

In this study, change in surface composition by alkaline earth element in one of the most promising electrolyte material - La0.9Sr0.1Ga1-xMgxO3-
δ (LSGM)- were investigated. Samples of different Mg content x were subjected to anneals at high-(> 1000 K), intermediate ( 1000< T/K < 650) and low temperatures (>650 K). The composition of the very outermost surface layer was subsequently analyzed by means of low energy ion scattering (LEIS). In analyzing the results, the focus was set on differences in A and B side surface coverage and changes with temperature, time and composition.

Moreover, links between Ni diffusion at interfaces observed in devices employing LSGM and the here described surface segregation phenomena in the same material were established.

It was found that Mg2+ in B site was first segregated but after annealed for longer period, Sr2+ in A site was segregated and so the surface segregated cation was changed depending on the annealing period. Decreasing Mg content, Mg segregation is not observed and this is related with the Ni diffusion in LSGM film prepared by dip coating method.
Electrochemical and Thermal Catalytic Syntheses of Ammonia over Yttrium-Doped Barium Zirconate and Cerate Perovskites Supported Ruthenium Catalysts
Authors: Shimoda Naohiro , Kobayashi Yusuke , Kimura Yutaka , Satokawa Shigeo
Published: February 2020

To resolve a global serious problem on energy consumption by human, the development of various new processes which a renewable energy and a surplus electric power generated from thermal and nuclear power plants are converted to the energy easy to handle is required. As one possible process, a technological process that electrical energy is convert to a chemical substance, so-called energy carrier, is raised. As a candidate of energy carrier, methylcyclohexane (MCH), ammonia (NH3), hydrogen peroxide (H2O2), formic acid (HCOOH) are considered in recent years. In the present work, we have paid attention to NH3. In other words, it is an electrolysis process to produce NH3 from the nitrogen contained in air and the hydrogen supplied by the electrolysis of water. For this electrochemical synthesis process, H2O or H2 is oxidized to proton at the anode, and proton is transported through the proton conducting electrolyte to the cathode. And then, N2 is reacted with proton and reduced to NH3 at the cathode. The lower the operation temperature, the more effective the electrolysis synthesis process of ammonia from N2 and H2O, compared with a conventional Harber-Bosch process. However, the development of solid electrolyte exhibiting high conductivity at lower temperature and the selection of electrode catalyst materials and electrode design to improve the reaction rate of ammonia synthesis for the cathode are required. Therefore, in this study, we have focused on the Ru based catalyst which is well known to be excellent catalysts for thermal catalytic synthesis of ammonia. Furthermore, Ba-Zr-Y and Ba-Ce-Y perovskite-type oxides exhibiting high proton conductivity have been used as a support material to improve the cell performance for electrochemical ammonia synthesis.

Firstly, the Ru/Ba-Zr-Y and/or Ba-Ce-Y perovskites solid catalyst was prepared, and its thermal catalytic property for ammonia synthesis was evaluated using a fixed bed flow reactor. As results of comparison tests, Ru/Ba-Zr-Y catalyst showed higher activity than Ru/Ba-Ce-Y catalyst. Furthermore, it was found that an addition of 10wt% of Y component to BaZrO3 perovskite enhances the catalytic performance significantly. And noted that Ru/Ba-Zr-Y catalyst exhibited higher performance than a conventional Ru-Cs+/MgO catalyst. Based on various characterization, we consider that electron transfer from Ba-Zr-Y perovskite to Ru species enhances the dissociation of N-N bond, leading to the high activity for ammonia synthesis. Additionally, in the present work, we have studied the effect of current loading to the catalyst on the catalytic performance for ammonia synthesis to evaluate the applicability of Ru/Ba-Zr-Y catalyst to an electrode catalyst.

 

Acknowledgments

This work was supported by CREST, Japan Science and Technology Agency.
Recent Developments in 3D Multiphysics Modelling of Whole Fuel Cell Systems for Assisting Commercialisation and Improved Reliability
Authors: Peksen Murat , Al-Masri Ali , Peters Roland , Blum Ludger , Stolten Detlef
Published: February 2020

3D multiphysics modelling of fuel cell components and fuel cell systems has been a core research field since many years. The simulation assisted research and development improves the understanding and overall success of the fuel cell technology, in particular the high temperature SOFC technology. The ultimate goal has been to support the commercialisation of the technology. This can be enhanced by improving the understanding and knowledge of the utilised fuel cell systems. Especially, gaining detailed information about their durability and life duration is of paramount importance. As a fuel cell system consists of many components like the fuel cell stack, reformer, afterburner, heat exchanger etc., it is important to account for the coupled processes, occurring within each component and their interaction with the neighbour components. This needs to be mastered, in order to improve the overall technology. However, this requires a large amount of experimental facilities, which have also limits. Even the presence of long-term testing results of individual solid oxide fuel cells are not sufficient yet to declare their autonomous performance as the same within the system. Moreover, many years are required that is constraining the scientists; thus, the assistance of 3D multiphysics modelling is attractive. If we consider that the technology has heating-up, operation and shut-down stages, broad knowledge is required for a safe and reliable SOFC development. For this purpose, the developed full scale multiphysics model reflecting a 5kW full integrated SOFC module is employed for the solution of the complex 3D problem and to gather invaluable information about various questions. The used numerical model of the complex 3D system depicts the true physical resolution of the components, as to account for the complex geometrical effects. Material non-linearity, including the temperature dependence of material properties, as well as the material models that describe the elastic, plastic and creep deformation of the materials are implemented within the model. Each component process and parameters are determined from component and system test facilities. To shed light to the long-term system behaviour, recent attention has been given to the steady operation and the durability response of the interacting components. The detailed 3D stress-strain field of the whole system could be analysed and invaluable practical information about the critical locations within the interacting whole system could be determined. To interpret the long-term reliability of the system, the thermomechanical fatigue behaviour of the critical system regions have been investigated in detail to predict and understand the durability under cyclic load. The results give a flair of the life expectation of a system subjected to current circumstances.
Degradation of (La,Sr)(Co,Fe)O3-Δ SOFC Cathodes at the Nanometre Scale and below
Authors: Ni Na , Cooper Samuel , Skinner Stephen J. , Williams Robert , McComb David
Published: February 2020

For developing solid oxide fuel cells operating at intermediate temperatures (ITSOFCs), metallic materials have become a preferential choice for the interconnect due to their low cost and excellent physical and chemical properties. However the presence of chromium in all commonly used metallic alloys has been found to cause poisoning of the cathode leading to rapid electrochemical performance degradation of the cathodes including one of the most promising (La,Sr)(Co,Fe)O3-δ (LSCF) perovskite oxides [1-3]. Despite the extensive research on the chromium deposition and poisoning processes, careful microstructural studies, especially at the nanoscale, are rare, which can provide valuable information for the fundamental understanding of the Cr poisoning mechanisms required for developing Cr tolerant cathode materials.  

     In this paper, we examine the Cr poisoning mechanisms in (La0.6Sr0.4)0.95(Co0.2Fe0.8)O3-δ (LSCF6428) materials by correlating the bulk electrochemical properties of the cell with their structural and chemical change at multi-scales down to the nanometer level. Cells with LSCF cathodes were prepared, and the effect of Cr poisoning on the electrochemical behavior of the cell was assessed by impedance spectroscopy. The change in nano/microstructure and chemistry due to poisoning were studied in parallel by a combination of advanced ion and electron microscopy techniques including focus ion beam (FIB) tomography, high resolution (scanning) transmission electron microscopy ((s)TEM) and analytical STEM.

     The systematic combination of bulk and high-resolution analysis on the same cells allows, for the first time, to directly correlate Cr induced performance degradation with subtle and localized structural/chemical changes of the cathode down to the atomic scale. Up to two orders of magnitude reduction in conductivity, oxygen surface exchange rate and diffusivity were observed in Cr poisoned LSCF6428 samples. These effects are associated with the formation of nanometer size SrCrO4; grain boundary segregation of Cr; enhanced B-site element exsolution (both Fe and Co); and reduction in the Fe valence, the latter two being related to Cr substitution in the LSCF phase. The finding that significant degradation of the cathode happens before obvious microscale change points to new critical SOFC degradation mechanisms effective at the nanometer scale and below, which provide new insight for the development of future poisoning resistant electrode materials not only for SOFCs but also for other devices such as solid oxide electrolysis cells.

References

[1]       M.C. Tucker, H. Kurokawa, C.P. Jacobson, L.C. De Jonghe, S.J. Visco, J. Power Sources 160 (2006) (1) 130.

[2]       S.P. Jiang, X.B. Chen, Int. J. Hydrog. Energy 39 (2014) (1) 505.

[3]       S.N. Lee, A. Atkinson, J.A. Kilner, J. Electrochem. Soc. 160 (2013) (6) F629.
Atomistic Simulation of Solid Electrolyte Interphase (SEI) Using Reactive Force Field
Authors: Choi Woon Ih , Park Min Sik , Shim Youngseon , Lee Hyo Sug , Shin Jaykwang
Published: February 2020

Although solid electrolyte interphase (SEI) is of critical importance for battery performance, its theoretical understandings doesn’t reach the stage of practical uses to predict and guide interfacial chemistry for the purpose of improving battery cycle life. Among many approaches, molecular dynamics using reactive force field (ReaxFF) offers possibilities that describe complex chemistry of SEI in the level of atomistic scale. By mimicking electrochemistry that mixture electrolyte experiences in the context of charge-discharge, we were able to make theoretical SEI. In particular, we focus on FEC-derived SEI which is known to be effective on Si anode. We introduced several assumptions in our computational setting, which were inevitable for the sake of modeling. The potential and limitations of our modeling will be discussed by comparing computational results with recent in-situ experiments available in the literature.
Ab Initio Calculations of Ionic Conductivity in Lithium and Sodium Polyborate Solid Electrolytes
Authors: Wood Brandon C. , Varley Joel , Kweon Kyoung , Stavila Vitalie , Udovic Terrence John
Published: February 2020

A subset of alkali polyborates have recently been identified as highly promising solid electrolytes for next-generation batteries due to their superionic transition temperatures approaching room temperature and ionic conductivities exceeding 0.1 S/cm–1. However, the exact mechanisms driving the transport in these materials remain largely unknown. Here we use large-scale ab initio molecular dynamics calculations to characterize the diffusivity of the Li and Na species in a representative set of B12H12- and B10H10-based closoborane ionic conductors, focusing on the role of stoichiometry, volume, and dopant incorporation in enhancing ionic conductivity. Detailed analysis on representative materials is used to elucidate the specific conduction mechanism, which relies on frustrated competition between longer- and shorter-range interionic interactions. Our results support this class of materials as highly promising solid electrolytes and offer insights that can be used to tailor conductivity and stability for their use in next-generation battery technologies.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Na10TiP2Se12 As Novel Electrolyte for All-Solid-State Na-Battery
Authors: Zhang Dehui , He Liqing , Wu Dong , Lu Zhouguang
Published: February 2020

All-solid-state battery has the advantages of high safety, good stability and simple configuration [1]. To develop electrolytes with outstanding ion conductivity and stable and wide electrochemical window is indispensible for eventually commercial application of all-solid-state batteries [2,3]. Up to now, many kinds of solid electrolytes have been successfully prepared [4]. Herein, we designed and synthesized a novel kind of solid electrolyte material of Na10TiP2Se12 by a simple low temperature solid state method. The as synthesized Na10TiP2Se12 shows brown in color and exhibits a completely new structure (as shown in Figure 1) different from all raw materials which means the successful synthesis. The ionic conductivity of the as synthesized Na10TiP2Se12 at room temperature is determined to be 6.17×10-7S/cm by preliminary AC impedance measurement. Experiment conditions have been optimized to further improve the conductivity and stability of this solid electrolyte.

Acknowledgements

This work was financially supported by the Shenzhen Peacock Plan (KQCX20140522150815065)，the Natural Science Foundation of Shenzhen ( JCYJ20150331101823677) and the Science and Technology Innovation Foundation for the Undergraduates of SUSTC(2015x19 and 2015x12)

 

Reference

[1]Etacheri V, Marom R, Elazari R, et al. Challenges in the development of advanced Li-ion batteries: a review [J]. Energy & Environmental Science, 2011, 4(9): 3243-3262.

[2]He L, Li H W, Nakajima H, et al. Synthesis of a bimetallic dodecaborate LiNaB12H12 with outstanding superionic conductivity[J]. Chemistry of Materials, 2015, 27(16): 5483-5486.

[3]Richards W D, Tsujimura T, Miara L J, et al. Design and synthesis of the superionic conductor Na10SnP2S12[J]. Nature Communications, 2016, 7.

[4]Solid electrolytes: general principles, characterization, materials, applications[M]. Elsevier, 2015.

Figure 1
A Novel Solid Electrolyte Material (Li17Ge2P3S20) with High Ionic Conductivity
Authors: Wu Dong , He Liqing , Zhang Dehui , Lu Zhouguang
Published: February 2020

Organic liquid compound electrolytes are widely applied in conventional lithium-ion batteries. However, their disadvantages of unsafety and complexity of battery fabrication can hardly be avoided [1]. All-solid-state batteries without using liquid electrolytes provide an effective way to overcome these problems and studies on this field are increasing [2]. Solid electrolyte material is the critical factor to affect the electrochemical and cycle performances of all-solid-state batteries. For commercial application of all-solid-state batteries, high ionic conductivity and cyclability at room temperature are indispensable. Metal sulfides are in great potential to meet the practical application as solid electrolytes and a series of solid sulfur compounds with high ionic conductivities have been reported [3,4]. In this work, a new material Li17Ge2P3S20 with new crystal structure has been synthesized via a simple solid state reaction. The new structure is detected using XRD patterns as shown in Figure 1. AC impedance has been performed and the ionic conductivity of Li17Ge2P3S20 is determined to be 8.07×10-3 S/cm at room temperature. Experimental parameters have been optimized and elemental doping has been utilized to enhance the conductivity and stability of this material as solid electrolyte for all-solid-state lithium ion batteries.

Acknowledgement

This work was financially supported by the Shenzhen Peacock Plan (KQCX20140522150815065)，the Natural Science Foundation of Shenzhen ( JCYJ20150331101823677) and the Science and Technology Innovation Foundation for the Undergraduates of SUSTC(2015x19 and 2015x12)

References:

[1] Etacheri V, Marom R, Elazari R, et al. Challenges in the development of advanced Li-ion batteries: a review[J]. Energy & Environmental Science, 2011, 4(9): 3243-3262.

[2] Notten P H L, Roozeboom F, Niessen R A H, et al. 3‐D integrated all‐solid‐state rechargeable batteries[J]. Advanced Materials, 2007, 19(24): 4564-4567.

[3] Kamaya N, Homma K, Yamakawa Y, et al. A lithium superionic conductor[J]. Nature materials, 2011, 10(9): 682-686.

[4] Kato Y, Hori S, Saito T, et al. High-power all-solid-state batteries using sulfide superionic conductors[J]. Nature Energy, 2016, 1: 16030.

Figure 1
Influence of Solid Electrolyte Interphase Stabilization on Cycling Performance of Silicon-Graphite Composite Battery Anodes
Authors: Kim Jaeram , Jo Hyuntak , Nguyen Dan Thien , Jeon Do-Man , Yang A-Reum , Song Seung-Wan
Published: February 2020

Silicon-graphite composites have drawn significant attention as promising anode materials for higher energy density Li-ion batteries due to larger theoretical specific capacity of silicon than currently commercialized graphite.1 They, however, suffer from a large volume change during lithiation and delithiation, causing the particle cracking, structural degradation of the electrode, an instability of the solid electrolyte interphase (SEI) and finally leading to poor cycle life. In order to address the problems, several strategies in the aspects of improved electrical conductivity and buffering effect of volume change have been developed but the fabrication of silicon composites with carbon materials combined with the use of functional binder and electrolyte additives 2-
4 are recognized as a promising approach. In this presentation, we report the control of electrode-electrolyte interfacial reaction and the formation of a stable SEI layer using various additives, and SEI characterization using ATR FTIR spectroscopy combined with X-ray photoelectron spectroscopy.

In the conventional electrolyte of 1M LiPF6/EC:EMC (3:7 volume ratio), the half-cell with Si-graphite composite anode, which is cycled between 0.01 and 1.5 V at the rate of 0.2C, shows a rapid capacity fade and a low capacity retention of 68 % at the 50th cycle. On the contrary, the cell with the designed blended additives yields improved capacity retention to 81 %, with well-maintained coulombic efficiency of higher than 99 %. Further studies of additive-dependent SEI composition and stability and their correlation to cycling performance would be discussed in the meeting.

Acknowledgements

This research was supported by the Korean Ministry of Trade, Industry & Energy (10049609), and Nano-Material Technology Development Program by the Ministry of Science, ICT and Future Planning (2009-0082580).

 

References

1. Y. Zhang, X.G. Zhang, H.L. Zhang, Z.G. Zhao, F. Li, C. Liu, and H.M. Cheng, Electrochim. Acta, 51, 4994 (2006).

2. S.-W. Song. and S.-W. Baek, Electrochem. Solid-State Lett.,
12, A23 (2009).

3. J.-S. Kim, C. C. Nguyen, H.-J. Kim, and S.-W. Song, RSC Adv., 4, 12878 (2014).

4. D. T. Nguyen, J. Kang, K. M. Nam, Y. Paik, and S. W. Song, J. Power Sources, 303, 150 (2016)
Fabrication and Evaluation of Silver-Indium Catalysts for Electrochemical CO2 Reduction to CO
Authors: Park Hyanjoo , Choi Jihui , Kim Hoyoung , Hwang Eunkyoung , Ha Don-hyung , Paik Taejong , Ahn Sang Hyun , Kim Soo-Kil
Published: February 2020

CO2 has been one of the problematic greenhouse gases, and there have been a lot of efforts to reduce it through capturing, storage, and conversion [1,2]. Ultimately, CO2 needs to be reduced to high energy state fuels including CO. However, CO2 is stable molecule and requires high potential for electrochemical reduction process. Also, hydrogen evolution reaction (HER) occurs at similar potential, thus a selective catalytic reduction is essentially required for electrochemical reduction of CO2 to fuels, in this case CO [3]. So far, Au and Ag catalysts have been studied extensively as candidate catalysts for CO production [4]. Even though Au has provided slightly higher activity, Ag is continuously suggested as a reliable candidate with cost effectiveness.

 In this work, we developed AgIn catalysts through co-deposition method. It has been known to have large overpotential to HER, which will improve the selectivity of Ag in production of CO over H2. The co-electrodeposition was done through controlling the ratio of amounts of In and Ag precursors in the deposition bath. The fabricated catalysts were analyzed through FE-SEM for surface analysis, EDS to find out Ag and In composition, and XRD to identify the crystal structure and degree of alloy. Also, chronoamperometry (CA) was used to measure and calculate CO2 reduction efficiency using home-made H type cell. Gas chromatography (GC) was used to analyze produced amounts of CO. The results showed that AgIn catalysts was deposited in dendritic morphology and showed much better CO faradaic efficiency than Ag only catalysts.

 Reference

 1. Lu, Q.; Rosen, J.; Zhou, Y.; Hutchings, G. S.; Kimmel, Y. C.; Chen, J. G.; Jiao, F. Nat Commun
2014, 5.

 2. Rosen, J.; Hutchings, G. S.; Lu, Q.; Rivera, S.; Zhou, Y.; Vlachos, D. G.; Jiao, F. ACS Catalysis
2015, 5, 4293.

 3. Hall, A. S.; Yoon, Y.; Wuttig, A.; Surendranath, Y. Journal of the American Chemical Society
2015, 137, 14834.

 4. Zhou, L. Q.; Ling, C.; Jones, M.; Jia, H. Chemical Communications
2015, 51, 17704.
Electrochemical Conversion of Carbon Dioxide on the Exfoliated Single-Crystal Copper Membranes
Authors: Yoshihara Naoki , Noda Masaru
Published: February 2020

The electrochemical conversion of carbon dioxide (CO2) enables to produce hydrocarbons, which are widely utilized as fuels or industrial feedstock, at ambient pressure and room temperature. In addition, due to the improved power generation technology using renewable energy sources such as solar and wind, CO2 electrochemical conversion has attracted a great deal of interest as a novel technique to realize a sustainable carbon cycle [1-2]. In our previous work, single-crystal copper membranes were prepared by sputtering on specific support substrates such as c-plane sapphire or magnesium oxide [3]. CO2 conversion on our crystalline copper membranes evolved hydrocarbons more favorably than on commercial copper plates. However, a surface of such epitaxially grown copper membranes is no atomically flat. For CO2conversion into hydrocarbons effectively, the electrode of high quality and smooth single-crystal copper is required.

In this work, CO2electrochemical conversion was studied on the single-crystal copper membranes peeled off from a support substrates.In the experiments, single-crystal copper membranes used as the working electrode (WE) were deposited onto c-plane sapphire substrates with a power of 200 W at 200 °C by radio frequency magnetron sputtering (RFS-200S, ULVAC Corp., Japan) for 5 hr. The copper membranes deposited onto c-plane sapphire were identified as Cu(111) by XRD measurement. The crystalline copper membrane is able to be peeled away from a support substrate.

Figure 1 shows cyclic voltammograms on the exfoliated single-crystal copper membranes in the CO2-saturated 0.25 M K2HPO4+KH2PO4 electrolyte at a scan rate of 10 mV/s. In topside of the exfoliated copper membrane faced on a surface of c-plane sapphire, a significant decrease in current density started from −0.5 V vs. RHE, while those on backside started from −0.6 V vs. RHE. This suggests that an activity of CO2electrochemical conversion was contributed the surface smoothness of a copper membrane in addition to that of the crystallinity.

We also show hydrocarbon emissions for CO2conversion on the exfoliated single-crystal copper membranes, and the electrochemical mechanism based on carbonate ions concentration in the electrolyte is discussed.

Acknowledgement

This work is supported by the Shiraishi Scientific Research Grant.

Reference

[1] Y. Hori, I. Takahashi, O. Koga, and N. Hoshi, Journal of Molecular Catalysis A: Chemical, 199, 39–47 (2003).

[2] K. J. P. Schouten, E. P. Gallent, and M. T. M. Koper, ACS Catal., 3(6), 1292–1295 (2013).

[3] N. Yoshihara, M. Arita, and M. Noda, ECS Transactions, 66(24), 83-89 (2015).

Fiugre 1 Cyclic voltammograms for CO2 conversion on topside and backside of the single-crystal copper membranes peeled off from the c-plane sapphire substrates in the CO2-saturated 0.25 M K2HPO4+KH2PO4electrolyte.

Figure 1
NO Electrochemical Reduction on Pt Electrocatalysts: A DFT Approach
Authors: Chun Hee-Joon , Apaja Vesa , Honkala Karoliina , Greeley Jeff
Published: February 2020

Electrochemical denitrification is a promising technology for the removal of toxic nitrate and nitrite species from groundwater due to the process’s environmental compatibility, energy efficiency, safety, and product selectivity[1]-[3]. The adsorbed NO is generally considered to be a selectivity-determining species during this electrochemical potential-dependent reaction[4], [5]. Atomic-scale studies using density functional theory (DFT), in turn, can provide powerful molecular-level information about the elementary mechanisms of reductive NO electrocatalysis, and these basic building blocks can further serve as a starting point for future trends-based analysis on different transition metal surfaces.

In this work, we employ periodic, self-consistent DFT calculations to clarify the adsorption structures and thermochemistry of NO and its related reaction intermediate species on different Pt single crystal surfaces ((111) and (100)). Kinetics are further determined by calculating the activation barriers for N-O dissociation, protonation, and N-N bond formation. We begin by describing results for the reaction at low NO coverage (ca. 0.11 ML). After describing the thermodynamics (the adsorption) and kinetics (N-O bond breaking and protonation barrier) for the dentirification reaction scheme, a plausible mechanistic reaction pathway is proposed. Water-assisted protonation barriers are generally shown to be lower than barriers for non-electrochemical reactions, such as surface hydrogenation or N-O bond breaking[6]. Consistent with available experimental evidence, from the most probable reaction pathway, we conclude that ammonium ion would be the most favorable product that would evolve. There is no evidence for the formation of hydroxylamine (H2NOH) at low coverage. At higher NO coverages (ca. 0.45 ML), the relative energy states of the intermediates show a similar trend for the energetics when it is compared with the study with lower NO coverage. Next, N2O formation is examined. We find that trans-(NO)2 species could be a precursor state for the N­2O formation due to its lower kinetic barrier than barriers that are found for cis-type NO dimers. The simulation demonstrates that N2O could be formed at higher potentials through two protonations of trans-(NO)2 species, and the reaction is thermodynamically more favorable at higher NO coverage. This barrier could be surmountable at room temperature, and these mechanistic conclusions hold on both the (111) and (100) surfaces.

Finally, using the DFT results to determined rate constants, we construct a detailed kinetic Monte Carlo model of the overall NO electroreduction network. The model accurately tracks experimental NO stripping curves and provides estimates of the degrees of rate control of elementary reaction steps.
Strong Photoluminescence and Thermal Stability of Eu(III) Coordination Polymers with Thiophene-Based Bridge
Authors: Hirai Yuichi , Nakanishi Takayuki , Kitagawa Yuichi , Fushimi Koji , Hasegawa Yasuchika
Published: February 2020

Lanthanide coordination compounds, composed of lanthanide ions (Ln(III)) and specific organic ligands, are widely known to show sharp and strong emission due to the nature of f-f transition in lanthanide ions.1They are promising candidates for LEDs, chemical sensors, and solar cells applications. In order to compensate the small absorption coefficients of Ln(III) ions, various types of antenna ligands have been developed to harvest and transfer the energy from the light source to the Ln(III) ions through ligand to metal energy transfer upon excitation.

Our group have previously reported that the Ln(III) coordination polymers with phenylene-based bridging ligands show thermal stability above 300˚C due to the intermolecular CH/F and CH/π interactions.2

In this presentation, we demonstrate the design and synthesis of novel Ln(III) coordination polymers composed of Eu(III) ions, beta-diketonates, and thiophene-based bridging ligands in order to estabilish both high emission quantum yields and thermal stability. The decomposition temperature of these coordination polymers are estimated to be above 300˚C. According to the single crystal X-ray analyses, multiple intermolecular CH/F interactions are observed between single polymer chains because of the zig-zag coordination structure. They also exhibit intense red emission which is detectable to the naked eye under daylight. Emission spectra, quantum yields (Φ
total,
Φ

Ln), and lifetimes (τ
obs) are also measured to estimate the photophysical parameters such as radiative and non-radiative constants (k
r and k
nr, respectively).

References

1. J.C.G. Bünzli, C. Piguet, Chem. Soc. Rev., 34, 2005, 1048.

2. K. Miyata, T. Ohba, A. Kobayashi, M. Kato, T. Nakanishi, K. Fushimi, Y. Hasegawa, ChemPlusChem, 77, 2012, 277.
High Photostability of Fluorescent InP/ZnS Quantum Dots Embedded in Tmas-Derived Silica
Authors: Watanabe Taichi , Wada Chikako , Iso Yoshiki , Isobe Tetsuhiko , Sasaki Hirokazu
Published: February 2020

InP/ZnS core/shell quantum dot (QD) is suited to application to white LEDs, but the photoluminescence (PL) intensity decreases under continuous photo-excitation. This QD degradation is attributed to photo-oxidation, so it is needed to avoid contact between QD and air. In this study, we embedded InP/ZnS core/shell QD into tetramethylammonium silicate (TMAS)-derived silica monolith to improve its photostability.

Hydrophilization of InP/ZnS QD capped with 1-dodecanethiol was needed for embedding them into silica. For ligand exchange, 3-mercaptopropionic acid (MPA) was injected into a colloidal solution of InP/ZnS QD capped with 1-dodecanethiol at 240 °C. Then, InP/ZnS QD capped with MPA was dispersed in TMAS aqueous solution. Methyl L-(−)-lactate was added to the solution for gelation. Monolithic InP/ZnS@TMAS-derived silica composite was obtained after drying. InP/ZnS@polymethylmethacrylate (PMMA) composite was also prepared to compare with InP/ZnS@TMAS-derived silica composite in terms of photostability.

QD-silica composite exhibited high transparency due to homogeneous dispersion of InP/ZnS QD capped with MPA in TMAS aqueous solution. Carboxyl group of MPA is deprotonated under basic conditions, so InP/ZnS QD capped with MPA possesses negative charge in the basic TMAS aqueous solution. This causes electrostatic repulsion between QD and silicate anion, and hence high dispersibility of InP/ZnS QD capped with MPA in TMAS aqueous solution. The emission peak of InP/ZnS@TMAS-derived silica composite under 400 nm excitation was observed at 543 nm. To evaluate photostability, we examined PL intensity after continuous excitation for 180 min. PL intensity of InP/ZnS QD capped with MPA after continuous excitation was only 25% of the initial PL intensity. On the other hand, InP/ZnS@TMAS-derived silica composite retained 90% of the initial PL intensity. This result means protecting QD against air achieves high photostability. Furthermore, InP/ZnS@TMAS-derived silica composite was more photostable than InP/ZnS@PMMA composite, which retained 68% of the initial PL intensity. This indicates that the gas-barrier property of TMAS-derived silica is higher than that of PMMA.
Europium Tetrakis Dibenzoylmethide Triethylammonium: Synthesis, Additives, and Applications Review
Authors: Fontenot Ross , Bhat Kamala , Hollerman William A , Aggarwal Mohan
Published: February 2020

There are a number of techniques currently being used for damage detection and monitoring of civil, aerospace, and military structures and aircraft. However, the major drawbacks of the current techniques are that they do not provide in-situ and distributed sensing. Wiedemann and Schmidt defined triboluminescence (TL) as the emission of light produced by mechanical action. In recent years, triboluminescent materials have been proposed for use as the active element in smart structural sensors. To sense damage, these materials would be embedded into the structure. If damage occurs to this structure, the embedded triboluminescent material would give off visible light. This light could be transferred by lightweight fiber optics or wireless detector to a computer-based detection system to warn occupants in real time that a significant impact event has occurred. In addition, the triboluminescent based sensor could allow for real-time monitoring of both the magnitude and location of damage to the host structure. One of the brightest TL materials currently known is europium tetrakis dibenzoylmethide triethylammonium EuD4TEA.Since 2011, the authors have delved into the feasibility of enhancing the properties of EuD4TEA by (a) modifying the synthesis process and (b) determining the reproducibility of the synthetic procedure by measuring the batch variation error. Further, the study evaluated the possible techniques that can be incorporated in to the synthesis technique to enhance the TL property by (i) introducing various inorganic and organic dopants; (ii) optimizing dopant concentration; (iii) studying solvents effects on TL property; and (iv) evaluating the effects of ionizing radiation on TL properties. In addition, this research developed a simple apparatus for the measurement of TL properties in the laboratory using a two-fold technique consisting of measuring TL intensity and/or spectral characterization. This enabled for the determination of a unique decay time for a particular compound. In addition, impact studies have been conducted to correlate the impact energy (velocity) with TL emission, thus allowinga system to detect and evaluate the magnitude of the impacts. The spectra of these compounds have been analyzed in detail to investigate the cause of luminescence and designate the transitional energy levels for each of the peaks. The effect of introducing EuD4TEA into poly(methyl methacrylate) and its impact on the TL emission spectra were determined for sensor applications. This poster will provide a review of the important results of this research.
Non-Precious Metal Electrocatalysts for the Oxygen Reduction Reaction Based on Nitrogen Doped Graphene: Catalysts Development and Electrode Structure Design
Authors: Miecznikowski Krzysztof , Dembinska Beata , Zoladek Sylwia , Rutkowska Iwona Agnieszka , Skunik-Nuckowska Magdalena , Negro Enrico , Kulesza Pawel J , Di Noto Vito
Published: February 2020

The design of new functional nanomaterials for developing new electrocatalysts for oxygen reduction reaction (ORR) in acid and alkaline media. The research has been focused on developing carbon nanostructures especially graphene/graphene oxide materials with superior structural and functional properties for fuel cell applications. Electrocatalysts based on graphene and graphene-oxide (GO) are more homogeneous and possess properties such as excellent conductivity, good chemical stability and can be functionalized in a controlled manner. To facilitate fabrication, immobilization and distribution of non-precious metal nanoparticles, various types of graphene (e.g. reduced graphene oxide, RGO, and CFx graphene with carbon black) have been modified with the different transition metals (e.g. Co, Ni, Ag, Au, Cu, Mn) analogue of polynuclear Prussian Blue, namely with ultra-thin Co, and Ni hexacyanoferrate layers. Following the heat-treatment step at higher temperatures, some thermal decomposition of the cyanometallate network occurs and, consequently, metallic sites are generated. Their formation and distribution are facilitated by the voltammetric potential cycling in KOH electrolyte. The most promising electrocatalytic results with respect to the reduction of oxygen (the highest currents and the most positive electroreduction potentials) have been obtained when graphene nanostructures are combined or intermixed with Vulcan XC-72R nanoparticles. What is even more important that, due to the presence of the polynuclear cyanoferrate modifier or linker, the amounts of the undesirable hydrogen peroxide intermediate are significantly decreased. An electrocatalytic system, that utilizes metal hexacyanometallates nanoparticles modified graphene and graphene related materials, is developed and characterized here using transmission electron microscopy and such electrochemical diagnostic techniques as cyclic volammetry and rotating ring-disk voltammetry in a 0.5 M H2SO4 electrolyte and in a 0.1 M KOH electrolyte and upon introduction (as cathode) to the low-temperature hydrogen-oxygen fuel cell. Comparative measurements have been performed against the model noble metal (Vulcan-supported platinum nanoparticles) catalyst.
A Bifunctional ZnCo2O4 Electrocatalyst Derived from Zeolitic Imidazolate Frameworks for Oxygen/Hydrogen Evolution Reaction in Alkaline Media
Authors: Lee Lanlee , Bang Jin Ho
Published: February 2020

Development of bifunctional catalysts for oxygen/hydrogen evolution reaction has received greatly attention lately as fuel cells whose sources are oxygen and hydrogen are one of the possible alternatives for the current fossil fuel based energy resources. In particular, it has been important to design a materials that enables both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline electrolyte due to the difficulties of OER. Herein, porous ZnCo2O4 has been successfully synthesized as a bifunctional electrocatalyst by calcining a precursor derived from zeolitic imidazolate frameworks and characterized by various analytic methods such as X-ray diffraction, electron microscopy, and nitrogen adsorption/desorption analysis. Porous ZnCo2O4 shows a much lower overpotential than that of IrO2 which is an OER benchmarking catalyst. Furthermore, ZnCo2O4 also exhibits the electrocatalytic activity for HER in alkaline environment. The electrocatalytic performances have been investigated by electrochemical analyses.
Comparison of Voltammetric Techniques for the Electroanalysis of Dissolved Solids and Gases in Water, Acetonitrile and Room Temperature Ionic Liquids (RTILs): Unusual Behaviour for Gases
Authors: Hussain Ghulam , Silvester Debbie S.
Published: February 2020

Square wave voltammetry (SWV) and differential pulse voltammetry (DPV) are commonly used in electroanalysis, typically in aqueous solvents, as they are usually an order of magnitude more sensitive than linear sweep voltammetry (LSV)/cyclic voltammetry (CV), (e.g. detection limits as low as nanomolar are possible using SWV). These more sensitive techniques are often applied in the development of electrochemical sensors and biosensors over the last ten years due to the negligible capacitive current compared to faradaic current (in protic solvents).1,2 Over the last two decades there has been great attention focused on the improvement of electrochemical gas sensors to monitor toxic gases using amperometric gas sensors (AGSs), which typically employ water/sulphuric acid electrolytes as solvents. Room temperature ionic liquids (RTILs) have been attracting great attention3 as replacement electrolytes in AGSs due to their unique physical properties such as low volatility and negligible vapor pressure, wide electrochemical windows, high ionic conductivity, high chemical and thermal stability and their ability to dissolve a wide range of gases. To the best of our knowledge, there are limited studies on the sensitivity of SWV, DPV and LSV for the sensing of gaseous analytes in RTIL solvents. In this presentation, a comparison of three different electrochemical techniques (SWV, DPV and LSV) will be employed for two gases (ammonia and oxygen) in RTILs. As a control, oxygen gas will also be studied in acetonitrile and water solvents, and dissolved solid analytes are also studied (K3Fe(CN)6in water, ferrocene in acetonitrile and ferrocene in RTILs). For all dissolved solid analytes, SWV gave the highest current response compared to DPV and LSV, respectively. For dissolved gases, the behavior was different. For oxygen, LSV gave larger currents (although relatively comparable) to SWV, with DPV giving the lowest currents. For ammonia, LSV was far superior to both SWV and DPV and was consistent throughout eight different RTIL solvents. This suggests that the generally accepted methods for low concentration analyte detection may not apply for dissolved gases.

References:

(1) Carl H. Hamann, A. H., Wolf Vielstich. Electrochemistry, 2nd, Completely Revised and Updated Edition; Wiley-VCH, Weinheim, 2007, p 550.

(2) Chen, A.; Shah, B. Analytical Methods
2013, 5, 2158-2173.

(3) Buzzeo, M. C.; Hardacre, C.; Compton, R. G. Analytical Chemistry
2004, 76, 4583-4588.
Molybdenum-Based Nanomaterials As High Efficient Electrocatalysts for HER
Authors: Wu Zexing , Wang Jie , Xin Huolin L. , Wang Deli
Published: February 2020

a, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China

b, Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA

* Email: wangdl81125@hust.edu.cn

Electrochemical hydrogen evolution reaction (HER) as an efficient and eco-environmental approach to produce hydrogen has attracted tremendous attention1. Currently, the most efficient catalysts for HER are platinum group metals (e.g. Pt). However, the scarcity and high cost of precious metals limit their large-scale applications2. Therefore, it is of great importance to explore highly active catalysts for HER based on earth-abundant materials for the large scale hydrogen generation in both acid and alkaline media3.

Here, carbon supported different molybdenum-based materials (MoP, MoS2, Mo2C) have been systematically synthesized via a simple solvothermal-high temperature treatment method. Different morphologies were obtained such as few layers and nanoparticles structures (Figure 1a and b). Electrochemical tests reveal that the prepared molybdenum- based electrocatalysts exhibit excellent HER performance in both acid and alkaline electrolytes (Figure 1c and d). This could be attributed to the excellent conductivity and the exposed substantial active sites for the nano-structure. In acid medium, carbon supported MoP exhibits the best catalytic activity for HER with an overpotential of 136 mV at a current density of 10 mA cm-2. While Mo2C-C possess the most predominant catalytic performance in alkaline medium compared with MoP and MoS2 with an overpotential of 149 mV. Unexpectedly, in the present work, carbon supported MoS2 possess outstanding catalytic activity in both acid and basic electrolytes which is not common for molybdenum chalcogenides reported. This probably due to the low conductivity and strongly layer numbers dependent on the the active sites. Based on the facile preparation method and excellent electrocatalytic activities, this work will open a novelty avenue to prepare earth abundant based catalysts for energy conversion and storage.

Figure 1. TEM images of MoS2-C (a) and Mo2C-C (b). LSVs of molybdenum compounds in 0.5 M H2SO4(c) and 1 M KOH (d).

Acknowledgements

This work was supported by the National Natural Science Foundation (21306060, 21573083), the Program for New Century Excellent Talents in Universities of China (NCET-13-0237), the Doctoral Fund of Ministry of Education of China (20130142120039).

References

1. Y. Jiao, Y. Zheng, M. Jaroniec and S. Z. Qiao, Chem. Soc.

Rev., 2015, 44, 2060-2086.

2. H. Wang, D. Kong, P. Johanes, J. J. Cha, G. Zheng, K. Yan,

N. Liu and Y. Cui, Nano Lett., 2013, 13, 3426-3433.

3. J. Tian, Q. Liu, A. M. Asiri and X. Sun, J. Am. Chem. Soc.,

2014, 136, 7587-7590.

Figure 1