bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Non-Platinum Cathode Catalysts for Direct-Methanol Alkaline Fuel Cells
Authors: Kruusenberg Ivar , Ratso Sander , Vikkisk Merilin , Kanninen Petri , Kallio Tanja , Kannan Arunachala Mada , Tammeveski Kaido
Published: February 2020

The development of novel catalyst materials for oxygen reduction reaction (ORR) is one of the key topics in fuel cell research. In order to replace expensive noble-metal based catalysts that have been primarily employed as cathode catalysts in low-temperature fuel cells, different carbon-based materials that possess lower price, better availability and improved chemical stability have been investigated. An attractive approach is to employ nitrogen-containing carbon nanomaterials for this purpose 1-3.

   In this work the electrochemical reduction of oxygen has been studied on nitrogen-doped carbon nanomaterials modified glassy carbon (GC) electrodes. N-doped carbon nanotubes (N-CNT) and N-doped few-layer graphene/carbon nanotube (N-FLG/CNT) composite materials were investigated as catalyst materials. Dicyandiamide (DCDA) was used as nitrogen precursor for nitrogen doping of carbon nanomaterials. The doping was achieved by pyrolysing nanocarbon materials in the presence of DCDA at 800 °C. The CNT or FLG/CNT-to-nitrogen precursor mass ratio was 1:20. Electrochemical experiments were carried out in 0.1 M KOH using the rotating disk electrode (RDE) method. GC electrodes were modified using carbon nanomaterial suspension in isopropanol in the presence of Fuma-Tech FAA3 ionomer. The fuel cell performance of N-doped carbon materials was investigated by fabricating membrane-electrode assemblies (MEAs) using Fuma-Tech FAA3 membrane and for comparison purposes a commercial Pt/C catalyst was used as cathode material.

  The RDE experiments showed extraordinary electrocatalytic activity of N-doped carbon nanomaterials toward the ORR in alkaline media.  A comparative study of direct methanol alkaline fuel cell performance was also performed. The power density curves are presented in Fig. 1. The MEAs with N-CNT, N-FLG/CNT and commercial 60% Pt/C cathode catalysts had power densities of 0.92, 0.72 and 0.72 mW cm−2 respectively, using methanol as fuel on anode side and pure O2 gas on cathode side. The results obtained in this work show that N-FLG/CNT and N-CNT catalysts possess excellent ORR activity in alkaline media and could be used as alternative cathode catalysts in alkaline anion-exchange membrane fuel cells.

References

1. I. Kruusenberg, S. Ratso,  M. Vikkisk, P. Kanninen, T. Kallio, A.M. Kannan, K. Tammeveski, J. Power Sources, 281, 94, 2015.

2. M. Vikkisk, I. Kruusenberg, U. Joost, E. Shulga, I. Kink, and K. Tammeveski, Appl. Catal. B: Environ.,
147, 369, 2014.

3. S. Ratso, I. Kruusenberg, M. Vikkisk, U. Joost, E. Shulga, I. Kink, T. Kallio, and K. Tammeveski, Carbon, 73, 361, 2014.

Figure 1
Design of Low pH Stable and Highly Active (Ti, Zn) Doped RuO2 Electrocatalysts for Electrochemical Water Oxidation
Authors: Kishor Koshal , Saha Sulay , Gupta Manish Kumar , Bajpai Anshuman , Chatterjee Moitrayee , Sivakumar Sri , Pala Raj Ganesh
Published: February 2020

High overpotential, low stability and cost of the electrocatalysts represent significant challenges for oxygen evolution reaction (OER) operating in the acidic medium. In this regard, blending active (usually unstable) and passive (usually not active) components is one of the methods to tackle this challenge. Here, active Zn and passive Ti are blended in Ru-based oxides through co-electrodeposition method. The composition of the electrodes has been optimized by controlling the electrodeposition bath concentration. The surface roughness of the resultant electrode is increased due to introduction of ‘chemical inhomogeneity’ by Ti and ‘structural inhomogeneity’ through Zn.  It has been found that incorporation of Zn and Ti additives increase both activity and stability of electrodes.  The maximum catalytic activity is found in the composition of Ru0.259Ti0.736Zn0.006Ox with a current density of 63mA/cm2 at an operating voltage of 1.35V (vs Ag/AgCl). The activity of this electrode is four times higher than electrodeposited RuO2 and also higher than other possible binary combinations in Ru-electrodes (RuTi, RuZn). The stability of the electrodes among the co-electrodeposited electrodes are found to be in order of co-electrodeposited RuZn<co-electrodeposited RuTi<co-electrodeposited RuTiZn.The increase in catalytic activity of the co-electrodeposited electrodes can be attributed to the combination of lowering of activation energy thereby increasing site activity and increase of available active sites due to promotion of roughness in surface by the Zn and Ti. The increased stability may be attributed to intermixing of additives leading to formation of porous stable surface layer as suggested by impedance spectroscopy.
Computational Simulation of Thermal and Chemical Phenomena for a Honeycomb-Structured Catalytic Reforming Reactor
Authors: Raoufi Arman , Kapadia Sagar , Newman James C.
Published: February 2020

A fully coupled numerical simulation is used to investigate the catalytic partial oxidation of methane over a honeycomb-structured Rh/Al2O3 coated catalyst. The transport of mass, momentum, energy and species in a reforming reactor are simultaneously solved using a three dimensional fully implicit unstructured finite volume approach. The nonlinear system of equations is solved by Newton’s method. Eight gas-phase species (CH4, CO2, H2O, N2, O2, CO, OH and H2) are considered for the simulation. The surface chemistry is modeled by detailed reaction mechanisms including 38 heterogeneous reactions with 20 surface-adsorbed species for rhodium catalyst and solved using the mean-field approximation model to obtain the surface convergence and reaction rates. The numerical results are compared with the experimental data and good agreement is observed. The simulation is performed for a reforming reactor with a channel density of 600 cpsi (channels per square inch). The governing equations for fluid and solid regions of the monolith are simultaneously solved with considering the catalytic combustion at their interface. The performance of the reforming reactor is numerically studied. A finite element approach is used to obtain the thermal stresses based on the temperature field obtained from the solid/fluid FVM solver.

Figure 1
Comparision of Electrochemical Properties of Lithium Sulfur Battery with Lithium Foil Anode and Li Powder Anode
Authors: Cho Sung Ho , Yoon Woo Young
Published: February 2020

Lithium Sulfur (Li-S) battery has a theoretically high specific capacity of 1675 mAh/g, which one of the most promising energy source for electric vehicles (EVs), hybrid electric vehicles (HEVs). However, Li-S batteries have problems resulting from the polysulfides dissolution into the electrolyte, volumetric extension of sulfur and insulating property of elemental sulfur. These causes make the loss of active materials and the capacity fading phenomenon. Even we address the as-mentioned issues, we necessarily encounter the formation of dendrite on the lithium metal anode. In our research, we use a lithium powder as an anode material to suppress the dendritic issue of lithium metal. The examination was conducted by comparing between the lithium foil and lithium powder. The cyclic voltammetry were tested at the scan rate of 0.1mV/s and 0.5mV/s with voltage range of 1.5V to 3.0V. Cells were tested at the current densities of 0.2 C-rate and 0.5 C-rate with 1.7V to 2.8V.
Focused Ion Beam Reduced Graphene Oxide Micro-Supercapacitors with Unprecedented Energy and Power Densitites
Authors: Chakraborty Banerjee Parama , Lobo Derrek Lobo , Easton Christopher , Majumder Mainak
Published: February 2020

Miniaturization of energy storage devices with high energy and power densities can reduce the footprint of micro-devices being used in our daily life. Micro-supercapacitors with planar geometries offer several advantages, such as, the ability to control and reduce the distances ions travel between two electrodes, easy integration to micro devices as the separator and the electrodes are in the same plane, and offer the potential of being extended into 3D without compromising the inter-electrode separation distances. In this study, we have used focused ion beam technology (which is capable of producing reduced graphene oxide patterns and complex shapes in insulating films of graphene oxide with a possible spatial resolution down to ~20 nm in a mask-less and direct write approach) to directly write miniaturized planar electrodes of reduced graphene oxide on films of graphene oxide (GO).  We have optimised the ion-beam irradiation and have investigated the influence of ion beam irradiation on the resultant microstructure and the electrochemical properties of the resultant reduced graphene oxide films. Subsequently, using the optimized ion-beam irradiation, interdigitated electrode designs (40 μm long and 3.5 μm wide fingers with ultra-small inter-electrode spacing of 1 μm) have been generated, which have demonstrated a large capacitance (102 mF/cm2), ultra-small time response (0.03 ms), low equivalent series resistance (0.35 mΩ cm2), and have retained 95 % of the specific capacitance after 1000 cycles at an ultrahigh current density of 45 mA/cm2.  These performance metrics show unprecedented improvements on several aspects of supercapacitor performance over existing reports due to the miniaturized electrode dimensions and minimal damage to the graphene sheets. We believe our results can provide opportunities for large-scale fabrication of arrayed, planar, high performance micro-supercapacitors with a small environmental footprint.
In Situ Study of Strain-Dependent Ion Conductivity of Stretchable Polyethylene Oxide Electrolyte
Authors: Kelly Taylor , Moradi Ghadi Bahar , Berg Sean , Ardebili Haleh
Published: February 2020

There is a strong need in developing stretchable batteries that can accommodate stretchable or irregularly shaped applications including medical implants, wearable devices and stretchable electronics. There has been a fair amount of work exploring the development and performance of stretchable electrodes, but very little for stretchable electrolytes.  Solid polymer electrolytes are ideal candidates for creating fully stretchable lithium ion batteries because of their mechanical and electrochemical stability, thin-film manufacturability and enhanced safety. However, the characteristics of ion conductivity of polymer electrolytes during tensile deformation are not well understood.

We have investigated the effects of tensile strain on the ion conductivity of thin-film polyethylene oxide (PEO) through an in situ study.  The results of this investigation demonstrate that both in-plane and through-plane ion conductivities of PEO undergo steady and linear growth with respect to the tensile strain.  This increasing trend in conductivity infers that the structural changes induced in the polymer electrolyte results in altered and improved ion conduction.  The coefficients of strain-dependent ion conductivity enhancement (CSDICE) for in-plane and through-plane conduction were found to be 28.5 and 27.2, respectively.

We hypothesize that the stretching and aligning of the amorphous polymer chains decreases the degree of tortuosity in the polymer, allowing for faster, and less obstructed ion transport. Semi-crystalline PEO consists of a crystalline phase and an amorphous phase.  The amorphous phase is generally present along the edges of the crystallites where the polymer chains are disordered, twisted and entangled and tie one crystallite to another.  The semi-crystalline conformation of PEO can be seen using polarization light microscopy, which confirms the growth and extension of the amorphous regions as the chains stretch and disentangle due to tensile strain.

In conclusion, the present work confirms the feasibility of using solid polymer PEO as a stretchable electrolyte for next generation stretchable batteries.
Influence of Porous Separators on the Ionic Conductivity of Nonflammable Liquid Perfluoropolyether Electrolytes
Authors: Devaux Didier , Chang Yu Hao , Villaluenga Irune , Chen Xi chelsea , Chintapalli Mahati , Balsara Nitash P.
Published: February 2020

Conventional Lithium-ion coin cell batteries contain a volatile flammable liquid electrolyte, impregnated in a porous separator. This leads to a serious safety issue with, for example, the possibility of flammable reaction products and internal short-circuits.[1] Commercial microporous polyolefin membranes, made of semi-crystalline polymers as polyethylene (PE) and polypropylene (PP), have been widely used as battery separators. [2] The main functions of the separator are to act as a physical barrier to prevent short-cut between the two electrodes and to allow ionic transport. Ionic transport within the separator depends on several factors such as the separator geometry, porosity and tortuosity, the electrolyte resistance and wettability.[3] Thus, the presence of the separator leads to an effective ionic conductivity lower than the bulk electrolyte conductivity, and an increase of the Li battery internal resistance.

The recent development of non-flammable liquid electrolytes based on functionalized perfluoropolyethers (PFPEs) opened the path of safe Li-ion batteries.[4, 5] PFPE is chemically resistant, non-crystalline, and nonflammable exhibit low glass transition temperature and low toxicity. It was demonstrated that a methyl carbonate-terminated perfluoropolyether (see Figure 1) is suitable for lithium battery operation, but optimization is necessary to improve the performance. So far little is known on the transport properties of this new class of non-flammable liquid electrolytes within the separator. As for any conventional liquid electrolyte, investigating the nature of the separator and its effect on the effective ionic conductivity is required to achieve an optimal battery design.

We investigated the physico-chemical and electrochemical properties of three commercial separators: a PP monolayer, a trilayer PP-PE-PP and a polytetrafluoroethylene (PTFE). The ionic conductivities of low molecular weight PFPEs, with dimethyl carbonate or ethoxylated alcohol end-groups, doped with the lithium salt LiTFSI was measured as a function of the temperature either in the bulk or in the presence of the separators. For comparison, a conventional liquid electrolyte made of 1M LiPF6 in a mixture of ethylene carbonate and dimethyl carbonate was also studied. In addition, the effective ionic conductivity of each electrolyte impregnated in the separator is modeled based on the bulk electrolyte conductivity and a separator morphological form factor.

References

[1] J.-M. Tarascon, M. Armand, Nature, 414 (2001) 359-367.

[2] S. S. Zhang, Journal of Power Sources, 164 (2007) 351-364.

[3] K. M. Abraham, Electrochimica Acta, (1993) 1233-1248.

[4] D.H.C. Wong et al., PNAS, 111 (2014) 3327-3331.

[5] D.H.C. Wong et al., Chemistry of Materials, 27 (2015) 597-603.

Figure 1

Figure 1
Sulfur Impregnated Expanded Graphene Cathode for High Performance Lithium Sulfur Batteries
Authors: Abbas Syed Ali , Wang Pen-Cheng , Chu Chih-Wei
Published: February 2020

Commercialization of high energy lithium sulfur battery (LSB) is hindered by low conductivity of sulfur, dissolution of lithium polysulfide’s in electrolyte and deformation of cathode through volume expansion during charge/discharge phenomenon. In order to address these issues, we present unique one step sulfur impregnated expanded graphene structure (S-EG) by melt diffusion strategy. The hollow structure not only provides a large space for sulfur expansion during cycling, but is also helpful in trapping lithium polysulfides. Moreover, conductive nature of graphene enables higher sulfur utilization. Electrochemical tests disclose that the sample having 64% sulfur content in S:EG(4:1) composite can deliver capacity as high as 1405mAh/g at 0.05C . An ultralow decay of 0.082% per cycle was observed when the battery S:EG(4:1) was run for 1000cycles at 0.25C, which is far superior to pristine sulfur cathode. C-rate tests further confirmed the high retention capability (82%) of sulfur impregnated expanded graphene structure, during the current range of 0.05C to 1C. The versatility of our cathode was also tested by making flexible battery and testing under different stress conditions, hence showing flawless performance, this economical and simple strategy having high sulfur content gives an ideal platform for commercialization of LSB.

Figure 1
Electrochemical Capacitor of MnFe2O4 with Organic Li-Ion Electrolyte
Authors: Chien Jen-Hao , Wu Nae-Lih
Published: February 2020

Compared with batteries, electrochemical capacitors have the potential for providing higher power density and good cyclability. Pseudocapacitance results from either superficial or multi electron-transfer faradaic reactions with fast charge/discharge properties. An increasing number of metal oxides exhibiting pseudocapacitive behaviors have been discovered in recent years. We have previously discovered a new nanocrystalline oxide material having the formula of MnFe2O4that have so far been the only oxide electrode showing pseudocapacitance in both aqueous and organic Li-ion electrolytes. The discovery of this material has opened up the possibility of setting up a high voltage asymmetric supercapacitors of substantially enhanced energy density over the state-of-the-art EDLC organic supercapacitors.

    In this study, MnFe2O4 spinel oxide electrodes was synthesized and characterized for supercapacitor applications using organic Li-ion electrolyte. The change in structure, valence state and local atomic arrangement upon charging/discharging are investigated with in operando X-ray analyses. The operation voltage window is carefully determined in view of leakage current for the upper voltage limit. The lower voltage window is selected to maximize the energy density of the spinel oxide electrode. For the purpose of increasing the energy density of cell up for the demand of electronic devices, asymmetric capacitor is assembled using the spinel oxide as positive electrode and pre-lithiated silicon coated graphite (SGF) as negative electrode. It is shown that the asymmetric capacitor has greatly increased the energy density by asymmetric mass matching between anode and cathode and by extending the overall operation voltage window.

Figure 1
3D Porous Reduced Graphene Oxide Nanostructure As Electrode Materials for High Performance Flexible Gel-Type Supercapacitors
Authors: Lu Shih-Yuan , Wang Chun Chieh , Liang Ji-Yuan
Published: February 2020

Three-dimensional (3D) porous reduced graphene oxide nanostructure, termed starch/RGO, was prepared with a simple, fast, and scalable mix-and-heat process. The starch/RGO was composed of three-dimensionally well-connected reduced graphene oxide network glued together with starch derived carbon. The starch/RGO possessed several critical advantageous structural features, including well-dispersed, readily accessible micropores offering high specific surface areas and well-connected and highly conductive reduced graphene oxide network, making it an excellent electrode material for supercapacitors. The starch/RGO electrode performed well in both positive (0 – 1 V) and negative (-1 – 0 V) potential windows and was used to assemble flexible, gel-type symmetric supercapacitors. The starch/RGO//starch/RGO supercapacitor exhibited outstanding capacitive performances, excellent electrochemical reversibility, and high energy and power densities, the best among previously reported carbon material based gel-type symmetric supercapacitors. It also showed excellent mechanical stability under high angle bending and performed well in a wide temperature range. It is a promising candidate for next-generation supercapacitors, cost-effective, wearable, suitable for roll-to-roll mass production, and applicable in a wide temperature range.
Development of All-Solid-State Structural Supercapacitor Using an Epoxy Based Adhesive Polymer Electrolyte
Authors: Wang Yuchen , Qiao Xiaoyao , Zhang Chen , Karkkainen Ryan L , Zhou Xiangyang
Published: February 2020

While major efforts are paid to increase the specific energy and power of energy storage devices to meet the demand of transport systems, an alternative approach is to turn the structural components of the systems into energy storage devices. For example, an all electric airplane powered by structural supercapacitors or batteries with a relatively low specific energy would fly the same range as one powered by a conventional storage device with a very high specific energy.     

Structural supercapacitors were fabricated according to the schematic shown in Fig. 1. The graphite reinforcement (fiber) is attached with carbon nanofiber and mediators (redox molecules). The matrix is an ionic conducting polymer or adhesive polymer electrolyte. One of the main issues for structural supercapacitor is the low ionic conductivity of adhesive polymer electrolyte as separator and as matrix in reinforcement/electrode. The presence of mediators can increases the ionic conductivity in the electrode area up to 10-2 S/cm. A new method for preparing epoxy adhesive based dual functional polymer electrolyte was adopted. The ionic conductivity of PVDF/LiTFS/epoxy electrolyte can reach to 3x10-3 S/cm. All-solid-state structural supercapacitors with PVDF/LiTFS /epoxy electrolyte and the conventional supercapacitors with a high conductivity liquid electrolyte (0.1 S/cm) are fabricated and tested. They have similar size and weight.  The cyclic voltammetry (CV) curves show that the all-solid-state structural supercapcitors with two electrolytes have a similar specific charge capacity of ~4 mAh/g (Fig. 2 and Fig. 3). Also, the in-plane elastic constant is 1-2 GPa and the in-plane ultimate strength of the all-solid-state structural supercapacitor with PVDF/LiTFS /epoxy electrolyte is 20 MPa. The electrochemical properties and the strength of the structural supercapacitor as functions of the composition of the adhesive electrolyte and the composition of the electrode material are evaluated experimentally.

Figure 1
Nano-Confined Transition Metal Oxide Thin-Films Created Via Electrostatic Spray Deposition for Use As Anode Materials in Lithium Ion Batteries
Authors: Henriques Alexandra , Agrawal Richa , Chen Chunhui , Wang Chunlei
Published: February 2020

The development of high capacity rechargeable lithium-ion batteries is crucial given the insatiable energy demands that come with the rapidly-developing technological landscape. One of the major areas of research focus is the development of high performance advanced electrochemical materials. Transition metal oxides (MxOy) are one of the most widely studied classes of materials given their high theoretical capacities. However, such materials often exhibit large volumetric expansion during the cycling processes due to their lithium storage mechanisms, in addition to poor electronic conductivities. One of the methods to resolve these issues is the confinement of nano-scale particulates of various transition metal oxides with the interest of improving their charge storage capability, rate capability, and the longevity of their performance with cycling. Confinement of metal oxide nanoparticles (e.g. SnO2) within carbon nanotubes has been shown to improve the performance of these anode materials versus unconfined metal oxides. The increased surface area, enhanced interfacial charge storage and enhanced electrical conductivity contribute to improved electrochemical performance. Here, electrostatic spray deposition (ESD) is used to create a thin film of the anode materials of interest for subsequent property testing of the assembled LIBs. This presentation will give the details of the techniques used to produce the desired anode materials and their electrochemical characterization as LIB anodes.
Dimensionally Stable and Fast Charging Graphite-Silicon Planar Composite Anode for Li-Ion Batteries
Authors: Wu Nae-Lih , Yang Nai-Hsuan , Wu Yu-Shiang , Chou Jackey
Published: February 2020

Advanced Li-ion batteries (LIBs) have been developed to have high capacity density, long cycle life, and high-rate performance for portable electronics, electric vehicles (EVs), and renewable energy storage. Graphite is currently the predominant anode material for commercial LIBs because it has a low cost, low charge/discharge plateau potential, satisfactory specific capacity (372 mAh g-1), and substantially high dimensional stability; its essential role in high-energy LIBs is expected to continue. Si is a potential Li-insertion anode material that has a substantially higher capacity than graphite but is susceptible to large (>300% when fully lithiated) volume expansion. The cyclic dimensional variations during charge/discharge cycles result in pulverization and electrical disconnection from the conductive paths of the Si active materials, leading to rapid capacity reduction during the cycles. In spite of a large amount of literature devoted to solving this issue in the past years, long-lasting Si anode up to now remains as a formidable challenge. On the other hand, composite anodes comprising graphite and limited amount of Si or Si oxide may be attractive transient products for advanced high-energy LIBs before viable Si-dominant anodes are realized. Moreover, improvement in the rate capability of Si-based anodes is needed for meeting the power requirements of various applications.

In this presentation, a planar graphite-silicon composite Li-ion battery anode showing substantially higher capacities than graphite, fast-charging capability, and exceptional cycle stability will be described. The Si oxide-coated graphite flake (SGF) composite anode for Li-ion batteries (LIBs) synthesized by a unique microwave-heating process of graphite flakes (GFs) in a solution made of liquid polysiloxanes as the Si-containing precursor. Microwave-heating of the GFs induces the deposition of a conformal Si-containing conformal layer on the GF surfaces, which is subsequently turned into oxide-graphite-oxide sandwiched planar composite structure. The resulting SGF exhibits a reversible specific capacity of nearly 480 mAh g-1, 97% capacity retention at the current density of 2.5 A g-1 (~5C-rate), and 94% capacity retention after 500 cycles with an average Coulombic efficiency > 99.9%. Coating the composite with a thin layer of conducting polymer further enhance the overall specific capacity greater than 520 mAh g-1. The work suggest a new strategy for both designing and synthesizing high-performance anode materials for LIB applications.

Figure 1
Polymer-Templated Carbon Hybridized Nanostructured Transition Metal Oxide As Advanced Lithium-Ion Anodes
Authors: Jiang Beibei , Li Bo , Lin Zhiqun
Published: February 2020

An enormous spectrum of applications of lithium-ion batteries (LIBs), particularly in electric vehicles (EVs), hybrid EVs and electric grids, invokes essential requirements on their energy storage capabilities. However, the most common commercial graphite anode material still exhibits a relatively low theoretical specific capacity of 372 mAh g-1, which cannot meet the demand of the high-energy applications noted above. To date, a wide variety of anode materials with much higher capacities have been extensively investigated. In this regard, transition metal oxides (MxOy, where M is Fe, Co, Ni, Cu, Sn, Mn, etc.) clearly stand out as the promising alternatives to graphite owing to their attractive higher theoretical capacities (＞ 600 mAh g-1), low cost, environmental friendliness and wide availability containing earth-abundant elements. To further achieve high rate capability, hybrid nanomaterials with more conductive carbonaceous materials have been constructured.  The ability to create a synergistic effect of nanostructure engineering and its hybridization with conductive carbonaceous material is highly desirable for attaining high-performance lithium ion batteries (LIBs). However, it remains challenging to achieve this synergy.

Here we propose a general method to create a synergistic effect of nanostructure engineering and its hybridization with conductive carbonaceous material. Star-like and bottlebrush-like poly (acrylic acid)-block-polystyrene (PAA-PS) diblock copolymer and polystyrene-block-poly(acrylic acid)-block-polystyrene (PS-PAA-PS) triblock copolymer with controlled dimensions will be synthesized through atom transfer rapid polymerization (ATRP). Through a strong coordination bonding between the metal moiety of inorganic precursors and the functional groups of PAA (-COOH), the inorganic precursors can be selectively incorporated into the space formed by the PAA block. As a result, nanostructured transition metal oxide solid nanocrystals and hollow nanocrystals can be synthesized guided by the PAA-PS and PS-PAA-PS templates, respectively. In addition, by changing the polymeric templates from star-like to bottlebrush-like structure, the transition metal oxide nanocrystals varied from isotropic (i.e. nanoparticles, hollow nanoparticles) to anisotropic (i.e. nanorods, nanotubes). The diameter of the transition metal oxide nanocrystals is determined by the dimension of the PAA part, and it could be easily changed by varying the molecular weight of PAA part in the polymeric templates. Morever, the polymeric template not only serves as an easy control over the size and shape of the inorganic nanocrystals, but also acts as carbon source when calcinated at high temperature at argon atmosphere. We demonstrated that the carbon-hybridized nanocrystals obtained by the polymer templating method would be superior anode materials for LIBs.
The Influence of Fe Substitution in Lanthanum Calcium Cobalt Oxide on the Oxygen Evolution Reaction in Alkaline Media
Authors: Abreu-Sepulveda Maria , Bridges Craig A , Manivannan A. , Paranthaman Mariappan P , Quesnel David J
Published: February 2020

The effect due to systematic substitution of cobalt by iron in La0.6Ca0.4Co1-xFexO3 towards the oxygen evolution reaction (OER) in alkaline media has been investigated. These compounds were synthesized by a facile glycine-nitrate synthesis and the phase formation was confirmed by X-ray diffraction and Neutron Diffraction elemental analysis. The apparent OER activity was evaluated by quasi steady state current measurements in alkaline media using a traditional three-electrode cell. X-ray photoelectron spectroscopy shows iron substitution causes an increase in the surface concentration of various cobalt oxidation states. Tafel slope in the vicinity of 60 mV/decade and electrochemical reaction order towards OH- near unity were achieved for the unsubstituted La0.6Ca0.4CoO3. A decrease in the Tafel slope to 49 mV/decade was observed when iron is substituted in high amounts in the perovskite structure. The area specific current density showed dependence on the Fe fraction, however the relationship of specific current density with Fe fraction is not linear. High Fe substitutions, La0.6Ca0.4Co0.2Fe0.8O3 and La0.6Ca0.4Co0.1Fe0.9O3 showed higher area specific activity towards OER than La0.6Ca0.4CoO3 or La0.6Ca0.4FeO3. We believe iron inclusion in the cobalt sites of the perovskite helps decrease the electron transfer barrier and facilitates the formation of cobalt-hydroxide at the surface. Possible OER mechanisms based on the observed kinetic parameters will be discussed.

Figure 1
Hierarchically Nanostructured MoS2 Catalyst Synthesis for High Efficient Hygrogen Evolution Reaction Via Electrospinning
Authors: Lee Kyu Hwan , Choi Sung Mook , Hahm Myung Gwan , Cho Byungjin , Rheem Youngwoo , Myung Nosang Vincent
Published: February 2020

Hydrogen is considered as an energy storage and carrier for future energy demand. The ideal resource of hydrogen is water, as it is abundant and contains no carbon. Sustainable hydrogen can be produced from water splitting using electricity from renewable energy sources. Water splitting requires the HER, which needs the catalytic activity. While platinum and other precious metals are the best catalyst for the HER, replacing rare and expensive catalysts with earth-abundant materials would represent a significant step toward making hydrogen as an alternative energy source and facilitate the transition to a hydrogen economy. Hence, new efficient materials for renewable hydrogen production are greatly needed.

In this presentation, we will present that cost-effective way to synthesize hierarchically nanostructured MoS2 nanofibers and demonstrate them ability to produce hydrogen by water splitting. We fabricated and optimized a perpendicularly grown nanosheets on nanofiber core with high exposure of catalytic active edge sites and good electrical contact with core nanofibers using electrospinning process, which can produce the nanomaterials on industrial scale.
(Invited) Supramolecular-Driven Formation of an Elusive Phthalocyanine-C60 Fullerene Bisadduct Triad
Authors: Torres Tomas , Bottari Giovanni , Trukhina Olga , Guldi Dirk M. , Kahnt Axel , Mateo Luis-Manuel , Lavarda Giulia
Published: February 2020

Phthalocyanines (Pcs) are planar, two-dimensional aromatic macrocycles which possess outstanding electrical and optical properties that make them perfect building blocks for their incorporation into multifunctional materials. Similarly, the excellent electron-accepting property of C60 fullerene renders this carbon nanostructure an ideal molecular partner for photo- and electroactive molecular systems such as Pcs.

Although several reports have appeared on the preparation of Pc-based, mono-functionalized fullerenes, not many examples have been reported concerning the double functionalization of C60 fullerene by Pcs, which remains problematic due to the formation of a large number of regio- and/or stereoisomers.

Here, we report a novel example of controlled bisaddition over C60 fullerene in which the occurrence of π-π supramolecular interactions between structurally-rigid, Pcs addends in solution led to the formation of a Pc2-C60 bisadduct triad in a regio- and stereocontrolled fashion. In the Pc2-C60 triad, the two Pc units are interacting through intramolecular π-stacking interactions, as demonstrated by several techniques (i.e., DABCO titration experiments, ground- and excited state photophysical studies, HPLC analysis, electrochemical studies, etc.).
(Invited) The Regioselectivity of Bingel-Hirsch Cycloadditions on IPR Endohedral Metallofullerenes
Authors: Garcia-Borràs Marc , Osuna Sílvia , Luis Josep M , Echegoyen Luis , Solà Miquel
Published: February 2020

Given the large number of possible non-equivalent bonds of Endohedral MetalloFullerenes (EMFs), the elucidation of the preferred addition sites for a target reaction is tremendously challenging.1 The development of a set of simple rules able to rationalize the preferred regioselectivities by solely inspecting the fullerene structure would be extremely appealing for the whole fullerene community. This communication describes a set of predictive criteria called Predictive Aromaticity Criteria (PAC), to a priori identify the most reactive bonds of a given EMF towards the Bingel-Hirsch (BH) cycloaddition based on a simple evaluation of the cage structure, and without need to perform any expensive theoretical calculation or experimental measure.2

We take as starting point the investigation of the BH addition of diethylbromomalonate on all non-equivalent bonds of Sc3N@D3h-C78 using density functional theory calculations. From the Sc3N@D3h-C78 analysis, a set of rules that we called Predictive Aromaticity Criteria (PAC) is derived, which are further applied to predict the most favorable BH adducts for the challenging case of Sc3N@D5h-C80. The predictions based on PAC are afterwards fully confirmed by both the computational and experimental results of the complete study of the regioselectivity of BH reaction to Sc3N@D5h-C80. These results provide conclusive evidence on the reliability of the PAC, indicating that these rules are general and applicable to any BH reaction on IPR EMFs. Moreover, this work provides clear evidence of the key role played by the local aromaticity of the cage in EMF functionalization.2-5

References:

[1] M. Garcia-Borràs, S. Osuna, M. Swart, J.M. Luis and M. Solà, Chem. Soc. Rev.,
2014, 43 (14), 5089

[2] M. Garcia-Borràs, M. R. Cerón, S. Osuna, M. Izquierdo, J.M. Luis, L. Echegoyen, M. Solà, submitted for publication, 2015.

[3] M. Garcia-Borràs, S. Osuna, M. Swart, J.M. Luis and M. Solà, Chem. Commun., 2013, 49 (12), 1220

[4] M. Garcia-Borràs, S. Osuna, M. Swart, J.M. Luis, L. Echegoyen, Miquel Solà, Chem. Commun.,
2013, 49 (78), 8767

[5] M. Garcia-Borràs, S. Osuna, M. Swart, J.M. Luis and M. Solà, Angew. Chem. Int. Ed., 2013,  52 (35), 9275

Figure 1
(Invited) Distorted Aromatics and Their Related 1D and 2D Materials
Authors: Mateo-Alonso Aurelio
Published: February 2020

Polycyclic aromatic hydrocarbons (PAHs) are receiving a great deal of attention because of their increasingly better performance in organic electronic applications. Among these, PAHs containing N atoms (N-PAHs) are particularly interesting since their electronic structure, stability, solubility, and supramolecular organization can be modulated by varying the number and position of N atoms.

In general, PAHs are planar structures but they can adopt twisted conformations as the result of the steric strain induced by overcrowding or congestion in key positions of the aromatic core. twisted-PAHs have shown enhanced solubility and unique optoelectronic and chiroptical properties as an effect of their distorted molecular structure.

We have developed a general strategy that provides access to a new family of twisted-N-PAHs (0D) with different twist angles by introducing silyl groups with different size and rigidity, providing direct experimental correlation between twist size and properties. In addition, this methodology has been successfully implemented in the preparation of 1D and 2D materials. The most recent advances of these materials including synthetic routes, optoelectronic properties, self-organising properties, and potential applications will be discussed.

 

References

[11] L. Jiang, A.C. Papageorgiou,* S. Cheol; Ö. Sağlam, J. Reichert,* D.A. Duncan, Y.-Q. Zhang, F. Klappenberger; S. More, R. Bhosale, A. Mateo-Alonso* and J.V. Barth ACS Nano
2016,DOI: 10.1021/acsnano.5b06340. [10] A. Mateo-Alonso Chem. Soc. Rev.
2014, 43, 6311-6324. [9] A.B. Marco, D. Cortizo-Lacalle, C. Gozalvez, M. Olano, A. Atxabal, X. Sun, M. Melle-Franco, L.E. Hueso, and A. Mateo-Alonso Chem. Comm.
2015, 51, 10754-10757. [8] R. Garcia, M. Melle-Franco and A. Mateo-Alonso Chem. Comm.
2015, 51, 8037-8040.[7] R. García, S. More, M. Melle-Franco, A. Mateo-Alonso Org. Lett.
2014, 16, 6096−6099. [6] G. Tregnago, C. Fléchon, S. Choudhary, C. Gozalvez, A. Mateo-Alonso, F. Cacialli App. Phys. Lett., 2014, 105, 143304. [5] S. More, R. Bhosale, A. Mateo-Alonso Chem. Eur. J., 2014, 20, 10626-10631. [4] S. More, S. Choudhary, A. Higelin, I. Krossing, M. Melle-Franco, A. Mateo-Alonso Chem. Comm., 2014, 50, 1976-1979. [3] S. Choudhary, C. Gozalvez, A. Higelin, I. Krossing, M. Melle-Franco, A. Mateo-Alonso Chem. Eur. J., 2014, 20, 1525-1528. [2] S. More, R. Bhosale, S. Choudhary, A. Mateo-Alonso Org. Lett.
2012, 14, 4170-4173. [1] N. Kulisic, S. More, and A. Mateo-Alonso Chem. Comm.
2011, 47, 514-516.
(Invited) Polypeptides/C60 Complexes and Their Applications
Authors: Solladie Nathalie
Published: February 2020

One of our research field concerns porphyrin-functionalized α-polypeptides to control the spatial organization of the chromophores and enable exciton migration through the pool of porphyrins to mimic the light harvesting antennae of the photosynthetic system.1

      In the photosynthetic system, the solar energy is collected by pigment molecules attached to the light harvesting complexes, in which the chlorophylls are held in a parallel orientation by fairly short a-helical polypeptides. When a photon hits one of the chlorophylls, the absorbed energy spreads extremely rapidly to the others until the reaction center is reached.1 Succeeding in organizing the porphyrins in a similar way as nature does should provide information about the relation existing between the orientation of the chlorophylls and the efficiency of nature in transferring an excited state over a very long distance and with minimal loss of energy.

      The right-handed 310 helical conformation adopted by our poly-L-lysine functionalized with eight porphyrins induces an overlap of the chromophores (studies realized in collaboration with Prof. T. Keiderling, University of Chicago, US), which thus present sufficient electronic coupling to promote a good exciton migration within the molecular wire.

      The properties of our peptides with pendant porphyrins were studied extensively in collaboration with with Professor S. Fukuzumi (Univeristy of Osaka, Japan) and applications were found as organic photovoltaic cells,2 multiple photosynthetic reaction centers3 and for the successful purification of Single-Walled Carbon Nanotubes.4

Acknowledgements

This work was supported by the CNRS and the French Ministry of Research. 

References

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T. Hasobe, K. Saito, P. V. Kamat, V. Troiani, H. Qiu, N. Solladié, K. S. Kim, J. K. Park, D. Kim, F. D'Souza, S. Fukuzumi, J. Mater.
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 Kenji Saito, Vincent Troiani, Hongjin Qiu, Nathalie Solladié, Takao Sakata, Hirotaro Mori, Mitsuo Ohama,  Shunichi Fukuzumi, J. Phys. Chem. C  2007, 111, 1194-1199.

Figure 1
(Invited) Concave Host Molecules Containing Phosphorus Atoms for Fullerenes
Authors: Yamamura Masaki , Nabeshima Tatsuya
Published: February 2020

The recognition of fullerenes (C60 and its higher analogues) is one of the most intensive research subjects in supramolecular and host-guest chemistry. Bowl-type p-conjugated molecules, for example, corannulene or sumanene, are promising host molecules because their concave surfaces closely resemble fullerene segments and can fit precisely to the convex surface of C60. In particular, these molecules are attractive because of their potential to function as chiral hosts based on “bowl-chirality”. However, racemization easily underwent in many of chiral bowl-type molecules. We envision a strategy for the design of a chiral concave molecule using a phosphorus-doping method, which can play a crucial role in construction of the concave structure. We now report the synthesis of the chiral concave molecule by extension of the p-surface ofphosphorus-containing concave molecule.

We synthesized the C
3-symmetric chiral concave mole-cule having a phosphorus atom at the center and resolved the enantiomers. The chiral concave structure was revealed by X-ray analysis. The concave molecule exhibited strong CD signals with a large anisotropy, the detail of which was confirmed by TD DFT calculation. In the co-crystal with C60, four molecules of enantiopure perfectly wrapped the surface of C60. MALDI-TOF mass and NMR spectra also supported the concave-convex interaction between the host molecule and C60. Furthermore, the observa-tion of the ICD signal of the guest fullerene indicates the transfer of the chiroptical properties of the host molecule to the guest. These results suggest that the chiral host is a component of a chiral self-assembled host for C60. The self-assembly of the concave molecules and the properties of the host-guest complex with fullerene will be presented.

Figure 1
(Invited) Topological Winding Number Change and Broken Inversion Symmetry in a Hofstadter's Butterfly
Authors: Bockrath Marc
Published: February 2020

Recently several research groups have demonstrated accurate placement of graphene on hexagonal BN (hBN) with crystallographic alignment. Due to the resulting superlattice formed in the graphene/hBN heterostructures, an energy gap, secondary Dirac Points, and Hofstadter quantization in a magnetic field have been observed. Using aligned layer transfer we are able to produce graphene/hBN heterostructures with ~1 degree alignment accuracy, and measure the transport properties of the resulting systems. We observe an additional π Berry’s phase shift in the magneto-oscillations when tuning the Fermi level past the secondary Dirac points, originating from a change in topological winding number from odd to even when the Fermi-surface electron orbit begins to enclose the secondary Dirac points. At large hole doping inversion symmetry breaking generates a distinct hexagonal pattern in the longitudinal resistivity versus magnetic field and charge density. This results from a systematic pattern of replica Dirac points and gaps, reflecting the fractal spectrum of the Hofstadter butterfly.
(Invited) Physics of Electronic Transport in Low-Dimensionality Materials for Future FETs
Authors: Fischetti Massimo V
Published: February 2020

The scaling of electronic devices has continued unabated for the past 5 decades, despite repeated predictions of the "end of scaling". The "more than Moore" slogan has been, and still is, viewed by industry as a need to explore realistic low-to-medium-risk avenues, some already in production -- such as strained Si/Ge or high-κ dielectrics, some yet to be translated to products in the near future or never -- such III-V semiconductors or tunnel-FETs. On the contrary, Academia has looked far ahead, even beyond carbon-based electronics (carbon nanotubes, graphene, nanoribbons). Now that the ULSI technology is looking at a feature size of 5 nm by 2026, even more “improbable” alternatives are considered, including transition metal dichalcogenides (TMDs), silicene/ane, germanene/ane (together with other *enes and *anes), topological insulators, Weyl semimetals, and other strongly correlated fermion systems.

Here I will first discuss the fact that, if we really wish to scale to 5 nm, simple electrostatic scaling laws demand that we take two-dimensional materials very seriously, despite their thermodynamic instability (Mermin-Wagner theorem) and the related technological difficulties. I will first consider how electronic transport in non mirror-symmetric 2D crystals (e.g., silicene, germanene, stanene, TMDs of the 1T/T’ crystal structure)  may be severely affected by coupling of the electrons with the acoustic flexural modes (ZA-phonons). I will then consider whether graphene has any chance of replacing Si by looking at how the extremely promising electronic properties it exhibits in its ideal form become much less interesting when it becomes a component of some non-ideal structure (such when supported and gated and/or in nanoribbon form). Finally, I will discuss a couple of very interesting admittedly improbable but fun ideas: 1. The Bose-Einstein condensation in bilayer systems (motivating UT-Austin’s BiSFETs) as an example of how issues of practical implementation may regrettably transform an excellent idea into a pure academic exercise; and 2. Monolayer tin (“stannanane”) as a 2D topological insulator with potential applications in spintronics and low-power high-performance devices (… assuming we can make it, of course…). For the entire discussion I will keep density functional theory (DFT), empirical pseudopotentials, and transport equations in the background.

This work qas done in collaboration with Shela Aboud, Bo Fu, Jiseok Kim, Sudarshan Narayanan, Ana Suarez Negreira, Zhun-Yong Ong, Cathy Sachs, and William Vandenberghe.