bluuebunny/crossref_metadata_2025_split huggingface dataset:
First-Principles Molecular Dynamics Studies of Proton Transport in Hydrogen-Bonded Media
Authors: Tuckerman Mark E. 
Published: February 2020

Proton transport in aqueous and non-aqueous hydrogen-bonded media has long been an area of intense study due to its fundamental importance in emerging energy technologies such as hydrogen fuel cells and in biological problems such as proton pumping. Our understanding of proton transport phenomena is based on the concept structural diffusion of a topological defect in the hydrogen bond network generally attributed to C. J. T. von Grotthuss. Within this picture, long-range proton transport is driven by specific structural rearrangements in the local hydrogen bonding environment, however, pinning down the specific microscopic mechanisms in different media remains an immense challenge that has an immediate impact on the problem of designing novel materials for enhancing the proton transport process. In this talk, I will show how first-principles molecular dynamics has contributed to our understanding of proton transport phenomena in a variety of systems including aqueous acidic and basic solutions (in the latter, the relevant transport process is of hydroxide ions), aand phosphate based materials including pure phosphoric acid and its mixtures with heterocycles. In phosphate based systems, the dielectric properties are also of immense interest, and I will discuss the calculation of these from first-principles molecular dynamics. In general, it will be shown that proton transport in aqueous systems relies largely on local fluctuations in the hydrogen bond network while phosphate systems, by contrast, transport protons along extended, polarized chains in a manner much closer to the original picture suggested by von Grotthuss. Such mechanistic studies can help inform the process of membrane design for electrochemical devices such as fuel cells.

Figure 1
Increasing Energy Storage in Activated Carbon Based Ultra-Capacitors through Plasma Treatment
Authors: Muriel Marcelis L. , Narayanan Rajaram , Bandaru Prabhakar R 
Published: February 2020

The relatively low cost, high surface area/mass ratio (>1000 m2/g), and ease of manufacture, of activated carbon (AC) makes it the prototypical material for electrochemical capacitor (EC) electrodes. However, the net obtainable capacitance is hampered by a space charge capacitance (Csc
), which adds in series with the expected double-layer capacitance (Cdl
). We present a method to enhance the capacitance of AC electrodes based on plasma processing techniques previously used on few-layer graphene (FLG) and carbon nanotubes1, where a three-fold enhancement in the measured capacitance was obtained. We will indicate the development of a novel AC electrode that is of low pore size2, and which has been purposefully introduced with charged defects via Argon ion irradiation. Extensive characterization using electrochemical techniques such as cyclic voltammetry, impedance spectroscopy, as well as structural characterization through the use of Raman spectroscopy will be reported. Our work will show that the ion-irradiation would lead to a change (i) of the Cdl

through modulating the effective charge storage surface area, as well as through (ii) a decrease of the Csc

through the addition of charged states3. Additionally, we will probe the possible contribution to the net measured capacitance, due to the introduced charges, from a parallel pseudocapacitance, (Cp
), composed of Faradaic charge-transfer or redox reactions4.
References:
[1] Narayanan, R., Yamada, H., Karakaya, M., Podila, R., Rao, A.M., and Bandaru, P.R. 2014

[2] Chmiola, J., Yushin, G., Gogotsi, Y., Portet, C., Simon, P., and Taberna, P.L. Science 313, 1760 (2006).
[3] Hoefer, M.A., and Bandaru, P.R. Journal of Applied Physics 108, 034308 (2010).
[4] Conway, B.E. J. Electrochem. Soc.
1991, 1539-1548.
Nanoporous-Carbon As an Intercalation Host Material to Enable Multivalent Ion Electrochemical Energy Storage
Authors: Siegal Michael P. , Yelton W. Graham , Schwarz Haiqing 
Published: February 2020

We study the use of nanoporous-carbon (NPC) as an electrically conductive host material for Mg2+ intercalation. Negligible progress for multivalent energy storage via intercalation into existing carbonaceous materials has been made due to insufficient interstitial/interplanar spacing within the crystallographic structures to host the larger sizes of partially-solvated multivalent ions. However, NPC has high surface area with open and accessible porosity, controllable via mass density, which can minimize the diffusional resistance. Here, we grow NPC directly on stainless-steel disks, which are used as anodes to fabricate coin cells with solid Mg cathodes and a Grinard-based electrolye. NPC mass density is controlled during growth, ranging from 0.06 – 1.0 g/cm3, and correlates directly with electrochemical characterizations. In particular, cyclic voltammetry (CV) scans for NPC with density ~ 0.5 g/cm3 are consistent with the reversible intercalation of Mg ions. Higher density NPC yields capacitive behavior, most likely resulting from the smaller interplanar spacings between graphene sheet fragments and tighter domain boundaries; lower density NPC results in asymmetrical CV scans, consistent with possible structural degradation resulting from mass transport through such a soft carbon material.
Briefly, NPC grows via pulsed-laser deposition with controllable mass densities ranging from ~ 0.05 to 2.0 g/cm3. The internal structure of NPC self-assembles during growth and consists of nano-fragments of aligned graphene sheet stacks with interplanar spacings expanded by as much as 55% compared to crystalline graphite. Indeed, typical crystalline domain sizes are only 1 – 2 nm in length, as determined by high-resolution transmission electron microscopy; hence, NPC consists of randomly-oriented graphene nano-crystallites with expanded interplanar spacings, and with a plethora of grain boundaries to enable rapid diffusion of species into an entire volume. Ionic intercalation into graphite is well known. Reducing the mass density of NPC increases the interplanar spacings. Therefore, the advantages of using NPC to study Mg2+intercalation include the tunability of the interplanar spacings and the ability to deposit it onto any substrate material without using binder materials, both increasing the fraction of available carbon surface atoms and simplifying the interpretation of measurements. This suggests the potential to successfully develop NPC as an intercalation host for multivalent energy storage.
This work is supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Biomass Based Carbon Nanospheres As Electrode Materials in Lithium Ion Batteries
Authors: Arie Arenst Andreas , Lee Joong-Kee 
Published: February 2020

In the past decades, the development of nano- carbon materials with well-defined characteristics such as fullerenes, nanotubes and graphene have been a very active area of research. Carbon nanospheres (CNSs) is other class of nanostructured carbon materials, and have shown good prospects for application as alternative LIB anodes. CNSs possess some remarkable characteristics such as high specific capacity and good rate capability as anode materials in LIB. Those specific characteristics are attributed to a combination of several factors, including a short diffusion paths for Li+ ions; good porosity and high surface area. CNSs can be synthesized by various techniques which influence the characteristics of resulting carbons in terms of sphere size, size distribution, crystallinity and microstructure. The synthesis process of CNSs include the chemical vapor deposition, hydrothermal carbonization, laser ablation and polymerization –carbonization. Carbon based materials have been initially synthesized from petroleum-derived compounds. Because of the depletion of carbon deposits and very serious concerns on global climate change and environmental pollution, the use of renewable natural resources such as biomass for production of carbon materials has been intensively explored in recent years. In this work, the synthesis of carbon nano-spheres onto the surface of activated carbon support was carried out by thermal assisted catalytic pyrolysis technique and utilizing palm oil as renewable and eco-friendly carbon source. The structure and morphology of the resulting nano carbons are examined with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) and cyclic test of the carbon product as an anode material for lithium ion batteries are also investigated. From TEM observations, it can be shown that CNSs has turbostratic structure in the presence of Fe-metal catalyst. The CNSs have a stable cycle performance up to 100 cycles at a constant current density of 100 mA/g, showing its potential as an anode material in lithium-ion batteries.
(Invited) Mechanistic Studies of the Oxygen Reduction Reaction Electrocatalyzed By N-Doped Graphitic Carbon Materials
Authors: Li Liang-shi , Li Qiqi , Noffke Benjamin , Raghavachari Krishnan 
Published: February 2020

The oxygen reduction reaction (ORR) is a crucial step in biological and industrial energy production. To directly convert fuels to electricity in devices such as fuel cells, electrocatalysts alternative to Pt or Pt alloys have been actively sought after, especially those with high performance, high endurance, and low cost. And for this reason N-doped graphitic carbon materials including carbon black, activated carbon, graphite, nanotubes, graphene, etc. have been intensively studied. Despite the recent progress, mechanistic studies of these materials are particularly difficult due to the inhomogeneity and complexity of the catalysts available. Consequently, our understanding has been mainly empirical, and improvements of the catalysts are primarily based on trial and error.
Herein we present our recent studies on well-defined, N-doped graphene nanostructures for the electrocatalyzed ORR. By combining experimental and theoretical work, we show that a two-electron reduction of the carbon is a key step in activating the oxygen. We also show that the dielectric environment of the catalysts play an important role in dictating the selectivity of the reaction.
Fe and N Functionalized-Ordered Mesoporous Carbon with Different Morphologies: Role of Fe on Surface Properties and Electrocatalytic Activity
Authors: Yang Dea-Soo , Song Min Young , Bae Eunjin , Yu Jong-Sung 
Published: February 2020

Because of their high energy conversion efficiency, low pollution, low operating temperature, high power density, and wide range of applications, fuel cells have received a plethora of attention. Oxygen reduction reaction (ORR) takes place usually on Pt loaded on different carbon supports, but their large-scale commercial application has been precluded mainly by the high cost of the requisite noble metal. To overcome all the drawbacks of Pt or Pt-based catalysts, various efforts have been devoted to find its proper substitute. Heteroatom-doped carbon catalysts, due to their high stability, excellent electrocatalytic performance, and economic viability over costly Pt-based catalysts are being pioneered as a suitable alternative.
Although heteroatom-doped porous carbon materials have evolved as one of best possible solutions in this regard, the probable synergy of heteroatom doping and textural properties has not been well investigated yet in details. In this work, a detailed investigation is carried out on Fe and N-functionalized ordered mesoporous carbon (FeN-OMC) as electrocatalyst ORR in both alkaline and acidic media. The FeN-OMCs with different morphology are synthesized by pyrolysis of iron phthalocyanine-infiltrated corresponding SBA-15 silica templates. The as-synthesized FeN-OMC materials show excellent electrocatalytic ORR activity with nearly four electron transfer process. While the activity in alkaline media is nearly equal to or better than commercial Pt catalyst in terms of onset potential and diffusion-limited current density, it closely follows in acidic media, which is a tremendous achievement for non-precious metal catalysts developed till date. The most interesting observation is that not only heteroatom, but textural properties also affect catalytic activity profoundly. The physical presence of Fe species may be necessary in the synthesis of active heteroatom-doped carbon for high ORR activity, but may be not necessary any more for the as-prepared doped carbon to play as electrocatalyst for ORR. Despite of being prepared with similar Fe and N content, the catalytic ability of FeN-OMC materials is gradually increased with decrease in mesopore channel length with maximum activity in thin platelet FeN-OMC. These observations demonstrate that structural morphology in addition to heteroatom and other textural properties, has significant synergistic influence on ORR catalysis in heteroatom-doped carbon materials.
Microwave-Assisted Solvothermal Synthesis of Pd-MnO2 Hybrid at Onion-like Carbons: Electrocatalytic Oxidation of Alcohols in Alkaline Media
Authors: Ejikeme Paul M. , Makgopa Katlego , Raju Kumar , Ozoemena Kenneth I. 
Published: February 2020

The use of less toxic glycerol, (a non-flammable, volatile, and little-valued residue of biodiesel production), ethanol as well as ethylene glycol (EG) as fuel may be an interesting alternatives to methanol for Direct Alcohol Fuel Cell (DAFC) technology. The volumetric energy densities of glycerol, ethanol and EG are 5.80, 6.31 and 5.97 kW h L-1 compared to 5.81 kW h L-1for methanol makes them good fuel cell candidates [1-2]. The secret to the efficient electrocatalysis of alcohols is the use of efficient nanocatalyst. Palladium-based catalysts have emerged as the most viable electrocatalysts for alcohol in alkaline electrolytes. To harness the great catalytic potential offered by Pd, and to reduce cost, Pd-based alloys supported on different carbon supports are constantly used in direct alcohol fuel cells (DAFCs).
In this work, palladium-manganese oxide nanoparticles supported on carbon nano onions (Pd-MnO2/OLC) were synthesized using the microwave-assisted solvothermal technique. Palladium-manganese oxide nanoparticles supported on Vulcan carbon (Pd@MnO2/XC–72) were also synthesized using the same technique for comparison. The catalysts were characterized using XRD, XPS, FESEM and HRTEM techniques. Electroxidation of the alcohols was performed in 0.5 M alcohol / 0.5 M KOH via cyclic and linear sweep voltammetry, chronoamperometric and elelctrochemical impedance spectroscopy.
Results obtained show that the catalyst supported on OLC exhibited the highest current density and least charge transfer resistance relative to the catalyst supported on XC–72. Pd-MnO2/OLC gave the best result amongst the catalyst synthesized with respect to the current density, and electrochemical stability as well as exhibited the least charge transfer resistance in all the alcohols studied. For instance, the onset oxidation potential and current density of the glycerol oxidation process were -0.5386 V and 5.58mAcm-2, respectively. The implications of these results relative to methanol oxidation using the best catalyst system synthesized are discussed.

References

1. L.M. Palma, T.S. Almeida, A. R. de Andrade, ECS Trans. 2013 58(1): 651-661.
2. X. Zhang, P.K. Shen, Int. J. Hydrogen Energy 2013, 38, 2257-2262
Engineering Carbon Nanotubes As Oxygen Reduction Catalysts for Solid Acid Fuel Cells
Authors: Evoen Vanessa , Tavassol Hadi , Haile Sossina M 
Published: February 2020

We report on the effect of the chemistry of multi-walled carbon nanotubes (CNTs) on the oxygen reduction reaction (ORR) in solid acid fuel cells (SAFCs) based on the proton conducting electrolyte cesium di-hydrogen phosphate (CDP). CDP undergoes a super-protonic phase transition at ~2300C (10-6 S/cm2-10-2 S/cm2), under humidified gas atmosphere, making it a suitable fuel cell electrolyte. Due to the high cost of using platinum as the state of the art oxygen reduction reaction (ORR) catalyst, significant effort has been devoted to developing non-precious catalysts.
In this work we explore the suitability of functionalized carbon nanotubes as ORR catalysts. Composite electrodes of fine micron-sized CDP particles and CNTs were prepared by mechanical milling and applied to either side of a dense membrane of CDP, in turn, placed between carbon paper current collectors. The CNTs were acquiring commercially and included both hollow (standard) and bamboo CNTs. In both cases, in addition to non-functionalized forms of the CNTs, both amine-functionalized and acid-functionalized analogs were evaluated. Electrochemical activity was measured by A.C. impedance spectroscopy under humidified oxygen (pH20 of 0.4 atm) at 2400C.
Of the non-functionalized CNTs, the bamboo structure was found to have a higher activity than the hollow structure, with an area specific electrode resistance of 1700 ohm cm2 vs 3500 ohms cm2. Functionalization of the CNTs led to orders of magnitude increase in the ORR activity. In particular, the electrode resistance values dropped to ~350 ohms cm2 for the amine functionalized CNTs and ~40 ohms cm2 for the carboxylic acid functionalized hollow CNTs. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) of the electrodes showed a relationship between the chemistry of the CNTs and the degree of mixing in the CNT/CDP composite, which may contribute to the differences in electrochemical behavior.
In Vivo Glucose Measurement Using Fine Needle Type Amperometric Glucose Sensor
Authors: Yasuzawa Mikito , Edagawa Kazuaki 
Published: February 2020

Fine needle type glucose sensors having outer membrane layers of heparin and urokinase were prepared. Glucose sensor properties were evaluated by in vitro measurement in phosphate buffer solution and horse serum, and in vivo measurement using the veins of rabbit. Glucose sensors were implanted using cannula and the blood glucose levels were influenced by the injection of glucose and insulin. Definite glucose was hardly observed at the days of implantation, while clear response was obtained after several days. This may due to the recovery from the damage of blood vessel received on the process of sensor implantation. Good correlation between in vitro blood glucose levels was obtained at especially low glucose level. Clear glucose sensor response was obtained even after 10 days of implantation. The formation on thrombus was not observed on the surface of sensor implanted for 10 days. This indicate that the glucose sensor with outer membrane of heparin and urokinase have excellent biocompatibility.

Figure 1
(Plenary) High Efficiency Coupling of Chemical Sensing to Chemical Treatment in Low-Dimensional Nanofluidic Structures
Authors: Xu Wei , Grismer Dane A. , Zaino Lawrence P. , Ma Chaoxiong , Foster Erick , Bohn Paul W. 
Published: February 2020

We are interested in the design and construction of nanostructured architectures that couple molecular transport (analyte/reagent delivery), chemical sensing (optical or electrochemical) and subsequent chemical processing withinin the same physical construct. The ultimate goal of these experiments is to produce chemical reagents in situ and consume them directly at a proximal reaction site, all within the confined geometry of a low-dimensional nanostructure, so that chemical transformations may be realized with optimal efficiency. To realize this goal we are developing sensing strategies that efficiently match electron transfer and spectroscopic probing to low-dimensional, i.e. zero- and one-dimensional nanostructures. In one example, we are studying the tight coupling of electrokinetic nanofluidics to electron transport for high efficiency in situ reagent generation. Solvent electrolysis at an upstream can be used to generate H2 or O2 for downstream catalytic reduction or oxidation reactions. Chronocoulomtery is performed simultaneously with fluorescence imaging in order to follow the reagent generation quantitatively, then model proton-coupled electron transfer reactions can be used down stream to follow the spatial distribution of reagent through the co-generated OH- or H+. Because transport and electron transfer are intimately coupled, high efficiency conversions are achieved. The extremely small Peclet numbers characteristic of nanofluidic flow mean that the efficiency of electrochemical treatment is improved to near 100% efficiency in nanofluidic architectures compared to diffusion-limited efficiencies of 5-10% in microfluidic structures.
Development of Biofilm-Based Electrocatalytic Materials for Biosensing and Bioenergetics
Authors: Kulesza Pawel J 
Published: February 2020

Biofilms, are polymeric aggregates of microorganisms, in which cells adhere to each other on the electrode surfaces. Such systems are characterized by extracellular electron transfers involving c-type cytochromes (heme-containing proteins). Biofilms can be grown on inert carbon electrode substrates tend to exhibit electrocatalytic properties towards oxygen and hydrogen peroxide reductions in neutral media. The processes have been found to be further enhanced by introduction of multi-walled carbon nanotubes (MCNTs) that are modified with ultra-thin layers of organic (e.g. 4-(pyrrole-l-yl) benzoic acid. We expect here attractive electrostatic interactions between carboxyl-group containing anionic adsorbates and positively charged domains of the biofilm with c-type cytochrome enzymatic sites. Coexistence of the above components leads to synergistic effect that is evident from positive shift of the oxygen reduction voltammetric potentials and significant increase of voltammetric currents. Most likely, the reduction of oxygen has been initiated at the molecular (e.g. intentionally added cobalt porphyrin redox centers), whereas the undesirable hydrogen peroxide intermediate are further decomposed at the cytochrome sites.
An additional subject of interest is the process of carbon dioxide (CO2) reduction. There has been a growing interest in catalytic systems capable of efficient conversion of carbon dioxide into fuels. One of the promising electrocatalytic materials exhibiting high activity in this process is a macromolecular complex of palladium (II) with Schiff-base-ligands. Reduction of carbon dioxide may lead to carbon-based fuels and its derivatives.
Fabrication of the biofilm based matrices for anodic reactions has also been considered. To facilitate electron transfers between the electrode surface and the redox protein centers, the concept of codeposition of multi-walled carbon nanotubes within the bioelectrocatalytic film has also been pursued here. First, carbon nanotubes are modified with ultra-thin layers of tetrathiafulvalene (TTF) or poly(dimethyldiallylammonium chloride) (PDDA) mediators. Their presence is expected to facilitate flow of electrons from the enzyme (e.g. glucose oxidase) active sites through biofilm to the electrode surface. Combination of intentionally derivatized carbon nanotubes with biofilm matrtices and the appropriate enzymes seems to produce biocatalytic systems capable of effective oxidation and sensing of glucose or ethanol in the neutral buffered solution.
Collaboration with W. Lotowska, E. Szaniawska, E. Seta, M. Gierwatowska, B. Kowalewska and I.A. Rutkowska (from Faculty of Chemistry) as well as A. Raczkowska and K. Brzostek (from Faculty of Biology) is acknowledged.