bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of a Carbon-Based Non-Precious Metal Catalyst Fehmta/C for Oxygen Reduction Reaction
Authors: Xiong Zhongping , Si Yujun
Published: February 2020

A non-precious metal catalyst for oxygen reduction reaction was prepared by a simple method and using cheap materials. The basic steps include: 0.40g of FeCl3.6H2O was dissolved in 5 ml ethanol, and then the solution was uniformly mixed with 0.5g of acetylene black. The obtained mixture was dried at 50℃ and was mechanically ground with 0.5g of hexamethylenetetramine for 30 minutes. Then the precursor was heat-treated at 700℃ for 2 hours under nitrogen atmosphere and a catalyst named FeHMTA/C was got. Figure 1 shows the ORR catalytic activities of acetylene black and FeHMTA/C catalyst. It can be seen that the untreated acetylene black has not ORR activity. However, there is an obvious reduction process with an onset reduction potential of 0.56V (vs. SCE) in the voltammogram of FeHMTA/C catalyst as shown in Figure1(c). This process corresponds to the oxygen reduction reaction, which shows the FeHMTA/C catalyst has good ORR activity.

Acknowledgments

This work was supported by the Specialized Research Fund for the Doctoral Program of Sichuan University of Science and Engineering (No. 2012RC16) and the Opening Project of Key Laboratory of Green Catalysis of Sichuan Institutes of High Education (No. LYJ1206, LYJ1401).

Figure 1 Linear sweep voltammograms of (a) acetylene black and (c) FeHMTA/C catalyst in 0.5M H2SO4 solution saturated by O2, and (b) FeHMTA/C catalyst in 0.5M H2SO4 solution saturated by N2
.
Development of MEAs with Pt/Mesoporous Carbon as a Cathode Catalyst
Authors: Minamida Yasuto , Noda Zhiyun , Hayashi Akari , Sasaki Kazunari
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) have recently been paid great attention owing to commercialization of fuel cell vehicles (FCVs) since 2015. However, PEFCs still have some problems to be overcome, such as improvement of cost and durability for the next generation. In our study, improvement on durability of electrocatalysts is targeted by reducing the mobility of Pt particles on the carbon support. Particularly, Pt particles are introduced into the nano-space of Mesoporous Carbon (MC), which has the nano-channel structure with a diameter of ca. 10 nm. Such encapsulation of Pt in the carbon nano-space leads to successfully reducing the mobility of Pt. MEAs have been prepared with such electrocatalysts as cathode materials, and the sufficient performance has been confirmed, so far. In this study, we have particularly focused on the triple phase boundary formed inside the carbon nano-space. The methods of Nafion introduction were controlled in order to study how they influence on IV performance and durability.

Electrocatalysts were synthesized from platinum (Ⅱ) acetylacetonate as a precursor by supporting ca. 30 wt% Pt on our original MC, and named as Pt/MC. Pt/MC was used only for the cathode. For the anode, a commercial Pt/Ketjen black catalyst (TEC10E50E, TKK Corp.) was in use. Then, MEAs were prepared by spraying the slurry of electrocatalysts and Nafion on the both sides of Nafion membrane, followed by hot-pressing. The solvents for introducing Nafion into carbon nano-space were controlled by ethanol or hexafluoropropanol.

Based on our previous research work, introduction of Nafion into carbon nano-space is known to depend on the kind of solvents[1]. Therefore, in this study, MEAs were made using hexafluoropropanol, which was thought to be more suitable for introduction of Nafion than regular ethanol. Besides the initial performance of MEAs, their durability was also evaluated, using the cycle test at the potential range where the dissolution and re-precipitation of Pt particles occurs[2]. As a result, the initial activity was higher for MEAs made with ethanol, whereas durability was higher for MEAs made with hexafluoropropanol. Successful formation of the triple phase boundary has led to the increase in durability. Further, we are now working on improving the initial activity by optimizing introduction methods of Nafion.

References

[1] A. Hayashi et al. J. Phys. Chem. C, 113(28), 12149 (2009).

[2] A. Ohma et al., ECS Trans, 41 (2011) 755.
SnO2 As an Effective Protection Layer of Electrospun Carbon Nanowires Based Catalyst for PEMFC Applications
Authors: Ercolano Giorgio , Marichy Catherine , Silva Ricardo Manuel , Caputo Gianvito , Jones Deborah J , Roziere Jacques , Cavaliere Sara , Pinna Nicola
Published: February 2020

Proton exchange membrane fuel cells (PEMFC) can provide clean and long lasting electrical energy while being portable and operated at relatively low temperatures. However, a reduction of the fabrication costs and an improved durability are pivotal to a successful market introduction of this technology. A more effective utilisation of the highly priced Pt catalyst and the use of more durable materials for the catalyst supports are the core of the development of novel, market ready PEMFC. This could be achieved by moving away from the current standard based on Pt nanoparticles supported on amorphous carbon.

We propose a novel catalyst obtained combining electrospinning of carbon nanowires and microwave Pt synthesis with atomic layer deposition of a protective functional metal oxide layer. We studied the morphology and electrochemical properties of this novel structure and demonstrated that the addition of a thin SnO2 layer deposited by ALD increase the durability without reducing the Pt activity for the oxygen reduction and that synergistic utilisation of the oxide and Pt can increase the activity towards methanol and ethanol oxidation.
Pt Catalysts Supported on Polybenzimidazole-Grafted Graphene for PEMFCs
Authors: Li Zhe-Fei , Zhang Hangyu , Yang Fan , Stanciu Lia , Xie Jian
Published: February 2020

The performance of a PEMFC is dominated by its catalyst performance, which depends on the size and distribution of the catalyst on the surface of the carbon support. A functionalized carbon support allows better dispersion of the catalyst nanoparticles, which can reduce the aggregation of metal nanoparticles and, consequently, improve the catalyst performance.1 Graphene is single-atomic-layer-thick carbon atoms arranged in a hexagonal lattice, which is the thinnest catalyst support for Pt catalyst nanoparticles. Graphene has many advantages over conventional carbon black catalyst support, like high electronic conductivity, surface area, mechanical strength, and excellent stability.2 All of these unique properties make the graphene as an ideal candidate for Pt catalyst support in polymer electrolyte fuel cells (PEFCs).3 In this work, covalently-functionalized graphene with polybenzimidazole (PBI) was employed as the catalyst support. The Pt nanoparticles were uniformed deposited onto graphene/PBI due to a strong interaction between PBI and Pt. Such Pt catalyst supported on the PBI grafted graphenes will benefit the MEA for PBI membrane based PEMFCs. The synthesized catalysts were characterized using rotating disk electrode (RDE) for their elctrocatalytic performance.

The Cyclic voltammetry (CV) curves of graphene/PBI supported Pt catalyst at a scan rate of 20 mV/s in N2-saturated 0.1 M HClO4 is shown in Figure 1. The electrochemical active surface area (ECSA) was calculated to be about 55 m2
Pt/gPt, which is comparable with that of commercial E-TEK Pt/C catalyst (58 m2
Pt/gPt). The high ECSA value suggests the uniform distribution of Pt on the surface of graphene/PBI. Accelerated degradation tests (ADT) were also evaluated by monitoring the changes in electrochemical surface area during voltage cycling between 0.6 V and 1.2 V at a scan rate of 20 mV/s in N2-saturated 0.1 M HClO4. After 1000 cycles, a relatively surface area loss of more than 81% was observed in commercial catalyst. In comparison, the relative surface area loss of graphene/PBI supported Pt catalyst was 57%. The increase in the stability of catalyst may result from the strong binding of Pt nanoparticles onto PBI-grafted graphene. In conclusion, the high ECSA and excellent durability of graphene/PBI supported Pt catalyst illustrates the advantage of polybenzimidazole-grafted graphene as a catalyst support in PEMFCs.
Impact of Water Flow Rate on Current Efficiency in Solid Polymer Water Electrolyzer Under 2 MPa Condition
Authors: Ito Kohei , Maeda Yusuke , Sakaguchi Takuya , Inada Akiko , Nakajima Hironori
Published: February 2020

When solid polymer water electrolyzer is operated under high pressure conditions, large pressure difference forms between anode and cathode, causing crossover of produced gas, especially for hydrogen gas, and reducing its current efficiency. Supplying water into cathode channel, in addition to anode, is a countermeasure to decrease the crossover, because the water flow improves to drain the hydrogen gas outside of cell, leading to suppression of the crossover and increase of the efficiency. This countermeasure for the crossover is investigated by SPWE operation under 2 MPa condition with visualization of hydrogen bubbles in the SPWE. The investigation revealed that supplying water into cathode channel increased the efficiency within several percent under 0.33 A/cm2. Enhanced detachment of hydrogen bubbles from the surface of current supplier, which was confirmed by the visualization, increased the efficiency.
An Improved EVB Model for Proton Transport in Polymer Electrolyte Membrane
Authors: Mabuchi Takuya , Tokumasu Takashi
Published: February 2020

The heart of Polymer electrolyte fuel cells (PEFCs) is polymer electrolyte membrane (PEM) that separated the reactant gases and conducts protons. In the nanoscopic structure of the membrane, ion clusters are formed by water molecules gathered vicinity of sulfonate groups which are hydrophilic parts of Nafion membrane, and proton transport (PT) are largely attributed to the nanoscopic structure of polymer membranes and water aggregations. Thus, many macroscopic simulations that are based on continuum theory have found it difficult to discuss the relation between the structural and dynamical properties of protons within the membrane in previous experimental studies. It is critical to understand the PT mechanisms through polymer membrane and clarify an important link between the membrane nanostructure and the PT properties. In the bulk aqueous solution, it is observed that proton mobility is roughly 5 times higher than other cations such as K+ which have an ionic radius similar to the hydronium ions. This property of PT is attributed to a combination of proton hopping, known as the Grotthuss mechanism, and vehicular mechanism where protons diffuse in solution as a hydrated form (e.g. hydronium ions). Many research efforts have been focused on understanding the PT mechanism using theoretical basis for the proton hopping models such as the empirical valence bond (EVB) approaches which allow PT phenomena to be simulated accurately in MD simulations. In Nafion membranes, it is considered that proton hopping transport still takes place although the water dynamic property in the bulk aqueous solution is inhibited by a lack of bulklike water structure at low water contents. Although the PT properties including hopping mechanism in hydrated polymer membrane have been studied using the original two-state EVB method by Walbran et al., the diffusion of water was found to be significantly higher than that of protons as well as that of real water in their model. In this study, a revised EVB model has been developed based on the previous study of the two-state EVB model, the impact of the proton hopping mechanism on the structure and dynamics properties of protons in hydrated Nafion membrane has been investigated at different hydration levels. The new EVB model in bulk water predicts a significantly enhanced transport in comparison with previous hopping models, which largely improves the agreement with the available experimental data. We have determined the diffusion coefficients of protons and water molecules in hydrated Nafion membrane as a function of hydration level, and the results are in good agreement with experimental data for the studied hydration levels. Proton hopping mechanism is found to become more significant at higher hydration levels. The influence of the sulfonate groups on the PT properties have also been investigated in this study. Our simulation results provide insight into quantitative information about PT properties in atomic level.
RuO2 Nanosheet Modified Pt-Based Catalysts as CO Tolerant PEFC Anode
Authors: Sugimoto Wataru , Takimoto Daisuke , Ohnishi Tomohiro
Published: February 2020

PtRu/C are presently used as the anode catalyst for residential polymer electrolyte fuel cells. Anode catalysts with increased CO tolerance is desired since trace amounts of CO residing in reformates poisons the catalysts. In addition, catalyst degradation due to gradual loss of Ru is known to occur due to start/stop cycles. Thus efforts have been made to develop CO-tolerant electrocatalysts with high durability. The addition of nanostructured oxides has shown some promising results. In an earlier study, the authors showed that the addition of oxide nanosheets to carbon supported Pt-based catalysts can act as co-catalysts for the oxidation of adsorbed CO and enhance the durability [1-3]. Here we have studied catalyst activity and durability of PtxRuy/C catalysts modified with RuO2.1 nanosheets (RuO2.1ns) towards the hydrogen oxidation reaction in the presence of CO.

RuO2.1ns were derived from layered K0.2RuO2.1.nH2O [4]. Commercially available PtxRuy/C were modified with RuO2.1ns following previously described methods [5,6]. Catalytic activity was measured using rotating disk electrodes in 0.1 M HClO4 (25oC) in pure H2 (j(H2)) or 300 ppm CO/H2 (j(CO/H2)). Chronoamperometry was conducted at 20 mV vs RHE at 400 rpm.

The composite catalyst RuO2.1ns-Pt/C had the same ECSA and j(H2) value as Pt/C, indicating that RuO2.1ns does not impede H2 diffusion to the Pt surface. The j(CO/H2) value of RuO2.1ns-Pt/C was 18% higher than Pt/C.

The j(CO/H2) value of RuO2.1ns-PtRu/C after 1000 consecutive cycles between 0.05 and 0.4 V vs. RHE (v = 100 mV/s) was compared with Pt2Ru3/C. The initial j(CO/H2) of RuO2.1ns-PtRu/C was similar to PtRu/C and Pt2Ru3/C. After cycling, the j(CO/H2) of RuO2.1ns-PtRu/C was 20% higher than commercial catalysts.

This work was supported in part by the “Polymer Electrolyte Fuel Cell Program” from the New Energy and Industrial Technology Development Organization (NEDO), Japan.

[1] W. Sugimoto, T. Saida, Y. Takasu, Electrochem. Commun., 8, 411 (2006).

[2] T. Saida, W. Sugimoto, Electrochim. Acta, 55, 857 (2010).

[3] T. Saida, N. Ogiwara, Y. Takasu, W. Sugimoto, J. Phys. Chem. C, 114, 13390 (2010).

[4] W. Sugimoto, H. Iwata, Y. Yasunaga, Y. Murakami, Y. Takasu, Angew. Chem. Int. Ed.,42, 4092 (2003).

[5] D. Takimoto, C. Chauvin, W. Sugimoto, Electrochem. Commun, 33, 123 (2013).

[6] C. Chauvin, T. Saida W. Sugimoto, J. Electrochem. Soc., 161, F318 (2014).
Development of Pt-Free Carbon-Based Catalyst for PEFC Cathode Prepared from Polyacrylonitrile
Authors: Chokai Masayuki , Daidou Takahiro , Nabae Yuta
Published: February 2020

Carbon-based catalyst for PEFC cathode was prepared from polyacrylonitrile (PAN) by adopting PAN-based carbon fiber chemistry. The PAN prepared on radical polymerization was stabilized in air. The stabilized PAN was pyrolyzed in nitrogen. Finally the carbon-based catalyst was obtained after activation in ammonia. On half cell testing with rotating disc electrode (RDE) measurement, the catalyst prepared with appropriate amount of Fe species in pyrolysis process showed high oxygen reduction reaction (ORR) activity. Additionally, a membrane electrode assembly comprising of the carbon-based catalyst as cathode catalyst was prepared and its PEFC performance was also demonstrated.
Fabrication of Metal Nanowires Containing Highly Controllable Nanospaces
Authors: Sada Takao , Fujigaya Tsuyohiko , Nakashima Naotoshi
Published: February 2020

Hollow nanostructures are of scientific and technological interest in the broad applications due to their ability to interact with other materials not only at their surfaces, to modulate refractive index, to improve the catalytic activity and to lower the density of nanostructures [1]. To prepare hollow structures, various methods such as versatile template methods based on the removal of sacrificial template [2] and simple templateless method [3] have been developed and enable to incorporate the void space or nanospaces into various nanostructures such as the nanosphene, nanocubes, nanorods and nanowires. Among these nanostructures, porous nanowires have much attention in the many field because they acquire the above advantages of hollow structures as well as the advantage of 1 D structures [4]. On the other hand, the precise control of pore size, volume and density in arbitrary structures is important because the size, volume and density directly determine the new ability depending on the nanospaces to provide the desired functions. Herein, we report the facile, high-throughput and novel route to fabricate the metal nanowires containing highly controllable nanospaces.

　The metal nanowires containing highly controllable nanospaces were fabricated by the template method based on the removal of sacrificial template. We choose Nickel (Ni) as the metal and Silver (Ag) as the sacrificial template. We confirmed the Ni nanowires containing highly controllable Ag segment were fabricated by the pulsed electrodeposition in Anodic Aluminum oxide template. After etching the Ag segment, we clearly observed the Ni nanowires containing highly controllable nanospaces. By taking the advantage of the well controllability of the electroplating conditions such as the time of the deposition and the concentration of the plating solution, we found the size and the pitch of the hollowed segments were successfully controlled.

[1] Y. Zhao et al., Advanced Materials
2009, 21, 3621.

[2] F. Carusoet al., Science
1998, 282, 1111.

[3] Y. Yin et al., Science
2004, 304, 711.

[4] H. Jiang et al., Chemical Communications
2012, 48, 4465.
Enhancement of Electron Transfer Rates in Iodine/Iodide Ionic Liquid through Catalyzing the Chemical Step of I-I Bond Splitting: Development of Semi-Solid Redox Electrolyte Capable of Fast Charge Propagation
Authors: Rutkowska Iwona Agnieszka , Orlowska Justyna M. , Marks Diana , Kulesza Pawel J.
Published: February 2020

The ability of platinum nanostructures to induce splitting of I-I bond in the iodine molecule is explored here to enhance electron transfers in the iodine/iodide redox couple and thus to accelerate charge transport in the respective room-temperature 1,3-dialkylimidazolium cation based ionic liquid. There has been growing recent interest in room-temperature ionic liquids, especially those with 1,3-dialkylimidazolium cations due to their such important features as negligible vapor pressure, high ionic conductivity and thermal stability, fairly wide electrochemical window, and ability to dissolve organic and inorganic solutes. The resulting redox-conducting electrolytes have several advantages: high conductivity, low vapor pressure, high iodide concentration and good electrochemical stability. Among disadvantages is their high viscosity that certainly contributes to the low diffusion coefficient of the oxidized form of the redox couple if the charge transport mechanism is truly physical. It was established that platinum induces electron transfers within the iodine/iodide redox system. Strong interactions of Pt or Pd with iodide or iodine were also postulated. Formation of the monolayer type coverages (on platinum or palladium) of strongly adsorbed monoatomic iodine together with weakly bound electroactive iodine/iodide was also postulated. By using solid-state voltammetric (both sandwich-type and microelectrode based) methodology, we demonstrate in the present work that effective (apparent) diffusion coefficients have significantly increased upon incorporation of the iodine-modified Pt or Pd nanoparticles and, in particular, the carbon-nanotube (multi-walled) supported iodine-modified Pt nanostructures. The Dye Sensitized Solar Cell utilizing the dye-covered TiO2 and the iodine/iodide ionic liquid electrolyte admixed with the iodine-modifed Pt based nanostructures has yielded reasonably higher efficiencies and better physicochemical parameters in comparison to the analogous Pt-free system.

In the present work, we explore the respective interfacial (electrocatalytic) phenomena on nanostructured platinum or palladium (namely Pt or Pd nanoparticles that three-dimensionally distributed in the electrolyte phase), and we utilize them to enhance iodine/iodide electron transfers and to develop systems capable of fast charge propagation. To further improve charge distribution within the redox-conducting electrolyte, we have also introduced multi-walled carbon nanotubes (as supports for dispersed iodine modified Pt nanoparticles) into our hybrid system.
Effect of SAM Chain Length on Mediated Amperometric Detection of Glucose
Authors: Suroviec Alice H
Published: February 2020

Self-assembled monolayers with reactive terminal functionality are frequently used for constructing chemical sensors. The sensors can subsequently be modified by covalent attachment or electrostatic deposition of other materials to introduce specificity at the surface for the sensing application. Electrostatic deposition is a simple method used to build structures at an interface, and is a method that can be easily adapted for biological molecules (e.g. proteins, enzymes, etc.) without compromising the integrity of the protein/enzyme. When depositing biological molecules, however, the chain length can affect the kinetics of the glucose oxidase/glucose reaction. This research used cyclic voltammetry to measure the Michaelis-Menton kinetics of the glucose oxidase reaction with glucose in the presence of a mediator. The Michaelis-Menton kinetics were measured using three different thiols of varying lengths. The length of the chain was shown to have an effect where the shortest chain had significantly different kinetics compared to the longer chains.
Examining the Electrodeposition Mechanism of Manganese Dioxide Using In-Situ Small Angle X-ray Scattering
Authors: Donne Scott W , Dose Wesley M , Dupont Madeleine F
Published: February 2020

Manganese dioxide thin films, produced by anodic electrodeposition, have been found to exhibit extremely high specific capacitance. However, their capacitive performance decreases markedly as the film thickness increases, so despite exhibiting specific capacitance values of up to 2000 F/g (for extremely thin films), their applications are limited due to their low volumetric capacitance.

The enhanced performance of thin films is largely due to their high specific surface area and conductivity, both of which decrease as the film thickness increases. Improving the performance of thicker films requires synthesis methods in which the morphology of the films can be tailored to optimise surface area and conductivity. To achieve this, the mechanism by which manganese dioxide is electrodeposited must be fully understood.

In this work, manganese dioxide was deposited onto a platinum electrode from a solution of MnSO4 in H2SO4. The deposition process was examined in-situ using small angle x-ray scattering (SAXS) using a synchrotron x-ray beam.

SAXS analysis was used characterise the material at different stages throughout the deposition. Features such as the pore size and particle size and shape were obtained from the data, showing how the morphology of the film changes as deposition is occurring. The deposition solution and deposition potential were varied in order to find the optimum deposition conditions required to create high performance thin film capacitors.

The performance of the thin films was analysed using standard electrochemical techniques including cyclic voltammetry and constant current charge discharge.
Electrochemical Study of the Interaction between Silicon n–type (100) and Hydroxyl Radicals
Authors: Muñoz Eduardo Carlo , Heyser Cristopher Alejandro , Hasse Ulrich , Scholz Fritz
Published: February 2020

Semiconductor materials offer electronic properties that make them promising for being employed in the molecules detection in different environments. The present study proposes the analysis of changes in electrochemical responses of crystalline silicon (n–Si) after the interaction with hydroxyl radicals (•OH) in aqueous media.

In a first stage, the synthesis of hydroxyl radicals was done by means two procedures: (i) Fenton reaction and (ii) H2O2 photochemical decomposition using a UV digester for this purpose. Variables in these processes were time and hydrogen peroxide concentration in order to determine the dependence of these parameters on silicon–hydroxyl radical interaction.

After each immersion in radicals (separately both methods •OH of generation), it was performed a chemical cleaning treatment on silicon, which consisted: i) without further treatment; ii) HCl treatment or iii) HF treatment. This last was done to avoid the presence of silicon oxide (SiO2) on the semiconductor surface. Subsequently, n–Si was placed in a three electrodes cell: silicon as working electrode, Ag / AgCl, KCl (saturated) as a reference electrode (0.197 V vs SHE) and a platinum counter electrode. After were registered the corresponding voltammograms in a potassium chloride (KCl 0.1 M) solution at different pH values. In order to study the pH dependence on the interaction between substrate – reactive species (Si – •OH) were analyzed the current and the peak potential shift for each experimental conditions. Finally, Atomic Force Microscopy (AFM) was done to observe morphological changes in the substrate surface.
Characterization and Electrochemical Determination of Diclofenac in the Presence of CTAB
Authors: Cid-Cerón Mireya Marlenne , Guzmán-Hernández Dafne Sarahia , Ramirez-Silva Maria Teresa , Rojas-Hernández Alberto , Palomar-Pardavé Manuel , Romero-Romo Mario A.
Published: February 2020

An electrochemical study is presented for the nonsteroidal anti inflammatory drug called Diclofenac at pH 1 and 7, where the protonated and anionic species predominated respectively. It was found that in the presence of CTAB an adsorption process was carried out for both the protonated and the anionic species, respectively. Also, the critical micelle concentration for the system was determined in an aqueous medium. The analytic parameters like the detection and quantification limits in aqueous medium, and the sensitivity for this molecule were determined.
Ultrafast Anodic Growth of TiO2-Nanotubes with Semi-Metallic Properties
Authors: Hahn Robert , Schmuki P. , Kirchgeorg Robin
Published: February 2020

Self organized nanotubular structures of transition metal oxides grown on their metallic substrates, especially titanium [1], have attracted great scientific and technological interest due to the possibility to exploit their functional properties (such in photo-catalysis, electro-catalysis, solar energy conversion and as host for Li storage) in a nanotubular morphology. In contrast to the conventional way to grow anodic TiO2 nanotubes, which is an optimized electrochemical treatment of Ti in fluoride containing electrolyte (for an overview see [2]) this work reports on the growth of nanotubes by so-called RBA (rapid breakdown anodization).[3] This nanotube growth-process is in comparison extremely fast (seconds instead of hours) and leads to surface coatings consisting of dense packed bundles of nanotubes with very high aspect ratios (tube length up to 50 micrometer, tube diameter of ~40 nanometer). In addition, this method provides a new route for an insitu electrochemical doping during the growth of TiO2 nanotubular layers with various transition metals to adjust i.e. the photocatalytic activity [4]. The second part of the presentation will demonstrate that alternatively the electronic and optical properties [5] of these TiO2 nanotubes can be significantly modified, showing semi-metallic behavior by a high temperature reduction treatment in acethylene or ammonia creating a suitable platform for highly conductive surface area electrodes which is important i.e. sensing applications. [6]

Literature:

[1] V. Zwilling, M. Aucouturier, E. Darque-Ceretti, Electrochim. Acta, 45, 921 (1999).

[2] S. Berger, R. Hahn, P. Roy, P. Schmuki Phys. Status Solidi B247, 10, 2424 (2010).

[3] R. Hahn, J. M. Macak, P. Schmuki, Electrochem. Commun.,9, 947 (2007).

[4] M. Stark, R. Hahn, M.S. Killian, P. Schmuki Catal. Sci. Technol., 3, 1765 (2013).

[5] R. Hahn, F. Schmidt-Stein, J. Salonen, S. Thiemann, Y.Y. Song, J. Kunze,

V.-P. Lehto, P Schmuki, Angewandte Chemie - International Edition 48 (39), 7236 (2009).

[6] R. Hahn et al submitted
Atomic-Layer Electroless Deposition on Noble Metal Powders
Authors: Robinson David B. , Cappillino Patrick J. , Buffleben George M. , Salloum Maher , Benson David M. , Stickney John Lewellen
Published: February 2020

Palladium has important applications in an array of fields including hydrogen storage and sensing, chemical catalysis and fuel cells. It offers high volumetric power density in metal hydride batteries and pseudocapacitors. However, the rates of hydride formation and hydrogen release in such applications are often limited by the high stability of the surface hydride formed on Pd. Theoretical and experimental reports suggest that adlayers of metals that form weaker surface Pd-H interactions can destabilize the surface hydride, which should facilitate hydrogen transport.

We have developed a room-temperature electroless atomic layer deposition (ALD) technique in which we grow such layers on palladium powder. This is in contrast to electrochemical ALD, which requires applying a current to a substrate, and to gas-phase ALD, which requires elevated temperatures that can damage some substrates. Exposing a suspension of powder to dilute hydrogen/nitrogen gas mixtures causes a surface hydride to form. Subsequent addition of a solution containing noble metal salts displaces the surface hydride with the reduced metal in a surface-limited reaction. This process can be repeated, and the thickness of the surface coverage increases, as shown by X-ray photoelectron spectroscopy.

This technique requires no specialized equipment, and makes use of benign reagents. It is surface-limited in nature, but is not limited to an electrode. This confers important advantages of high scalability and compatibility with complex surface topologies; conductive substrates are not required. We believe that this versatile technique could be widely applied by synthetic chemists to take advantage of enhanced catalytic properties of near-surface alloys.

In addition to details on the preparation and characterization of Pd powder with adlayers of other noble metals, we will show evidence of enhanced hydrogen transport in these samples. A kinetic model for this process that includes gas flow, solid-state hydrogen diffusion and surface hydride formation will be presented.

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. SAND2013-8925A
Oxidation of Hydrogen Peroxide at Electrodeposited Platinum on Carbon Microelectrodes
Authors: Burgess Jim
Published: February 2020

Several genetic diseases are known to exhibit increased or decreased cellular cholesterol. A noninvasive means of characterizing cholesterol efflux at the human mucosa (oral cavity) may allow resolution of these disease states. Disk carbon microelectrodes are partially modified with electrodeposited platinum. Cholesterol oxidase is covalently linked to the platinum crystallites. The electrode is position in contact with the mucosa and the subject’s index finger is immersed in a beaker containing the reference electrode. Accumulation of enzymatically produced hydrogen peroxide is achieved by periodic oxidative depletion. A double potential pulse waveform allows background correction. Characterization experiments for electrode preparation will be discussed. Application of the measurement to cystic fibrosis monitoring and treatment is proposed.
Enhanced Oxygen Evolution Reaction Activity of LaFeO3 with Co-Pi Decoration
Authors: Peng Qi , Wen Yanwei , Shan Bin , Chen Rong
Published: February 2020

With the continuing energy demand and environmental deterioration by conventional coal and gasoline, it is urgent to develop renewable energy. Among many methods, water splitting to generate clean hydrogen fuels is among the most promising one. Many perovskites such as SrTiO3, NaTaO3 and AgNbO3 have become candidates materials for water splitting due to their high catalytic activity and flexible structures. However, the H2 production efficiency is relatively low at visible light regime because of the large band gap of most perovskite materials. From the view point of optical absorption, LaFeO3 with a band gap of 2.07eV [1] shall be a good candidate. Nonetheless, the poor oxygen evolution reaction (OER) performance of LaFeO3severely limits its water-splitting efficiency. To solve the problem, OER improvement is needed.

RuO2, IrO2 and Pt are the conventional OER catalyst [2-3], but they are of high cost. Co-Pi, an amorphous cobalt-phosphate-based material, is reported having a low over potential for OER in the phosphate buffer solution at pH 7~8[4] and its coating on hematite promotes the photoelecrochemistry performance effectively [5]. We report here the combination of the low cost Co-Pi with LaFeO3 to enhance the OER activity of LaFeO3. We demonstrate that an effective negative shift of 100meV for the onset potential with Co-Pi coating as OER improvement. The photoelectrochemical properties and its mechanism will also be discussed.

References:

K.M. Parida, Inter. J. of Hydrogen Energy, 35, 12161~12168 (2010).

E. Tsuji, A. Imanishi, K. I. Fukui, Y. Nakato, Electrochim.Acta, 56, 2009 (2011).

L. Ouattara, S. Fierro, O. Frey, M Koudelka, C. Comninellis, J. Appl. Electrochem, 39, 1361 (2009).

M. W. Kanan, D. G. Nocera, Science, 321, 1072–1075, 2008.

D. K. Zhong, D. R. Gamelin, J. Am. Chem. Soc, 131, 6086–6087,2009.
Binary Ionic Liquid Mixtures for Supercapacitor Applications
Authors: Lall-Ramnarine Sharon , Suarez Sophia , Zmich Nicole , Ewko Damian , Ramati Sharon , Cuffari David , Sahin Meriam , Adam Yara , Rosario Emely , Paterno Domenec , Wishart James
Published: February 2020

The need for improved energy storage capability in supercapacitors has prompted the use of ionic liquids as alternatives to acetonitrile based solvents. Despite the advantages of supercapacitors, their use in transportation is not favorable because of the deterioration of organic solvents with increasing temperatures and their high vapor pressures. We report here on the synthesis and characterization of ionic liquids optimized for use in supercapacitors. The cations were designed to bear ether substituents which are known to lower the viscosity of ILs. ILs and binary mixtures of ILs based on pyrrolidinium, imidazolium and dicationic ammonium cations bearing ether substituents and bis(trifluoromethylsulfonyl)amide [NTf2
-] anions have been synthesized, purified and characterized. The halide salts were synthesized by reaction of the amine with 2-bromoethylethylether. They were then converted to the NTf2 salts after purification. The structures of the salts were confirmed using H-1 and C-13 Nuclear Magnetic Resonance spectroscopy. The dicationic ILs were used as the solutes in the binary IL mixyures. The binary IL mixtures have been analyzed for their transport properties using NMR. The work at BNL was supported by the BNL Office of Educational Programs and the DOE Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract # DE-AC02-98CH10886.
Lanthanum Activity, Activity Coefficients and Solubility in Gallium-Indium Liquid Alloys
Authors: Dedyukhin Alexander S. , Shchetinskiy Andrey V. , Volkovich Vladimir A. , Yamshchikov Leonid F. , Osipenko Alexandr G.
Published: February 2020

Precipitation method is one of the simplest direct techniques for determining solubility of metals in liquid alloys. The main parameter influencing the separation of liquid and solid phases is their density. In our case the difference of densities of gallium-indium alloys and intermetallic compounds of lanthanum with gallium and indium is sufficient for separation of solid (intermetallic compound) and liquid phases during holding the supersaturated alloy at desired temperature. In the present study solubility of lanthanum was determined in binary Ga-In alloys containing 21.4 (eutectic), 40 and 70 wt.% In at 298–1081 K.

Time required for achieving equilibrium in Ga-In-La system was determined in a preliminary set of experiments. The experiments were performed at constant temperature with the samples of liquid alloys taken at certain time intervals. The amount of lanthanum added to the alloy exceeded its solubility limit. An example of the obtained results for Ga-40wt.% In alloy at 423 and 673 K is shown in Fig. 1. The minimum time needed for reaching constant La concentration was four hours and in the subsequent experiments this time interval was used as holding time between sampling the alloy.

Solubility of lanthanum in Ga-In eutectic alloy at 298–1081 K is shown in Fig. 2. The temperature dependence of lanthanum solubility has an inflection around 515 K which is most likely associated with increasing viscosity of the liquid alloy and difficulties in precipitating solid phase. Similar results were obtained for the alloys containing 40 wt.% indium at 428–983 K, Fig. 3, and 70 wt.% indium at 425–987 K, Fig. 4.

After each experiment the alloys were cooled to room temperature and intermetallic phases formed crystalline precipitates. The crystals were needle-shaped, from 2 to 8 mm in length. X-ray diffraction analysis showed that the precipitates consisted of two intermetallic phases, Ga3La and Ga6La. An example of the XRD pattern of the crystals precipitated from Ga-40 wt.% In based alloys is given in Fig. 5. The XRD patterns of the precipitates formed in Ga-21.4 wt.% In and Ga-70 wt.% In were similar.

Analysis of the samples showed that in all studied Ga-In systems (containing up to 70 wt.% In) only intermetallic compounds of lanthanum with gallium were formed irrespectively of indium content in the alloy, the only difference being in the ratio between Ga3La and Ga6La. Decreasing gallium content in the alloy resulted in increasing fraction of Ga3La intermetallic compound in the solid phase. Indium in the studied systems acted merely as an inert additive.
Ionic Liquid-Based Solvents for Natural Fiber Welding: Impact of Solvent System Composition
Authors: Brown E. Kathryn , Haverhals Luke M. , Fox Douglas M , De Long Hugh C. , Trulove Paul C.
Published: February 2020

Certain ionic liquids (ILs) are known to be efficient solvents for biopolymers, in particular for cellulosic and silk based materials1. The ionic liquid solvent efficiency is strongly impacted by the presence of both impurities (e.g., water, residual reagents) and intentional additives (e.g., co-solvents or diluents)3,4. Natural fiber welding (NFW), the process of controlled partial dissolution and regeneration of biopolymers,5-7 is also affected by the presence of impurities and additives8.

In this work we investigate the impact of impurities and additives on NFW. The extent of NFW was characterized by x-ray diffraction, ATR-IR, SEM, and mechanical property testing. These data are correlated with solvent physical properties, such as viscosity, density, and surface tension, as well as with solvent properties as indicated by their Kamlet-Taft parameters.

For some of the systems investigated, there is a maximum solvent composition where polar aprotic solvents in conjunction with IL are more efficient at NFW than the IL alone. Surprisingly, this composition occurs when the mole ratio of IL to solvent is less than one to one. Understanding the factors that influence welding in these systems allows for greater control over the NFW process and facilitates the formation of functional biopolymer composite materials.

References

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Phillips, D. M.; Drummy, L. F.; Conrady, D. G.; Fox, D. M.; Naik, R. R.; Stone, M. O.; Trulove, P. C.; De Long, H. C.; Mantz, R. A. J Am Chem Soc., 2004, 126, 14350.

Rinaldi, R. Chem. Commun., 2011, 47, 511.

Mazza, M.; Catana, D. A.; Vaca-Garcia, C.; Cecutti, C. Cellulose, 2009, 16, 207.

Haverhals, L. M.; Reichert, W. M.; De Long, H. C.; Trulove, P. C. Cellulose, 2010, 2985, 425.

Haverhals, L. M.; Sulpizio, H. M.; Fayos, Z. A.; Trulove, M. A.; Reichert, W. M.; Foley, M. P.; De Long, H. C.; Trulove, P. C.Cellulose, 2012, 19, 13.

Haverhals, L. M.; Nevin, L. M.; Foley, M. P.; Brown, E. K.; De Long, H. C.; Trulove, P. C. Chem.Commun., 2012, 48, 6417.

Haverhals, L. M.; Brown, E. K.; Foley, M. P.; De Long, H.; Trulove P. ECS Trans, 2012, 50, 6
Inkjet Printing Ionic Liquids for the Fabrication of Surface Structures on Biopolymer Substrates
Authors: Sweely Kurt D. , Fox Eric T. , Brown E. Kathryn , Haverhals Luke M. , De Long Hugh C. , Trulove Paul C.
Published: February 2020

Inkjet printing has become an increasingly popular tool for materials science research due to its ability to rapidly create small devices with excellent precision and reproducibility. Recent studies have utilized inkjet printing for the construction of inexpensive devices using ink-mimicking solutions containing various materials of interest (magnetic, sensing, electronic)[i],[ii],[iii]. By varying the chemical nature of these inks, inkjet printing becomes a robust, versatile, and accessible tool for small scale material fabrication.

Ionic liquids (IL) have been the focus of materials research for some time due to their unique physical and chemical properties. Of significant interest is their ability to solubilize biopolymers such as cellulose and silk[iv]. When paired with inkjet printing, these ILs allow for variable, reproducible modification of biopolymers. By incorporating materials of interest into these IL inks, inkjet printing presents an extremely powerful tool for small scale fabrication with a myriad of applications. In this research we will discuss the modification of surface structures through the inkjet printing of neat IL, IL’s containing nano and micro-scale particles, and IL/polymer solutions.

[i] Delaney, J. T., Jr.; Smith, P. J.; Schubert, U. S. Inkjet Printing of Proteins. Soft Matter, 2009, 24, 4866.

[ii] Singh, M.; Haverinen, H. M.; Dhagat, P.; Jabbour, G. E. Inkjet Printing – Process and Its Applications. Adv. Materials, 2010, 22, 673.

[iii] Hu, C.; Bai, X.; Wang, Y.; Jin, W.; Zhang, X.; Hu, S. Inkjet Printing of Nanoporous Gold Electrode Arrays. Anal. Chem.
2012, 84, 3745.

[iv] Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. Dissolution of Cellulose with Ionic Liquids. J. Am. Chem. Soc., 2002, 18, 4974.
ORR on Platinum Single Crystal Electrodes. pH Effects
Authors: Herrero Enrique
Published: February 2020

Oxygen reduction reaction is a structure sensitive reaction, as the studies with single crystal electrodes demonstrates. Additionally, anion adsorption and pH also affects significantly the activity of the platinum electrodes. In this communication, we will describe recent results on the effects of pH and anion adsorption on the activity of platinum single crystal electrodes for the ORR. In acidic solution, the highest activity is observed for surfaces with a high step density both in perchloric and sulfuric acid media. This fact implies that the step is an active site for the ORR in these acidic media. However, a completely different scenario is found in alkaline solutions. In 0.1 M NaOH, the Pt(111) electrode has the highest activity and the presence of steps significantly diminishes the activity of the surface. Moreover, the extrapolation of the results suggests that the activity of the step is very small in comparison with that of the (111) terrace. Initially, it could be expected that the activity of the electrode in 0.1 M NaOH and 0.1 M HClO4 was the same, because there is no specific adsorption of anions in both media, and the only possible adsorbed species at the onset of the ORR is OH. However, the observed differences between both media clearly indicates that significant changes in the interphase occurs associated with the pH change. These results will be analyzed in view of the experimental and DFT calculations to determine the role of the possible adsorbed species on the surface in the activity of the surface for the oxidation.
Stability and Activity of Core-Shell and Alloy Catalysts for Proton Exchange Membrane Fuel Cells (PEMFC)
Authors: Virkar Anil V.
Published: February 2020

State-of-the-art PEMFC use platinum-based catalysts as cathodes. The high cost of Pt and tendency for catalyst degradation at the cathode is the principal reason for devising ways of minimizing the amount of Pt used and ways to enhance catalyst activity and durability. Approaches used to decrease the Pt loading include alloy formation and forming core-shell catalyst with non-noble metal as the core. Alloying as well as the formation of core-shell catalyst alters both the thermodynamics (specifically the chemical potential of Pt) as well as the activity for the oxygen reduction reaction. Extensive literature exists on the processing and characterization of alloy catalysts and core-shell catalysts. The activity as well as the stability of the catalyst also depends on the nature of the support. For instance, it is known that the stability of the catalyst depends on whether or not the support surface is functionalized with certain groups. The stability of the catalyst depends on the nature of the environment it is exposed to, the composition and structure of the catalyst, particle size distribution, the operating cell voltage, and the type and the nature of the support. Virtually all aspects of the stability of the catalyst can be described in terms of classical thermodynamics and the role of coupled transport through the catalyst support and aqueous/ionomer medium. The main objective of this presentation is to demonstrate the role of classical thermodynamics and the kinetics of coupled transport in designing stable and highly active catalysts as cathodes for PEMFC.