bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of High Capacity Catholyte Material for Non-Aqueous Redox Flow Batteries
Authors: Huang Jinhua , Su Liang , Ferrandon Magali , Brushett Fikile , Burrell Anthony K. , Zhang Lu 
Published: February 2020

Non-aqueous redox flow batteries (NRFBs) have attracted increasing attention due to their significant potential to integrate the renewable energy sources (e.g., solar and wind) into electrical grid. Unlike the traditional rechargeable batteries which store energy within solid electrodes, the active materials of NRFBs are stored in a flowable phase in two external tanks and pumped to a power-generating electroreactor. This configuration offers remarkable flexibility in terms of energy, power and even safety control. Material development of redox active molecules, especially redox active organic molecules (ROMs) is crucial to enable the extensive deployment of this energy storage technology. A family of dimethoxybenzene based molecules has drawn significant attention due to their excellent electrochemical behavior as NRFB catholytes. In this presentation, our recent efforts toward the high capacity catholyte material deriving from our previous research on 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxybenzene) will be discussed. The developing story of those new ROMs as well as their electrochemical reversibility, solubility, conductivity, and galvanostatic cycling will be covered.
Electrochemical Modification of Carbon Surfaces with Functional Polymers
Authors: Devadoss Anando , Xue Cuihua , Tsai Han-Kuan 
Published: February 2020

Surface modification of carbon materials with biological molecules under ambient condition is desirable for construction of biosensor and bioelectronic devices. Some of the desirable factors for surface modification are (i) robust attachment of biomolecules for stable biosensor response, (ii) high surface coverage of biomolecules for good signal/noise ratio and wide dynamic range, and (iii) rapid modification under ambient condition for facile and scalable manufacturing.
A new method to electrochemically modify carbon electrodes using a benzothiadiazole-based conjugated polymer will be discussed. The method provides rapid modification of carbon materials with biomolecules, robustly attached to the surface through the polymer. The usefulness of the method will be demonstrated by construction of an electrochemical cholesterol biosensor. The biosensor exhibits amperometric detection of cholesterol in buffer and serum samples in presence of a soluble mediator. Details regarding the preparation of biomolecule-coupled polymer, surface modification and sensor performance will be discussed.
The Mechanism of Electrochemical Oxygen Reduction: A Combined DFT and in-Situ ATR-IR Study on Model Semiconductor Surfaces Ge(100) and ZnO
Authors: Biedermann P. Ulrich , Nayak Simantini , Erbe Andreas 
Published: February 2020

The electrochemical oxygen reduction reaction (ORR) is a fundamental reaction with relevance in many fields including fuel cells and corrosion. The reaction mechanism is controversially debated and strongly dependent on the electrocatalytic surface, electrolyte, pH and applied potential. Many studies have focused on high-performance noble metal catalysts, however, semiconducting oxides often form at the metal/electrolyte interface. Therefore we have studied the ORR mechanism at model semiconductor electrodes, using a combination of in-situ attenuated total reflection infrared (ATR-IR) spectroscopy and DFT modeling. We have identified several reaction intermediates on the n-type Ge(100) surface [1,2] and on zinc oxide by their characteristic vibrational modes.
The reaction mechanism in terms of elemental steps of electron transfer and proton transfer and hence including charged intermediates is studied with DFT. The model is based on small clusters representing the surface interacting with the solvated ORR intermediates. Solvent effects were treated by a combination of explicit water molecules and a self-consistent reaction field approach. The influence of pH and electrode potential on the energetic course of the ORR reaction is analysed. We identify the catalytically active surface site and propose a detailed catalytic cycle in terms of electron transfer, proton transfer and bond breaking/forming as elemental steps. The calculated IR-frequencies agree well with our experimental results.
[1] S. Nayak, P.U. Biedermann, M. Stratmann, A. Erbe, Pys. Chem. Chem. Phys. 15, 5771 (2013)
[2] S. Nayak, P.U. Biedermann, M. Stratmann, A. Erbe, Electrochimica Acta 106, 472 (2013)
Using Vapor-Grown RuxPty and RuxPdy Nanoparticles to Investigate the Hydrogen Oxidation Reaction Mechanisms in Alkaline Electrolyte
Authors: St. John Samuel , Atkinson Robert W. , Unocic Raymond R , Papandrew Alexander B. , Zawodzinski Thomas A. 
Published: February 2020

We have developed a method for the synthesis of metallic and alloy nanoparticles dispersed on carbon supports that is based on a chemical vapor deposition process. This technique is applied here to investigate the mechanism of the hydrogen oxidation reaction (HOR) in alkaline media for which competing theoretical frameworks have been proposed in the literature. Such frameworks either hypothesize that molecular hydrogen dissociative adsorption (Tafel step) is rate limiting or that electron transfer (Volmer/Heyrovsky step) is rate limiting.
Our objective was to elucidate the HOR reaction mechanism using Tafel slope data collected in alkaline media while using small changes in alloy composition to look for trends in the changes of M-H binding energy as a descriptor for activity changes. Such data will be used to inform future in situ investigations of adsorbate coverage and binding energy using x-ray spectroscopy.
Pt, Pd, Ru, as well as alloys of RuxPty and RuxPdy nanotubes were synthesized from metal-organic precursors onto Vulcan carbon support. Standard electrochemistry was conducted in conventional three-electrode cell hardware with a working electrode deposited onto glassy carbon with a Pt wire counter electrode and a double-junction Ag/AgCl reference electrode. Electrochemical data were collected at 2500 rpm under 1 atm H2 in 0.1M KOH at 1 mV/s to minimize the contribution from capacitive currents. HOR activity was measured using staircase voltammetry, averaging the sampled current over the last 20% of the dwell time. Data were fit according to the standard Tafel analysis approach to determine Tafel slope along with fits by specific electrochemical models particular to a Tafel or Volmer rate-determining step.
HAADF-STEM images of the nanoparticles and XRD data suggest alloyed nanoparticles with some intraparticle atomic clustering. Electrochemical charging currents were consistent with similar surface and bulk compositions. The activity results revealed that the rate-determining step depends upon the choice of alloy materials and that both mechanisms present themselves accordingly. Additionally, the Pt-rich alloys with Ru exhibited HOR activity several times higher than pure Pt and comparable to the mass-transport limited current. These results suggest not only that a low-cost, alkaline anode catalyst is possible, but also that it is tantalizingly close to reality.
Investigation of Mass Transport in Mesoporous Semiconducting Thin Film Electrodes
Authors: Meunier Carl , Roberts Ethan , Remsen Edward E. , Haverhals Luke M. 
Published: February 2020

Development of novel thin film electrodes may enable new commercial products ranging from in vivo biosensors to solar cells. A critical consideration that assists the engineering of working devices is mass transport of electro-active species and solvent/electrolytes within porous thin film electrodes. Our presentation will focus on the fabrication and characterization of transport within thin film electrodes fabricated from titanium dioxide nanospheres, nanorods and nanotubes via sol-gel methods. We will present initial characterization data for films deposited on indium tin oxide coated glass slides by doctor blade techniques. Results include bright field and phase microscopy characterizations that probe the pore structure, surface morphology, and that yield physical dimensions of the films. Electron microscopy data will be presented that characterize particle dimensions and morphological differences resulting from multiple processing procedures. Powder x-ray diffraction data will be presented that investigate the crystal structure of the semiconducting films. Finally, mass transport properties as investigated by cyclic voltammetric techniques will be presented. Results will be correlated with fabrication techniques and associated material types and morphologies.
Study of the Kinetics of Redox Active Polymers in Non-Aqueous Media Under High Mass-Transfer Conditions Using Scanning Electrochemical Microscopy
Authors: Lichtenstein Timothy , Rodríguez-López Joaquín 
Published: February 2020

We present on the use of Scanning Electrochemical Microscopy (SECM) to quantify the reaction kinetics of redox active polymers with molecular weights between 21 and 318 kDa that have been shown as promising mediators for non-aqueous redox flow cell batteries. [1] The promise of these mediators is that they are highly soluble in cost effective organic solvents, e.g. up to 2.7 M in acetonitrile, have tunable size, and reversible electrochemical behavior. However, it is not well understood how the kinetics of electron transfer, and its mechanisms, might change on these polymers with increasing size and concentration. Experiments have also shown that these polymers produce electroactive films on Pt and C electrodes, therefore elucidating the charge transfer properties of these films is important in evaluating their electrochemical performance under flow conditions. SECM can be used by combing the information obtained from approach curves in the feedback mode with the steady state voltammetry at ultramicroelectrodes of known size to determine the electron transfer rate and other kinetic information. [2] Imaging of polymer films in the feedback mode can also complement with useful information about the heterogeneity of charge transfer and charge transport on working electrodes. Fundamental knowledge of the kinetics of redox active polymers allows for better prediction of the effects of size and functionalization for analogous systems.
[1] Gavvalapalli, N.; Hui, J.; Cheng, K.; Lichtenstein, T.; Shen, M.; Moore, J.S.; Rodríguez-López, J. J. Am. Chem. Soc. 2014, 136, 16309-16316
[2] Mirkin, M. V.; Bard, A. J. J. Anal. Chem.
1992, 64, 2293–2302.
Charge-Transfer and Photocatalytic Hydrogen Production By Hydrogenase Photobiohybrids
Authors: King Paul W , Brown Katherine A , Mulder David W , Ratzloff Michael W , Lubner Cara 
Published: February 2020

Hydrogenases are metalloenzymes that catalyze H2 activation at of ≥104 s-1 using base metals (Fe, Ni, S) and a polypeptide framework. Understanding the structural properties of hydrogenases, including the cataltyic site cofactors, has provided inspiration for designing highly functional synthetic catalysts. We have been invetigating hydrogenase structure-function and use as electrocatalysts on nanostructured electrodes, and photocatalysts in solution-phase assemblies with nanomaterials. In both cases, the hydrogenase provides the catalytic power for converting photo(electro)chemical energy into H2. The chemistry of (nano)materials can be used control their physical and molecular properties over a wide-range of energy and size scales for integrating with the catalytic and sturctural propeties of hydrogenases. As a result, the biohybrid complexes are being investigated as models to determine how material compositions, charge-transfer interfaces and bulk properties affect the mechanisms that support photocatalysis. A summary of our recent progress in this area of research will be presented.
Controlled Layer-By-Layer Polymer/DNA Coating of Carbon Nanotubes for Gene Delivery Applications
Authors: Majedi Fatemeh Sadat , Keshvari Hamid , Hasani-Sadrabadi Mohammad Mahdi , Renaud Philippe , Tayebi Lobat 
Published: February 2020

Considering the growing attention toward gene delivery, different vectors have been developed; viral and non-viral. Although viral vectors have shown higher DNA transfection efficacies, but features such as their complicated preparation procedure, the risk of being immunogenic, and their limited capacity for gene transfer, has led scientists to think about non-viral carriers. Using nanoparticles as genetic carriers introduced a new era in this field. Due to their ease of functionalization, less toxicity, and higher capacity, nanoparticles are now considered as suitable carriers for gene delivery. Moreover, one-dimensional nanomaterials have proved to have better cell internalization. As an interesting method to form or manipulate polymeric nanoparticles, we have recently developed microfluidic devices for having adjustable and uniform particles at nanoscale. Applying variable central and lateral flows, the resulted particles can be tuned as our desires. In the present work, we have used short length carbon nanotubes (CNTs) as our carrier due to its needle like structure that makes it suitable for cell internalization. Then it is coated it in a layer-by-layer procedure, through sequentional microfluidic platform, with Chitosan (decorate CNT with positive charges), plasmid DNA, and again Chitosan (protect DNA and provide positive charges). The first chitosan layer balances the charge for better DNA interaction, performed in the first micromixer, and the final chitosan coat, which is done in the third micromixer, tunes the charge for better cell internalization. The results confirm the ability of our microfluidic systems to finely tune the coating thickness (in each step), DNA loading content, and the overall charge of these vectors which can affect the protein expression of target cells.
(Invited) Anti-Ambipolar, Gate-Tunable p-n Heterojunctions
Authors: Hersam Mark C. 
Published: February 2020

The recent emergence of two-dimensional (2D) materials has enabled the realization of atomically thin heterostructure devices [1]. Of particular interest are heterojunctions based on p-type and n-type semiconductors since these devices possess non-linear, gate-tunable transport characteristics. Here, we demonstrate a gate-tunable p-n heterojunction diode using thin films of semiconducting single-walled carbon nanotubes (s-SWCNTs) and single-layer molybdenum disulfide (SL-MoS2) as p-type and n-type semiconductors, respectively [2]. The vertical stacking of these two direct band gap semiconductors forms a heterojunction with electrical characteristics that can be tuned with an applied gate bias over a wide range of charge transport behavior ranging from insulating to rectifying with forward-to-reverse bias current ratios exceeding 104. The transfer characteristic of this p-n heterojunction shows a unique 'anti-ambipolar' behavior with two off-states at either extreme of the gate voltage range and a current maximum in the middle. The continuous transition from positive to negative transconductance in an anti-ambipolar characteristic enables operation of analog communication circuits with a reduced number of circuit components compared to unipolar transistors. Anti-ambipolarity can be widely generalized to heterojunctions of other materials such as s-SWCNTs and n-type amorphous indium gallium zinc oxide (a-IGZO), ultimately leading to all solution processed p-n heterojunctions at the wafer scale [3].
[1] D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks, and M. C. Hersam, "Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides," ACS Nano, 8, 1102 (2014).
[2] D. Jariwala, V. K. Sangwan, C.-C. Wu, P. L. Prabhumirashi, M. L. Geier, T. J. Marks, L. J. Lauhon, and M. C. Hersam, "Gate-tunable carbon nanotube-MoS2 heterojunction p-n diode," Proc. Nat. Acad. Sci. USA, 110, 18076 (2013).
[3] D. Jariwala, V. K. Sangwan, J.-W. T. Seo, W. Xu, J. Smith, C. H. Kim, L. J. Lauhon, T. J. Marks, and M. C. Hersam, "Large-area, low-voltage, anti-ambipolar heterojunctions from solution-processed semiconductors," submitted, 2014.
Covalent Functionalization of Graphene
Authors: Hirsch Andreas 
Published: February 2020

We will report on new covalent functionalization concepts for graphene. For this purpose we reductively activate graphene to generate metal graphenides. These intermediates can be quenched by electrophiles such as diazonium compounds, alkyl iodides, iodonium salts, protons and bromine. For the representative structural characterization of the reaction products we have developed statistical Raman spectroscopy and Raman microscopy together we TGA/MS/GC. This allows us to determine not only the precise degree of functionalization but also allows for the investigation of the spatially resolved product homogeneity. In some case the degree of functionalization is so high that yellow fluorescent graphene derivatives were obtained.
Precision Engineering of Co-Laminar Flow Cells for Electrochemical Energy Conversion
Authors: Goulet Marc-Antoni , Kjeang Erik 
Published: February 2020

Most electrochemical cells used for energy conversion utilize a physical separator such as an ionomer membrane to keep reactants separated and prevent a mixed potential from reducing energy efficiency. A new class of electrochemical cell achieves this separation by design of channel dimensions such that reactant flows remain laminar. These co-laminar flow cells (CLFC)1,2, which include both fuel cells and flow batteries, are generally microfluidic and constrained in operation by the diffusion time of reactants across the channel. Due to their small scale and lack of a membrane, these co-laminar flow cells are both simpler and lower cost devices which make them well suited as an experimental platform for understanding electrochemical energy conversion. The cells in this study are based on flow-through porous carbon electrodes with vanadium redox reactants dissolved in sulfuric acid as both fuel and oxidant. This presentation reveals some of the advancements made with these cells over the past year and the lessons learned which may be applied to larger scale conventional flow batteries and fuel cells.
Some of the topics to be discussed include electrode enhancement to improve the limiting reaction rate, supported by both ex situ and in situ characterization of the flow-through porous electrodes. Reaction kinetics are studied using a custom-developed three-electrode analytical cell for electrochemical analysis of flow-through porous electrodes. Multiphysics modeling work based on this characterization provides insight into some of the design principles which can be used to maximize the power density of these devices.

Acknowledgements

Funding for this research provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for Innovation, and British Columbia Knowledge Development Fund is highly appreciated.

References:

1. Goulet, M.-A. & Kjeang, E. Co-laminar flow cells for electrochemical energy conversion. J. Power Sources
260,186–196 (2014).
2. Kjeang, E. Microfluidic Fuel Cells and Batteries. (Springer, 2014).
A Novel Titanium/Manganese Redox Flow Battery
Authors: Dong Yong-Rong , Kaku Hirokazu , Hanafusa Kei , Moriuchi Kiyoaki , Shigematsu Toshio 
Published: February 2020

Toward the realization of a low-carbon society, renewable energies such as wind and solar power have been promoted rapidly around the world. Since such renewable energies have a fluctuating power output due to the variability of weather, the increasing amounts of such energy sources will bring stability problems to conventional power system. Electrical energy storage systems are expected to solve these problems, and large-scale batteries attach more attention than ever. Redox flow (RF) batteries have several advantages comparing to solid batteries, such as easy to capacity scale up, long cycle life, real time state of charge (SOC) monitor, which make them the most suitable for power network stabilization.
RF batteries have been enthusiastically developed worldwide, since its principle was publicized in the 1970s by NASA[1], all vanadium system as a representative of them has been put in practical applications[2]. To meet the growing demand for electrolytes, it is generally desired that active metals should be lower cost, higher electrode potential and stable supply than vanadium. Mn(II)/Mn(III) redox couple as a positive active material meets the requirements mentioned above. However, Mn(III) ion is chemically unstable and tends to disproportionate to Mn(II) ion and MnO2 oxide, which make it difficult to be used in flow batteries.
We found that the precipitation of MnO2 can be effectively suppressed by containing Mn ions as well as Ti(IV) ions in positive electrolyte. We gained a very good cycle charge-discharge performance in a cell test, even at SOC in a range of more than 100%, in this case SOC is calculated on Mn(II)/Mn(III) one-electron reaction. It considered that Ti(IV) ions exiting in positive electrolyte suppress the Mn(III) disproportion reaction, as well as particle growth of MnO2. The theoretical energy density of positive Mn and negative Ti electrolytes RF battery is around 26kWh/m3, which is comparable to that in all vanadium RF battery.

References

[1] N. H. Hagedorn, NASA Redox Storage System Development Project Final Report, DOE/NASA/12726-24, NASA TM-83677(1984)
[2] T. Shigematsu, Redox Flow Battery for Energy Storage, SEI Technical Review, Number 73, (October, 2011)
Non-Destructive High-Resolution Conductivity Mapping of Thin-Film Battery Electrodes
Authors: Riet Adriaan A , Sedgewick J Scott , Vogel John E , Clement Derek , Cutler Andrew D , Mazzeo Brian A , Wheeler Dean R 
Published: February 2020

Accurately determining electronic conductivity of thin-film battery electrodes is not trivial, especially with the metallic current conductor still attached. A fast and reliable method would be of use for quality control and optimization purposes in battery manufacture, and would provide insight into the effects of changes in the fabrication process on the electrode structure.
We report a four-line probe that has been used to make high-resolution maps of local electrode conductivity on the micron scale. A computer-controlled apparatus allows precise control of pressure on the sample and positioning of the probe. A significant part of the work was developing a novel hybrid numerical-analytical model to invert the experiment, allowing a separate determination of film conductivity and contact resistance at the current collector in real time on a desktop computer. We will discuss the amount of local conductivity variation within representative electrode films.
This work was supported by the U.S. Department of Energy through the BMR program.

Figure 1