bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Superoxide Anion in the Oxygen Reduction Reaction in Non-Aqueous Electrolytes with a Proton or Lithium Source
Authors: Zhang Yelong , Zhang Xinmin , Wang Jiawei , Chen Yuhui , McKee William C. , Bruce Peter G. , Xu Ye , Peng Zhangquan 
Published: February 2020

The non-aqueous Li-air (O2) battery has generated a great deal of research interest because it potentially possesses far greater gravimetric energy storage density than today’s rechargeable battery technologies.1-4 Presently non-aqueous Li-O2 batteries suffer from irreversible reactions, including those due to impurities such as residual protons and proton-containing compounds that can react with reduced oxygen species. To eliminate or alleviate the undesired reactions, it is crucial to have a fundamental understanding of the reactive oxygen species involved in the oxygen reduction reaction (ORR).
In this talk we will present the results of a series of electrochemical studies of the ORR on a gold electrode in non-aqueous dimethyl sulfoxide (DMSO) electrolytes containing a proton or lithium source with TBAClO4 as supporting ions. The superoxide anion (O2
-), the one-electron reduction product of O2, is identified in situ spectroscopically in both systems. When the DMSO contains phenol as the proton source, O2
-, not HO2, appears as the first stable intermediate during the ORR upon cathodic scans, with H2O2 co-appearing at high overpotentials.5 When instead LiClO4 is added to DMSO, again O2
- is the first reaction intermediate to be detected, whereas surface LiO2 does not appear until the potential is much more negative of the Li2O2 formation potential. The stability of O2
- vs. the other reduced O2 species is rationalized based on first-principles theoretical modelling and calculations. Our studies show that the ORR mechanism depends intimately on the electrode potential and electrolyte composition, and contribute new mechanistic understanding for this reaction that is of fundamental importance to electrochemical energy storage and conversion technologies.
1. P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J.-M. Tarascon, Nat. Mater. 2012, 11, 19.
2. J. Lu, L. Li, J.-B. Park, Y.-K. Sun, F. Wu, K. Amine, Chem. Rev.
2014, 114, 5611.
3. A.C. Luntz, B.D. McCloskey, Chem. Rev.
2014
, 114, 11721.
4. R. Black, B. Adams, L.F. Nazar, Adv. Energy Mater.
2012, 2, 801
5. Z. Peng, Y. Chen, P.G. Bruce, Y. Xu, Angew. Chem. Int. Ed.
2015, 54, 8165.
The Peformance of Nano Urchin-like NiCo2O4 Modified Activated Carbon As Air Cathode for Microbial Fuel Cell
Authors: Li Kexun , Ge Baochao 
Published: February 2020

A nano urchin-like NiCo2O4 has been successfully synthesized via a facile and scalable hydrothermal method. A NiCo2O4 modified active carbon air cathode was designed, optimized and fabricated. The maximum power density of the microbial fuel cell with newly developed cathode is 2.28 time higher than bare active carbon and is comparable to the commercial available Pt/C, reaching 1730 ± 14 mW m-2. The modified active carbon showed remarkable improvement in activity towards the oxygen reduction reaction, which was due to the lower charger transfer, lower activation barrier, and higher exchange current density. Electrochemical evaluation showed a direct four-electron the oxygen reduction reaction on NiCo2O4 modified active carbon, compared to a two-stage process on bare active carbon. The non-precious NiCo2O4 could be considered as a promising alternative to the costly Pt.
(Invited) Development of Semiconductor Quantum Dots and Their Interfacial Dynamics for Solar Energy Conversion
Authors: Tachibana Yasuhiro 
Published: February 2020

Semiconductor quantum dots (QD) have received considerable interest as a novel material in solar energy conversion devices. The attractive property of these dots is known as “quantum size effect”, where the band gap energy becomes larger by reducing QD size. By employing this concept, the light absorption wavelength range can be tuned by controlling the QD size. In addition to this effect, by selecting appropriate elements, the light absorption range can be selected from UV or visible to near infrared region. This wavelength tunability is particularly attractive to designing a photocatalytic device such as solar water splitting, hydrogen generation or CO2 fixation devices.
The potential energy levels of the QD conduction and valence bands can also be adjusted with the QD size. An appropriate size will be selected to optimize efficient photo-induced charge separation and to retard charge recombination at the QD interfaces (Optimum Gibbs free energy difference), thereby facilitating performance improvement of solar energy conversion devices.
We are also interested in elucidating mechanisms of photocatalytic reactions at semiconductor interfaces. In particular, identification of interfacial reaction rates would be useful to design appropriate structures and selection of nanomaterials.
In this presentation, we will show some designs of synthesizing semiconductor quantum dots. Also, some examples of identifying interfacial dynamics employing time-resolved laser spectroscopies will be presented.
This work was financially supported by JST PRESTO program, Japan. The author also acknowledges Australian Research Council (ARC) LIEF grant (LE140100104) and the Office for University-Industry Collaboration, Osaka University, for the financial supports.
(Invited) Photoelectrochemical Investigation of Ta3N5 Films on TCO Substrates Synthesized Via Atomic Layer Deposition for Photocatalytic Water Splitting
Authors: Hamann Thomas 
Published: February 2020

Solar driven photoelectrochemical (PEC) water splitting is a promising method to store solar energy in chemical bonds. Tantalum nitride (Ta3N5) has recently emerged as a promising candidate for PEC water splitting. Most of the studies on Ta3N5 begin with a similar synthetic route, consisting of an initial oxidation of Ta(0) metal to Ta(IV), followed by ammonolysis at elevated temperatures ( > 850 °C). Despite the simplicity of this method, there are also several drawbacks. Importantly, the high temperature ammonolysis limits the utilization of transparent conductive oxide (TCO) substrates which are necessary for fundamental photoelectrochemical measurements. In addition, lack of viable TCOs thwart use of Ta3N5 as the top electrode in a tandem PEC cell.
As a solution to the above problems, we will present the synthesis of Ta-doped TiO2 (TTO) as a TCO substrate via atomic layer deposition (ALD) which we found to be stable in reducing atmospheres. ALD was also used to directly deposit thin films of Ta3N5 on TTO. While initial attempts produced as-deposited films are primarily amorphous TaOxNy, these films can be nitridized to Ta3N5 at far more moderate conditions compared to all previous reports and ALD–deposited tantalum oxide analogue films. The photoelectrochemical properties of the TTO/Ta3N5 films were investigated and the PEC water oxidation performance was analyzed. The excellent material control reported here allowed for a detailed material structure – function relationship to be determined and a path to improved performance elucidated. Initial results of a modified procedure, including ALD precursor and temperature variations, which allowed the direct synthesis of crystalline Ta3N5 on TTO substrates, will also be presented.
(Invited) Hierarchical Inorganic Assemblies for the Photocatalytic Reduction of CO2 By H2o
Authors: Frei Heinz 
Published: February 2020

The multi-electron processes of CO2 reduction and H2O oxidation, which constitute the essential reactions of sunlight to fuel conversion (artificial photosynthesis) require efficient coupling of light absorber and catalyst. Using all-inorganic heterobinuclear units such as ZrOCo anchored on high surface area silica, we have developed photodeposition methods for the directional assembly of nanometer sized catalyst clusters for H2O oxidation or CO2 reduction with proper coupling to the binuclear light absorber. Copper oxide nanoclusters were assembled adjacent to the Zr acceptor sites of the heterobinuclear unit, and light driven reduction of CO2 upon excitation of the ZrOCo unit demonstrated. Illumination of the ZrOCo chromophore coupled to a metal oxide nanocatalyst for H2O oxidation affords closing of the photocatalytic cycle in the absence of sacrificial agents. Time resolved FT-IR spectroscopy provided detailed mechanistic insight into the multi-electron reactions of H2O oxidation and CO2 reduction on the metal oxide catalyst surfaces under reaction conditions, with surface intermediates and their kinetics uncovered for the first time.
To achieve CO2 photoreduction by H2O under product separation on the nanoscale, Co3O4-SiO2 core-shell nanotubes were developed in which the inner surface acts as efficient water oxidation catalyst while the nanoscale silica layer with embedded molecular wires serves as a proton conducting, gas impermeable separation membrane with tight control of electron transport. Completing the photocatalytic cycle on the nanoscale seeks to minimize side reactions and efficiency degrading transport processes. Characterization of the assembly by transient spectroscopy and photoelectrochemical measurements will be discussed.
References
Zhang, M.; de Respinis, M.; Frei, H. Nature Chem.
2014, 6, 362.
Kim, W.; Yuan, G.; McClure, B. A.; Frei, H. J. Am. Chem. Soc.
2014, 136, 11034.
McCure, B. A.; Frei, H. J. Phys. Chem. C
2014, 118, 11601.
Kim. W.; Frei, H. ACS Catal.
2015, 5, 5627.
Yuan, G.; Agiral, A.; Pellet, N.; Kim, W.; Frei, H. Faraday Discuss.
2014, 176. 233.
Edri, E.; Frei, H. J. Phys. Chem. C
2015, 119, 000.
A Differential Electrochemical Mass Spectrometric (DEMS) Study of the Electrocatalytic Reduction of CO2 on Cu and Au/W Electrode Surfaces
Authors: Javier Alnald , Baricuatro Jack Hess , Kim Youn-Geun , Soriaga Manuel P 
Published: February 2020

This work describes the employment of differential electrochemical mass spectrometry (DEMS) to investigate selectively pre-adsorbed reactants and (postulated) intermediates as a supplementary experimental approach in the study of the reaction mechanism of the Cu-catalyzed electrochemical reduction of CO2. The results show the following empirical inferences: (i) CO is one of the first products of CO2 reduction, as well as the first intermediate in more advanced reactions that include formation of hydrocarbons and oxygenates; this is in conformity with the (almost) unanimously held view. (ii) Formaldehyde, HCHO, is not a precursor for C=C double-bond formation. (iii) HCHO is an intermediate for the production of methane and ethanol. (iv) Methane and ethanol can be generated from adsorbed CO via two ways: one requires a theoretically postulated surface species, CO protonated on the C atom, and the other involves adsorbed HCHO, constituted after the rate-limiting CO-protonation step. (v) The generation of CH4 and CH3CH2OH from CO has a much higher activation barrier than from HCHO; not unexpected since the formaldehyde intermediate is formed after the slow Cu–OCH formation and, consequently, is not highly activated.
This work also presents a study based on DEMS that tested the theoretical prediction suggesting the viability of a bimetallic near-surface alloy (NSA) made up of Au and W as a CO2-reduction electrocatalyst selective towards the formation of methanol as a product, away from methane, ethylene or ethanol typically produced using Cu as the catalyst. At an overlayer NSA that consisted of n monolayers (ML) of Au on a polycrystalline W electrode, W(pc)-n[(1×1)-Au], no methane, methanol, ethylene or ethanol were detected when the coverage of Au was at submonolayer (n = 0.5) or multilayer (n ≥ 2) coverages. However, when the overlayer contained only 1 ML of Au, methanol was generated exclusively. The anticipated CH3OH-product-selectivity of the W(pc)-(1×1)-Au NSA has thus been (qualitatively) confirmed. The CH3OH-selective activity was 52 µA cm-2 for a Faradaic efficiency of 0.50%; the bulk of the current was expended towards H2 evolution and, since the topmost layer was Au, most likely in the production of CO and formates that cannot be studied by DEMS.
Electrochemical CO2 Reduction: Screening of Material Libraries and Improving Selectivity of Cu By Mixing It with Co
Authors: Grote Jan-Philip , Zeradjanin Aleksandar R. , Cherevko Serhiy , Savan Alan , Breitbach Benjamin , Ludwig Alfred , Mayrhofer Karl J.J. 
Published: February 2020

Using CO2 and converting it into useful products or even fuels is considered as a “dream reaction”. However even after over 30 years of research in the field of electrochemical CO2 reduction the “dream” didn’t come true and still remains a scientific and technical challenge. Two main applications can be considered for the electrochemical CO2 reduction: (1) The operation as storage technology to compensate the unavoidable energy fluctuations produced by renewable energy source like wind or sun and (2) the syntheses of valuable products like ethylene. Whilst in gas-phase heterogeneous catalysis the conceptual understanding about converting CO2 into fuels and the applied processes are well developed, electrochemical CO2 reduction is still in a stage where fundamental research is inevitably necessary to prove feasibility before large-scale implementation. On the contrary distinct advantages are the direct use of electrical energy, a potential dependent and therefore customizable product distribution and operation at ambient pressure and temperature.
Main reasons for a so far not realized commercial application are (1) the low selectivity for valuable products on hydrocarbon producing electrodes and thereby a costly product separation, (2) the low energy efficiency as a cause of high overpotential on the working electrode and (3) the oxygen evolution as counter reaction, that also shows high overpotential and in addition to that catalyst degradation by dissolution.
In order to address the fundamental understanding of the reduction processes on various types of material combinations, we have developed an electrochemical technique that enables (1) screening of thin-film material libraries with different experimental parameters, (2) investigating catalyst activity and stability of electrodes in parallel by inductively coupled plasma mass spectrometry (ICP-MS) and (3) analyzing the selectivity of catalysts for certain products via online electrochemical mass spectrometry (OLEMS).
First results utilizing this approach will be presented; the focus will be in particular on the shift in selectivity towards C2 products of the electrochemical CO2 reduction on Cu-Co thin film composition spread samples at ambient temperature and pressure. Due to a high resolution composition analysis we were able to find a composition where production of C1 species is suppressed, while in return C2 production is enhanced. Utilization of this technique deepens understanding of fundamental processes and shows its high potential for improving performance of electrochemical CO2 reduction.
A Paper-Based Electrochemical Sensor Array for Detection of Hydrogen Peroxide
Authors: Shamkhalichenar Hamed , Choi Jin-Woo 
Published: February 2020

A sensitive and rapid detection of hydrogen peroxide (H2O2) is important in biomedical, food, and environmental analysis. The enzyme-based electrochemical detection of H2O2 may provide simple, accurate, and rapid process; however, due the thermal and chemical deformation of enzymes during the fabrication process, these sensors may suffer from instability [1]. Recently, some particles which has electrocatalytic properties toward H2O2 has been employed to develop electrochemical sensors. Of these, iron oxide (Fe3O4) and copper oxide (CuO) nanoparticles have shown good electrocatalytic properties toward H2O2 [2, 3]. However, one common drawback of these sensors is lack of selectivity owing to the fact that these catalysts shows electrocatalytic properties toward various analytes in the solution. Here, we present a novel paper-based electrochemical sensor based on modified carbon nanotube electrode, which can reduce the matrix effect in multi-analyte solutions. Paper-based sensors have become of great interest for fabricating inexpensive, simple, and disposable sensors. Carbon nanotube electrode ink has been modified using CuO and Fe3O4, and an electrode array made of modified and bare carbon ink solutions is developed by utilizing screen-printing of carbon ink solutions on paper. Figure shows the developed paper-based sensor array design. Moreover, a multichannel potentiostat circuit has been developed in order to investigate the amperometric response of the sensor array on H2O2 solution. The potentiostat can control three working electrodes independently, and it is also working with a USB port as power source. Since these modified electrodes show a unique response to different electroactive species, the results can be interpreted using a statistical method to compromise the interference from other electroactive species in the solution. Further, solutions with various concentration of H2O2 and interfering species has been tested using the portable potentiostat in order to assess the matrix effect originated from the interfering species in H2O2 detection.
References
[1] M. Song, S. Hwang and D. Whang, “Non-enzymatic electrochemical CuO nanoflowers sensor for hydrogen peroxide detection,” Talanta, vol. 80, no. 5, pp. 1648-1652, 2010.
[2] M. Lin and H. Leu, “A Fe3O4-based chemical sensor for cathodic determination of hydrogen peroxide,” Electroanalysis, vol. 17, no. 22, pp. 2068-2073, 2005.
[3] X. Miao, R. Yuan, Y. Chai, Y. Shi and Y. Yuan, “Direct electrocatalytic reduction of hydrogen peroxide based on Nafion and copper oxide nanoparticles modified Pt electrode,” Journal of Electroanalytical Chemistry, vol. 612, no. 2, pp. 157-163, 2008.

Figure 1
Rapid Detection of Pathogens By a 3D Biomolecular Filter and Automated Biosensor Measurement System for Liquid
Authors: Du Songtao , Horikawa Shin , Liu Yuzhe , Chai Yating , Hu Jiajia , Chin Bryan A 
Published: February 2020

A new method of rapid detection of pathogens by 3D biomolecular filtering and automated indexing plate measurement has been demonstrated. In this process, a liquid containing pathogens is passed through a 3D biomolecular filter composed of planar arrays of MagnetoElastic (ME) biosensors held by a magnetic field. This filter captures specific target pathogens (in our demonstration case, Salmonella) in the liquid as it passes over the filter. The experiment will be under different Salmonella concentrations, different flowing rate, different number of ME biosensors and different solution volume. Capture of the pathogens is by specific biomolecular recognition, not size exclusion as with traditional filters. After the entire liquid has passed over the filter, the magnetic field is shut off and the individual biosensors collected and dried. The biosensors are then placed on an indexing plate consisting of an array of rectangular cavities approximately 10% larger in size than the ME biosensors. A vibrating table is used to vibrate the ME biosensors into motion until each cavity of the plate is occupied by a single ME biosensor. The biosensors are then measured by sequentially positioning the sensors under a surface scanning detection coil for measurement of the final resonance frequency of the biosensors using an automated translation system. In this manner, a single sensor can be measured in less than 2 seconds with 1000 sensors being measured in less than 30 minutes.
Electrochemical Dissolution of a Microneedle System for Controlled Drug Release in Smart Devices
Authors: Anderson Ashleigh , Davis James 
Published: February 2020

The majority of conventional controlled release technologies tend to be based around encapsulant systems in which a polymeric binder or gel typically responds to changes in the local environment in which the delivery device has been placed. The contents are often released when the particle, capsule, film or droplet is exposed to the appropriate physico-chemical trigger (typically a change in pH) with the time-release-dose delivery characteristics controlled through manipulation of the encapsulant formulation. In this communication, the adaptation of this core strategy for use in the next generation of transdermal microdevices or smart patch is explored. The core rationale of this work relates to the development of microneedle patches through which a drug could be transported across the skin barrier upon activation by an appropriate electrochemical trigger.
The microneedle in this case serves as the entry point through the strateum corneum whilst acting as a physical barrier to the transport of the drug from a reservoir within the patch. Upon activation, the microneedle dissolves thereby allowing the release of the therapeutic agent as indicated in Figure 1A,B.
The methodology proposed herein focuses on the ability to control the dissolution of the conductive composite microneedle through an application of a specified potential trigger. Central to this approach is the design and fabrication of a novel nanostructured conductive film based on a composite of carbon nanoparticles and cellulose acetate phthalate (CAP). This is created through the solvent cast method onto a silicone microneedle template shown in Figure 1C. Under normal conditions, the conductive coating remains intact but, upon imposing a reducing potential on the carbon composite layer, the local pH is increased which results in the solubilisation of the pH sensitive CAP binder components. The latter is the structural glue that holds the microneedle together and thus the subsequent swelling effectively leads to the dissolution of the microneedle architecture and the release of the drug. The presentation covers three aspects: the design and characterisation of the carbon composite microneedles, the ability to electrochemically manipulate the structural integrity of the needles and the ability to effect the controlled release of model drugs such as codeine, methotrexate and fentanyl.

Figure 1