bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nickel (III) Salt Dispersed Poly-aniline film: Preliminary SECM Examination
Authors: Haque Inam ul 
Published: February 2020

Various matrices including poly-aniline have been used recently to incorporate nickel salts within the polymer. These films have been shown to be of utility for exploiting the oxidizing characteristic associated with nickel (III) under the right conditions, for example when the film is subjected to anodic bias.
Preliminary SECM examination of the above films was undertaken. The results suggested the presence of active sites on the surface originating from higher-valent nickel cation.
Reference
Inam-ul-Haque, Aakifa Raza and Shamaila Sadaf, Dispersed nickel oxide films for electro-oxidation of 1, 4-butanediol, Journal of the Chemical Society of Pakistan, 33 (1) 21-28 (2011).
Acknowledgments
Inam-ul-Haque thanks German Academic Exchange Service, DAAD, for a study and research stay; September to November 2010 at Department of Pure and Applied Chemistry University of Oldenburg Germany, and gratefully acknowledges kind and gracious hospitality of Professor Dr Gunther Wittstock.
Changes in Photoanodes during Solar Water Oxidation, the Wet Part of Artificial Photosynthesis
Authors: Braun Artur 
Published: February 2020

Combination of animate matter with inanimate matter poses a difficult task for materials engineers, but opens up new horizons for scientists. I present the case where the iron oxide photoanode for photoelectrochemical solar water splitting is functionalized with C-phycocyanin, a protein known from blue green algae which has a light harvesting complex - one important structural motif in natural photosynthesis. The low cost and abundant mineral has a number of positive properties that make it suitable as a photoanode in photoelectrochemical cells (PEC). However, some deficiencies in its electronic structure prevent it from outperforming its costly and less abundant competitors in terms of quantum efficiency and photocurrent. Further functionalization of hematite with phycocyanin, i.e. coating and covalent cross linking, causes a doubling of the photocurrent. Detailed structural and spectroscopic analysis shows that it is the chromophore porphyrin in the phycocyanin which survives harsh pH conditions and provides also a light funnelling effect, which in the end makes an enhanced photocurrent. Our operando combination of PEC water splitting with soft x-ray spectroscopy provided new insight in the interaction of DC bias and photo-excitation with iron oxide. Anodization of hematite at bias potentials from 300 to 700 mV during illumination forms at least two new pre-edge structures in the O1s NEXAFS spectra, which can be assigned to eg spin up symmetry transitions in the O2p CTB and in the Fe3d-type UHB. We find a parallel evolution of the relative spectral weight of these transitions with the photocurrent vs. DC bias, strongly supporting that two types of electron holes are contributing to the historically suggested two types of photocurrent in hematite. The experiment was carried out entirely in situ during x-ray spectroscopy and strongly supports previous speculations that the electronic structure of the surface, and not only the short hole diffusion length in the bulk, may impede the performance of hematite photo-anodes. Meanwhile, we have made progress with probing also bio-organic motifs and hybrids with spectroscopy methods.
[1] D.K. Bora, A. Braun, E.C. Constable, “In rust we trust”. Hematite - the prospective inorganic backbone for artificial photosynthesis, Energy Environ. Sci.6, 407 (2013).
[2] A. Braun, K. Sivula, D. K. Bora, J. Zhu, L. Zhang, M. Grätzel, J. Guo, E. C. Constable, Direct observation of two electron holes in hematite during photo-electrochemical water splitting, J. Phys. Chem. C 116 (23) 16870 (2012).
Wide Bandgap Copper Indium Gallium Disulfide Thin Film Materials for Photoelectrochemical Hydrogen Production
Authors: Gaillard Nicolas 
Published: February 2020

Photoelectrochemistry (PEC) is one of the most efficient methods to produce alternative fuels, although the efficiency, cost, and durability of lab-scale systems are currently not at the level required to make this technology economically feasible. The chalcopyrite material class provides exceptional candidates to meet the requirements identified for cheap, sustainable solar fuels production. As we recently reported, co-evaporated 1.7 eV CuGaSe2 offers very high-saturated photocurrent densities (>15 mA.cm-­2), long durability (>400 hours) and high Faradaic efficiency (>85%). However, CuGaSe2 photocathodes suffer from non-ideal surface energetics, requiring additional PV cells to drive the water splitting process. The hybrid photo-electrode (HPE) device, in which one PEC electrode is placed on top of one solar cell, is by far the most efficiency approach for unbiased solar water splitting. Unfortunately, CuGaSe2’s narrow bandgap prohibits this integration scheme.
In the present communication, we report on our efforts to synthesize 1.8-2.2 eV band-gap chalcopyrite materials for PEC water splitting. Specifically, we investigated the effect of sulfur on the optical and photoelectrochemical characteristics of the copper chalcopyrite material class. Using co-evaporated 1 μm-thick CuGaSe2 as baseline system, we demonstrate that the substitution of selenium with sulfur is accomplished through a simple annealing step. As a result, a dramatic change in optical properties was observed, with a bandgap increase from 1.6 eV (CuGaSe2) to 2.4 eV (CuGaS2). Then, by simply adjusting the indium content in the film during the initial growth process, the bandgap of sulfurized copper chalcopyrite was decreased from 2.4 eV to 2.0 eV. X-ray diffraction data indicated successful bulk sulfurization by the shift of the prominent (112), (220), and (312) reflections to higher angles. PEC analyses revealed an anodic shift of the flatband potential with increasing bandgap when compared to CuGaSe2. This suggests that the bandgap modification in sulfurized films primarily stems from a downward shift of the valence band, an ideal situation for p-type PEC systems. Saturated photocurrent densities of 5 mA/cm2 were achieved with 2.0 eV red CuIn0.3Ga0.7S2 photocathodes in 0.5M H2SO4 under AM1.5G simulated illumination. From this proof of concept experiment, we have further developed new synthesis approaches and innovative characterization protocols to achieve PV-grade wide bandgap sulfide-based chalcopyrites capable of generating photocurrent densities in the 10-15 mA/cm2 range.
A Facial Liquid Plasma-Induced Polymerization of a Highly Ion-Conductive Polymeric Membrane
Authors: Choi Ho-Suk , Tran Quoc-Chinh 
Published: February 2020

We first report the synthesis of a highly ion-conductive polymeric membrane through using a liquid plasma system under an atmospheric pressure. The 1-butyl-3-methylimidazolium tetrafluoroborate ([BMI]BF4) and Triton X-100 were used as reacting monomers. These radical monomers, which form cross-linked polymeric films after reaction, are generated at a gas-liquid interface through the irradiation reaction of plasma species with a homogenous solution of [BMI]BF4 and Triton X-100. The as-synthesized polymer films were eventually observed at the gas-liquid interface under an atmospheric pressure. The thickness of the polymer film was controlled with different molar ratios of [BMI]BF4 and Triton X-100, and plasma reduction time. The maximum thickness of polymer film was 3.043 µm after plasma irradiation for 10 min at a molar ratio of 65:1 for [BMI]BF4:Triton X-100. Furthermore, the application of the synthesized polymer film as an alternative lithium ion conductive polymer leads to high ionic conductivity as well as small impedance as seen in Figure 1 and 2.

Figure 1
Covalently Cross-Linked Cholesterol Oxidase for an Indirect Detection Cholesterol Biosensor
Authors: Ashby Jarryd Noah , Ramasamy Ramaraja P. 
Published: February 2020

Nearly a third of the population in the United States suffer from high cholesterol. This condition approximately doubles one's risk of cardiovascular disease, which is the leading cause of death in the country. As such, increasingly cost-effective, robust, easy-to-use, and accurate methods of detection of cholesterol are necessary to curtail such health risks. A particularly accurate method for this includes enzymatic electrochemical detection; however, most electrochemical detection methods use enzyme-modified electrodes developed based on the physisorption of enzymes onto the electrodes. This approach does not result in high activity and severely limits the enzyme stability on the electrode. This can be mitigated by immobilizing the enzyme onto carbon nanotubes using molecular tethers. Our biosensor was fabricated using Cholesterol oxidase, from Streptomyces, immobilized on multi-walled carbon nanotubes (MWCNT) with 1-pyrenebutanoic acid, succinimidyl ester (PBSE) as a molecular tethering agent. The biosensor shows a linear detection region ranging from at least 0.03-0.5 mM and high selectivity against common interferents, such as glucose at less than five percent.

Fig. 1:(top): Differential Pulse Voltammetry study of Cholesterol oxidase immobilized on MWCNT with PBSE in an oxygen-saturated 0.1 M phosphate buffer (pH 7.4) at varying cholesterol concentrations ranging from 0 to 0.5 mM. (bottom): Standard plot of cholesterol concentration versus amperometric signal (change in peak current).

Acknowledgments:

The authors extend gratitude to Dr. Nicole S. Sampson of Stony Brook University for the cholesterol oxidase enzyme used herein.
* Corresponding Author: rama@uga.edu

References:

1. R. P. Ramasamy, H. R. Luckarift, D. M. Ivnitski, P. B. Atanassov, and G. R. Johnson, High electrocatalytic activity of tethered multicopper oxidase–carbon nanotube conjugates. Chem. Commun.,
2010, 46, 6045-6047.

Figure 1
Influence of Probe Size and Probe Position for Local Electrochemical Impedance Spectroscopy
Authors: Vivier Vincent , Camila Molena de Assis , Abreu Caio P. , Costa Isolda , de Melo Hercilio G. , Keddam Michel 
Published: February 2020

Local electrochemical impedance spectroscopy (LEIS) has received a significant attention these last two decades mainly for corrosion applications [1, 2]. The assessment of local current density in solution requires the measurement of at least 3 local potentials in the electrolytic solution using 3 independent micro-reference electrodes positioned close to the electrochemical interface. Then, the different contributions of the local current density (namely the normal and the radial components) are obtained using the Ohm’s law. The spatial resolution is mainly governed by the probe size, the distance between the two independent potential probes (i.e. silver micro-wires), and the distance between the probes and the interface. Interestingly, resolutions in the micrometre range have already been reported [3], but the apparition of two main drawbacks accompanies the diminution of the probe dimension.
First, a non-negligible capacitance is observed in the high-frequency domains corresponding to a coupling capacitance between two of the micro-wires, as shown in Fig. 1.
Second, the position of the reference electrode for measuring the potential and calculating the local impedance plays a significant role [4]. Indeed, depending on the location of the probe for measuring the potential, the measurement may be insensitive to local heterogeneity. As a result, such a measurement is no longer a local impedance measurement since it is obtained as a ratio of global potential to local current density.
In this paper, we present experimental results on platinum electrode and on the steel / copper system in order to characterize the influence of the probe size and the probe positioning. A specific attention will be paid to data analysis, and some guidelines for performing LEIS measurements (probe characterisation and probe positioning) will be presented.
[1] R.S. Lillard, P.J. Moran, H.S. Isaacs, A novel method for generating quantitative local electrochemical impedance spectroscopy, J. Electrochem. Soc. 139 (1992) 1007-12.
[2] V.M.-W. Huang, S.-L. Wu, M.E. Orazem, N. Pebere, B. Tribollet, V. Vivier, Local electrochemical impedance spectroscopy: A review and some recent developments, Electrochim. Acta 56 (2011) 8048-57.
[3] I. Annergren, D. Thierry, F. Zou, Localized electrochemical impedance spectroscopy for studying pitting corrosion on stainless steels, J. Electrochem. Soc. 144 (1997) 1208-15.
[4] E. Bayet, F. Huet, M. Keddam, K. Ogle, H. Takenouti, Local electrochemical impedance measurement: scanning vibrating electrode technique in ac mode, Electrochim. Acta 44 (1999) 4117-27.
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Fig. 1: dual probe used for measuring local electrochemical impedance spectroscopy and equivalent circuit used for taking into account the stray capacitance ascribed to this setup.

Figure 1
Finite Elements Approach to Predicting Impedance Response of Geometrically Convoluted Samples
Authors: Vanýsek Petr , Vyroubal Petr , Haňka Jiří , Novák Vitězslav , Maxa Jiří 
Published: February 2020

The geometry of a sample is of utmost importance in interpretation of impedance measurements and correlating them to the properties of the studied material. The first, always considered, issue is inclusion of the geometrical dimensions, so that capacitance and resistance of a sample can be interpreted and reported for proper comparison based on values per unit dimensions. In ideal measurements the samples prepared are a prioriprepared in simple geometries, allowing proper electric contact connections so that the calculations are simplified and measurements in a single laboratory, even without data interpretation, lend themselves to quick visual side-by-side comparison.
However, such arrangement is not always possible and therefore we investigated, by method of computer simulation, dependence of impedance results on geometry of a sample and location of electrode connection. As an example is a ceramic disc with grain and boundary resistance and capacitance, that could be encountered in studies of advanced high temperature materials, e.g.,for sensors of high-temperature fuel cells. The disks prepared by various methods of synthesis are contacted on their flat sides to the impedance analyzer circuitry. Our study correlates the (simulated) measured data to data that would be expected if perfectly symmetrical all-covering contacts were used.
While in part the correlation reveals that a simple multiplication factor can be used in some cases to correct for the geometry of the electrode placement, under conditions of more extreme electrode placements the response is such, that equivalent modeling of the obtained impedance data is not adequately described only by RC circuits. Instead, a constant phase element has to be introduced.
The simulation for this work was done using the ANSYS software package. The figure shows the geometric layout used for simulation. In this case a sample disk of a 30-mm diameter, thickness 7 mm is connected to the measurement circuit by two symmetrical, centrally placed metal circular electrodes of diameter 14 mm. In the process of simulations the size of the electrodes and their placement vs. the centerr of the sample was varied. For the data fitting to the suitable equivalent circuits was used the ZView package from Scribner Associates.
This work was supported by the project “CEITEC - Central European Institute of Technology” (CZ.1.05/1.1.00/02.0068) from European Regional Development Fund.

Figure 1
Wetting of Nano-Confined Electrodes By Lithium-Ion Battery Electrolytes Using Multiple Beam Interferometry
Authors: Moeremans Boaz , Cheng Hsiu-Wei , Garces Hector , Padture Nitin , Hardy An , Renner Frank Uwe , Valtiner Markus 
Published: February 2020

The interface with the electrolyte is a decisive feature in the design of composite battery electrodes, which typically contain active material particles, conductive material, and polymer binder. A detailed understanding of the electrolyte layering and wetting of materials such as graphene, graphites, metals such as aluminum or even gold, silicon, and metal oxides are ultimately important for improving crucial lithium-ion battery mechanisms. In particular the solid electrolyte interphase (SEI) and lithium-ion mobility at electrode interfaces are still not well understood.
Here we use the (Electrochemical) Surface Forces Apparatus (SFA) (1) to address the wetting behavior of nano-scale-confined lithium-ion battery electrodes by battery electrolytes. After its introduction in the 1970s by Israelachvili and Adams (2), the SFA has been used to investigate interfacial phenomena in fields varying from geoscience to microbiology (3). Figure 1 shows a detail of the SFA-setup that was used for the experiments. White light is thereby guided through a flat contact area of two semi-transparent SFA disks, causing interference patterns which are analyzed using a spectrometer. Monitoring the pattern throughout the experiments allows to follow electrolyte wetting behavior in the confined contact area.
Some of the investigated surfaces were mica, gold and graphene. For instance for graphene, a unique combination of rigid and mobile lithium-ion containing electrolyte layers was observed. Figure 2 shows a typical population mapping of a SFA-experiment which focused on the initial wetting behavior of a battery electrolyte (EC/DEC - LiPF6) on dry mica, gold and graphene surfaces. After an initial drop of about 1.8 Å in the inter-mirror distance, which is due to the excretion of a monolayer of adsorbed water from the initially dry interface, the wetting process of the electrolyte was only in the case of graphene able to overcome the contact force.
Similar observations were made when nano-confined gaps were wetted with ionic liquids. Molecular beam interferometry is a versatile and powerful tool for studying such nanoscaled wetting processes using battery electrodes including ionic liquids or organic solvents.
REFERENCES
1. M. Valtiner et al., Langmuir, 28, 13080 (2012)
2. J. N. Israelachvili and G. E. Adams, Nature, 262, 774 (1976)
3. S. Raman, M. Valtiner, et al., Nature Communications, 5, 5539 (2014)

Figure 1
High Energy X-Ray Used to Investigate the Synthesis of Full Concentration Gradient Cathode
Authors: Li Yan , Xu Rui , Ren Yang , Lu Jun , Wu Huiming , Wang Lifen , Miller Dean , Sun Yang-Kook , Amine Khalil , Chen Zonghai 
Published: February 2020

Nickel-rich lithium transition metal oxides can deliver a high specific capacity during cycling, but there is a concern about the highly reaction between the cathode and the non-aqueous electrolytes. To maintain high specific capacity and improve cycling performance , we have employed solid state reaction to synthesize a full concentration gradient (FCG) cathode, which has a nominal composition of LiNi0.6Mn0.2Co0.2. It is designed to provide a nickel-rich core to deliver high capacity and a manganese-rich outer layer to provide enhanced stability and cycle life. The solid-state reaction to form a high performance nickel-rich cathode material is a complicated multiple-step reaction. Therefore, in situ high-energy X-ray diffraction was utilized to study the structural evolution during the solid-state synthesis of FCG cathode. We found that both the pre-heating step and the sintering temperature were critical in controlling phase separation of the transition metal oxides and minimizing the content of Li2CO3 and NiO, both of which deteriorate the electrochemical performance of the final material. The insights revealed in this talk can also be utilized for the design of other nickel-rich high energy-density cathode materials.
Probing Electrochemically-Induced Structural Changes and Defects Affecting Li-Ion Intercalation and De-Intercalation in High Capacity Orthosilicate Cathodes
Authors: Lu Xia , Chiu Hsien-Chieh , Arthur Zachary , Zhou Jigang , Wei Huijing , Chen Ning , Gauvin Raynald , Jiang De-Tong , Zaghib Karim , Demopoulos George P. 
Published: February 2020

Li-ion batteries (LIBs) have already made tremendous progress supplying power for multiple devices used in our daily life. Now LIBs are gradually entering the plug-hybrid and fully electric vehicles. Safety and high specific capacity enabling long range driving between charges are among industry’s priorities in this domain. One cathode material group that potentially can provide solutions to these priorities is lithium metal silicates. Orthosilicates, Li2

M
SiO4, where
M

= Fe, Mn, Co, Ni, are characterized by a theoretical specific capacity that is twice that of LiFePO4, namely 340 vs. 170 mAh/g1
,2. In this presentation, we report on the synthesis and electrochemical/structural evaluation of different phase (monoclinic and orthorhombic) Li2(Fe,Mn)SiO4 materials using a combination of organic-assisted hydrothermal and reducing annealing treatment steps. During the electrochemical process, we find that the Li2FeSiO4 cathode demonstrates rate- and phase- dependent capacity changes upon lithiation/delithiation3. We have probed these changes by conducting both in-situ/postmortem synchrotron XRD/XANES and first-principle calculations of the structure/phase stabilities and Li ion diffusion properties of monoclinic Li2FeSiO4 orthosilicate. It is revealed that formation of Li-Fe antisite defects play a key role in destabilizing the orthosilicate structure and “catalyzing” the monoclinic-to-orthorhombic transition. Furthermore the charge compensation mechanism that is essential in achieving more than one Li extraction is discussed accordingly as well as the Li-ion diffusion properties are analyzed. The rich insight obtained from these Li2FeSiO4 studies is invaluable as we move towards the design and testing of stable orthosilicate structures with fully reversible 2-Li intercalation capacity for high-energy next generation LIB cathodes.
References
1. A., Nyten; A., Abouimrane; M., Armand; T., Gustafsson & J. O., Thomas, Electrochemical performance of Li2FeSiO4 as a new Li-battery cathode material. Electrochem. Commun.
7, 156-160, (2005).
2. M. Saiful Islam et al., Silicate cathodes for lithium batteries: alternatives to phosphates? J. Mater. Chem., 2011, 21, 9811.
3. Xia Lu; Huijing Wei; Hsien-Chieh Chiu; Raynald Gauvin; Pierre Hovington; Abdelbast Guerfi; Karim Zaghib and George P. Demopoulos, Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals, Sci. Rep. 5 (2015) 8599.