bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Behavior of Niobium Complexes in Chloride-Fluoride Melts with Addition of Alkaline Cations
Authors: Vetrova Daria A. , Popova Anna V. , Kuznetsov Sergey A. 
Published: February 2020

The goal of the present research was the study of Mg2+, Ca2+, Sr2+ and Ва2+ (Me2+) strongly polarizing cations influence on the standard rate constants of charge transfer (ks
) for the redox couple Nb(V)/Nb(IV) in NaCl-KCl(equimol.)-K2NbF7 (I) and NaCl-KCl(equimol.)-NaF(10 wt.%)-K2NbF7 (II) melts. Electrochemical studies were carried out in the temperature range of 973-1173 K by cyclic voltammetry. Voltammetric curves were recorded at a glassy carbon electrode vs. a glassy carbon quasi-reference electrode. The sweep rate (v) varied from 0.4 up to 2.0 V s-1. The electrochemical redox process:
Nb(V) + e- ↔ Nb(IV) (1)
was classified as quasi-reversible at a sweep rate ν>0.5 V s-1. The values of k
s were calculated by using the Nicholson’s method [1]. It was shown that k
s increase with increasing temperature. It is due to increase in the number of particles capable of overcoming the potential barrier for the electron transfer process.
Addition of alkaline earth metal cations resulted in increasing of ks
to the certain ratio of Me2+/Nb(V) for the all alkaline earth metal cations due to substitution of Na+ and K+ cations by Me2+ in the second coordination sphere of niobium complexes that leads to decreasing of niobium fluoride complexes strength. Further addition brought to some decrease of the standard rate constants because the viscosity of melts increasing which brings to decrease of the diffusion coefficients.
The temperature dependences of molten salt systems with addition of strongly polarizing cations were determined and the activation energies of charge transfer were calculated. Values of activation energy for systems with strongly polarizing cations are considerably less than activation energies of the initial systems.
The standard rate constants in molten salt system (I) were higher than in the melt (II) due to lower viscosity. It was determined that in the melt (I) ks
a little bit increased with increasing scan rate probably due to the secondary electrode process which accompanied redox process (1). In the system with sodium fluoride (II) the redox process (1) occurs at more negative potentials that allow eliminating the secondary process.
References:
[1] R.S.Nicholson, J. Anal. Chem., 1965. Vol. 37 (1965), 1351.
[2] B.B. Damaskin, O.A.Petriy, Introduction of electrochemical kinetics, Vysshaya Shkola Publ., Moscow, 1975 (in Russian).
Interaction of 3D Conductive Polymer-Reticulated Vitreous Carbon Composites in Ionic Liquid As Energy Storage Material
Authors: Schoetz Theresa , Ponce de León Carlos , Bund Andreas , Ueda Mikito 
Published: February 2020

Energy storage technologies, which combine high specific energy and power with sustainability and low costs, are fundamental drivers for an energy sustainable society. Conductive polymers in highly stable and non-toxic ionic liquid (IL) electrolytes have been proposed as possible systems that combine these advantages. Recently, it has been demonstrated that poly(3,4-ethylenedioxythiophene) (PEDOT) can undergo a redox reaction like in a battery and at the same time perform the characteristics of a capacitor by being doped/charged (de-doped/discharged) by anions from the IL. The storable amount of charges depends on the generated doping/de-doping sites in the polymer, which is a function of the electrode potential. These so called “hybrid-battery-capacitor” system combines the faradaic and capacitive properties in a single electrode [1,2], providing the possibility to improve cell voltages and energy densities.
High surface area materials such as three-dimensional conductive reticulated vitreous carbon (RVC) substrate, provide large surface area for electro-polymerisation of a thin film nano/micro-porous PEDOT active material (“footprint-area” [3]). The resulting composite has large capacitance supported by the rigid carbon substrate which helps to stabilise the typical swelling/contraction process observed in conducting polymers during the electrochemical charge/discharge process.
This study focuses on the synthesis and characterisations of thin electro-active PEDOT films on RVC substrates by electro-polymerisation in IL. The polymer synthesis produced a uniform film on the RVC with a high number of doping/de-doping sites in Lewis neutral 1-ethyl-3-methylimidazolium chloride aluminum chloride (EMImCl-AlCl3) IL with AlCl4
- as doping/de-doping anion.
The interaction of the conductive polymer films with the ionic liquid electrolyte are characterised by combined in-operando atomic force microscopy (AFM) and electrochemical quartz crystal microbalance measurements (EQCM), distinguishing the predominant battery or capacitor behaviour per doping/de-doping site and the correlated changes of the polymer structure as function of the electrode potential.
[1] Chemical Reviews 110 (2010) 4724–4771.
[2] Chemical Society Reviews 44 (2015) 1777–1790.
[3] Advanced Materials 26 (2014) 2440–2445.
Graphical abstract: (A-C) PEDOT electro-polymerised on RVC and (D) schematic illustration of the three-dimensional RVC-PEDOT composite, which is doped (charged) and de-doped (discharged) with AlCl4
- anions of a chloroaluminate ionic liquid.

Figure 1
(Invited) A Fast and Sensitive Detection Method for Detecting CO2 Reduction Products and Local pH
Authors: Zhang Fen , Co Anne C. 
Published: February 2020

The electrochemical pathway of CO2 reduction reaction (CO2RR) remains a promising technique to convert CO2 to value-added chemicals (e.g. CO, CH4, HCOOH, CH3OH, etc), which helps alleviate our dependence on fossil fuels as well as mitigate the rising CO2 concentration in the atmosphere. Nowadays, most of the CO2RR study focus on designing novel catalysts to improve their activity and selectivity. However, to evaluate the performance of new catalysts, a long time electrolysis (e.g. 30 min to several hours) is usually required to build up the concentration of products (both gaseous and liquid) enough before product analysis is performed by gas chromatography-mass spectrometry (GCMS) or nuclear magnetic resonance (NMR). This results in a long “pre-concentration-collection-detection” cycle and it greatly limits the efficiency of catalyst screening process as well as increases the energy cost. In addition, for catalysts that degrade quickly with time (within minutes), it is nearly impossible to monitor their product distribution change using traditional detection methods, which directly leads to the product information loss during the study of their degradation mechanisms. Therefore, it is urgent to develop a novel and sensitive detection method that can perform product analysis in a very short time scale (e.g. within minutes).
In this work, we present a systematical study of using RRDE as a fast and reliable detection method for quantifying CO2RR products generated from both heterogeneous (e.g. Pt, Au, Sn) and homogeneous (e.g. [NiII(cyclam)]2+) catalysts. Local pH change during Au and Sn catalyzed CO2RR are also carefully investigated. The fast detection towards single product systems (e.g. H2, CO) and mixture product systems (e.g. H2 and HCOO-, H2 and CO) are discussed in detail. Based on Hori’s classification, catalysis systems of Pt, Au and Sn encompass nearly 90% of the heterogeneous CO2RR reduction products. Our results show that, compared with traditional detection methods (e.g. GCMS, NMR), RRDE shows a superior detection sensitivity (e.g. LOD
ring ~10-18 moles of H2, defined in this work) as well as a significant short detection time (<1 min). Meanwhile, the product distribution as a function of applied electrolysis potential could be easily extracted from the detected ring voltammograms, which provides important information for the evaluation of catalysts’ performance.
Electrochemical Ammonia Synthesis in Molten Salts
Authors: McPherson Ian James , Sudmeier Tim , Fellowes Joshua , Tsang Shik Chi Edman 
Published: February 2020

Ammonia is one of the most significant chemical products on the planet due to its central role in agriculture, as well as its use in a wide variety of chemical processes. More recently it has also attracted interest as a carbon-free energy vector, with an energy density similar to that of methanol and immediate compatibility with existing storage and distribution infrastructure. Current ammonia production relies on natural gas for both the hydrogen and the energy required by the high temperature, high pressure Haber-Bosch reaction. This technology consumes over 1% of all global energy and, in Europe, is responsible for 1% of all carbon emissions (1). New processes based on renewable power are therefore urgently required.
Electrochemical reduction of nitrogen to ammonia has been demonstrated in a number of systems, although very slow kinetics and competing reduction of protons to hydrogen has severely limited their efficiency, particularly in protic media (2). One promising approach operates in a molten LiCl-KCl eutectic, the unique electrolyte stabilising the unusual nitride anion and enabling direct reduction of nitrogen gas (3). It has been proposed that this ion can then react with hydrogen or even water at an anode to form ammonia in an electrochemically driven process. Despite promising initial rates and current efficiencies, there has been very little development of the proposed cell, particularly in terms of electrocatalyst composition and morphology.
Here we setup the proposed cell to investigate the feasibility of this approach. We use various methods to deposit metals (Ni, Co, Mo, Fe) onto carbon felt supports to produce a range of different gas electrodes. These electrodes are tested for ammonia synthesis from nitrogen and hydrogen and compared with the rates at a Ni foam electrode used in initial reports.

References

1. Proceedings of the International Fertiliser Society 2008, 639
2. V. Kyriakou, I. Garagounis, E. Vasileiou, A. Vourros, M. Stoukides, Catalysis Today 2017, 286, 2–13.
3. T. Murakami, T. Nishikiori, T. Nohira, Y. Ito, J. Am. Chem. Soc. 2003, 125 (2), 334–335.
Photochemical Nitrogen Fixation on Titania
Authors: Hatzell Marta C. , Liu Yu-Hsuan 
Published: February 2020

Photocatalysis is the ideal solution to sustainable ammonia synthesis, as it will enable the distributed production of fertilizers and fuels from reactants that are readily available at ambient conditions: air, water and photons. Given the massive amount of energy currently expended to produce and transport fertilizer, such a process would have an enormous impact on energy consumption and carbon emissions [1,2,3]. Photocatalytic nitrogen reduction has been demonstrated over titania catalysts, although the production rates are too low to be practical. Despite the enormous promise of this reaction, there is little understanding of the fundamental chemical and physical processes that enable it. In this presentation, defects, like oxygen vacancies, and dopants like iron and carbon have been demonstrated to enhance photocatalytic activity for TiO2 for nitrogen fixation. The results indicate that the defects and dopants aid in promoting nitrogen adsorption which consequently may drive photocatalytic performance. Furthermore, insight acquired through ambient pressure XPS and DRIFTs provide new insight into the role this process may play in natural environments.
[1] Medford, Andrew J., and Marta C. Hatzell. "Photon-driven nitrogen fixation: current progress, thermodynamic considerations, and future outlook." ACS Catalysis 7.4 (2017): 2624-2643.
[2]Schrauzer, G. N., Strampach, N., Hui, L. N., Palmer, M. R., & Salehi, J. (1983). Nitrogen photoreduction on desert sands under sterile conditions. Proceedings of the National Academy of Sciences, 80(12), 3873-3876.
[3]Doane, T. A. (2017). The Abiotic Nitrogen Cycle. ACS Earth and Space Chemistry, 1(7), 411-421.
Ligand Engineered MnO Catalytic Nanoparticles As an Efficient Charge Transfer Mediator for Photoelectrochemical Water Oxidation
Authors: Lee Mi Gyoung , Jang Ho Won 
Published: February 2020

Photoelectrochemical (PEC) water splitting is regarded as one of the most promising approaches for the generation of hydrogen as a renewable and carbon-free fuel. Bismuth vanadate (BiVO4) has been recognized a highly promising photoanode material for solar water splitting. However the PEC performance of BiVO4 remains significantly poorer than the theoretical value due to the severe recombination of photogenerated charge carrier near the solid/electrolyte interface. A novel strategy is therefore essential for the progress of highly efficient PEC water splitting. The band edge positions of semiconductors determine their functionality in photoelectrochemical water splitting. While surface modification on the catalytic surface is known to enable to facilitate modification of the band structure, its crucial role in water splitting efficiency has not yet been fully understood.
Here, we firstly demonstrate the ligand engineering effect of manganese oxide Co-catalyst nanoparticles (MnO NPs) on bismuth vanadate (BiVO4)-based cascade anodes, and achieve a remarkably enhanced photocurrent density of 6.25 mA/cm2 at the 1.23 V versus reversible hydrogen electrode. It is the highest value among the previously reported BiVO4-based anodes. We verified that improved photoactivity is closely related to the substantial shifts in band edge energies that originate from both the induced dipole at the ligand/MnO interface and intrinsic dipole of the ligand. In particular, combined spectroscopic analysis and electrochemical study revealed the clear relationship between the surface structure driven by the ligand treatment and the band edge positions of MnO NPs for photoelectrochemical water oxidation. Our systematic study provides general strategy for enabling new active semiconductor photocatalyst and is applicable to solar water splitting system.
Electrochemistry of Particulate Electrodes Based on Magnetite Aggregates
Authors: Accogli Alessandra , Molazemhosseini Alireza , Magagnin Luca 
Published: February 2020

In current research, micro and nanoparticulate electrode materials have taken their place because they offer a large internal surface area with respect to the macroscopic dimensions of such electrodes [1]. The nano-impact method is a powerful tool that enables the characterization of individual particulate nano-objects in solution and study of their reactivity [2]. A three electrodes setup system working as a standard electrochemical cell is typically used. Magnetite (Fe3O4) nanoparticles with the strongest saturation magnetization of all naturally occurring iron oxides, combined with properties such as low toxicity, good biocompatibility, high stability, and low production costs, have attracted a lot of interest [3]. There is also substantial interest in their use as magnetic fluids, in data storage, in catalysis, and as electrode materials.
In this work, magnetite micro and nanoparticles have been synthetized by chemical precipitation method in presence of surfactants or functional organic polymer. The use of surfactants to stabilize these synthesized nanoparticles is crucial, as Fe3O4 nanoparticles have high surface energies and tend to aggregate. They also have high chemical activity. Magnetite particles are used as particulate electrode in different fluid and characterized into a three electrodes cell in order to evaluate their electrochemical behavior. A deeper understanding of the particulate electrode has been performed in situ on supported particles through electrochemical AFM/STM measurements, highlighting the behavior of the single aggregate. Together with the charge transfer characterization as a function of particles size and concentration, functionalization and fluid composition, practical applications of the particulate electrodes will be presented. Specifically, the use of particulate electrodes in the production of electrochemical sensors for glucose detection will be discussed.

References

Noack, H. Weller, A. Eychmu1ller, J. Phys. Chem. B, 106 (2002) 8514-8523

V Sokolov et al., Phys.Chem.Chem.Phys., 19 (2017) 28

Murugappan, ChemElectroChem, 1 (2014) 1211 – 1218
Ferrocenyl-Based Signal Amplification across Self-Assembled Monolayers in Electrochemical Biosensors
Authors: Mayall Robert Matthew , Renaud-Young Margaret , Luong Samantha , Creager Stephen E , Birss Viola 
Published: February 2020

A major challenge in effectively treating infections is to provide timely diagnosis of a bacterial or viral agent. Current cell culture methods require > 24 hours to identify the cause of infection. The Toll-Like Receptor (TLR) family of proteins from the human immune system can rapidly identify classes of pathogens and has been shown to work well in an impedance-based biosensor, where the protein is attached to a Au electrode via a self-assembled monolayer (SAM). While the sensitivity of these sensors has been good, they contain a high resistance (>1 kΩ) SAM, generating relatively small signals and requiring longer data collection times, which is ill-suited to implementation outside of a laboratory.
Here, we describe a refined approach to increasing the signal magnitude and decreasing the measurement time of a TLR-4 biosensor by inserting a redox-active ferrocenyl-terminated alkane thiol into a mixed SAM containing hydroxyl- and carboxyl-terminated alkane thiols. The introduction of ferrocene into the SAM provides an avenue for the electrochemical mediation of soluble redox couples. This dramatically increases the measured current across the SAM when compared to SAMs that do not contain such a redox-active moiety, with confirmation of the intended surface modification of the Au electrodes obtained using a variety of advanced surface techniques.
It is shown that these TLR-4 biosensors, utilizing the ferrocene-based SAMs, exhibit a ≤ 1 kΩ interfacial resistance that can be measured in less than one minute. These biosensors respond selectively to their intended target, Gram-negative bacteria, while remaining insensitive to Gram-positive bacteria or viral particles. These sensors were further interrogated with an inexpensive (< $100) open-source hand-held potentiostat that could be easily employed in a non-laboratory setting, including in remote or third-world applications.

Figure 1
Simultaneous Determination of Young’s Modulus and Residual Stress in PECVD a-SiC from Postbuckling Vibration of MEMS Beams
Authors: Pratap Rudra , Behera Amruta Ranjan 
Published: February 2020

Silicon carbide is a highly desirable material for MEMS sensor applications due to its robustness against harsh environments, especially high temperature and chemically corrosive environments. It is also an excellent material for high frequency applications due to its high Young’s modulus (E). Unfortunately, it is also a very difficult material to grow on silicon as crystalline SiC. In comparison, it is much easier to grow SiC by PECVD and integrate into a MEMS stack. However, the PECVD grown SiC is amorphous and its material properties vary considerably depending on the process parameters. For example, the Young’s modulus of PECVD grown a-SiC has been reported in the range of 138-196 GPa. This large variation makes it difficult to design MEMS structures with desirable characteristics using a specific value of E. The other significant process induced uncertainty is due to the residual stress (σ) in the structure. In order to have reliable response from the micromechanical structures made of such SiC, it is important to have reliable values of both the residual stress and the Young’s modulus.
In this work, we report a method for simultaneous determination of E and σ by designing the test structures in the form of fixed-fixed beams and using their frequency response in buckled state. We exploit the invariance of even mode frequencies on residual stress to uncouple the effects of E and σ on the frequency, thus making it possible to determine E, along with another possible unknown- the underetch length. We subsequently use this information to find the residual stress from the odd mode frequencies. This evaluation requires a single sweep of frequency response from the buckled beam. The only condition here is that the beams have to be designed such that they result in buckled structures after release. This condition is essential, as only the buckled state guarantees the invariance of even modes on residual stress. Compared to other methods for determination of these properties, the advantage here is that we use a single method of measurement – LDV based frequency response measurement and a single type of test structures. Since the proposed method does not involve electrostatic actuation, in general it is applicable for dielectric thin films.
In order to ensure repeatability, we have used measured results from more than 100 test structures. For the procedure to work, we need at least one of each even and odd mode frequencies to estimate the unknown parameters. Since in our experiment we are able to measure first four frequencies, we have two modes each from odd and even category. Thus there are total four modal combinations of measured data available to proceed with estimation of material properties, i.e. 2nd – 1st, 2nd – 3rd, 4th – 1st, 4th – 3rd. However not all of these combinations are always equally feasible. We have developed a good understanding of the circumstances, which favours use of one combination against the others.
(Invited) Using Airbrushes to Pattern Reagents and Electrical Components on Flexible Substrates
Authors: Fan Hugh , Cassano Christopher , Sondhi Kartik , Nishida Toshi 
Published: February 2020

This paper is related to two subject areas. One subject area is point-of-care (POC) testing, which includes lateral flow assays that use paper as the substrate material to carry a sample toward the detection zone. The other subject area is flexible electronics, which could lead to wearable sensors and other devices.
We report using airbrushes to pattern reagents and conductive inks onto a variety of flexible substrates including paper, thermoplastics, and elastomers. On paper substrates, we patterned small molecules, proteins, and DNA for sensing and biomarker detection. A range of operational parameters were used to control the line width and pattern contours. We employed an airbrush to pattern lines and dot arrays from hundreds of µm to tens of mm. Both enzymatic assays and DNA hybridization have been demonstrated in paper devices to show that the airbrushing method is amenable with various reagents and it has a potential to make paper-based devices more accessible.
On both thermoplastics and elastomers, we explored the use of an airbrush to pattern electrical components and compare it with screen-printing. Among these substrates, elastomers such as polydimethylsiloxane (PDMS) are more stretchable than thermoplastics such as thermoplastic polyurethane (TPU). However, commercial conductive materials such as silver inks are not formulated to be adherent to PDMS. As a result, we developed a surface modification method to achieve better adhesion. We compared airbrushed resistors with screen-printed resistors and studied their adhesion and abrasion resistance. Changes in the resistance of resistors fabricated on both PDMS and TPU were investigated after they are stretched numerous times. Other electronic components and circuits have also been fabricated on flexible substrates.