bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Investigation of Titanium Electrode in Aqueous Tetrafluoroborate Solution and in Aqueous Formate Solution
Authors: May Michael , Paul Elizabeth , Katovic Vladimir 
Published: February 2020

Titanium alloy electrodes are widely employed as both cathodes and anodic substrates. The superior corrosion resistance and low density of titanium makes it a useful material for industrial applications. In oxygen containing environments such as air or water, a thin titania layer spontaneously forms on bare titanium surfaces. Historically, the operative surface states of titanium have been termed: active [essentially metallic], transitional, and passive [comprising a titania over-layer]. In this project, the electrochemical response of a titanium electrode in contact with aqueous tetrafluoroborate solution [or in contact with aqueous formate solution] was monitored to tentatively identify the surface states.
Tetrafluoroboric acid is strongly ionizable in water and resultant HBF4 solutions are able to oxidize various metals. Starting with either HBF4 or KBF4, the electrochemical response of a titanium disk electrode in contact with aqueous tetrafluoroborate solutions [sparged with argon gas] was recorded. Cyclic voltammograms of 0.1 molar HBF4 on titanium, without additional electrolyte, showed two cathodic features near -0.51 V and -0.95 V versus Ag-AgCl electrode [see figure below]. The more negative feature is posited to correspond to active state titanium with H2 evolution. Scan reversal near -0.95 V to the positive direction promptly generates a prominent anodic peak near -0.65 V though the post-peak current remains anodic and rather steady out to +2.0 V. The prominent anodic peak may correspond to dissolution of titanium metal. Interestingly, the shapes of the cyclic voltammograms of aqueous KBF4 solutions were experimentally determined to be pH dependent.
By contrast, formic acid is weakly ionizable in aqueous solutions. Cyclic voltammograms of 3.5 molar HCO2H solutions on titanium showed a cathodic feature near -0.87 V that may correspond to active state titanium and, upon positive direction scanning, an anodic feature that starts near -0.25 V and plateaus after +0.2 V. The anodic plateau is posited to correspond to passive state titanium. Cycling between about +0.55 V and -1.0 V led to a detectable negative potential shift in the H2 evolution reaction [possibly due to titania formation during positive scanning]. At the similar hydrogen ion condition of pH 1, cyclic voltammograms of aqueous HCO2H and HBF4 were different: the prominent anodic peak was not observed for formic acid.

Figure 1
Polarization Controlled Electrocatalytic and Photoelectrocatalytic Activity of Ferroelectric Catalyst
Authors: Kushwahab Himmat Singh 
Published: February 2020

The coupling effect between ferroelectric polarization and electrochemical processes makes possible the engineering of charge-carrier conduction characteristics at the heterojunction between a polarized ferroelectric catalyst and a chemical solution. It is well known that ferroelectricity can affect a material's surface physics which result into enhance catalytic properties. Ferroelectric materials have spontaneous polarization, which can be reoriented between equivalent domain states by an applied electric field. Therefore, ferroelectrics are potential material to achieve switchable surface chemistry for electrochemical applications.
In this work we are going to present polarization controlled electrocatalytic and photoelectrocatalytic activity of ferroelectric catalyst. The increase in remnant polarization shows appreciable enhancement in the electrochemical and photoelectrochemical activity towards OER in alkaline medium and waste water treatment. The photoelectrocatalytic acitivity was investigated for hazardous pharmaceutical pollutants.
Microstructure Analysis of Polymer Electrolyte Membrane Fuel Cell Catalyst-Ionomer Inks and Cathode Catalyst Layers By Ultra Small Angle X-Ray Scattering
Authors: Kariuki Nancy , Myers Deborah J , Fongalland Dash , Bonastre Alex M. , Sharman Jonathan 
Published: February 2020

The successful development of novel materials for polymer electrolyte membrane fuel cell (PEMFC) electrodes is hindered by the lack of a fundamental understanding of the complex, multicomponent nature of the catalyst layer (CL), the interplay of its components, and their independent and cooperative effects on the effective properties. One of the most prevalent methods for preparing PEMFC membrane-electrode assemblies is the thin film decal transfer (DT) method, which involves dispersing the catalyst powder and perfluorosulfonic acid ionomer in a solvent media to form a catalyst ink, and then forming a porous thin film CL which is then transferred to the membrane via hot-pressing. To achieve maximum performance, the CL needs to have (i) the maximum interface of ionomer and catalyst for the anode and cathode reactions, (ii) the appropriate pore structure to allow gas and water diffusion, and (iii) ionomer networks that bind the carbon aggregates together, providing structural integrity for the catalyst layer and a proton conduction path. For optimization, the type of solvent, solvent-to-solids ratio, and ionomer-to-carbon ratio are variables which affect the resulting CL structure and performance. Characterization of both catalyst inks and catalyst layers is necessary to understand how processing, structure, properties, and performance are all related.
In this study, a systematic approach was taken to study the microstructure of the catalyst ink formulations and the prepared CLs using ultra-small-angle X-ray scattering (USAXS). By combining USAXS with small angle X-ray scattering (USAXS-pinSAXS), it is possible to obtain scattered intensity spanning over several decades in scattering vector, q (q = 4πsinθ/l), which can provide size and structural information from 1 nm to 6 mm. USAXS-pinSAXS measurements were performed at the Advanced Photon Source (APS) at Argonne National Laboratory. Multiple-level curve fitting, using a suite of macros written for Igor Pro-based software, was used to extract from the scattering data the particle size, size distribution, and geometry of the carbon-supported Pt and Pt-alloy aggregates in catalyst-ionomer-solvent inks and catalyst layers. The USAXS-pinSAXS study showed formation of aggregated microstructures, which are different for the Pt and Pt-alloy catalyst inks and catalyst layers.
A Comprehensive DFT Guide for Highly Efficient Electrochemical Ammonia Synthesis on New Class of Electrocatalysts
Authors: Abghoui Younes , Skulason Egill 
Published: February 2020

The results of a comprehensive computational screening for new electrocatalysts that are stable, active and selective towards electrochemical reduction of nitrogen to ammonia at room temperature and ambient pressure is presented on a range of transition metal nitride surfaces. Density functional theory (DFT) calculations are used to study the thermochemistry of cathode reaction so as to construct the free energy profile and to predict the required onset potential for activation of nitrogen to ammonia via a Mars-­van Krevelen mechanism. Five crucial criteria are investigated in this work to identify promising electrocatalysts for electrochemical ammonia formation in aqueous media; (1) identification of the reaction mechanism and calculation of the nitrogen splitting barrier, (2) investigation of the catalytic activity and quantification of the potential-determining/rate-determining steps, (3) determination of kinetic or thermodynamic barriers for vacancy diffusion into the bulk, (4) investigation of the stability of the surfaces against poisoning in an electrochemical environment, and (5) estimation of the potential required for removal of any oxygen atoms that may adsorb onto the surface upon exposure to electrochemical environment. With this approach, the (100) and (111) facets of the rocksalt as well as the (100) and (110) facets of the zincblende structures of all the naturally occuring d-block elements in the priodic table are scrutinized. The most promising candidates turned out to be the (100) facets of the rocksalt structure of VN, CrN, NbN and ZrN that should be able to form ammonia at ­-0.51 V, ­-0.76 V, -­0.65 V and -­0.76 V vs. SHE, respectively. All are found to be much more active towards nitrogen reduction than towards the competing hydrogen evolution reaction, in contrast to pure metals, which largely evolve hydrogen. Therefore, higher current efficiencies towards ammonia is expected at low onset potentials. An additional benefit to the present analysis is that the method presented in this work may be applicable to other aqueous phase heterogeneous catalytic reactions, where a Mars-van Krevelen mechanism is operative with both selectivity and activity being key catalytic criteria.
Figure caption: Free energy diagram for NH3 formation via a Mars–van Krevelen mechanism on the (100) facet of RS VN where all the possible adsorption sites for H are investigated and the most energetically favourable site and therefore the most stable intermediates are depicted.

Figure 1
One-Step Synthesis of Hydrangea-like Cu2O@N-Doped Activated Carbon As Air Cathode Catalyst in Microbial Fuel Cell
Authors: Li Kexun , Liu Ziqi 
Published: February 2020

In present study electrochemical deposition technology was used to modify the activated carbon (AC) cathode with hydrangea-like Cu2O and notrogen simultaneously, and the performance was improved greatly. The maximum power density was 1613±25 mW m-2, 84% and 62% more than controls repsectively. The electrochemical performances of cathodes were evaluated by Linear sweep voltammetry, exchange current density (i0) and Electrochemical impedance spectroscopy. Hydrangea-like mophology provided more active sites and channels for electrons of oxygen reduction reaction. X-ray XRD, FTIR and XPS results the existence of oxygen vacancy, crystal defects, acidic functional groups and hydrophilic functional groups, and C-N bond, especially pyridine, pyrrole and quaternary N, played a significant catalytic role in oxygen reduction reaction. Electrodeposition is a promising way to modifi AC cathode with metal and nitrogen at the same time.
The Addition of Ortho-Hexagon Nano Spinel Co3O4 to Improve the Performance of Activated Carbon Air Cathode Microbial Fuel Cell
Authors: Ge Baochao , Li Kexun 
Published: February 2020

Commercial Co3O4 and ortho-hexagon spinel nano-Co3O4 (OHSNC) were doped in the AC at a different percentage (5%, 10% and 15%) respectively to enhance the performance of microbial fuel cell (MFC). The maximum power density of MFC with 10% OHSNC doped cathode was 1500 ± 14 mW m-2, which was 97.36% and 41.24% higher than the bare AC air cathode and commercial Co3O4 respectively. The electrocatalytic behavior for their better performance was discussed in detail with the help of various structural and electrochemical techniques. The OHSNC was characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results showed that the improved performance owed to both the enhancement of kinetics activity and the number of electron transfer in the ORR, and the internal resistance was largely reduced. Therefore, OHSNC was proved to be an excellent cathodic catalyst in AC air cathode MFC.
(Invited) Ion Diffusion in Ionic Liquids: Single Molecule Fluorescence Spectroscopy
Authors: Welton Tom , Edel Joshua B , McIntosh Alastair J.S. , Ivanov Aleksander , Nawawi Mohd A. B. 
Published: February 2020

An ionic liquid is an ionic substance in which its constituent ions are in motion. Consequently, it is not possible to understand the nature of an ionic liquid without understanding how its constituent ions move. However, gaining a thorough understanding the nature of ion motion in ionic liquids remains a fundamental challenge.
Single molecule fluorescence (SMF) confocal spectroscopy offers a powerful, but as yet largely underutilized tool to measure the diffusion of probe ions in an ionic liquid under a variety of conditions.
To enable SMF measurements, it was necessary to develop the synthesis of ionic liquids with very low background fluorescence. The SMF derived diffusivity of the cationic probe Rhodamine 123 in dilute (ca. 100 pM) solutions in [C4C1im][NTf2] solutions was compared to diffusivity of the ionic liquid cations derived from Pulse Gradient Stimulated Echo NMR measurements. The SMF derived diffusivity of the cationic probe Rhodamine 123 was measured under various applied potentials and throughout the system’s relaxation back to its unperturbed state. This relaxation was found to be markedly slower than in salt solutions in molecular solvents.
The Effect of Pressure on the Role of Tfsa Conformational Exchange in Ionic Liquids
Authors: Suarez Sophia , Rua Armando , Cuffari David , Pilar Kartik , Hatcher Jasmine , Ramati Sharon , Wishart James 
Published: February 2020

A comprehensive study of multi-nuclear (1H, 2H, and 19F) magnetic resonance self-diffusion coefficients (D) and spin-lattice relaxation times (T1) was done as functions of both temperature and pressure on selectively deuterated 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (EMIM TFSA) ionic liquid isotopologues and related ionic liquids. While variable temperature studies provided useful insight, pressure dependent studies were more elucidating as discussed below. First, stronger electric field gradients were indicated in the alkyl chain region compared to the imidazolium ring of EMIM TFSA as determined from variable temperature 2H T1. Second and most significantly, variable pressure measurements of the EMIM and TFSA diffusion revealed independent motions for the cations and anions, with that of the TFSA anions being slowed much more by increasing pressure than for the EMIM cations. Activation volumes were determined from the pressure dependent D data and values of 28.8 ± 2.5 cm3/mol and 14.6 ± 1.3 cm3/mol were obtained for TFSA and EMIM respectively. Typically, smaller activation volumes support less restriction in motion. One possible explanation for this difference in behavior between EMIM and TFSA is that increasing pressure limits the conformational mobility of the TFSA. Third, variable pressure 2H T1 data shows two T1 regimes, for the MD3 and D2 isotopologues between 0.1-100 and 100-250 MPa respectively. These two regimes could represent dissimilar arrangements for the EMIM cation. Activation volumes determined from the pressure dependent 2H T1 data were 21 and 25 (0-100 MPa) and 11 and 12 (100-250 MPa) cm3/mol for the MD3 and D2 isotopologues, respectively. These and other details will be discussed.
(Invited) High Pressure Investigation of Charge Transport in Ionic Liquids
Authors: Paluch Marian , Wojnarowska Zaneta 
Published: February 2020

The purpose of this presentation is to present recent results obtained from the high pressure studies of the charge transport in ionic liquids. The experimental data from high pressure dielectric measurements will be analyzed in term of the density scaling concept [1,2]. As a result we will show that there is a relationship between intermolecular potential, thermodynamics and electrical transport properties of investigated ionic liquids. In the second part of the presentation we will focus on the decoupling phenomenon between viscosity and dc-conductivity in protic ionic liquids at various temperature and pressure conditions [3-5]. Finally, the general rules governing the charge transport in this class of ionic liquids will be formulated.

References:
1. M. Paluch, S. Haracz, A. Grzybowski, M. Mierzwa, J. Pionteck, A. Rivera-Calzada and C. Leon, J. Phys. Chem. Lett. 1 987 (2010)
2. M. Paluch, Z. Wojnarowska, P. Goodrich, J. Jacquemin, J. Pionteck and S. Hensel-Bielowka, Soft- Matter 11, 6520-6526 (2015)
3. Wojnarowska, Z.; Roland, C. M.; Swiety-Pospiech, A.; Grzybowska, K.; Paluch, M. Phys. Rev. Lett. 108015701 (2012)
4. Wojnarowska, Z.; Wang, Y.; Pionteck, J.; Grzybowska, K.; Sokolov, A.P.; Paluch, M. Phys. Rev. Lett.
111225703 (2013)
5. Z. Wojnarowska, K. J. Paluch, E. Shoifet, C. Schick, L. Tajber, J. Knapik, P. Wlodarczyk, K. Grzybowska, S. Hensel-Bielowka, S. P. Verevkin, and M. Paluch, J. Am. Chem. Soc., 137 1157 (2015)
Electrochromic Devices with Ionic Liquid Based Electrolyte By Room Temperature Process
Authors: Kim Haekyoung , Lee So Hee 
Published: February 2020

Electrochromic devices (EC), which dynamically change colour under applied potential, are widely studied for use in energy-efficient smart windows. To improve the viability of smart windows, many researchers are utilizing nanomaterials, which can provide electrochromic devices with improved coloration efficiencies, faster switching times, longer cycle lives, and potentially reduced costs. The flexible electrochromic films are promising film for applications in automobiles, buildings, etc.
Here, we synthesized nanostructured tungsten trioxide (WO3) particles for electrochromic materials. The thin layers with nanostructured materials of WO3 inks were coated at room temperature, solution-processed method. For comparing the effects of electrolyte, electrochromic devices were fabricated with various kind of electrolyte, which can be optimized to obtain higher performances. Two types of polymer based electrolytes were fabricated and characterized. The operation voltages were controlled with electrolyte types and compositions. Ionic liquid based electrolyte showed higher ionic conductivity than liquid type or polymer type electrolyte. Also EC with the liquid electrolyte exhibited 40% of coloring/bleaching efficiencies and EC with the polymer gel electrolyte 60%. All solid EC could be fabricated with the polymer gel electrolyte, which exhibited the higher coloring / bleaching efficiencies than that with the liquid. The effects of composition and process variables will be discussed.
The Ionogel of N-Butyl-N-Methylpyrrolidinum Bis(trifluoromethanesulfonyl) Imide and Polyvinylidenefluoride-Co-Hexafluoropropylene for Flexible Lithium Ion Battery
Authors: Chen Hwang-Sheng , Chang Chien-Min , Lee Ching-Feng , Wang Pin-Han , Chen-Yang Yui Whei 
Published: February 2020

Rechargeable lithium ion batteries (LIBs) have been applied in portable electronics and electricity powered transportation due to the high energy and power density. Unlike the traditional batteries packed in a cylindrical type, currently, most LIBs used in the consumer electronics (like smart phones and pads) are prismatic batteries. To meet the requirement of the electronics with particular shape such as wearable devices the flexible energy storage devices have been developed. For the safety concern, the solid electrolytes, such as polymer electrolyte, are developed to avoid leakage of liquid electrolyte. Nevertheless, the larger interfacial resistance between the solid electrolyte and electrodes and less flexibility reduced its application. Therefore, the gel-type electrolytes are favored because lithium ion is more easily to transport in gel electrolyte than solid electrolyte. Yet, as reported, certain amount of the organic solvents such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) have been usually used with polymers in the traditional gel electrolytes, causing the suspicion of solvent leakage. In this work, the solvent-free polymer-based ionogel electrolyte (IGE) composed of nonflammable and thermally stable N-butyl-N-methylpyrrolidinum bis(trifluorome­thanesulfonyl) imide (PYR14TFSI) room temperature ionic liquid and polyvinylidenefluoride-co-hexafluoropropylene (P(VdF-HFP)) are prepared by the solution casting method. The thermal and electrochemical properties are determined by the DSC and DMA measurements. The electrical properties are investigated by the linear sweep voltammetry, cyclic voltammetry and impedance spectroscopy. It is found that the as-prepared ionogel electrolytes are flexible self-standing films with wide electrochemical windows. The best conductivity obtained at room temperature is 6.0 × 10−4 S cm−1. The highest capacity of the half-cell (Li/IGE/LiFePO4) achieves 143 mA h g-1 at 0.2C rate. And even after 50 cycles, the capacity retains 135 mA h g-1at 0.2C. This study reveals that the ionogel electrolyte is a promising safe electrolyte for application in the flexible LIBs.
Acknowledge:
The authors gratefully acknowledge the Ministry of Science and Technology and Chung Yuan Christian University, Taiwan, R. O. C. for supporting this research work.
(Invited) Direct Comparison of Molecular and Metal Oxide Catalysts on Hematite for Photoelectrochemical Water Oxidation
Authors: Wang Dunwei 
Published: February 2020

Photoelectrochemical (PEC) water splitting promises a direct route toward solar-to-chemical energy conversion. To address the challenges associated with the slow kinetics of complex reactions such as water oxidation, catalysts have been applied onto photoelectrodes. While PEC performance improvement is often reported, the detailed mechanisms underpinning the improvements are poorly understood. In the case of heterogeneous oxide-based catalysts such as Co-phosphate, NiFeOx and IrOx, various electrochemical and spectroscopic studies have pointed to the slowdown of surface recombination as a key reason for the improvement. Due to the complex chemistries involved by these heterogeneous catalysts, however, little is known about whether fast charge transfer plays a role. Here we report a study that corrects this deficiency. Our strategy is to directly compare two catalysts systems, heterogenized Ir-complex water oxidation catalysts (het-WOC) and heterogeneous IrOx catalysts, on hematite photoanode. Using a combination of intensity modulated photocurrent spectroscopy (IMPS), photoelectrochemical impedance spectroscopy (PEIS) and kinetic isotope effect (KIE), we present compelling evidence that points the different functional mechanisms exhibited by the two different types of catalysts. The het-WOC improves the performance of hematite by speeding up hole transfer for water oxidation. The surface recombination rates remain unchanged. The IrOx catalysts, on the other hand, slows down surface recombination. New understandings of the photoelectrode|water interface are estabilished.