bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous Detection of Carbamates and Organophosphate Pesticides at Bare Boron-Doped Diamond Electrodes
Authors: Bentin Ella , Foord John S. 
Published: February 2020

Carbamate and organophosphate compounds are widely used pesticides because of their high insecticidal activity, and sometimes as nerve agents because of their crippling inhibition of the enzyme acetylcholinesterase (AChE)1. These compounds accumulate in the food chain and can hijack the nervous system of the target organisms indiscriminately. Traditional electrochemical methods of pesticide detection rely on layered structures atop noble metal or carbon electrodes to assist the loading of AChE, which produces currents proportional to its inhibition level. One of the clear advantages of boron-doped diamond (BDD) as an electrode material is its greater potential window in aqueous solutions, compared to conventional electrode materials2. This allows redox behaviour at extended potentials to be observed without damage to the electrode.
Cyclic, differential-pulse, and square-wave voltammetric techniques were used to probe carbaryl (CB), carbofuran (CF), and malathion in Carmody buffers of pH 2–12. Oxidation of CF occurred at the three overpotentials 1.31 V, 1.44 V, and 1.69 V, and a broad reduction peak was observed at 1.10 V, referred against Ag|AgCl. Compared with the oxidation of CB at 1.35 V, these electrochemical differences allowed for simultaneous detection of both compounds. This non-enzymatic sensor demonstrated a linear calibration over a concentration range of 1–100 µM for CB (R=0.9834) and CF (R=0.9938). After exposure to 1 mM malathion, a reduction peak appears that is highly sensitive to pH, attributed to a complex carbon–oxygen adsorbate that is robust to aggressive cleaning methods and only removable by hydrogen plasma etching. This malathion modified surface may be advantageous in future applications such as pH sensing. The oxidised BDD demonstrated failsafe reproducibility, a linear response, and low detection limits at medically relevant concentrations.

References

Kostelnik, P. Kopel, A. Cegan, M. Pohanka, Sensors, 17 (2017) 676.

V. Macpherson, Phys. Chem. Chem. Phys.,
17 (2015) 2935-2949.
Machine-Learning Enabled Search for the Next-Generation Catalyst for Hydrogen Evolution Reaction
Authors: Wei Sichen , Baek Soojung , Reyes Kristofer , Yao Fei 
Published: February 2020

As a zero-emission, eco-friendly fuel, hydrogen gas can be generated via electrochemical (EC) water splitting. Achieving high-efficiency water splitting requires the use of a catalyst to minimize the overpotential to drive the hydrogen evolution reaction (HER). Noble metals such as platinum (Pt) can provide an excellent catalytic activity for HER but are too expensive and scarce for broad applications. Therefore, the development of active HER catalysts made from low-cost materials constitutes a crucial challenge in the utilization of hydrogen energy.
Earth-abundant transition metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2), have been discovered recently, which exhibit good activity and stability for electrocatalytic reactions. In order to fully explore the untapped potential of MoS2, the synthesis recipe for MoS2needs to be optimized. Such an optimization process needs scientists to search through a combinatorically large space of experimental parameters, which will be time-consuming and costly if using conventional trial-and-error approaches.
In this report, MoS2 HER catalytic activity optimization is performed by examining different combinations of synthesis parameters during the hydrothermal process. To investigate the structure-activity relationship, scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy and various electrochemical characterizations have been conducted. A strong correlation between hydrothermal conditions and HER performance matrix has been observed. In order toaccelerate the search for the best synthesis recipe, machine-learning (ML) techniques have been introduced to help identify the optimal parameter combinations for producing MoS2. The hydrothermal parameters with the corresponding onset potentials and Tafel slopes are adopted as prior knowledge and are incorporated into the Bayesian Optimization model. The model will be able to guide the wet chemical synthesis of MoS2and yield the most effective HER catalyst eventually.
Evaluation of Changes in Bond Parameters in Sulfolane Under the Influence of Electron Donating Substituents
Authors: Yasko Andrey , Khamitov Edward , Kuzmina Elena , Kolosnitsyn Vladimir 
Published: February 2020

Sulfolane is a promising solvent for electrolytes in lithium-ion batteries, because it possesses high thermal and oxidative stability, high flash point, well dissolves lithium salts. However, sulfolane has a high melting point (27.5 °C) and viscosity (0.01029 Pa • s at 30 °C). High melting point and viscosity due to the tendency of sulfolane to self-association. To reduce the degree of self-association is possible by introducing various substituents into the sulfolane molecule.
The aim of the work was to investigate how the introduction of substituents into the sulfolane molecule affects its chemical stability. Chemical resistance was judged by changes in bond orders.
Presented work summarizes the results of quantum-chemical calculations of the bond orders in the sulfolane molecule and its substituted analogs, including methyl-, ethyl-, propyl-, vinyl- and allylsulfolanes (Figure 2).
Quantum chemical calculations were performed using the Gaussian09 software package. The optimization procedure was performed using the TPSS/cc-pVTZ method. Analysis of wave functions and calculation of bond orders by “fuzzy” method were performed in MultiWfn software package.
The objects of study were sulfolane and analogs with electron donor substituents. A total of 21 structures. The nature of the change in bond orders shows the influence of the position of substituents on electron density distribution. It has been established that the substitution of hydrogen atoms for this groups has the greatest influence on the order of the C – S and C – C bonds, reducing it, and the smallest on the S = O bond. This is especially clearly observed when hydrogen atoms attached to carbons connected to sulfur are substituted. These data show the possible paths of reduction reactions.
This work was performed as part of a Government Order to Ufa Institute of Chemistry of the Russian Academy of Sciences by the Ministry of Science and Higher Education of the Russian Federation (Theme No. AAAA-A17-117011910031-7) Russia and was also financially supported by the Russian Science Foundation (project No 17-73-20115).

Figure 1
Ionic Conductivity and Thermal Stability of Polyethylene Glycol Based Polymer Electrolytes Containing Phosphonium Ionic Liquids
Authors: Nomizu Daiki , Tsunashima Katsuhiko , Sakaguchi Yuki , Higashi Toshikazu , Yamada Hirohisa , Matsumiya Masahiko 
Published: February 2020

Room-temperature ionic liquids (RTILs), i.e. organic molten salts with melting points below 100 ◦C, have been regarded as potential media in various chemical systems due to the fact that RTILs have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, no measurable vapor pressure, high thermal stability, low flammability, etc. On the other hand, polyethylene glycol (PEG) is widely used as an electrolyte for lithium polymer secondary batteries from the viewpoint of considerable interaction with lithium ions. However, PEG does not show sufficient ionic conductivity because partial crystallization proceeds at temperatures below the melting point.1 In order to solve such a problem, various types of RTILs have been investigated for the PEG based polymer electrolytes; however, RTILs based on quaternary phosphonium cations have rarely been employed for the polymer application despite the fact that the phosphonium RTILs offer both high conductivity and thermal stability.2 In this work, we report the preparation of the PEG-based polymer electrolytes containing phosphonium RTILs, examining their physicochemical properties such as conductivities, thermal decomposition temperatures, etc.
The preparation of the phosphonium RTILs was performed by aqueous ion exchange reaction of the precursor quaternary phosphonium halides with lithium bis(trifluoromethylsulfonly)amide (TFSA). The RTILs and PEG were mixed at a mass ratio of 4:6 to prepare the polymer electrolytes. The conductivities of the polymer electrolytes were evaluated by an ac impedance measurement. The thermal decomposition temperature of the polymer electrolytes obtained was measured by a thermogravimetric analysis.
As shown in Fig. 2, it was found that relatively high conductivities were observed in phosphonium RTIL based polymer electrolytes when compared to those in the polymer electrolytes prepared by using the corresponding ammonium RTILs. This result seems to be due to the relatively high transport property of the phosphonium RTILs. The thermal decomposition behavior of the phosphonium RTIL based polymer electrolytes will be discussed.
References

D. Fauteux, A. Massucco, M. McLin, M. van Buren, J. Shi, Electrochim. Acta, 40, 2185 (1995).

K. Tsunashima, M. Sugiya, Electrochem. Commun., 9, 2353 (2007).

Figure 1
Probing the Influence of Solvation Entropy on Li+/Li Redox in Aprotic Electrolytes
Authors: Leverick Graham , Nienhuis Janet , Crabb Emily , France-Lanord Arthur , Stephens Ryan M. , Grossman Jeffrey C. , Shao-Horn Yang 
Published: February 2020

Solvation plays a vital role in determining the thermodynamics1 and kinetics2 of both homogeneous and heterogeneous redox reactions, as well as bulk electrolyte properties such as ionic conductivity. While the enthalpic contribution of aprotic solvents are well understood through empirically measured solvation parameters such as the Gutmann donor and acceptor number3, the contributions of solvation entropy on redox reactions, particularly in nonaqueous solvents, is not well understood. In this work, we consider the effect of solvent, counter anion and salt concentration on the solvation entropy of Li+ ions. Through probing the reaction entropy of the Li+/Li redox couple in a variety of salt and solvent systems, we find in a fully dissociated electrolyte, such as LiTFSI in DMSO, that the solvation entropy depends mostly on the activity and mobility of Li+ ions. Alternatively, in electrolytes with significant ionic association, such as LiTFSI, LiTfO and LiTFA in DME, more complex and non-ideal behavior is observed. The results of this study enable a stronger fundamental understanding of the role of entropy on solvation, promoting rational design of electrolytes in aprotic systems.
References

D. G. Kwabi et al., Angewandte Chemie International Edition, 55, 3129–3134 (2016).

R. A. Marcus, Reviews of Modern Physics, 65, 599–610 (1993).

V. Gutmann, Electrochimica Acta, 21, 661–670 (1976).
Free-Standing Carbon Electrodes for the Oxygen Evolution Reaction
Authors: Song Feihong , Ding Yuxiao , Lin Yangming , Heumann Saskia , Schloegl Robert , Mechler Anna Katharina 
Published: February 2020

N-functionalized hydrothermal carbon materials (N-HTC) with spherical morphology were prepared by hydrothermal synthesis utilizing glucose and urotropine as starting materials, which makes the synthesis cost-efficient, environmental friendly and allows simple scale-up. The molar ratio of glucose and urotropine has been varied and the powder materials were pelletized, resulting in mechanically stable disc electrodes. By increasing the amount of nitrogen, N-contents from 5 wt% up to maximal 8 wt% were obtained after pyrolysis at 1000 °C. The pellet can then be used as an anode for alkaline water splitting. In literature, there are still no direct evidence of metal-free carbon as electrocatalyst for oxygen evolution reaction. By comparing the N-functionalized sample and without functionalization, we found that the former has superior stability under water splitting condition (relative high potential). Up to one week of stable oxygen production was achieved. The result indicates that nitrogen facilitates oxygen evolution reaction. Besides, the nitrogen species also hinders carbon corrosion, proved by a simple Hoffmann cell measurement. Pellets with different synthesis condition as well as nitrogen content are compared in order to get the optimized synthesis condition.
For better understanding, methylene blue adsorption and mercury intrusion porosimetry are used to characterize the pore structure of the carbon materials. The relative work function and conductivity of the carbon pellet are determined by Kelvin-probe and Van-der-Pauw methods, respectively. A conventional three-electrode assembly is used to characterize the electrochemical performance, including activity, stability as well as mass transport property by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy (EIS). A transmission line equivalent circuit model is used to fit the EIS complex spectra, where the diffusion resistance and reaction resistance can be determined. The two resistances are very important reaction key performance indicator for oxygen evolution reaction, as it can distinguish a diffusion process from a reaction. The gas products as well as electrolyte after electrochemical test can be analysed by mass spectrometry, ESI-MS, UV-VIS spectroscopy, etc. From the mass spectrometry results, the mole fraction of oxygen in the total product gas can be determined, determining the selectivity of the reaction. Besides, water diffusion NMR measurements before and after electrochemical test shows changes in the water interaction, which can be correlated to Nitrogen species changes in the electrode.
This study demonstrates that N-functionalization improves the stability of HTC for oxygen evolution reaction providing a promising pathway for the future energy conversion and storage.
(Invited) PEFC Electrode Layer Development Via Complementary in Situ Diagnostics and Ex Situ Characterization
Authors: Van Cleve Timothy , Khandavalli Sunil , More Karren L. , Osmieri Luigi , Wang Guanxiong , Star Andrew G. , Kabir Sadia , Cetinbas Firat , Kariuki Nancy N. , Park Jaehyung , Ulsh Michael , Medina Samantha , Mauger Scott A , Pylypenko Svitlana , Myers Deborah J. , Neyerlin K.C. 
Published: February 2020

Ink formulation and electrode design optimization is often an iterative process, in which conclusions from in situ performance/ diagnostics as well as ex situ characterization (e.g. microscopy and tomography) are relayed to a model. The model then identifies fundamental limiting phenomena which are to be improved in the next iterative cycle. This process often takes several iterations to ensure an optimal combination of ionic and gas phase accessibility to the active site.
The proper integration of materials to enable high performing low temperature fuel cell operation has never been more crucial to realizing the isolated (e.g. half-cell or ex-situ) improvements of advanced electrocatalysts, supports and ionomers. Variables such as ink formulation (i.e. solvents and solvent ratios), processing method, ionomer chemistry, carbon morphology/porosity and even the presence or absence of Pt, can impact the ink level interactions of the materials set and subsequently alter the final electrode morphology. The resulting electrode structure can in turn influence active site accessibility and ORR activity as well as oxygen transport resistance and electrode proton conductivity.1–5

Here, the development and utilization of in situ diagnostics designed to probe specific phenomena (e.g. catalyst/ionomer interactions, molecular and Knudsen diffusion, electrochemical active site accessibility and catalyst layer proton resistance) will be utilized to contrast the ink, processing and fabrication methods necessary to achieve high performance PGM (e.g. Pt/C and Pt alloy/C) and PGM-free (e.g. FeNx/C) electrocatalysts based electrodes.
References

A. Orfanidi, P. J. Rheinländer, N. Schulte, and H. A. Gasteiger, J. Electrochem. Soc., 165, F1254–F1263 (2018).

S. Khandavalli et al., ACS Appl. Mater. Interfaces, 10, 43610–43622 (2018).

D. Myers, https://www.hydrogen.energy.gov/pdfs/review15/fc106_myers_2015_o.pdf.

F. Xu et al., Langmuir, 26, 19199–19208 (2010).

D. A. Cullen et al., J. Electrochem. Soc., 161, F1111–F1117 (2014).
Quantifying Concentration Distribution in an Organic Redox Flow Battery Using in-Plane Neutron Radiography
Authors: Forner-Cuenca Antoni , Greco Katharine Virginia , Kowalski Jeffrey A , Boillat Pierre , Brushett Fikile R. 
Published: February 2020

Redox flow batteries (RFBs) are promising rechargeable electrochemical devices for grid-scale energy storage, but further cost reductions are needed for ubiquitous adoption of this technology [1]. While recent research trends have focused on molecular discovery [2], advances in the science and engineering of electrochemical reactors can lead to cost reductions via increased power density and/or decreased component cost. Key to such efforts is deconvolution of coupled transport and kinetic processes within operating device and, to this end, imaging diagnostics, such as X-ray tomographic microscopy [3], infrared thermography [4], and electrochemiluminescence imaging [5], have been employed to visualize relevant properties (e.g., fluid distribution, temperature) in RFBs. However, obtaining quantitative property descriptions at high resolution and under representative operation conditions remains a challenge.
In this presentation, we introduce neutron radiography as an operando characterization method for RFBs which is particularly sensitivity to organic materials with high hydrogen content. To demonstrate the potential of this diagnostic tool, we characterize active species concentration distribution within a redox flow cell in a single electrolyte configuration with a nonaqueous electrolyte containing TEMPO/TEMPO+. We use subtractive neutron imaging [6] in combination with isotropic labelling to deconvolute the concentration of different electrolyte materials (i.e. supporting salts, active species). To resolve the concentration profiles across the different layers, we employ the in-plane imaging configuration [7] and correlate these profiles to cell performance via polarization and electrochemical impedance spectroscopy.
References

Darling et al., Energy & Environmental
Science, 7, 3459 (2014).

A. Kowalski et al., Current Opinion in Chemical Engineering, 13, 45 (2016).

Tariq et al., Sustainable Energy & Fuels, 2, 2068 (2018).

Tanaka et al., Journal of Energy Storage, 19, 67 (2018).

Rubio-Garcia et al., Electrochemistry Communications, 93, 128 (2018).

Boillat et al., Journal of The Electrochemical Society, 162(6), F531 (2015).

Boillat et al., Electrochemistry Communications, 10(4), 546 (2008).

Acknowledgments
We gratefully acknowledge the financial support of the Swiss National Science Foundation (P2EZP2_172183) and the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the United States Department of Energy.
What Your Students Ought to Know about Electrochemistry (But Ask Us Instead)
Authors: Spinner Neil , Paschkewitz Timothy , Peroff Alex , Sun Li 
Published: February 2020

“Have you made sure your reference electrode is connected to your potentiostat? Are you even using a reference electrode?”
Electrochemistry equipment manufacturers frequently find themselves in the position where they are providing guidance and troubleshooting advice to graduate students and industry technicians. In addition to these expected services, the role we find ourselves often playing is auxiliary academic advisor. Over the years, our electrochemists have collected numerous anecdotes about a variety of apparent research catastrophes, and graduate advisors may be personally surprised to learn the kinds of stories we have heard. While there are certainly instances when reported problems are valid and require in-depth technical assistance with the instrument, it is not uncommon for the problem to be traced to a gap in fundamental or practical electrochemical knowledge.
When an issue is encountered in an electrochemical experiment, the underlying problem is either the fault of the chemistry or the instrument. This creates tension between the student or technician and the electrochemical equipment manufacturer, and we find that blame is often reflexively passed onto us during a phone call or email exchange. However, the simplicity, and sometimes unintentional comedy, of many of these issues may suggest the heart of the problem is fear of asking one’s advisor, or of damaging equipment from improper use.
In this presentation, we will share some of the recurring problems we encounter from bewildered students and technicians across the world, and use these stories to alert lab directors about some common deficiencies we have observed. While we are sympathetic to the varying methods, busy schedules, and tight deadlines of the average academic advisor (or industry supervisor), our experience of repeatedly filling in basic knowledge gaps suggests there may some simple, practical steps that can be taken with those who are beginning electrochemical research to build a strong foundation for future success.
Electrochemical Tutorials on Diffusion: Models and Demonstrations with Physical Therapy Putty
Authors: Parr Daniel Lee , Leddy Johna 
Published: February 2020

Although diffusion is a pervasive concept in chemistry, minimal discussion in chemical education literature provides intuitive explanation of diffusion and mass transport. Explanation of diffusion is often given as a dichotomy: (1) a drunken sailor described by a discrete binomial distribution and (2) a continuous solution of the diffusion (heat) equation. As the dichotomy suggests, there is a persistent dislocation between the drunken sailor and error functions as the two explanations do not align to provide a unified and intuitive explanation of this important and fundamental concept.
Here, we present an introduction to diffusion through models and demonstrations to bridge the intuition gap of diffusion in the classroom. Discrete diffusion is explained initially with the classic drunken sailor narrative and also by the Galton board (Figure 1). The Galton board provides a much improved and intuitive explanation of discrete diffusion via hands-on demonstration of the binomial probabilities.
Transition into continuous diffusion evolves from an explanation of flux (Figure 2.) and concentration gradients, the drivers of diffusion. Finally, we provide a demonstration suitable for any classroom with diffusion of physical therapy putty. The broadening of a physical therapy putty disk with time is modeled with the diffusion equation. Time dependence of the putty radius is observed and compared with the standard diffusion length metric.

Figure 1