bluuebunny/crossref_metadata_2025 huggingface dataset:
The Preparation of NaCrO2 and Biomasss-Derived Hard Carbon for Sodium-Ion Batteries
Authors: Liu Xin , Sun Wanda , Mao Jing , Shao Guosheng
Published: February 2020

Among all components in battery, cathode material is one of the most crucial parts, for cathode material contributes a lot to a battery’s good performance. Sodium-ion batteries (SIBs) have attracted more and more attention for large-scale electrical energy storage due to the abundance and wide distribution of Na resources. Recently, researchers focus on layered transition metal oxide, for its stable structure. NaCrO2 is one of the most promising sodium layered transition metal oxides as cathode material in SIBs, because of its excellent thermal stability and compatibility with non-aqueous electrolyte. Furthermore, certain remarkable advantages of NaCrO2 have been reported, including a high theoretical capacity of about 250 mAh g-1, although its practical reversible capacity is approximately 100 mAh g-1.

Hard-carbon are considered as one of the most promising anode materials for sodium-ion batteries (SIBs), but there are still two main disadvantages of high cost and low initial coulombic efficiency to be overcomed for practical SIBs.

Herein, we report preparation of layered NaCrO2 as sodium-ion battery cathode material using a gel-combustion method and a cheap pinecone derived biomass-bassed hard carbon (PHC) using a simple carbonization method as anode material for SIBs.

The electrochemical performance of layered NaCrO2 is greatly affected by the calcination temperature due to difference microstructure and carbon content. The NaCrO2 calcined at 850℃ shows the best electrochemical performance with a reversible capacity of 90 mAh g-1 at a current density of 20 mA g-1, along with a high initial coulombic efficiency and good cycling performance. To further study the microstructure of NaCrO2, XRD and FESEM are used to study the structure and morphology of NaCrO2.

The performance of PHC is greatly affected by the carbonization temperature due to different microstructure and impurity. The PHC carbonized at 1400℃ shows the best electrochemical performance with a reversible capacity of 345 mAh g-1 at a current density 30 mA g-1, along with a high initial coulombic efficiency of 85.4% and good cycling performance. To further study the microstructure of PHC, the amorphous structure is demonstrated by X-ray diffraction (XRD), Raman spectroscopy as well as high-resolution transmission electron microscopy (HRTEM).

We make a full cell using NaCrO2 as cathode material and PHC1400 as anode material. The initial coulombic efficiency is 93%. The initial charge specific capacity based on anode material is 311 mAh g-1, and the initial discharge specific capacity was 289 mAh g-1 at a current density 30 mA g-1. The specific capacity based on anode is 150 mAh g-1 after 200 cycles. The full cell shows excellent electrochemical performance benefited by well-prepared cathode and anode materials.
Weavable Lithium-Ion Batteries Based on Fibrous All-in-One Monolith Electrodes with a Biological Gluing Layer
Authors: Shin Kyu Hang , Park Hae Won
Published: February 2020

Owing to rapid development of wearable electronics, demand for energy storage devices with high flexibility, light weight, and improved energy density has been remarkably increasing. Even though previous researchers have developed various types of flexible batteries, not many of them are weavable, stretchable and having high capacity at the same time. In this work, we fabricated fibrous all-in-one electrode threads to make truly weavable lithium ion batteries(LIB). They are enabled by nanosized hybrid active layers with biological gluing inner layer and protective outer membrane shell. Each thread is comprised of four distinct concentric coating layers, a carbon fiber core as current collector, a conductive biological gluing layer, active materials, and a porous membrane layer. Nanosized LiFePO4/C-rGO and Li4Ti5O12/rGO are used for cathode and anode threads. Enhanced mechanical strength of electrode threads was achieved by biological glue that can hold the active materials from the fibrous core and an inline coating process of porous membrane layer on active materials. This unique all-in-one structure and mechanical stability allowed twisting and hierarchical weaving for higher energy density of the batteries. The fibrous monolith LIB showed a high linear capacity of 1.6 mAh cm-1 and this value could be further enhanced with the way of twisting multiple threads. The fibrous LIB could also be woven into a fabric presenting stable operation under 50% of elongation via encoded structural deformation in the fabric structure.
A Novel Sulfonated Aromatic Polymer Membrane with Different Pendant Groups for Vanadium Redox Flow Batteries (VRFBs)
Authors: Wang Tongshuai , Han Junyoung , Kim Kihyun , Lee Jannice , Bae Chulsung , Kim Sangil
Published: February 2020

Vanadium redox flow batteries (VRFBs) have received extensive attention due to its attractive features for the large-scale energy storage because of their design flexibility, high energy efficiency, absence of intercalation/deintercalation and stress build-up in electrodes, and safe operation. One of the most critical components in VRFB is an ion exchange membrane (IEM) which can prevent cross mixing of the multivalence vanadium ions, while it still allows the transport of protons (or anions) to complete the circuit. However, the trade-off relationship of proton exchange membrane (PEM) limits the energy efficiency (EE) of the VRFB due to low coulombic efficiency (CE) caused by vanadium ion cross over through the membrane or high membrane resistances. Anion exchange membrane (AEM) suffers from poor chemical stability and low voltage efficiency due to low ion conductivity.

In this study, we synthesized a series of novel sulfonated aromatic polymer membranes having high proton conductivity as well as proton selectivity. Vanadium/hydronium ion permeability, proton conductivity, area resistance, and ion exchange capacities of the membranes were measured. The single cell VRFB performance with the prepared membranes was evaluated and compared with the one using a commercial Nafion 212 membrane. The effect of the pendent group structure on the membrane ion selectivity and battery performance was also discussed.

It was found that the incorporation of aromatic structures on the pendent groups effectively improved the ion selectivity of membranes which can overcome the limitations of the trade-off relationship between the proton conductivity and selectivity. The membrane with aromatic pendent groups (BP-Ar-SH) shows 7 times higher vanadium/proton ion selectivity than that without aromatic groups (BP-SH) (5.18 vs. 0.75) and 3 times higher than Nafion 212 (5.18 vs. 1.78). As a result, the VRB single cell equipped with the BP-AR-SH membrane shows significantly better performance in comparison to the cell with Nafion membranes, as high as 90.05% EE (vs. 73% EE of Nafion) at 20 mA/cm2. The cycle stability test shows that efficiencies of the membrane remain almost unchanged after running more than 50 cycles. Our results strongly suggest that the BP-Ar-SH membrane may provide a breakthrough toward the development of high-efficiency VRFB systems.
Advanced Mg Ion Electrolytes Enabling Mg/S Rechargeable Batteries
Authors: Liu T. Leo , Luo Jian , Bi Yujing
Published: February 2020

Mg is earth abundant and low-cost (ca. 24 times cheaper than Li), and as an anode material, Mg is safe to use without dendrite formation (vs. Li, Li-ion, or Na-ion batteries). Its high gravimetric capacity (2,333 Ah/kg) and high reduction potential (-2.37 V vs SHE) allow the assembly of high-energy density batteries. However, despite rapid research progress, the lack of high performance Mg2+ conductive electrolytes still presents a primary technical hurdle for developing practical Mg batteries. The presentation will cover our research efforts in developing high performance Mg electrolytes for Mg rechargeable batteries. Specifically, we will present the synthesis and electrochemical performance of ternary Mg/MgCl2/AlCl3 (MMAC) electrolytes and other Mg electrolytes. For example, the MMAC electrolyte in DME exhibit 100% Coulumbic efficiency, and 164 mV ovpotenail for Mg deposition, and 3.7 V vs Mg anodic stability. Solution and interfacial chemistry of the presented Mg electrolytes will be discussed in detail. In addition, we will share our results on applying advanced MMAC electrolytes with additives in developing high energy density Mg/S rechargeable batteries. Our preliminary data showed that Mg/S batteries using the MMAC electrolytes could deliver 800 mAh/g capacity at a rate of 100 mA/g.

References:

(1) Luo, J; .He, S.; Liu, T. L.* ACS Energy Letters 2017, 2, 1197-1202. (2) He, S.; Luo, J. Liu, T. L.*, J. Mater. Chem. A 2017, 12718-12722. (3) He, S.; Neilson, K. V.; Luo, J..; Liu, T. L.*, Energy Storage Mater 2017, 8, 184-188. (4) Liu, T.;* Shao, Y.; Li, G.; Gu, M.; Hu, J.; Xu, S.; Nie, Z.; Chen, X.; Wang, C.; Liu, J. J. Mater. Chem. A.
2014, 2, 3430. (5) Liu, T.;* Cox, J. T.; Hu, D.; Deng, X.; Hu, J.; Hu, M. Y.; Xiao, J.; Shao, Y.; Tang, K.; Liu, J. Chem. Commun.
2015, 51, 2312. (4) Filed US patent applications on Mg electrolytes (4) Group website: www.tianbiaoliu.org.
(Invited) Surface Hydrogen Bonding Effects. The Use of Redox Probes to Induce the Reversible Reorganisation of Electrografted Films
Authors: González Felipe J. , Morales-Martínez Daniel
Published: February 2020

The electrochemical oxidation of tetrabutylammonium carboxylates on carbon surfaces is typically performed following a global non-Kolbe mechanism [1], whose reactive intermediates allow the grafting of carbon surface with organic moieties [2]. Several characterisation strategies have been used to obtain information about the properties of the grafted film, among them is the use of reversible redox probes [3]. In this case, it has been observed that that the behaviour of the redox probe on the grafted surface is not stable and varies during cycling procedures in cyclic voltammetry [4]. Therefore, in this work, grafted carbon surfaces bearing alkyl-ester, alkyl-ketone, alkynyl and saturated chains were prepared to demonstrate that the variability in the behaviour of 1,4-benzoquinone as redox probe is due to a reversible reorganization effect of the grafted film [5]. The voltammograms of the first reduction wave of the redox probe on the different modified electrodes change during cycling procedures. However, the stand time of these modified electrodes in the electrolyte solution allows the recovery of the initial voltammograms. The changes observed between cycling and stand time are cyclical and can be understood through a reversible reorganization effect of the grafted film, which is attributed to hydrogen bonding interactions between the functional groups present in the structure film and the water present in solvent.

References

[1] H.J. Schaeffer, Topics in Current Chemistry, 1990, 152, 90

[2] C.P. Andrieux, F. González, J.M. Savéant, J. Am. Chem. Soc., 1997, 119 4292

[3] A.C. Cruickshank, E.S.Q. Tan, P.A. Brooksby, A.J. Downard, Electrochem. Commun., 2007, 9 1456-1462.

[4] A.O. Solak, L.R. Eichorst, W.J. Clark, R.L. McCreery, Anal.
Chem., 2003, 75, 296

[5] D. Morales-Martínez, F.J. González, Electrochem.
Commun., 2016, 62, 21
Peroxynitrite Detection and Quantification on Selenide-Based Grafted Interfaces
Authors: Kalil Haitham , Fouad Farid , Bayachou Mekki
Published: February 2020

Peroxynitrite (PON) is a reactive oxygen-nitrogen metabolite that has been linked with both oxidation and nitration reactions in biological systems. PON is a major cytotoxic agent that is implicated in a host of pathophysiological conditions. It is the primary product of the reaction of superoxide anion-radical and nitric oxide radical under oxidative stress, inflammatory reactions, and other related conditions. Some literature reports highlight the deleterious physiological reactivity of PON with different cellular targets including DNA, proteins, and lipids in cell membranes. On the other hand, other reports identify counterintuitive cytoprotective roles of this species under certain conditions. The balance of deleterious reactivity versus potential cytoprotective roles of PON is apparently driven by its dynamic concentration.

Accurate determination of PON concentration is inherently difficult due to its high reactivity and the low target concentration range that is relevant to biological systems. Various methods for PON determination have been reported including indirect spectroscopic assays and, recently, direct electrochemical methods. In this regard, viable electrochemical probes for PON detection, including catalytic interfaces for PON detection, are still lacking, and work in this area is still in its early stages.

In this work, we prepared an interface grafted with a selenium-based compound for sensitive electrochemical determination of PON. First, we describe the preparation and grafting of 4,4' diaminodiphenyl selenide on graphite and indium-tin oxide electrodes. We characterized the modified interfaces using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). We will present and discuss these findings as well as results on the performance of the selenide-based grafted electrodes as peroxynitrite sensing interfaces using voltammetry and dose-response amperometry. The modified electrodes showed a significant enhancement in peroxynitrite oxidative current compared to controls. We will show that the enhancement in peroxynitrite signal is the result of an electrocatalytic mechanism where the grafted selenide compound at the oxidized state mediates the oxidation of peroxynitrite at the electrode surface. To the best of our knowledge, this is the first time a selenium-based compound electrochemically grafted at an electrode surface is used for catalytic detection and quantification of peroxynitrite.
(Invited) The Impact of Polyelectrolyte Dynamics on the Electrochemical Reactivity of Soluble Redox-Active Polymers
Authors: Rodriguez-Lopez Joaquin
Published: February 2020

In this presentation, I will discuss recent findings regarding the impact of polyelectrolyte dynamics on the charge percolation and electrolysis efficiency of soluble Redox-Active Polymers (RAPs). RAPs[1] and their colloidal form (RACs)[2] are a new class of materials for energy storage in fluid dispersions for a novel concept in size-exclusion flow batteries.[3] Despite RAPs displaying excellent charge storage properties, their complex electrochemical reactive pathways are just becoming elucidated. RAPs and RACs rely on intra-particle electron transfer to yield quantitative charge accessibility and high rate in order to achieve full electrolysis.[4] Charge mobility via inter-pendant electron hopping combines with their polyelectrolyte nature to exhibit a rich electrochemical behavior that is strongly modulated by specific and non-specific interactions with the electrolyte. In this talk, I will highlight the impact of several variables on the electrochemical signatures created by RAPs and RACs.

The mechanistic characterization of RAPs and RACs requires a spectrum of powerful electrochemical techniques, ranging from bulk methods to single-particle analysis. I will describe how the application of nano-resolved electrochemical microscopy techniques and Raman spectroscopy has helped us understand the mechanisms of individual electrochemical entities.

These experiments provide us with unprecedented versatility to identify kinetic bottlenecks, such as charge trapping, and to determine the maximum current densities attainable in flow devices. Altogether, the combination of novel structural motifs, the identification of structure-reactivity relationships, and the use of advanced electrochemical techniques, results in new directions to make better polymers for a new concept in redox flow batteries.

[1] J. Am. Chem. Soc. 2014, 136, 16309.

[2] J. Am. Chem. Soc. 2016, 138, 13230.

[3] Acc. Chem. Res. 2016, 49, 2649.

[4] Chem. Mater. 2016, 28, 7362.

*This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.
(Invited) Understanding and Predicting Transitions in Proton Coupled Electron Transfer
Authors: Frontana Carlos Eduardo
Published: February 2020

Proton Coupled Electron Transfer (PCET) mechanisms include all kinds of reactions where concurrent/stepwise processes are involved. Unraveling the distinctive character of a given mechanism is therefore a issue of importance, as concerted mechanisms lead to formation of products, avoiding the formation of high energy intermediates and are important for catalysis, while stepwise steps allow explaining the reactivity where radical species (either neutral or charged), can be invoked. Therefore, studies are not only directed to distinguish between both mechanistic alternatives, but to rationalize their significance in the reactivity of molecules and aggregates. For this purpose, simple trends using model organic compounds have been studied and allow to identify the structural characteristics that a given species must bear to induce any path. Within the workgroup, systematic analysis with series of nitro aromatic compounds [1,2] where Electron Transfer Controlled Hydrogen Bonding (a specific type of PCET process), show the influence of both the basicity of the electrogenerated anion radical and the acidity of the proton donor, describing the trends using descriptors of reactivity derived from changes in the local density of the molecule [3]. Using this approach, we have been able to analyze critical parameters where Hydrogen Bonding can lead to Proton Transfer, thus probably becoming concerted proton transfers. Results are therefore discussed in this work, along with the theoretical analysis described, its own limitations and some recent extensions for multiple-bodies approaches. Also, experimental changed where self-protonation occurs are presented, where we have been able to identify the "non-innocent" character of hydrogen bonding donors within the structures, leading to prior of forward hydrogen bonding interactions. Finally, some results of the influence of hydrogen bonding in the changes in electron transfer entropy are presented.

[1] Martínez-González, E.; C. Frontana, J
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Org
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Chem
. 2014, 79, 1131-1137

[2] Martínez-González, E.; Armendáriz-Vidales, G.; Ascenso, J. R.; Marcos, P. M.; Frontana C. J. Org. Chem. 2015, 80, 4581-4589

[3] Gázquez, J. L.; Cedillo, A.; Vela, A. J. Phys Chem. A. 2007, 111, 1966-1970

Figure 1
Effect of Heteroatom Bridge in the Transfer Electron Process of O-Aminebenzamides and Quinazolinendiones Evaluated By Electrochemistry
Authors: Espinoza Karla Alejandra , Manzo-Cruz Lizette , Pérez-Zamora Juan Alberto , Oropeza-Guzman Mercedes Teresita , Z. Flores-López Lucia , Olguin Luis David , Rivero Ignacio A
Published: February 2020

Electrochemistry characterization of organic compounds is a topic of great interest, due to electron transfer process is related with important biological process. The voltamperometry cyclic is an accurate technique to evaluate the redox process in antiepileptic drugs. Research groups have reported the synthesis of multivalent compounds that increase pharmacological response, in comparison with monovalent pharmacophores.1-3

In this work we synthetized divalent sedative drugs type: o-aminobenzamides (OAB) and 2,4-quinazolinendiones (QZD); these alkaloids present biological properties such as, antipsychotics and anticonvulsants, these properties can be evaluated through electron transfer capacity.

The results show the electrochemical small library of six compounds that was prepared using the OAB and QZD structures as pharmacophores, with ethylene and polyethylene glycol, as bridge. Electrochemistry studies were performed to determine the redox potentials of the compounds with different electrodes Pt, Au and vitreo carbon. These tests gave relevant information to attribute the electron transfer capability of these structures, being Pt electrode the one that gave more information of redox in the OAB and QZD compounds.

Kovacic, R. Somanathan, M. Inzunza. Rev. Chem. Soc. 47(2003), 146.

A. Rivero, K.A. Espinoza, R. Somanathan, Molecules, 9(2004), 609.

R. Ames, P. Kovacic, K. P. Kadaba, F.P Kiser, Epilepsia, 33(1992), 936.

Figure 1
The Influence of the Binder on the Investigation of Electrocatalysts for Oxygen Evolution Reaction in Alkaline Water Electrolysis
Authors: Narangoda Praveen Vidusha , Neugebauer Sebastian , Schloegl Robert , Mechler Anna Katharina
Published: February 2020

Rotating disc electrode (RDE) technique is a useful and commonly accepted technique for the performance evaluation of electrocatalysts for the oxygen- reduction (ORR) and evolution (OER) reactions.[
1] To characterize new catalysts, composite thin film electrodes are casted on RDE tips (TF-RDE) where polymers are typically utilized as binders to immobilize the powder electrocatalysts onto the substrate.[
1b] Literature surveys show Nafion® as a feasible binder for the investigation of alkaline OER catalysts. However, Nafion® was developed for application in PEM fuel cells that rely on the transport of protons rather than anions.[
2] To our best understanding, there is no systematic investigation on the influence of polymer binders in alkaline OER. As shown in Figure 1, Nafion® can affect the OER performance, especially described by the phenomenon of gas bubble retention on the electrode surface during chronopotentiometry (Figure 1C) and a significant influence of the amount of binder added to the thin film.[
3]

Here we will present a TF-RDE study of a benchmark catalyst (Ni, Co- Oxide, Sigma Aldrich) on glassy carbon and gold substrates, prepared with commercially available binders (Nafion®, Aquivion®, PTFE and Fumion®). We used a standardized preparation and measurement protocol to ensure comparability and reproducibility. The results show a significant influence of the choice of binder on the measured OER performance. These differences are discussed with respect to the binder properties in terms of hydrophilicity or functional groups, as well as their corrosion behavior under OER conditions.

[1] a) K. J. J. Mayrhofer, D. Strmcnik, B. B. Blizanac, V. Stamenkovic, M. Arenz, N. M. Markovic, Electrochimica Acta
2008, 53, 3181-3188; b) J. Suntivich, H. A. Gasteiger, N. Yabuuchi, Y. Shao-Horn, Journal of The Electrochemical Society
2010, 157, B1263-B1268; c) T. Reier, M. Oezaslan, P. Strasser, ACS Catalysis
2012, 2, 1765-1772.

[2] a) M. Paidar, K. Vazac, M. Roubalik, K. Bouzek, in Hydrogen Days, Prague, Czech Republic, 2015; b) S. Jung, C. C. L. McCrory, I. M. Ferrer, J. C. Peters, T. F. Jaramillo, Journal of Materials Chemistry A
2016, 4, 3068-3076.

[3] K. Zeng, D. Zhang, Progress in Energy and Combustion Science
2010, 36, 307-326.

Figure 1
Spreadsheet-Based Cyclic Voltammetry Simulation of Mediated Ferrocyanide Oxidation By Ferrocene Derivatives in Alkanethiol-Based Self-Assembled Monolayers on Gold Electrodes
Authors: Creager Stephen E , Mayall Robert Matthew , Birss Viola
Published: February 2020

Electron-transfer mediation reactions via surface-confined redox molecules in monolayer assemblies on electrodes have been studied for decades, but treatments that consider the electrode reaction in terms of microscopic rates for the relevant reactions are not so common. The critical reactions are (1) electron transfer between the immobilized redox molecule and the electrode, and (2) electron exchange between the immobilized redox molecule on the electrode and a second redox molecule in solution. Analytical solutions are available for limiting cases, e.g. no concentration polarization or convective mass transfer via electrode rotation, but not for the general case of cyclic voltammetry in quiescent solution, with full accounting of concentration polarization during the scan. This talk will present a spreadsheet-based digital simulation of this specific situation. A key element needed for the simulation is the surface flux condition, which is solved analytically as a kinetics problem considering reactions 1 and 2 above with a steady-state assumption. Simulated voltammograms will be presented and compared with experimental data for ferrocene-containing monolayers mediating ferrocyanide oxidation in solution. The simulation model allows for prediction of trends with respect to systematic changes in ferrocene surface coverage, ferrocyanide concentration, relative redox potentials for ferrocene and ferrocyanide redox, ferrocene oxidation / reduction rate constant, potential scan rate, and other parameters. Application in electrochemical biosensing at monolayers that also contain bioaffinity ligands will also be considered.

Figure 1
(Europe Section Allessandro Volta Medal) From Nanobiosensors to Scanning Bipolar Electrochemistry
Authors: Schuhmann Wolfgang
Published: February 2020

Measurement of physiological relevant molecules in and at individual cells with minimal disturbance of the cellular function is a key challenge in single-cell analysis. Ad­vantages of nanoscale electrochemical probes include their high spatial and tempo­ral resolution as well as a low substrate consumption. Carbon nanoelectrodes (CNEs) with a tunable radius between a few and several hundreds of nanometres can be fabricated by pyrolytic decomposition of alkane gas in glass nanopipettes. Their needle-type shape and small size enable electro­chemical measurements inside of single living cells. Two potential applications of CNEs namely for the design of nanometer-sized amperometric biosensors, and as the basis for gate-modulated reduced graphene oxide based transistors are presented.

However, the probability that a nanosensor is positioned close to a release site is tiny. Hence, we propose to combine scanning electrochemical microscopy (SECM) with bipolar electrochemistry (BPE) as a new approach to image heterogeneous electrochemical surface processes. The core of the system is a closed bipolar electrochemistry configuration comprising as the bipolar electrode (BPE) a microelectrode as SECM tip (cathodic pole of the BPE) connected with a microelectrode tip (anodic pole of the BPE) in the second half cell. Reduction processes enabled by a suitably applied feeder electrode voltage difference at the SECM tip in the sample generation/tip collection mode are transduced into an optical read-out e.g. electrochemiluminescence at the other pole which is visualized with a high sensitive CCD camera. Evidently, this configuration can be extended to multi-barrel SECM tips thus being able to simultaneously visualize the release of compounds at multiple locations while positioning the multi-barrel microelectrode above a release site of interest.

Acknowledgement
: All coworkers who have contributed to this research are acknowledged namely Jan Clausmeyer, Vera Eßmann, Carla Santana Santos, Tsvetan Tarnec, Thomas Erichsen, Miriam Marquitan, Patrick Wilde, Thomas Quast, Corina Andronescu, Federica Mariani. The author is grateful to the project "Graphtivity" funded in the framework of the FLAG-ERA Joint Transnational Call (JTC) 2015 (Graphene Flagship) and the Deutsche Forschung­gemeinschaft in the framework of the cluster of excellence RESOLV (EXc1069).
Direct Demonstration of Unified Brønsted−Evans−Polanyi Relationships for Proton-Coupled Electron Transfer Reactions on Transition Metal Surfaces
Authors: Chun Hee-Joon , Zeng Zhenhua , Greeley Jeffrey
Published: February 2020

The existence of Brønsted-Evans-Polanyi (BEP) relationships, which relate elementary reaction barriers to reaction thermodynamics across a space of different catalysts, has been extensively investigated for reactions on traditional heterogeneous catalysts, and BEP’s are known to provide the central physical paradigm underlying the existence of volcano plots and other trends-based descriptions of catalytic reactivity. However, the extension of such relationships to elementary electrochemical reactions, simultaneously spanning a space of both different applied voltages and different catalyst surfaces, has been widely discussed but never verified. In this contribution, the BEP model is explicitly shown to describe both multiple catalyst surfaces and variable voltages in electrochemical environments. For proton-coupled electron transfer to surface nitrogen (N*) and nitric oxide (NO*), reaction energies and activation barriers are calculated using density functional theory on a parallel plate capacitor model at three different potentials and for nine different transition metal surfaces. Linear BEP relations that describe all potentials and catalyst surfaces are obtained for these elementary reactions, and the slopes of the correlations are shown to be directly related to the fractional coordinate of the transition states (FCTS) of the reactions. The results, which are explained in terms of Marcus Theory, prove a direct equivalence between unified BEP coefficients, describing both variable catalyst surfaces and voltages, and electrochemical symmetry factors and provide a straightforward means of estimating this quantify for proton-coupled electron transfer reactions on transition metal surfaces. The resulting relationships, in turn, could lead to predictions of electrocatalytic reactivity trends of enhanced accuracy and efficiency.
Probing Electrochemical Reactions at Individual Nanostructures: Applications in Electrocatalysis and Photoelectrochemistry
Authors: Saha Partha , Hill Joshua , Walmsley Joshua , Hill Caleb M.
Published: February 2020

The utilization of nanostructured materials in electrochemical systems for energy conversion and catalysis has shown great promise. Fundamental studies into these systems are challenging, however, due to their inherently heterogeneous nature. Variations in particle size, shape, coupling, etc. can complicate the interpretation of experimental results. While electroanalytical and optical detection schemes have been employed to study electrochemical reactions occurring at individual nanostructures, reported approaches are severely limited by sample throughput and/or assumptions necessary for data analysis. Herein, the use of a combined electrochemical and optical approach to the study of these systems is described. Scanning electrochemical cell microscopy is employed to directly measure the rate of electrochemical reactions at individual nanostructures, while optical spectroscopy is used to probe the geometry of these nanostructures in situ. This complementary approach allows for the correlation of reliable electrochemical kinetic data with structural information and for the effects of photoexcitation on electrochemical reaction rates to be examined in a direct, quantitative manner. Initial studies applying this methodology to model electrocatalytic and photoelectrochemical systems will be presented.
Effect of Pd/C, Au/C and PdAu/C Synthesized Using Ionic Liquids in the Electro-Oxidation of Crude Glycerol in Alkaline Media
Authors: Velázquez-Hernández Isaac , Lair Virgine , Álvarez-Contreras Lorena , Guerra-Balcázar Minerva , Arjona Noé
Published: February 2020

Crude glycerol as waste from the synthesis of biodiesel has been used in fuel cells to obtain electrical energy using mainly Pt-based electrocatalysts. In the present work, nanoparticles of Pd/C, Au/C and PdAu/C were synthesized and tested in the electro-oxidation reaction of crude glycerol. The synthesized materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HR-TEM) and cyclic voltammetry. On the other hand, crude glycerol was prepared by transesterification reaction in alkaline medium and temperature with edible vegetable oil, KOH and methanol. In addition, Pd, Au and PdAu were synthesized and supported on Vulcan® carbon via green chemistry using the 2-hydroxyethylammonium formate ionic liquid. The micrographs obtained by HR-TEM revealed the presence of hemispherical particles with sizes between 8 and 30 nm. The electrocatalytic evaluation performed by cyclic voltammetry at 0.1, 0.5, 1, 1.5 and 2 M in alkaline medium of glycerol and crude glycerol. Raman spectrum of crude glycerol showed bands of methanol, soaps and glycerol, and the Raman spectrum of purified glycerol exhibited the characteristically signals of analytical glycerol. The maximum current density peak (55 mA mg-1) was obtained employing PdAu/C at 2 M glycerol. On the other hand, for 2 M crude glycerol, PdAu/C showed two maximum current densities peaks at 0.18 and 0.44 V vs NHE, associated to the oxidation of methanol and glycerol from crude glycerol. In summary, PdAu/C can be used as an alternative to Pt-based electrocatalysts for the efficient usage of crude glycerol as fuel for energy conversion applications.
Electrochemical Characterization of Caffeic Acid in the Presence and Absence of SDS
Authors: Guzmán-Hernández Dafne Sarahia , Ramirez-Silva Maria Teresa , Romero-Romo Mario Alberto , Corona-Avendaño Silvia , Palomar-Pardavé Manuel
Published: February 2020

Caffeic acid (CA) ia classified as a hydroxycinnamic acid having three acidity constants and low stability in aqueous medium. This work proposes the use of sodium dodecyl sulfate (SDS) surfactant to confer stability to CA, performing the electrochemical characterization of the H3CA species at pH 1.44 in aqueous media, in the presence and absence of SDS. This study was carried out by cyclic voltammetry (CV) recorded over a carbon paste electrode (CPE) vs Ag/AgCl, beginning the potential sweep at Ei=0 = 0.400 V in the anodic direction. In the absence of SDS, the CA presents an oxidation peak at 0.527 V, but when the potential sweep is switched it is possible to observe a cathodic peak at 0.498 V; this study shows that the CA oxidation process is controlled by diffusion according with the Randles-Sevcik equation. However, in the presence of SDS the CV presents an oxidation peak at 0.561 V, although when switching potential sweep it is possible to observe a cathodic peak at 0.546 V. There exists a 0.029 V potential difference betwen the anodic and cathodic peak in the absence of SDS, while in its presense the potential difference is smaller, namely, 0.015 V. The CA anodic peak, in the presence of SDS, increases to 18.1 mA. The study shows that in the presence of SDS the CA oxidation is controlled through adsorption.
Spectroelectrochemical Detection of Pharmaceutical Compounds Using Carbon Screen Printed Electrodes
Authors: Fanjul Bolado Pablo , González García María Begoña , Junquera Pérez Alejandro , Hernández Santos David
Published: February 2020

Several analytical methods have been published concerning the determination of active pharmaceutical ingredients (APIs) in drug formulations or in environmental samples. The most commonly used are chromatographic techniques but these methods are time consuming, expensive, require complicated preconcentration processes and need sophisticated instruments. On the other hand, electrochemical methods present the advantage of high simplicity, high sensitivity, good stability and low cost. These instruments can also be portable, which is particularly suitable for on-site monitoring of pharmaceuticals in field analysis.

In the present work, Carbamazepine,
Ibuprofen, Clarithromycin, Naratriptan, Dopamine and Acetaminophen have been determined using different electrochemical techniques at screen printed electrodes (SPE). The spectroelectrochemical behavior of the voltammetric response of some of these APIs allows the selective detection of these compounds despite their similar oxidation potentials on SPEs. The analysis was carried out by simultaneously performing an electrochemical and an optical experiment, the corresponding voltabsorptograms obtained are presented, showing the correlation between the derivative voltabsorptograms at the maximum of absorbances and the electrochemical curve.

This work is supported by Innovec`EAU (SOE1/P1/F0173) project from the Interreg Sudoe 2014-2020 program funding by European Regional Development Funds
Physicochemical and Electrochemical Properties of FSA-Based Ionic Liquid Electrolytes for K-Ion Batteries
Authors: Yamamoto Takayuki , Matsumoto Kazuhiko , Hagiwara Rika , Nohira Toshiyuki
Published: February 2020

Ionic liquids (ILs) are good candidates as electrolytes for electrical energy storage (EES) devices due to their high safety and superior physicochemical and electrochemical properties. Although Li-ion batteries (LIBs) are good candidates for EES and many types of IL electrolytes for LIBs were already reported [1-3], the limited amount of lithium and cobalt resources may lead to the unstable supply of LIBs in the future. Thus, several groups including us developed IL electrolytes for Na-ion batteries (NIBs) utilizing low-cost and ubiquitous resources of sodium and iron [4-8]. However, the standard potential of Na+/Na redox couple is lower than that of Li+/Li redox couple, which reduces the energy densities of batteries [9].

Under these circumstances, we have focused on K-ion batteries (KIBs) and developed new IL electrolytes containing alkyl-pyrrolidinium and -imidazolium cations. For example, in the K[FSA]-[C3C1pyrr][FSA] (C3C1pyrr+ = N-methyl-N-propylpyrrolidinium) binary system [10], a mixed melt at x(K[FSA]) = 0.20 (molar fraction) shows a reasonably high ionic conductivity of 4.8 mS cm−1 and a wide electrochemical window over 5 V at 298 K. The electrochemical windows of M[FSA]-[C3C1pyrr][FSA] (M = K, Na, Li) are compared by cyclic voltammetry. As the result, the K-ion system shows a wider electrochemical window than Na-ion and Li-ion systems due to negative potential of the K+/K redox couple, which implies the feasibility of KIBs possessing higher energy densities.

Acknowledgments

This study was partly supported by MEXT program "Elements Strategy Initiative to Form Core Research Center" (since 2012; MEXT: Ministry of Education Culture, Sports, Science and Technology, Japan), and a research grant from Kansai Research Foundation for Technology Promotion, Japan.

References

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[2] M. Ishikawa et al., J. Power Sources, 162 (2006) 658-662.

[3] A. Guerfi et al., J. Power Sources, 175 (2008) 866-873.

[4] S.A.M. Noor et al., Electrochim. Acta, 114 (2013) 766-771.

[5] D. Monti et al., J. Power Sources, 245 (2014) 630-636.

[6] L.G. Chagas et al., J. Power Sources, 247 (2014) 377-383.

[7] C. Ding et al., J. Power Sources, 238 (2013) 296-300.

[8] K. Matsumoto et al., J. Power Sources, 265 (2014) 36-39.

[9] N. Yabuuchi et al., Chem. Rev., 114 (2014) 11636-11682.

[10] T. Yamamoto et al., J. Phys. Chem. C, 121 (2017) 18450-18458.
Formation of Rare Earth Phosphates in the Melts Based on NaCl–KCl Equimolar Mixture
Authors: Volkovich Vladimir A. , Ivanov Alexander B. , Chukin Andrey V. , Sukhikh Vladislav V. , Griffiths Trevor R.
Published: February 2020

Phosphate precipitation in molten chlorides is considered as a possible method for removing rare earth and alkaline earth fission product elements from technological melts at a final stage of pyrochemical reprocessing of spent nuclear fuels. Phosphates can be incorporated into a glass matrix in a high level waste vitrification process in preparation for a long term storage or disposal. There are a number of studies considering the formation of rare earth phosphates in the melts of technological interest, i.e. LiCl–KCl, NaCl–KCl, and NaCl–CsCl mixtures, but some uncertainty still remains concerning the conditions when different types of phosphates are formed. While the reaction in LiCl–KCl melts always produces normal orthophosphates (REPO4), double alkali metal-rare earth phosphates, e.g. M3RE(PO4)2 and M3RE2(PO4)3, can be formed in the melts not containing LiCl. The aim of the present study was investigating the effect of the initial phosphate-to-rare earth mole ratio on the outcome of the reaction.

The experiments were performed in the melts based on the equimolar mixture of sodium and potassium chlorides at 750 oC. The rare earth elements included Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu (heavier lanthanides not representing fission products were included for completeness). Sodium orthophosphate was used as a source of PO4
3– ions and the initial PO3
3– : RE3+ mole ratio was varied from 0.3–0.5 to 10. Formation of the phosphates was studied in the melts containing individual rare earth elements as well as a mixture of rare earths in the proportion simulating their abundance in the thermal neutron reactor spent fuel.

The experiments were performed under static conditions and the parameters analyzed included degree of RE precipitation, phase composition of the precipitate and size of particles in the solid phase. Analysis of the experimental results showed that at PO3
3– : RE3+ mole ratios below five only normal REPO4 phosphates were formed, while at the ratios above 8 double Na3RE(PO4)2 and/or K3RE(PO4)2 double phosphates were produced. Particle size of the rare earth phosphates varied from 0.1 to hundredths of microns and increasing the initial PO3
3– : RE3+ mole ratio resulted in increasing particle size. Complete conversion of RECl3 to phosphate required 2–5 times molar excess of the phosphate to the rare earth element.
Quantum-Chemical Study of the Titanium Complexes Stability in the Model System M2+ [Ti(3)F6]3-+12MCl2
Authors: Stulov Yuriy V. , Kremenetsky Vyacheslav G. , Kuznetsov Sergey A.
Published: February 2020

In our previous works, a basic approach is to calculate the parameters of model systems containing an anionic complex with an outer sphere (OS) cationic shell. For similar systems nM+⋅[NbF7], nM+⋅[CrCl6] (n = 1 – nmax) and others (system I), it has been demonstrated that the most thermodynamically stable compositions have some intermediate number of OS cations n < n
max, where n
max is the maximal number of OS cations held by a given complex. In another our papers, an approach was proposed for estimating the stability of particles with different composition of the second coordination sphere of complexes in more complex model systems –M+
3Cr(3)Cl6+18MCl and M2+Ti(4)F6+12MCl2, where M2+ - Mg, Ca, Sr, Ba (system II).

The aim of this study is the quantum-chemical substantiation of the existence stable particles in alkali halide melts of formed by a titanium halide complex and an OS cationic shell of a certain composition in a model system M2+∙[Ti(3)F6]3-+12MCl2.

The geometry optimization of structures was performed with the Firefly program package, partially based on the source code of the GAMESS(US) program, by the density functional theory DFT/UHF method with the use of the B3LYP hybrid functional. For the F and Cl atom quasi-relativistic basis set Stuttgart RLC ECP was used; for Ti, Ca, Sr and Ba – Stuttgart RSC 1997 ECP basis set and for Mg – CRENBL ECP. In all cases, the search for the optimized geometry was accompanied by control calculation of vibrational frequencies, and, thus, all the data reported correspond to true minimum of the potential energy surface (there are no imaginary frequencies).

Different from system type I, in the system II it was possible direct calculation of the interaction energy between particle and rest part of the model system. If the interaction energy between the OS shell and titanium complexes exceeds the energy of its interaction with the rest environment, there are presence in the system of such dynamic equilibrium, which ensures the existence of sufficiently stable complex particles of a certain OS composition.

The analysis of interactions in systems I and II on the example of Ti(3) complexes showed that there are discrepancies between the composition of the most stable complex particles in these systems. Allowance for the interaction of the particle "complex plus OS shell" with the surrounding ions gives a much more accurate estimate of the composition of the electroactive particles. Thus, using the model system of nM2+ +Ti(3)F6 for example, it was shown that the calculation parameters of this system may be used just as the initial assessment.
Double Salt Ionic Liquids for Lignin Hydrolysis: One Cation for Catalyst and Solvent Anions
Authors: Cui Xianbao , Li Kai , Choudhary Hemant , Shamshina Julia L. , Rogers Robin Don
Published: February 2020

Humanity has always relied on Nature for survival, but today we take oil as a feedstock and use it to produce chemicals to suit any purpose, from fuels and medicines to plastics. By reducing our reliance on Nature, we have forgotten our respect of Nature in the process. The world is now covered in oil in the form of non-biodegradable synthetic plastics which mar our landscapes and threaten our oceans. By 2050 there is predicted to be more plastic in the ocean than fish. At the same time, plastics represent a $654 billion market worldwide and are ubiquitous in modern life. Simply eliminating synthetic plastic use with no viable alternatives would be almost impossible and catastrophic from both a social and economic point of view.

Chemists make new chemicals and that has led to the development of a chemical industry that knows how to sell these chemicals. The more chemicals we make, the more the industry seeks new and better markets to sell them into. New, more sustainable technologies have been forced into the business of ‘replacements’ and must follow the same commercialization pathways as the old technologies they are trying to replace. The unsustainable practices, however, have often had decades or more head start and thus the economics to replace them are often insurmountable without government or policy intervention. The technologies to directly replace synthetic plastics with renewable biopolymers from plants and animals are there, but the consistencies of supply and economies of scale to make them competitive are not.

With a plethora of abundant natural and renewable resources (in terms of both quantity and diversity), from water purification - to cosmetics - to medical applications, the quality of human life can greatly benefit (and improve at the same time) from new, innovative technologies using building blocks obtained directly from plants and animals. With this mission in mind, we are exploring the entire range of the “biorefinery concept,” from dissolution, and conversion of plant and animal resources into value added chemicals and extraction of essential oils or vital chemicals, to isolation of pure biopolymers and production of new biomaterials from them. Because we can directly dissolve Nature’s raw materials, we can shape them, functionalize them, blend them, and use other non-chemistry means to produce advanced functional materials. These new, innovative materials represent new market opportunities which we will develop and promote.