Terms Of Electrochemistry Research Articles

Novel Ethylene Glycol Substituted Benzoxadiazole and Benzothiadiazole as Anolytes for Nonaqueous Organic Redox Flow Batteries

AbstractThe design of new organic materials for redox‐flow batteries is an actively developing topic in the field of energy storage. Herein, two novel redox‐active organic molecules were presented, based on benzoxadiazole and benzothiadiazole cores bearing ethylene glycol substituents, which were first synthesized and evaluated as anolytes in nonaqueous all organic redox flow batteries. These two molecules were compared with their unsubstituted analogs in terms of electrochemistry, solubility and RFB cycling behavior. Substituted benzoxadiazole and benzothiadiazole possess low redox potentials near −2.1 V vs. Fc/Fc+, increased solubility in organic solvents, reduced permeability through the membrane and higher stability under charge‐discharge cycling in laboratory RFB cells than unsubstituted counterparts.

Sacrificial Template-Assisted Mechanochemical Production of Highly Active Bifunctional Fe-N-C Catalysts

Bifunctional catalyst materials development for energy storage and conversion technologies is notoriously demanding in terms of electrochemistry (low stability, sluggish kinetics and high total overpotential (∆E)) and logistics (environmental safety, production methodologies and cost).Noble metal electrocatalysts are proven to be good bifunctional catalysts and as a result are being used as benchmark catalysts. However, the environmental and economic sustainability is severely compromised due to the scarcity of these metals. The alternative option is based on first-row transition metal heteroatom-doped carbon materials. Low cost, high availability, great electrocatalytic activity and stability promise to be a suitable noble metal free catalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR).This work showcases a high performance Fe-N-C type material with sustainable synthesis and efficient activity towards ORR and OER. Unlike various classical methods for electrocatalyst synthesis, the developed methodology combines mechanochemistry and application of sacrificial template, which yields materials with superior bifunctional oxygen electrocatalytic performance.

The Oxide Nanostructures Formation Mechanisms in Underwater Plasma in Terms of Electrochemistry

The Oxide Nanostructures Formation Mechanisms in Underwater Plasma in Terms of Electrochemistry

Fused Filament Fabrication‐Based Additive Manufacturing of Commercially Pure Titanium

Fabrication of titanium components is very cost intensive, partly due to the complex machining and limited recyclability of waste material. For electrochemical applications, the excellent corrosion resistance of pure titanium is of high importance, whereas medium mechanical strength of fabricated parts is sufficient for such a use case. For smaller parts, metal fused filament fabrication (MF3) enables the fabrication of complex metallic structures densified during a final sintering step. Pure titanium can be processed to near‐net‐shape geometries for electrochemical applications if the parameters and the atmosphere during sintering are carefully monitored. Herein, the influence of thermal debinding and sintering parameters on the fabrication of high‐density pure titanium using MF3 is investigated. Particular focus is placed on enhancing sintered density while limiting impurity uptake to conserve the high chemical purity of the initial powder material. Relative densities of 95% are repeatedly reached inside the bulk of the samples. An oxygen content of 0.56 wt% as a result of vacuum processing induces the formation of the retained α‐Ti phase (925 HV0.2) inside the α matrix (295 HV0.2). Fabricated parts exhibit high mechanical strength, albeit reduced elongation due to remaining pores, and, in terms of electrochemistry, enhanced stability toward anodic dissolution.

Screen-Printed Nickel-Zinc Batteries: A Review of Additive Manufacturing and Evaluation Methods.

The advent of personalized wearable devices has boosted the demand for portable, compact power sources. Compared with lithographic techniques, printed devices have lower fabrication costs, while still maintaining high throughput and precision. These factors make thick film printing or additive manufacturing ideal for the fabrication of low-cost batteries suitable for personalized devices. This article provides comprehensive guidelines for thick-film battery fabrication and characterization, with the focus on printed nickel-zinc (Ni-Zn) batteries. Ni-Zn batteries are a more environmental-friendly option compared with lithium-ion batteries (LIBs) as they are fully recyclable. In this work, important battery fundamentals have been described, especially terms of electrochemistry, basic design approaches, and the printing technology. Different design approaches, such as lateral, concentric, and stacked, are also discussed. Printed batteries can be configured as series or parallel constructions, depending on the power requirements of the application. The fabrication flow of printed battery electrodes for the laboratory-scale prototyping process starts from chemical preparation, mixing, printing, drying, pressing, stacking to finally sealing and testing. Of particular importance is the process of electrolyte injection and pouch sealing for the printed batteries to reduce leakage. This entire process flow is also compared with industrial fabrication flow for LIBs. Criteria for material and equipment selection are also addressed in this article to ensure appropriate electrode consistency and good performance. Two main testing methods cyclic voltammetry for the electrodes and charge-discharge for the battery are also explained in detail to serve as systematic guide for users to validate the functionality of their electrodes. This review article concludes with commercial applications of printed electrodes in the field of health and personalized wearable devices. This work indicates that printed Ni-Zn and other zinc alkaline batteries have a promising future. The success of these devices also opens up different areas of research, such as ink rheology, composition, and formulation of ink using sustainable sources.

Self-Standing and Binder Free Cathode: Facile and Scalable Fabrication with MWCNT for Recyclable and Sustainable Application of Li-O2 Battery

It’s well known that the Li-O2 battery can achieve theoretically1 ten times as much energy density (5200Wh/kg) as Li-ion battery but often limited in reality on the capacity and the cycling. In this system, the carbon cathode provides merely a framework for the lithium peroxide deposition but is not an active material. The dissolved oxygen in the electrolyte is indeed the active material. In other words, the capacity depends on the porosity and the framework architecture. Our previous X-ray tomographic study2 pointed out that a sparse structure is needed to increase the capacity by impeding the pore clogging and oxygen depletion. The conventional fabrication by evaporating the solvent of a slurry can only provide ~20% porosity which is insignificant. Other templating fabrications3,4 are often reported in the literature, but procedures are tedious. To fabricate sparse and self-standing cathode with the multi-wall carbon nanotubes (MWCNTs), we propose a facile and scalable two steps Buchner approach.The MWCNTs are firstly dispersed in a solvent by sonification. A direct filtration with the separator of a battery can omit a stacking step in the battery assembling (Figure 1). Preceded by a drying process, the cathode is then investigated in the overall cell for electrochemical performance and cyclability. The data of X-ray nano-Computed Tomography acquired in APS synchrotron (ID32) shows that the material is highly porous and the pores are fully filled with the discharge product Li2O2 which conducts to a capacity improvement. Impedance is utilized alongside with tomography data for a complementary understanding of the dominance between lithium ion and oxygen depletion during the discharge.The self-standing and flexible properties of such cathode even without polymer binder are beneficial for industrial application. We demonstrate the possibility of loading other particles with our approach. A gain of specific surface area for the deposition of lithium peroxide can be obtained with the loading at a price of the mechanical property detriment. Thereby, several percentages of loading are studied to obtain the best trade-off. Besides, bared carbon-nanotube framework with loaded particle trends to loss the structural stability. A sandwich-like structure is hence investigated for the efficiency of the particle confinement.Finally, our approach is highly eco-friendly. The solvent for nanotube dispersion can be reused after the filtration. And the aged cathode is entirely recyclable by proceeding a low-cost acid retreatment then ultrasonic re-dispersion. The impact of the recycling in terms of electrochemistry and pressure evolution have also been studied.Figure 1. (a) image of the homogeneous laid out cathode in a Buchner (b) SEM image of the intersection separator and cathode and (c) sandwich structure (d) electrochemical curve with pressure evolution Reference:(1) Abraham, K. M. A Polymer Electrolyte-Based Rechargeable Lithium/Oxygen Battery. Journal of The Electrochemical Society 1996, 143 (1), 1. https://doi.org/10.1149/1.1836378.(2) Su, Z.; De Andrade, V.; Cretu, S.; Yin, Y.; Wojcik, Michael. J.; Franco, Alejandro. A.; Demortière, A. X-Ray Nano-Computed Tomography in Zernike Phase Contrast for Study 3D Morphology of Li-O2 Battery Electrode. ACS Applied Energy Materials (submitted)(3) Cho, S. A.; Jang, Y. J.; Lim, H.-D.; Lee, J.-E.; Jang, Y. H.; Nguyen, T.-T. H.; Mota, F. M.; Fenning, D. P.; Kang, K.; Shao-Horn, Y.; et al. Hierarchical Porous Carbonized Co 3 O 4 Inverse Opals via Combined Block Copolymer and Colloid Templating as Bifunctional Electrocatalysts in Li-O 2 Battery. Advanced Energy Materials 2017, 7 (21), 1700391. https://doi.org/10.1002/aenm.201700391.(4) Gaya, C.; Yin, Y.; Torayev, A.; Mammeri, Y.; Franco, A. A. Investigation of Bi-Porous Electrodes for Lithium Oxygen Batteries. Electrochimica Acta 2018, 279, 118–127. https://doi.org/10.1016/j.electacta.2018.05.056. Figure 1

Electrochemical Investigation of Chemical Lift-off Lithography on Au and ITO

Chemical lift-off lithography (CLL) on Au and indium tin oxide (ITO) were investigated using electrochemical methods in terms of the coverage, stability, and substrate-dependence. Self-assembled monolayers (SAMs) of 11-mercaptoundecanol (MUO) on Au and hydroxyundecylphosphonic acid (HUPA) on ITO were patterned by an oxygen plasma-activated PDMS stamp. Siloxyl groups (SiOH) from the activated PDMS formed covalent bonds with the hydroxyl groups of the SAM (OH) on the Au and ITO substrate, which enables the detachment of the SAM molecules from the surface, called CLL. The interfacial properties of the SAM-modified electrodes and post-CLL electrodes were investigated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results revealed that ca. 78% of the SAM on Au is detached by CLL and the remaining SAM is stable during subsequent SAM formations. For alkanephosphonic acid on ITO, ca. 57% of the SAM was removed in terms of electrochemistry indicating the dependence of CLL on the anchoring groups. AFM images show the pattern formation by CLL on both Au and ITO.

Evidence for a nanosize effect on the structural and high performance electrochemical properties of V2O5 obtained via fluorine chemistry

In this study, we demonstrate the benefit of an original vanadium pentoxide (V2O5) nanostructuration on the electrochemical performances. This new synthesis way of high purity nanosized V2O5 consists in a facile fluorination reaction of micro-V2O5 in aqueous solution followed by a heat-treatment at low temperature (230°C). Highly porous calisson-like particles with crystallite sizes in the 13–30nm range are obtained. Remarkably, this nanostructured V2O5 exhibits outstanding rate capacities and cycling stabilities. This material can deliver reversible capacities of 260mAhg−1 at 15mAg−1 (C/10 rate) and 150mAhg−1 at 300mAg−1 (2C rate), as well as a stable capacity of 200mAhg−1 at C rate after 50 cycles. The unique structural features of nano-LixV2O5 electrodes are determined over the large Li composition range 0≤x<2 based on XRD and Raman microspectrometry experiments. We provide evidence that lithiation in nanosized V2O5 proceeds via solid solution state without domain boundaries: a single phase behavior of the ε’-type whose interlayer distance and unit cell volume linearly increase with x is revealed. This constitutes a disruption of the usual mirco-LixV2O5 phase diagram made of the successive appearance of the (α/ε), (ε/δ) and (δ/γ) wide biphasic regions. These limited and reversible structural changes combined with shorter Li diffusion pathways explain the huge improvement in electrochemical performances of nano-V2O5. These findings fully elucidate the peculiar voltage profile of nanosized V2O5 and give a unique insight into the impact of nanostructures in terms of electrochemistry and solid state chemistry.

Electrospun silk fibroin scaffolds coated with reduced graphene promote neurite outgrowth of PC-12 cells under electrical stimulation

Novel approaches to neural research require biocompatible materials capable to act as electrode structures or scaffolds for tissue engineering in order to stimulate or restore the functionality of damaged tissues. This work offers promising results that indicate the potential use of electrospun silk fibroin (SF) scaffolds coated with reduced graphene oxide (rGO) in this sense. The coated material becomes conductor and electroactive. A complete characterisation of SF/rGO scaffolds is provided in terms of electrochemistry, mechanical behaviour and chemical conformation of fibroin. The excellent biocompatibility of this novel material is proved with cultures of PC-12 cells. The coating with rGO improved the adhesion of cells in comparison with cells growing onto the surface of pure SF scaffolds. Also, the use of SF/rGO scaffolds combined with electrical stimulation promoted the differentiation into neural phenotypes reaching comparable or even superior levels to those obtained by means of the traditional treatment with neural growth factor (NGF).

The Planar Cyclooctatetraene Bridge in Bis-Metallic Macrocycles: Isolating or Conjugating?

A minor modification of the reported procedure for the synthesis of a corrole dimer that is fused by the cyclooctatetraene (COT) unit, (H3tpfc)2COT, allowed for its isolation in 18% yield. Of the two redox isomers that this interesting macrocycle does form, the current focus is on the reduced form, in which each subunit resembles that of monomeric corroles with a trianionic N4 coordination core. The corresponding bis-gallium(III) complex was prepared as an entry into the potentially rich coordination chemistry of (H3tpfc)2COT. Both X-ray crystallography and DFT calculations disclosed that the COT moiety is essentially planar with very unusual nonalternating C-C bonds. The same holds true for the bis-gallium(III) complexes [(Ga-tpfc)2]COT(py)2 and [(Ga-tpfc)2]COT(py)4, obtained with one and two pyridine molecules coordinated to each metal ion, respectively. The electronic spectra of both the free base and the gallium(III) complexes display an extremely low energy band (λmax at 720-724 nm), which points toward extensive π delocalization through the COT bridge. This aspect was fully addressed by examining the interactions between the two corrole subunits in terms of electrochemistry and DFT calculations of the oxidized and reduced macrocycle. The new near-IR bands that appear upon both oxidation (λmax 1250 nm) and reduction (λmax 1780 nm) serve as additional supporting evidence for this conclusion.

Influence of the Annealing Temperature to the Properties of LiNi0.5Mn1.5O4 High Voltage Spinel Cathode for Li-Ion Batteries

High voltage cathode materials are one of the most promising ways for the next generation of cathode materials for the lithium-ion batteries. Thanks to their high potential and capacity comparable with standard cathode materials as LiCoO2 or LiFePO4, they can reach much higher gravimetric energy density. As for any other cathode material, good crystallinity after synthesis is also very important for high voltage materials to reach a good electrochemical performance during cycling. This paper deals with the influence of annealing temperature on electrochemical properties of high voltage spinel cathode LiNi0.5Mn1.5O4. It was studied at three different temperatures of the synthesis in terms of electrochemistry and structure by SEM and in term of electrochemistry by cycling at different C-rate.

Polyimide binder by combining with polyimide separator for enhancing the electrochemical performance of lithium ion batteries

Lithium ion battery (LIB) has been assembled by a polyimide (PI) binder, which is prepared by one-pot solution polycondensation, and PI non-woven separator. Compared to the cell using the traditional PVDF binder and polyethylene (PE) separator, the cell with PI binder and PI separator (PI-PI) not only has a better thermal stability but also displays significantly improved electrochemical performance, especially rate performance and cycling behavior. The thermogravimetric analysis (TGA) shows that the temperature of the weight loss of 10% of PVDF and PI is 464.6°C and 525.9°C, respectively. The properties of the separator, including wettability, electrolyte uptake and mechanical performance are tested. Owing to the hydrophilic imide group and the rigid aromatic nucleus. These properties make a possibility of a battery to meet higher requirements. In the terms of electrochemistry, when the current density over 1C, the cell with PVDF binder and PE separator (PVDF-PE) only retains no more than 61% of its capacity at a rate of 0.05C. However the cell that based on PI-PI still maintains 72.6%. Besides, the cycle performance of PI-PI gains a significant improvement. It can stay over 85% capacitance retention ratio after 200 cycles at a rate of 1C, while the PVDF-PE is only 57.68%. The outstanding improvement of the rate capability is due to the reduction of internal resistance of the battery.

(Invited) Electrostatic and Electrochemical Nature of Liquid-Gated Electric-Double-Layer Transistors Based on Oxide Semiconductors

The electric-double-layer (EDL) formed at liquid/solid interfaces provides a broad and interdisciplinary attraction in terms of electrochemistry, photochemistry, catalysts, energy storage, and electronics because of the large interfacial capacitance coupling and their ability for high-density charge accumulation. Much effort has recently been devoted to the fundamental understanding and practical applications of such highly-charged EDL interfaces. For example, electric field control of carrier density with EDL in a transistor configuration has been used as a powerful tool to tune the electronic states of condensed matter. However, the intrinsic nature of the EDL charging, whether it is electrostatics or electrochemistry, and how to distinguish them are far from clear. Here, by combining electrical transport measurements with electrochemical impedance spectroscopy (EIS), we studied the charging mechanisms of highly-charged EDL interfaces between an ionic-liquid and oxide semiconductor, ZnO. The direct measure for mobile carriers from the Hall effect agreed well with that from the capacitance-voltage integration at 1 Hz, implying that the pseudo-capacitance does not contribute to carrier transport at EDL interfaces. The temperature-frequency mapping of EIS was further demonstrated as a “phase diagram” to distinguish the electrostatic or electrochemical nature of such highly-charged EDL interfaces with densities of up to 8×1014 cm-2, providing a guideline for electric-field induced electronic phenomena and a simple method for distinguishing electrostatic and electrochemical charging in EDLTs not only based on a specific oxide semiconductor, ZnO, but also commonly applicable to all types of EDL interfaces with extremely high-density carrier accumulation. 1. H. T. Yuan, H. Shimotani, J. T. Ye, S. J. Yoon, H. Aliah, A. Tsukazaki, M. Kawasaki, and Y. Iwasa, Electrostatic and Electrochemical Nature of Liquid-Gated Electric-Double-Layer Transistors on Oxide Semiconductors, J . Am . Chem. Soc. 132, 18402 (2010). 2. H. T. Yuan, H. Shimotani, A. Tsukazaki, A. Ohtomo, M. Kawasaki, and Y. Iwasa, Hydrogenation- Induced Surface Polarity Recognition and Proton Memory Behavior at Protic-Ionic-Liquid/Oxide Electric-Double-Layer Interfaces, J . Am . Chem. Soc. 132, 6672 (2010).

Effects of precipitation strengthening heat treatment for Al-Mg alloy

The corrosions resulting from defects in painting layers frequently occur in Al alloys, so the application of corrosion preventing systems is also very important. Optimum conditions in terms of electrochemistry in relation to solution treatment, quenching and artificial aging treatment were established in order to optimize precipitation strengthening conditions intended to enhance the strength of Al alloys. Slow strain rate tests (SSRT) at various applied potentials were conducted in potential range from −1.8 to −0.5 V. The results show that the maximum tensile strengths, elongations and time-to-fracture are shown to be high values. After precipitation strengthening heat treatment, a tendency appear that time-to-fracture increases as elongation increases. In the potential range from −1.3 V to −0.7 V, the specimens show excellent mechanical properties, and thus this range is considered to be a corrosion prevention range.

Electrostatic and Electrochemical Nature of Liquid-Gated Electric-Double-Layer Transistors Based on Oxide Semiconductors

The electric-double-layer (EDL) formed at liquid/solid interfaces provides a broad and interdisciplinary attraction in terms of electrochemistry, photochemistry, catalysts, energy storage, and electronics because of the large interfacial capacitance coupling and its ability for high-density charge accumulation. Much effort has recently been devoted to the fundamental understanding and practical applications of such highly charged EDL interfaces. However, the intrinsic nature of the EDL charging, whether it is electrostatics or electrochemistry, and how to distinguish them are far from clear. Here, by combining electrical transport measurements with electrochemical impedance spectroscopy (EIS), we studied the charging mechanisms of highly charged EDL interfaces between an ionic liquid and oxide semiconductor, ZnO. The direct measure for mobile carriers from the Hall effect agreed well with that from the capacitance-voltage integration at 1 Hz, implying that the pseudocapacitance does not contribute to carrier transport at EDL interfaces. The temperature-frequency mapping of EIS was further demonstrated as a "phase diagram" to distinguish the electrostatic or electrochemical nature of such highly charged EDL interfaces with densities of up to 8 × 10(14) cm(-2), providing a guideline for electric-field-induced electronic phenomena and a simple method for distinguishing electrostatic and electrochemical charging in EDLTs not only based on a specific oxide semiconductor, ZnO, but also commonly applicable to all types of EDL interfaces with extremely high-density carrier accumulation.

Hydrogenation-Induced Surface Polarity Recognition and Proton Memory Behavior at Protic-Ionic-Liquid/Oxide Electric-Double-Layer Interfaces

The electric-double-layer (EDL) formed at liquid/solid interfaces provides a broad and interdisciplinary attraction in terms of electrochemistry, photochemistry, catalysts, energy storage, and electronics. Especially in recent years, much effort has been devoted to the fundamental understanding and practical applications of transistor configurations with EDLs because of their ability for high-density charge accumulation. However, to exploit additional new functionalities of such an emerging interface is not only of great importance but also a huge challenge. Here, we demonstrate that, by introducing protic ionic liquid (PIL) as the gate dielectric for ZnO EDL transistors (EDLTs), small and chemically active ions, such as protons and hydroxyls, can serve as an adsorption medium to extend the interfacial functionalities of EDLTs. By selectively driving the H(+) or OH(-) groups onto ZnO channel surfaces with an electric field, the charged adsorbates interact with surface atoms in different adsorption mechanisms, showing remarkable variations in electron transport and providing a possibility for the recognition of surface polarity. Most significantly, the large hysteresis in the transfer characteristics of PIL-EDLTs makes the device available and promising for nonvolatile proton memory devices via surface hydrogenation and dehydrogenation processes. Such a finding provides us with new opportunities to understand liquid/solid heterogeneous interface phenomena and to extend the practical functions of EDLs through controllable interfacial interaction.

469—considerations on an electrochemical model of oxidative phosphorylation

Oxidative phosphorylation is reconsidered in terms of electrochemistry and irreversible thermodynamics. The non-vanishing proton balance of consecutive redox couples is taken to be the reason for a net transport of protons across the mitochondrial membrane. Differences between biological and galvanic cells are elaborated.