Electrochemistry and DFT study of galvanic interaction on the surface of monoclinic pyrrhotite(001)and galena(100)

The electrochemical interaction between galena and monoclinic pyrrhotite was investigated to examine its impact on the physical and chemical properties of the mineral micro-surface.This investigation employed techniques such as electrochemistry,metal ion stripping,X-ray photoelectron spectroscopy,and quantum chemistry.The electrochemical test results demonstrate that the galena surface in the electro-couple system exhibits a lower electrostatic potential and higher electrochemical activity compared to the monoclinic pyrrhotite surface,rendering it more susceptible to oxidation dissolution.Monoclinic pyrrhotite significantly amplifies the corrosion rate of the galena surface.Mulliken charge population calculations indicate that electrons are consistently transferred from galena to monoclinic pyrrhotite,with the number of electron transfers on the mineral surface increasing as the interaction distance decreases.The analysis of state density revealed a shift in the surface state density of galena towards lower energy levels,resulting in decreased reactivity and increased difficulty for the reagent to adsorb onto the mineral surface.Conversely,monoclinic pyrrhotite exhibited an opposite trend.The X-ray photoelectron spectroscopy(XPS)test results indicate that galvanic interaction leads to the formation of hydrophilic substances,PbS_(x)O_(y) and Pb(OH)_(2),on the surface of galena.Additionally,the surface of monoclinic pyrrhotite not only adsorbs Pb^(2+)but also undergoes S^(0) formation,thereby augmenting its hydrophobic nature.

Ionic liquid modified GC electrode for the direct electrochemistry of chloroperoxidase

Chloropcroxidase （CPO） was immobilized by konjac glucomannan （KGM） on the 1-butyl-3-methyl imidazolium tetrafluoroborate [BMIM][BF4]/Nafion modified glassy carbon eloctrode. The electrochemical behaviors of the immobilized CPO were investigated by cyclic voltammetry. The results showed that CPO was successfully immobilized on the GCE and underwent fast direct electron transfer reactions with the formal potential at -0.3 V vs. SCE. The modified electrode showed a good catalytic activity for elcctrocatalytical reduction of O2 and H2O2.

A semiconductor-electrochemistry model for design of high-rate Li ion battery

For designing batteries with high-rate and long-life, electronic/ionic transport and reaction must be unified for metal oxide electrodes. However, it remains challenging for effectively integrating the whole substrate/active materials/electrolyte interfaces. Herein by taking Li ion battery as example, we propose a semiconductor-electrochemistry model by which a general but novel insight has been gained into interfacial effect in batteries. Different from those traditional viewpoints, this derived model lies across from physics to electrochemistry. A reaction driving force can be expressed in terms of Fermi energy change,based on the tradeoff between electronic and ionic concentration at the reaction interfacial region. Therefore, at thermodynamic-controlled interface I of substrate/electrode, increasing contact areas can afford higher activity for active materials. Whereas at kinetically-governed interface II of electrode/electrolyte or inside active materials, it is crucial to guarantee high-reaction Li ionic concentration, with which some sufficient reaction degrees can reach.

Metal-organic frameworks-derived metal phosphides for electrochemistry application

Metal-organic frameworks(MOFs)with high porosity and variable structure have attracted extensive attention in the field of electrochemistry,but their poor conductivity and stability have limited their development.Materials derived from MOFs can maintain the structural diversity and porosity characteristics of MOFs while improving their electrical conductivity and stability.Metal phosphides play an important role in electrochemistry because they possess rich active sites,unique physicochemical properties,and a porous structure.Published results show that MOF-derived metal-phosphides materials have great promise in the field of electrochemistry due to their controllable structure,high specific surface area,high stability and excellent electrical conductivity.MOF-derived metal-phosphides with significant electrochemical properties can be obtained by simply,economical and scalable synthetic methods.This work reviews the application of MOF-derived metal phosphides in electrochemistry.Specifically,the synthesis methodology and morphological characterization of MOFs derived metal-phosphides and their application in electrochemistry are described.Based on recent scientific advances,we discuss the challenges and opportunities for future research on MOF-derived metal-phosphides materials.

Recent advances in the electrochemistry of layered post-transition metal chalcogenide nanomaterials for hydrogen evolution reaction

Layered two-dimensional(2 D)materials have received tremendous attention due to their unique physical and chemical properties when downsized to single or few layers.Several types of layered materials,especially transition metal dichalcogenides(TMDs)have been demonstrated to be good electrode materials due to their interesting physical and chemical properties.Apart from TMDs,post-transition metal chalcogenides(PTMCs)recently have emerged as a family of important semiconducting materials for electrochemical studies.PTMCs are layered materials which are composed of post-transition metals raging from main group IIIA to group VA(Ga,In,Ge,Sn,Sb and Bi)and group VI chalcogen atoms(S,selenium(Se)and tellurium(Te)).Although a large number of literatures have reviewed the electrochemical and electrocatalytic applications of TMDs,less attention has been focused on PTMCs.In this review,we focus our attention on PTMCs with the aim to provide a summary to describe their fundamental electrochemical properties and electrocatalytic activity towards hydrogen evolution reaction(HER).The characteristic chemical compositions and crystal structures of PTMCs are firstly discussed,which are different from TMDs.Then,inherent electrochemistry of PTMCs is discussed to unveil the well-defined redox behaviors of PTMCs,which could potentially affect their efficiency when applied as electrode materials.Following,we focus our attention on electrocatalytic activity of PTMCs towards HER including novel synthetic strategies developed for the optimization of their HER activity.This review ends with the perspectives for the future research direction in the field of PTMC based electrocatalysts.

Unveiling the redox electrochemistry of 1D,urchin-like vanadium sulfide electrodes for high-performance hybrid supercapacitors

Exploring novel versatile electrode materials with outstanding electrochemical performance is the key to the development of advanced energy conversion and storage devices.In this work,we aim to construct new-fangled one-dimensional(1D)quasi-layered patronite vanadium tetrasulfide(VS_(4))nanostructures by using different sulfur sources,namely thiourea,thioacetamide,and L-cysteine through an ethyleneaminetetraacetic-acid(EDTA)-mediated solvothermal process.The as-prepared VS4exhibits several unique morphologies such as urchin,fluffy nanoflower,and polyhedron with appropriate surface areas.Among the prepared nanostructures,the VS_(4)-1@NF nanostructure exhibited excellent electrochemical properties in 6 M KOH solution,and we explored its redox electrochemistry in detail.The asprepared VS_(4)-1@NF electrode exhibited battery-type redox characteristics with the highest capacity of280 C g^(-1)in a three-electrode assembly.Moreover,it offered a capacity of 123 F g^(-1)in a hybrid twoelectrode set-up at 1 A g^(-1)with the highest specific energy and specific power of 38.5 W h kg^(-1)and750 W kg^(-1),respectively.Furthermore,to ensure the practical applicability and real-world performance of the prepared hybrid AC@NF//VS_(4)-1@NF cell,we performed a cycling stability test with more than 5,000galvanostatic charge–discharge cycles at 2 A g^(-1),and the cell retained around 84.7%of its capacitance even after 5,000 cycles with a CE of 96.1%.

Understanding oxygen electrochemistry in aprotic Li-O_2 batteries

In the past decade, the aprotic lithium-oxygen(Li-O_2) battery has generated a great deal of interest because theoretically it can store more energy than today's lithium-ion batteries. Although considerable research efforts have been devoted to the R&D of this potentially disruptive technology, many scientific and engineering obstacles still remain to be addressed before a practical device could be realized. In this review, we summarize recent advances in the fundamental understanding of the O_2 electrochemistry in Li-O_2 batteries, including the O_2 reduction to Li_2O_2 on discharge and the reverse Li_2 O_2 oxidation on recharge and factors that exert strong influences on the redox of O_2/Li_2O_2. In addition,challenges and perspectives are also provided for the future study of Li—O_2 batteries.

Conversion electrochemistry of copper selenides for robust and energetic aqueous batteries

The development of highly safe and low-cost aqueous batteries is of great significance in the background of carbon neutrality.However,the practical deployment of aqueous batteries has been plagued due to their relatively low capacity and poor cycling stability.Herein,we propose unique conversion electrochemistry of copper selenides for robust and energetic aqueous charge storage.In situ X-ray diffraction and operando Raman techniques reveal a reversible transformation from CuSe to Cu_(2)Se through the intermediates of Cu_(3)Se_(2) and Cu_(1.8)Se.Such a conversion process activates the redox carrier of Cu^(2+)ion and delivers a remarkable rate capability of 285 mAh g^(-1) at 20 A g^(-1) and electrochemical durability up to 30,000 cycles.Furthermore,Cu^(2+)and H+coinsertion chemistry is proposed to facilitate the conversion process.As a proof-of-concept,a hybrid aqueous pouch cell coupling CuSe//Zn is capable of affording maximum energy and power densities of 190 Wh kg^(-1) and 1366W kg^(-1),respectively.

THE PULP ELECTROCHEMISTRY OF FLOTATION SEPARATION FOR STIBNITE-ARSENOPYRITE BULK CONCENTRATE

In the thermodynamics, for flotation separation of the SbAs bulk concentrate system there is no potential extent using butyl xanthate as collector. However in the kinetics, there exists 150 mV in reducing potential of butyl dixanthogen on the surface of stibnite and arsenopyrite. In this paper, their reducing kinetic difference of electrochemistry was confirmed by pure mineral flotation under controlled potential, the artificial SbAs bulk concentrate flotation separation and UVspectrophotometic analysis. The electrochemical separation of SbAs bulk concentrate has been carried out. qualified concentrate has been obtained. Sbconcentrate contains Sb 4944 %, As 044 %, Sbrecovery is 8783 % and Asconcentrate contains As 1096 %, Asrecovery is 9466 %.

INVESTIGATION ON ELECTROCHEMISTRY INSIDE STRESS CORROSION CRACKS OR PITS

Techniques are developed for studying the mechanism of localized corrosion and protectivemeasures against such corrosion are suggested.The pH values and composition of the occluded sol-ution at different propagation stages are determined.Measurements of the critical pH value and cor-rosion rate inside the occluded cells are conducted.Potential-pH diagrams depicting kinetic andthermodynamic behaviors of occluded cell corrosion are being established.The mechanism of inhibi-tion of pitting and stress corrosion cracking have also been investigated.

Predominating stable adsorption and direct electrochemistry of glucose oxidase on carbon nanotubes by oxygen-containing groups

Stable adsorption and direct electrochemistry of glucose oxidase （COx） occurred on nitric acid （HNO3）-treated multi-walled carbon nanotubcs （MWNTs） instead of as-received MWNTs, demonstrating the critical roles of oxygen-containing groups in stable adsorption and direct electrochemistry of GOx on carbon nanotubcs （CNTs）.

Direct Electrochemistry and Electrocatalysis of Hemoglobin at PAMAM Dendrimer-MWNTs-Au Nanoparticles Composite Film Modified Glassy Carbon Electrode

The direct electron transfer of hemoglobin at the PAMAM-MWNTs-AuNPs composite film modified glassy carbon electrode was studied. In a phosphate buffer solution（PBS, pH=7.0）, the formal potential（E^0） of Hb was -0.105 V versus SCE, the electron transfer rate constant was 4.66 s-1. E^0＇ of Hb at the modified electrode was linearly varied in a pH range of 5.0-8.0 with a slope of-49.2 mV/pH. The Hb/PAMAM-MWNTs-AuNPs/GCE gave an excellent electrocatalytic response to the reduction of hydrogen peroxide. The catalytic current increased linearly with H2O2 concentration in a range of 1.0× 10^-6 to 2.2× 10^-3 mol/L. The detection limit was 2.0× 10^-7 mol/L at a signal to noise ratio of 3. The Michaelis-Menten constant（Km^app） was 2.95 mmol/L.

Nanotube-based heterostructures for electrochemistry: A mini-review on lithium storage, hydrogen evolution and beyond

Nanotube-based mixed-dimensional or one-dimensional heterostructures have attracted great attention recently because of their unique physical properties and therefore potential for novel devices. Their chemical properties, however, were less explored but can be utilized for energy storage and conversion.In this review, we summarize the recent progress of nanotube-based low dimensional materials for electrochemistry, in particular, lithium storage and hydrogen evolution. First, we describe the atomic structure of low-dimensional heterostructures and briefly touch previous work on planar van der Waals heterostructures(2D+2D) in electrochemistry applications. Then we focus this review on the more recently developed nanotube-based, i.e., 1D+2D and 1D + 1D heterostructures, and discuss their various preparation approaches and electrochemical performances. Finally, we outline the challenges and opportunities in this direction and particularly emphasize the possibility of building high-performance electrodes using a single-walled carbon nanotube-based ultra-thin 1D heterostructure, and the importance of understanding the fundamental mechanism at atomic precision.

Direct Electrochemistry of Hemoglobin Immobilized in Sodium Alginate Film on the Ionic Liquid [BMIM]PF_6 Modified Carbon Paste Electrode

Room temperature ionic liquid （RTILs） [BMIM]PF6 was used as a new kind of binder to construct a chemical modified carbon paste electrode （CPE） and the direct electrochemistry of hemoglobin （Hb）, which was immobilized on the surface of RTIL/CPE with the film of sodium alginate hydrogel, was studied by cyclic voltammetry. The presence of RTILs improved the direct electron transfer of Hb and a pair of well-defined quasi-revesible redox peaks appeared in pH 7.0 B-R buffer solution. The cathodic and anodic peak potentials were located at -0.383 V and -0.305 V with the formal potential （E^0） at -0.344 V （vs. SCE）. In addition the immobilized Hb showed good electrocatalytic activity to the reduction of H2O2.

Electrochemistry of Hydroquinone Derivatives at Metal and Iodine-modified Metal Electrodes

The difference in the electrochemical behavior of hydroquinone and pyrocatechol at platinum and gold surfaces was analyzed using voltammetry and attenuated total reflection Fourier transform infrared spectroscopy. The results show that the hydroquinone derivatives are adsorbed on a gold surface with vertical orientation, which makes the electron transfer between the bulk species and the electrode surface easier than that in the case of flat adsorption of hydroquinone derivatives that occurs at a platinum electrode. The formation of the vertical conformation and the rapid process of electron transfer were also confirmed by quantum chemistry calculations. In addition, the pre-adsorbed iodine on the electrodes played a key role on the adsorbed configuration and electron transfer of redox species.

Synthesis, Fluorescence and Electrochemistry of Three New Ruthenium(Ⅱ) Complexes

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Recent development in researches of electrochemistry of sulphide flotation at Central South University of Technology

The recent development on flotation electrochemistry of sulphide minerals at Central South University of Technology is briefly summarized. General behavior of natural floatability, self and sulphur induced, and collector induced floatability of sulphide minerals are described. The mechanism is discussed based on Eh pH diagrams, voltammograms, energy band theory and molecular orbital theory.

Corrosive electrochemistry of jamesonite by cyclic voltammetry

The corrosive electrochemistry of jamesonite was studied by cyclic voltammetry. Every peak in voltammograms was identified through thermodynamic calculation. The results show an irreversible electrode process by the strong adsorption of oxidation elemental sulfur on jamesonite. A deficient-metal and sulfur-rich compound is formed under the potential of 80 mV at pH 6.86. The passive action by elemental sulfur occurs from 80 to 470 mV and S2O2-3, SO2-4 are produced at potential over 470 mV. The anodic peak producing SO2-4 is inhibited due to the deposition of PbSO4 at higher potential in Na2SO4 solution. The corrosive action of jamesonite becomes strong and the redox characterization similar to PbS, FeS and Sb2S3 appears at pH 9.18.

The Electrochemistry of Cytochrome c at a Viologen-thiol Self-Assembled Monolayer

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Direct Electrochemistry of Myoglobin in DDAB-Clay Composite Films

Ordered films were made by casting a mixture of aqueous dispersions of didodecyldimethylammonium bromide (DDAB)-clay composite and myoglobin (Mb) solution on pyrolytic graphite (PG) electrodes. The Mb-DDAB-clay film electrodes showed stable and reversible cyclic voltammetric responses in buffers and can catalyze the reduction of id (TCA).