scholarly journals ELECTROCATALYSIS OF THE OXYGEN REACTION ON THE MULTICOMPONENT OXIDES OF TRANSITION METALS

2021 ◽  
Vol 86 (12) ◽  
pp. 103-123
Author(s):  
Tetyana Maltseva ◽  
Valeriy Kublanovsky
Keyword(s):  
Transition Metals ◽  
Alternative Energy ◽  
Carbon Nanomaterials ◽  
Oxygen Electrode ◽  
Structural Features ◽  
Rechargeable Batteries ◽  
Oxide Surface ◽  
Transition Elements ◽  
Synthesis Of Nanoparticles ◽  
Multicomponent Oxides

The review presents the current state of research on oxides of transition metals as electrocatalysts for the both reactions of oxygen reduction and evolution, which are of key importance ones for electrochemical devices of alternative energy: metal-air rechargeable batteries and fuel cells with an oxygen electrode. The review includes the consideration of the thermodynamic, electronic and adsorption conditions for activation of the molecular oxygen by oxide surface, as well as the advantages of the oxide surfaces as catalysts in the alkaline electrolytes. The influence of the chemical composition and structural features of oxides of transition elements on the adsorption and chemisorption of water and oxygen, the formation of ionic forms at adsorption and the main factors, which influence on transfer of electrons, protons and oxygen, are considered. Synthesis of double and other multicomponent oxides and the usage of cationic doping expands the possibilities of forming the necessary properties of the electrocatalysts: porosity, thickness of hydrated layers, electronic and ionic conductivity, proton and electron-donor (acceptor) properties in a optimal combination. The oxide should have a metal with variable valence, and even better if there are two ones. Such oxides can be various structures based on Co2O3, MnO2, Ni2O3, Mn3O4, Fe2O3, and others. A qualitative leap in improving the performance of catalysts for electrode reactions with oxygen was made possible by the synthesis of nanoparticles, as well as nanocomposites with metallic and carbon materials. The some characteristics of the electroca­talytic activity of promising oxide electrocata­lysts, mainly, multicomponent ones, as well as the results of studies of oxide composites with carbon nanomaterials, are presented. Several of the most well-known oxide structures (spinel, perovskite, pyrochlor) are currently being studied as the most promising matrices for the efficient transfer of charge, oxygen, and metal ions. All of them are multicomponent. The most active non-platinum bifunctional catalysts for oxygen reactions concluded to be cobaltites with spinel structure. Nanocomposites based on cobalt and cobalt-manganese spinel are the most promising materials for use in alkaline rechargeable batteries, both in terms of cost and in terms of electrocatalytic activity as well as in terms of corrosion resistance.

Developments in Rechargeable Mno2Electrodes for Lithium Batteries

1988 ◽  
Vol 135 ◽  
Author(s):  
Michael M Thackeray
Keyword(s):  
Lithium Batteries ◽  
Lithium Battery ◽  
Electrode Materials ◽  
State Of The Art ◽  
Structural Features ◽  
Rechargeable Batteries ◽  
Current State ◽  
Alternative Systems ◽  
Battery Technology ◽  
Made In

AbstractConsiderable efforts are in progress to develop rechargeable batteries as alternative systems to the nickel-cadmium battery. In this regard, several advances have been made in ambient-temperature lithium battery technology, and specifically in the engineering of rechargeable lithium/manganese dioxide cells. This paper reviews the current state of the art in rechargeable Li/MnO2battery technology; particular attention is paid to the structural features of various MnO2electrode materials which influence their electrochemical and cycling behaviour in lithium cells.

Hydrogen Storage in Magnesium-Based Alloys

MRS Bulletin ◽  
1999 ◽  
Vol 24 (11) ◽  
pp. 40-44 ◽  
Author(s):  
R.B. Schwarz
Keyword(s):  
Energy Density ◽  
Hydrogen Storage ◽  
Alternative Energy ◽  
Distribution Systems ◽  
Electrical Energy ◽  
Clean Energy ◽  
Energy System ◽  
Liquid Hydrogen ◽  
Rechargeable Batteries ◽  
Oil Crisis

Magnesium can reversibly store about 7.7 wt% hydrogen, equivalent to more than twice the density of liquid hydrogen. This high storage capacity, coupled with a low price, suggests that magnesium and magnesium alloys could be advantageous for use in battery electrodes and gaseous-hydrogen storage systems. The use of a hydrogen-storage medium based on magnesium, combined with a fuel cell to convert the hydrogen into electrical energy, is an attractive proposition for a clean transportation system. However, the advent of such a system will require further research into magnesium-based alloys that form less stable hydrides and proton-conducting membranes that can raise the operating temperature of the current fuel cells.Following the U.S. oil crisis of 1974, research into alternative energy-storage and distribution systems was vigorously pursued. The controlled oxidation of hydrogen to form water was proposed as a clean energy system, creating a need for light and safe hydrogen-storage media. Extensive research was done on inter-metallic alloys, which can store hydrogen at densities of about 1500 cm3-H2 gas/ cm3-hydride, higher than the storage density achieved in liquid hydrogen (784 cm3/cm3 at –273°C) or in pressure tanks (˜200 cm3/cm3 at 200 atm). The interest in metal hydrides accelerated following the development of portable electronic devices (video cameras, cellular phones, laptop computers, tools, etc.), which created a consumer market for compact, rechargeable batteries. Initially, nickel-cadmium batteries fulfilled this need, but their relatively low energy density and the toxicity of cadmium helped to drive the development of higher-energy-density, less toxic, rechargeable batteries.

Can the Number of D Electrons in Transition Metals be Measured from White Lines?

1997 ◽  
Vol 3 (S2) ◽  
pp. 957-958 ◽  
Author(s):  
P. Rez
Keyword(s):  
Transition Metals ◽  
Energy Loss ◽  
Electron Energy ◽  
Transition Elements ◽  
White Line ◽  
Line Intensities ◽  
Continuum Region ◽  
The Matrix ◽  
Image Position ◽  
Electron Energy Loss

Sharp peaks at threshold are a prominent feature of the L23 electron energy loss edges of both first and second row transition elements. Their intensity decreases monotonically as the atomic number increases across the period. It would therefore seem likely that the number of d electrons at a transition metal atom site and any variation with alloying could be measured from the L23 electron energy loss spectrum. Pearson measured the white line intensities for a series of both 3d and 4d transition metals. He normalised the white line intensity to the intensity in a continuum region 50eV wide starting 50eV above threshold. When this normalised intensity was plotted against the number of d electrons assumed for each elements he obtained a monotonie but non linear variation. The energy loss spectrum is given bywhich is a product of p<,the density of d states, and the matrix elements for transitions between 2p and d states.

scholarly journals The Biological methods of selenium nanoparticles synthesis, their characteristics and properties

2020 ◽  
pp. 6-20
Author(s):  
O. Tsehmistrenko
Keyword(s):  
Metal Ions ◽  
Green Synthesis ◽  
Alternative Energy ◽  
Extracellular Polymeric Substances ◽  
Crop Yields ◽  
Production Optimization ◽  
Total Charge ◽  
Coating Agent ◽  
Synthesis Of Nanoparticles ◽  
Biological Methods

Nanotechnologies have an impact on every sphere of life, change approaches to environmental recovery, introduce new methods of disease analysis and prevention, treatment, drug delivery and gene therapy, affect the provision of environmentally friendly alternative energy sources, increase crop yields, animal and poultry productivity. Physical, chemical, biological methods of synthesis of nanoparticles, selenium in particular, their properties and the factors participating in reduction of metal ions to nanoparticles are considered. Limitations of nanoparticle synthesis inherent in the biological method (identification and isolation of bioactive fragment responsible for biomineralization of metal ions, analysis of ways to develop individual nanoparticles) and factors contributing to the intensification of nanoparticle production (optimization of pH, temperature, contact time, mixing degree) changes in the total charge of functional organic molecules on the cell wall). It has been proved that these factors affect the size, morphology, composition of nanoparticles and their efficiency during the synthesis. The model of green synthesis with the use of physicochemical means and their biomedical applications have been summarized. There are organisms used for the synthesis of NPs - terrestrial and marine bacteria, bacterial extracellular polymeric substances as bioreductants, fungi, yeast, algae, viruses, microorganisms. It has been demonstrated the biochemical ways of microorganisms in order to fight the toxicity of metals during the synthesis of nanoproducts and the factors that determine the toxicity of metals that are converted into nanoparticles (size, shape, coating agent, nanoparticle density and type of pathogen). The biological role of selenium and features of its influence on an organism in a nanoscale scale are shown. Key words: nanotechnologies, nanoselenium, bacteria, green synthesis, enzymes.

scholarly journals Acid-basic properties of chromium(III) oxide surface

2021 ◽  
Vol 57 (3) ◽  
pp. 270-277
Author(s):  
E. A. Shaporova ◽  
A. A. Zhukova ◽  
A. K. Baev ◽  
A. Yu. Sidorenko
Keyword(s):  
Binary Systems ◽  
Ionization Constant ◽  
Nitrate Solution ◽  
Structural Features ◽  
Oxide Surface ◽  
Acid Base ◽  
X Ray ◽  
Oxide Hydroxide ◽  
Nanosized Catalysts ◽  
Aqueous Nitrate Solution

The article is devoted to the study of the nature and number of acid-base centers on the surface of chromium(III) oxide obtained by precipitation from an aqueous nitrate solution. The curve of the distribution of the number of acidbase centers of the samples is plotted depending on the indicator of the ionization constant of indicators. It was determined that the main Lewis centers make the main contribution to the acidity of the samples; there are also Bronsted centers of different acidity. A comparative analysis of the structural features of the surface of oxides of chromium, zinc and binary systems Cr (III)–Zn (II) was carried out according to the results of X-ray phase analysis of oxides and thermolysis of the corresponding hydroxides. Based on this, the possibility of obtaining nanosized catalysts based on oxide-hydroxide systems of chromium with a number of 3d-metals obtained in the process of polynuclear hydroxocomplexation is predicted.

scholarly journals Recent Progress on Zinc-Ion Rechargeable Batteries

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Wangwang Xu ◽  
Ying Wang
Keyword(s):  
Energy Storage ◽  
Alternative Energy ◽  
Storage Systems ◽  
High Energy ◽  
Zinc Ion ◽  
Rechargeable Batteries ◽  
High Energy Density ◽  
Energy Storage Systems ◽  
Promising Alternative ◽  
Storage Technologies

Abstract The increasing demands for environmentally friendly grid-scale electric energy storage devices with high energy density and low cost have stimulated the rapid development of various energy storage systems, due to the environmental pollution and energy crisis caused by traditional energy storage technologies. As one of the new and most promising alternative energy storage technologies, zinc-ion rechargeable batteries have recently received much attention owing to their high abundance of zinc in natural resources, intrinsic safety, and cost effectiveness, when compared with the popular, but unsafe and expensive lithium-ion batteries. In particular, the use of mild aqueous electrolytes in zinc-ion batteries (ZIBs) demonstrates high potential for portable electronic applications and large-scale energy storage systems. Moreover, the development of superior electrolyte operating at either high temperature or subzero condition is crucial for practical applications of ZIBs in harsh environments, such as aerospace, airplanes, or submarines. However, there are still many existing challenges that need to be resolved. This paper presents a timely review on recent progresses and challenges in various cathode materials and electrolytes (aqueous, organic, and solid-state electrolytes) in ZIBs. Design and synthesis of zinc-based anode materials and separators are also briefly discussed.

scholarly journals Nitrogen-Doped Ordered Mesoporous Carbons Supported Co3O4 Composite as a Bifunctional Oxygen Electrode Catalyst

Surfaces ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 229-240 ◽  
Author(s):  
Jing Wang ◽  
Shuwei Zhang ◽  
Haihong Zhong ◽  
Nicolas Alonso-Vante ◽  
Dianqing Li ◽  
...  
Keyword(s):  
Precious Metal ◽  
Solvothermal Method ◽  
Oxygen Electrode ◽  
Rechargeable Batteries ◽  
Alkaline Media ◽  
Bifunctional Catalysts ◽  
Mesoporous Carbons ◽  
Ordered Mesoporous Carbons ◽  
Ordered Mesoporous ◽  
Regenerative Cells

It is increasingly useful to develop bifunctional catalysts for oxygen reduction and oxygen evolution reaction (ORR and OER) for fuel cells, metal-air rechargeable batteries, and unitized regenerative cells. Here, based on the excellent conductivity and stability of ordered mesoporous carbons, and the best ORR and OER activity of Co3O4, the composite Co3O4/N-HNMK-3 was designed and manufactured by means of a solvothermal method, using ordered N-doped mesoporous carbon (N-HNMK-3) as substrate, and then the bifunctional electrocatalytic performance corresponding to ORR, OER in alkaline media was carefully investigated. The results showed that Co3O4/N-HNMK-3 composite, a non-precious metal centered electrocatalyst, displayed excellent ORR performance (activity, selectivity, and stability) close to that of commercial 20 wt.% Pt/C and a promising OER activity near 20 wt.% RuO2/C. The outstanding bifunctional activities of Co3O4/N-HNMK-3 was assessed with the lowest △E value of 0.86 V (EOER,10 mA cm−2-EORR,−3 mA cm−2) with respect to the two commercial precious metal-based electrocatalysts.

Susceptibility of Chromium?Based Alloys of Transition Elements

1960 ◽  
Vol 13 (2) ◽  
pp. 451 ◽  
Author(s):  
WM Lomer
Keyword(s):  
Magnetic Properties ◽  
Transition Metals ◽  
Specific Heat ◽  
Room Temperature ◽  
Spin Moment ◽  
Transition Elements ◽  
Dilute Solutions ◽  
Spin Orientation ◽  
Local Moments ◽  
The Matrix

The magnetic properties of chromium�based alloys with the transition metals are very varied. Below room temperature it is believed that chromium is antiferrcmagnetic and in this paper we investigate briefly the nature of the influence of this antiferrcmagnetic matrix on the properties of dilute solutions of atoms carrying weIl�defined local moments of their own. It is shown that various anomalies in the susceptibility-temperature relations can be rationalized in terms of a model involving small spin orientation forces arising from the antiferromagnetism. Alloying with vanadium appears to reduce the spin moment on the chromium atoms, but to introduce no localized spins itself. The temperature.independent contribution of cobalt in solution is interpreted in terms of local spins locked by the antiferromagnetism of the matrix. The :results so far obtained suggest that careful specific heat measurements in the range 0--100 OK may disclose very significant anomalies in many of. these alloys.

scholarly journals Half- and mixed-sandwich metallacarboranes for potential applications in medicine

2019 ◽  
Vol 91 (4) ◽  
pp. 563-573 ◽  
Author(s):  
Marta Gozzi ◽  
Benedikt Schwarze ◽  
Evamarie Hey-Hawkins
Keyword(s):  
Organic Chemistry ◽  
Transition Metal ◽  
Transition Metals ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Structural Features ◽  
Biological Stability ◽  
Potential Applications ◽  
Sandwich Type ◽  
Isolobal Analogy

Abstract Today, medicinal chemistry is still clearly dominated by organic chemistry, and commercially available boron-based drugs are rare. In contrast to hydrocarbons, boranes prefer the formation of polyhedral clusters via delocalized 3c2e bonds, such as polyhedral dicarba-closo-dodecaborane(12) (closo-C2B10H12). These clusters have remarkable biological stability, and the three isomers, 1,2- (ortho), 1,7- (meta), and 1,12-dicarba-closo-dodecaborane(12) (para), have attracted much interest due to their unique structural features. Furthermore, anionic nido clusters ([7,8-C2B9H11]2−), derived from the neutral icosahedral closo cluster 1,2-dicarba-closo-dodecaborane(12) by deboronation followed by deprotonation are suitable ligands for transition metals and offer the possibility to form metallacarboranes, for example via coordination through the upper pentagonal face of the cluster. The isolobal analogy between the cyclopentadienyl(–1) ligand (Cp−) and [C2B9H11]2− clusters (dicarbollide anion, Cb2−) is the motivation in using Cb2− as ligand for coordination to a metal center to design compounds for various applications. This review focuses on potential applications of half- and mixed-sandwich-type transition metal complexes in medicine.

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