scholarly journals The Jahn-Teller Effect for Amorphization of Molybdenum Trioxide towards High-Performance Fiber Supercapacitor

Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Chenyang Yu ◽  
Hai Xu ◽  
Yujiao Gong ◽  
Ruyi Chen ◽  
Zengyu Hui ◽  
...  
Keyword(s):  
Amorphous Materials ◽  
Oxygen Vacancies ◽  
Molybdenum Trioxide ◽  
Particle Diameter ◽  
Rate Capability ◽  
Average Particle ◽  
Cyclic Stability ◽  
Teller Distortion ◽  
Degenerate Ground State ◽  
Jahn Teller

Amorphous pseudocapacitive nanomaterials are highly desired in energy storage applications for their disordered crystal structures, fast electrochemical dynamics, and outstanding cyclic stability, yet hardly achievable using the state-of-the-art synthetic strategies. Herein, for the first time, high capacitive fiber electrodes embedded with nanosized amorphous molybdenum trioxide (A-MoO3-x) featuring an average particle diameter of ~20 nm and rich oxygen vacancies are obtained via a top-down method using α-MoO3 bulk belts as the precursors. The Jahn-Teller distortion in MoO6 octahedra due to the doubly degenerate ground state of Mo5+, which can be continuously strengthened by oxygen vacancies, triggers the phase transformation of α-MoO3 bulk belts (up to 30 μm long and 500 nm wide). The optimized fibrous electrode exhibits among the highest volumetric performance with a specific capacitance (CV) of 921.5 F cm-3 under 0.3 A cm-3, endowing the fiber-based weaveable supercapacitor superior CV and EV (energy density) of 107.0 F cm-3 and 9.5 mWh cm-3, respectively, together with excellent cyclic stability, mechanical robustness, and rate capability. This work demonstrates a promising strategy for synthesizing nanosized amorphous materials in a scalable, cost-effective, and controllable manner.

scholarly journals Mitigation of Jahn–Teller distortion and Na+/vacancy ordering in a distorted manganese oxide cathode material by Li substitution

2021 ◽  
Author(s):  
Yanchen Liu ◽  
Chenchen Wang ◽  
Shuo Zhao ◽  
Lin Zhang ◽  
Kai Zhang ◽  
...  
Keyword(s):  
Cathode Material ◽  
Rate Capability ◽  
Sodium Ion ◽  
Sodium Ion Batteries ◽  
Teller Distortion ◽  
Oxide Cathode ◽  
Vacancy Ordering ◽  
Jahn Teller ◽  
Jahn Teller Distortion ◽  
Li Substitution

Li-Substitution in P′2-Na0.67MnO2 mitigates the anisotropic change of Mn–O bonds and Na/vacancy ordering, and hence significantly promotes its cycling stability and rate capability as a cathode material for sodium-ion batteries.

Comparation of Cu-Co-Mn Mixed Oxides and Hopcalite as Support in Synthesis of Diphenyl Carbonate by Oxidative Carbonylation of Phenol

2013 ◽  
Vol 750-752 ◽  
pp. 1287-1291 ◽  
Author(s):  
Hong Xia Guo ◽  
Jing De Lü ◽  
Hui Qiang Wu ◽  
Shu Juan Xiao ◽  
Jie Han
Keyword(s):  
Electron Microscopy ◽  
Oxygen Vacancies ◽  
Mixed Oxides ◽  
Particle Diameter ◽  
Oxidative Carbonylation ◽  
Average Particle ◽  
Diphenyl Carbonate ◽  
X Ray ◽  
The Difference ◽  
Oxygen Atoms

The difference of Cu-Co-Mn mixed oxides and hopcalite as support in synthesis of diphenyl carbonate by oxidative carbonylation of phenol was studied. The catalysts were characterized by transmission electron microscopy, scanning electron microscopy, X-ray power diffraction, and X-ray photoelectron spectroscopy. The results show that the average particle diameter of the former catalyst is about 40 nm, whereas the other catalyst is about 0.5 μm. The main crystal phase in the former catalyst is Co2MnO4and Pd0.5Pd3O4, which in the latter catalyst is CuMn2O4, CoMn2O4and Pd0.5Pd3O4.The oxygen atoms lose electrons and form oxygen vacancies in.Pd0.5Pd3O4and Co2MnO4of the former catalyst, which destroys the crystal integrity and prompts the oxygen adsorption on the crystal surface. The oxygen atoms lose electrons and form oxygen vacancies in.Pd0.5Pd3O4of the latter catalyst. Finally, it was found that the difference of the yield and selectivity of the both catalysts was not remarkable.

Energetic Materials Development at Technanogy Materials Development

2003 ◽  
Vol 800 ◽  
Author(s):  
Kevin C. Walter ◽  
Christopher E. Aumann ◽  
R. Douglas Carpenter ◽  
Edward H. O'Neill ◽  
David R. Pesiri
Keyword(s):  
Surface Area ◽  
Energetic Materials ◽  
Molybdenum Trioxide ◽  
Energetic Material ◽  
Particle Diameter ◽  
Average Particle ◽  
Materials Development ◽  
Aging Study ◽  
The Individual ◽  
Burn Rate

ABSTRACTAn energetic material has been routinely manufactured from nano-metric powders of aluminum (Al) and molybdenum trioxide (MoO3). When optimized, the burn-rate of these materials (∼400 m/s) exceeds that of conventional thermites (based on micron-sized powders), but is less than that of conventional explosives. Similar burn-rates around 350 m/s are measured for these “super-thermites” using n-Al powder in the size range between 30 and 90 nm in diameter (20–60 m2/g, 60–80 wt%Al) and an oxygen to fuel (O/F) mass ratio of 1.4. The burn-rate decreases when the surface area of the MoO3 is decreased from 64 to 40 m2/g, or when O/F is changed from 1.2. Thus, for each average particle diameter, there is an optimum burn-rate at an O/F ratio that depends on the wt%Al present in the material and the particle size distribution of the powder. The burn-rate is dependent on several materials and processing factors such as the quality of the nano-metric ingredients, the processing method, and exposure to air and light, so the effect of aging and environmental exposure on the individual ingredients has been investigated. The results of this powder aging study suggests that the surface area of n-MoO3 can decrease two-fold within 10–12 days, and the Al-metal content in n-Al can decrease as much as 50% over two years. Adequate handling and storage procedures must therefore be followed for the effective use of nano-metric powders and their super-thermite mixes.

The enhanced Jahn-Teller distortion boosts molybdenum trioxide superior lithium ion storage capability

2021 ◽  
Author(s):  
Henghan Dai ◽  
Jin Yuan Zhou ◽  
Gang Qin ◽  
Gengzhi Sun
Keyword(s):  
Energy Density ◽  
Electric Vehicles ◽  
Transition Metal Oxides ◽  
Molybdenum Trioxide ◽  
Lithium Ion ◽  
Teller Distortion ◽  
Portable Electronics ◽  
Ion Storage ◽  
Jahn Teller ◽  
Jahn Teller Distortion

Upgrading the energy density and cycle life of current lithium ion batteries are urgently needed for developing advanced portable electronics and electric vehicles. Amorphous transition metal oxides (TMO) with inherent...

The Interplay of Open-Shell Spin-Coupling and Jahn-Teller Distortion in Benzene Radical Cation Probed by X-ray Spectroscopy

2020 ◽  
Author(s):  
Marta L. Vidal ◽  
Michael Epshtein ◽  
Valeriu Scutelnic ◽  
Zheyue Yang ◽  
Tian Xue ◽  
...  
Keyword(s):  
High Harmonic ◽  
Open Shell ◽  
Spin Coupling ◽  
High Symmetry ◽  
Teller Distortion ◽  
Spectral Window ◽  
X Ray ◽  
Jahn Teller ◽  
X Ray Absorption ◽  
Jahn Teller Distortion

We report a theoretical investigation and elucidation of the x-ray absorption spectra of neutral benzene and of the benzene cation. The generation of the cation by multiphoton ultraviolet (UV) ionization as well as the measurement of<br>the carbon K-edge spectra of both species using a table-top high-harmonic generation (HHG) source are described in the companion experimental paper [M. Epshtein et al., J. Phys.<br>Chem. A., submitted. Available on ChemRxiv]. We show that the 1sC -> pi transition serves as a sensitive signature of the transient cation formation, as it occurs outside of the spectral window of the parent neutral species. Moreover, the presence<br>of the unpaired (spectator) electron in the pi-subshell of the cation and the high symmetry of the system result in significant differences relative to neutral benzene in the spectral features associated with the 1sC ->pi* transitions. High-level calculations using equation-of-motion coupled-cluster theory provide the interpretation of the experimental spectra and insight into the electronic structure of benzene and its cation.<br>The prominent split structure of the 1sC -> pi* band of the cation is attributed to the interplay between the coupling of the core -> pi* excitation with the unpaired electron<br>in the pi-subshell and the Jahn-Teller distortion. The calculations attribute most of<br>the splitting (~1-1.2 eV) to the spin coupling, which is visible already at the Franck-Condon structure, and estimate the additional splitting due to structural relaxation to<br>be around ~0.1-0.2 eV. These results suggest that x-ray absorption with increased resolution might be able to disentangle electronic and structural aspects of the Jahn-Teller<br>effect in benzene cation.<br>

Adsorption of safranine T from aqueous medium by nano mesoporous MCM-41: adsorption equilibrium, kinetics, and thermodynamics

2020 ◽  
Vol 10 ◽  
Author(s):  
Xiao-Dong Li ◽  
Qing-Zhou Zhai
Keyword(s):  
Electron Microscopy ◽  
Ph Value ◽  
Particle Diameter ◽  
Spherical Particles ◽  
Practical Significance ◽  
Average Particle ◽  
Average Pore ◽  
Kinetics And Thermodynamics ◽  
Safranine T ◽  
Mcm 41

Introduction: In industrial production, a small amount of saffron T emissions will cause increase of water color and increase of chemical oxygen consumption, so study of the decolorization of saffron T wastewater has an important practical significance. Methods: MCM (Mobil Composition of Matter)-41 molecular sieve was synthesized by hydrothermal method. Power Xray diffraction and scanning electron microscopy were used to characterize the sample. Safranine T dye was adsorbed from water by the MCM-41 prepared. Kinetics and thermodynamics of the adsorption were studied. Results: The MCM-41 sample presented spherical particles and regular. The BET (Brunner-Emmett-Teller) specific surface area of the sample determined by 77 K low temperature nitrogen adsorption-desorption isotherm was 932 m2 /g. Its average particle diameter was 110 nm. TEM (transmission electron microscopy) results showed that the sample structure presented a honeycomb pore structure and the average pore diameter was 3.0 nm. The results showed that when room temperature was 20 ± 1 ℃, adsorbate safranine T: adsorbent MCM-41 = 20 : 1，the optimum pH value of adsorption was 4.0 and contact time was 20 min, the adsorption rate reached 98.29% and the adsorption capacity was 19.66 mg/g. The entropy change and enthalpy change of the adsorption system are respectively ΔS0 = 157.5 J/(mol·K); ΔH0 = 21.544 kJ/mol. When temperature was 277.15, 293.15, 303.15 K，the free energy change was respectively △G1 0 = -22.107 kJ/mol, △G2 0 = -24.627 kJ/mol, △G3 0 = -26.202 kJ/mol. Conclusion: The adsorption of safranine T by MCM-41 belongs to a pseudo-second-order adsorption. This adsorption accords with the Freundlich equation and belongs to a heterogeneous adsorption. The adsorption is an endothermic reaction of entropy increase, being spontaneous.

Jahn-Teller Effect in Hexahydroxocuprate(II) Complexes

1995 ◽  
Vol 60 (9) ◽  
pp. 1429-1434
Author(s):  
Martin Breza
Keyword(s):  
Hydrogen Bonding ◽  
Quantum Chemical ◽  
Potential Surface ◽  
Hydroxyl Group ◽  
Chemical Calculation ◽  
Teller Distortion ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Extremal Values ◽  
Jahn Teller Distortion

Using semiempirical CNDO-UHF method the adiabatic potential surface of 2[Cu(OH)6]4- complexes is investigated. The values of vibration and vibronic constants for Eg - (a1g + eg) vibronic interaction attain extremal values for the optimal O-H distance. The Jahn-Teller distortion decreases with increasing O-H distance. The discrepancy between experimentally observed elongated bipyramid of [Cu(OH)6]4- in Ba2[Cu(OH)6] and the compressed one obtained by quantum-chemical calculation is explainable by hydrogen bonding of the axial hydroxyl group.

Unveiling the role of Mn-interstitial defect and particle size on the Jahn-Teller distortion of the LiMn2O4 cathode material

2021 ◽  
Vol 490 ◽  
pp. 229519
Author(s):  
Renier Arabolla Rodríguez ◽  
Nelcy Della Santina Mohallem ◽  
Manuel Avila Santos ◽  
Demetrio A. Sena Costa ◽  
Luciano Andrey Montoro ◽  
...  
Keyword(s):  
Particle Size ◽  
Cathode Material ◽  
Teller Distortion ◽  
Interstitial Defect ◽  
Jahn Teller ◽  
Limn2o4 Cathode ◽  
Jahn Teller Distortion

scholarly journals A Comparative Evaluation of Nanohydroxyapatite-Enriched Hydrogen Peroxide Home Bleaching System on Color, Hardness and Microstructure of Dental Enamel

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3072
Author(s):  
Riccardo Monterubbianesi ◽  
Vincenzo Tosco ◽  
Tiziano Bellezze ◽  
Giampaolo Giuliani ◽  
Mutlu Özcan ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Particle Diameter ◽  
Dental Enamel ◽  
Sem Analysis ◽  
Control Group ◽  
Average Particle ◽  
Color Analysis ◽  
Enamel Microstructure ◽  
Prismatic Structure ◽  
20 Nm

This study aimed to evaluate two hydrogen peroxide (HP)-based at-home bleaching systems in order to analyze whether nano-hydroxyapatite (nHA) addition may represent a reliable and safe solution for tooth whitening without altering dental microstructure and hardness. Human third molars (N = 15) were treated with two bleaching agents, one containing 6%HP (6HP) and the other 6% HP nHA-enriched (6HP-nHA) with average particle diameter ranging from 5–20 nm. Their effects on enamel were assessed using a spectrophotometer, Vickers microhardness (VMH) test and Scanning Electron Microscopy (SEM), comparing the treated groups with the non-treated control group (CTR). Color analysis revealed improvement in whiteness in both groups compared to CTR. VMH test results showed no differences among the groups. SEM analysis highlighted no evident changes in the enamel microstructure of tested groups compared to CTR. At high magnification, in 6HP group, a slight increase in irregularities of enamel surface morphology was observed, while 6HP-nHA group displayed removal of the aprismatic layer but preservation of the intact prismatic structure. These results suggest that the 6HP-nHA agent may be recommended to provide reliable whitening treatment, without damaging the enamel micromorphology and hardness.

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