MATERIALS CHEMISTRY AND PHYSICS
·
2024
·
IF 4.3
Fujia Ben,Dan Xu,Xinyuan Zhou,Taolin Yu,Jiale Wei,Wenjie Zhao
Based on the synergistic roles of defect dipoles and MnO 2 sintering aid, 0.8BaTiO 3 -0.2BiScO 3 (BTBS 0.2 ) ceramics with and without 0.3 wt% MnO 2 were prepared by a solid-phase reaction route. The impacts of MnO 2 dopant and sintering conditions on the crystalline structure, micro-morphology, dielectric, and energy storage properties were investigated in detail. The X-ray diffraction (XRD) and Raman results demonstrate the coexistence of tetragonal (T) and pseudo-cubic (pC) phases. The increased pC phase content caused by MnO 2 modification is beneficial for the improvement of the relaxation degree. The O 1s fine spectra of X-ray photoelectron spectroscopy (XPS) confirms a remarkable increase in the concentration of oxygen vacancy due to the acceptor Mn dopant, indicating the valence changes of Mn ions from Mn 4+ to Mn 3+ /Mn 2+ . The reduced dielectric loss is induced by the improved density and the pinning effect from the defect dipoles, thereby yielding a higher E b . An optimal energy density of W rec = 0.70 J/cm 3 with a high energy efficiency of η = 95.8 % at 140 kV/cm was realized in the BTBS 0.2 +Mn ceramic composition sintered at 1300 °C. Moreover, the ceramic also exhibits good temperature stability (30–120 °C). Therefore, the BTBS 0.2 +Mn ceramics have a promising application prospect in the energy storage field.
研究领域:
材料科学
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电介质物理
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产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2022
·
IF 6.364
Yan Yu,Weijia Guo,Yichao Zhen,Zhenyong Cen,An Ji,Hao Wu,Shujian Liang,Shan Xiong,Xiaohui Wang
The increasing cost of palladium has demonstrated the significant value of using inexpensive base metals as inner electrodes for RF/microwave multilayer ceramic capacitors . However, solving the co-sintering problem of dielectric ceramics with base metals such as copper is highly challenging, as sintering in a reducing atmosphere is required to prevent the oxidation of the base metals. In this work, the feasibility of sintering nonreducible MnO 2 -doped 0.95MgTiO 3 -0.05CaTiO 3 (95MCT) ceramics in a reducing atmosphere (H 2 -N 2 , p O 2 = 1 × 10 − 10 ∼ 1 × 10 − 11 MPa) at 1000 °C was investigated. The effects of the MnO 2 additive (1.6–2.4 mol%) on the phase structures, dielectric properties , and thermal stability were studied. Thermally stimulated depolarization current (TSDC) analysis and X-ray photoelectron spectroscopy (XPS) were conducted to characterize the oxygen vacancies and Mn ion valence state in MnO 2 -doped ceramics, indicating that Mn plays an important role in the dielectric properties, especially the extrinsic dielectric loss. With the optimized addition of 2.0 mol% MnO 2 , due to the decrease in oxygen vacancy concentration, the samples with ε r = 20.22 exhibited the attractive properties of a high insulation resistivity of IR = 3.65 × 10 14 Ω ∙ cm and a low dielectric loss of tan δ = 0.036 % , meeting the C0G specifications. The results show that the 2.0 mol% MnO 2 -doped 0.95MgTiO 3 -0.05CaTiO 3 ceramic is an outstanding nonreducible dielectric material for base-metal electrode RF/microwave multilayer ceramic capacitor applications with low cost, excellent dielectric properties, and high reliability.
研究领域:
材料科学
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电子工程
✓ 已验证
DOI
高影响因子
JOURNAL OF ELECTRONIC MATERIALS
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2022
·Vol. 51
·期 6
·2982-2994
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IF 2.047
Li Xueqin,Zhu Zhixiang,Ma Guang,Ding Yi,Wang Jinlong,Ye Zhiguo,Peng Xinyuan,Li Duosheng
Although MnO 2 possesses many advantages, such as a high theoretical specific capacity, resource abundance, easy synthesis and environmental friendliness, its poor electrical conductivity and low utilization seriously hinder its large-scale application as an electrode in supercapacitors. A MnO 2 and carbon nanotube (CNT) composite is co-deposited on flexible expanded graphite paper (EGP) by a facile method of composite brush plating. The three-dimensional conductive net of CNT in the composite greatly improves the supercapacitve and mechanical properties of MnO 2 electrode. The paper mainly studied (i) the choice of composite brush plating voltage and (ii) the effect of the concentration of active substance CNTs deposited on the performance of supercapacitor. When the current density is 20 A g –1 , the mass specific capacitance of the flexible CNT@MnO 2 /EGP electrode with an operation potential of 10 V in an electrolyte of 1.5 g L –1 CNTs dropped is 146 F g –1 . The CNT@MnO 2 /EGP/active carbon (AC)/carbon fibre cloth (CFC) flexible aqueous asymmetric supercapacitor (ASC) exhibits an energy density of 36.3 Wh kg –1 at a power density of 126.2 W kg –1 and high cycling stability with 91% capacitance retention after 4000 cycles. This study paves the way to provide a simple and novel technique for the mass production of flexible MnO 2 supercapacitor electrodes. Graphic Abstract The composite brush electroplating technology is successfully developed for fabricating flexible carbon nanotube@MnO 2 composite co-deposited on expanded graphite paper, which displays excellent capacitive performance and cycling stability in an aqueous media.
研究领域:
材料科学
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能源存储
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2015
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IF 2.999
Xin Guo,Li-Na Cong,Qin Zhao,Ling-Hua Tai,Xing-Long Wu,Jing-Ping Zhang,Rong-Shun Wang,Hai-Ming Xie,Li-Qun Sun
LiNi 1/3 Co 1/3 Mn 1/3 O 2 is successfully coated with MnO 2 by a chemical deposition method. The X-ray diffraction (XRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) results demonstrate that MnO 2 forms a thin layer on the surface of LiNi 1/3 Co 1/3 Mn 1/3 O 2 without destroying the crystal structure of the core material. Compared with pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 , the MnO 2 -coated sample shows enhanced electrochemical performance especially the rate capability. Even at a current density of 750 mA g −1 , the discharge capacity of MnO 2 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 is 155.15 mAh g −1 , while that of the pristine electrode is only 132.84 mAh g −1 in the range of 2.5–4.5 V. The cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) curves show that the MnO 2 coating layer reacts with Li + during cycling, which is responsible for the higher discharge capacity of MnO 2 -coated LiNi 1/3 Co 1/3 Mn 1/3 O 2 . Electrochemical impedance spectroscopy (EIS) results confirmed that the MnO 2 coating layer plays an important role in reducing the charge transfer resistance on the electrolyte–electrode interfaces.
研究领域:
材料科学
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电化学
✓ 已验证
DOI
高影响因子
Journal of Water Process Engineering
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2025
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IF 6.7
Xuanying Cai,Tiansheng Chen,Zhenhua Dai,Peiren Ding,Yinhao Dai,Peng Fan,Jihong Xu,Yuankui Sun,Xiaohong Guan
In cold regions, the freezing process typically presents difficulties for the remediation of contaminated soil and groundwater. However, in this work we report a freeze-assisted activation of peroxydisulphate (PDS) by β -MnO 2 for the degradation of phenolic compounds. The results showed that 60.8 % of 2,4-dichlorophenol (2,4-DCP) could be abated in frozen solutions at an initial pH of 6.5 within 2 h, whereas only 12.4 % of 2,4-DCP disappeared in aqueous solutions under other identical conditions. This enhancing effect was highly associated with the well-known freeze concentration effect, which could decrease the solution pH at the ice grain boundary by 2.4 units. Electron spin resonance (ESR) spectroscopic analysis and experiments with quenching agents and D 2 O suggested that radicals and singlet oxygen were not the major reactive species involved in the β -MnO 2 /PDS system. Instead, Raman analysis indicated that PDS may be bound to the surface of β -MnO 2 to form a reactive inner-sphere complex of MnO 2 -PDS*, which is proposed to account for the oxidative degradation of 2,4-DCP in aqueous and frozen β -MnO 2 /PDS systems. Chronoamperometric experiments further showed the redox potential of the β -MnO 2 /PDS system was as high as 1.2 V. This work highlights the possibility of applying the freezing effect to accelerate PDS activation by minerals abundant in environment and thus offers a promising strategy for pollution remediation in cold regions.
研究领域:
环境科学
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化学
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产品关联
DOI
高影响因子
RSC Advances
·
2017
·Vol. 7
·期 30
·18500-18507
·
IF 3.108
Xuecheng Liu,Yugo Osaka,Hongyu Huang,Jun Li,Zhaohong He,Xixian Yang,Huhetaoli,Shijie Li,Noriyuki Kobayashi
Increasing concern about sulfur dioxide (SO2) from diesel vehicle exhausts causing detrimental effects on NOx removal catalysts has resulted in the development of dry desulfurization filters for complete removal of SO2. In this study, a compact MnO2 filter was developed for diesel emission control. The SO2-capture behavior of the compact MnO2 filter was investigated by using a volumetric device in a low temperature range (200–400 °C) and low SO2 pressure conditions. The maximal capacity of the MnO2 filter was 304.1 mgSO2 per gMnO2 at 400 °C. Based on the experimental results, the required volume of the MnO2 filter was estimated as only 0.6 L for a diesel car with 30 000 km distance traveled per year. The thickness of the MnO2 filter had significant influence on its SO2-capture performance. The sulfate reaction mechanism was also discussed by using a grain model under four reaction temperature conditions for improving the efficiency of the design of the desulfurization filter. The sulfate process can be divided into two control stages (the chemical reaction control stage and the solid diffusion control stage) and the prediction models fit the experimental data well for both control stages, indicating that the two-stage grain model is suitable for the sulfate reaction between the MnO2 filter and SO2. The calculated apparent activation energy of 18.8 kJ mol−1 indicates that the MnO2 filter exhibits high activity for SO2 adsorption in a pure SO2 atmosphere.
研究领域:
环境科学
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化学工程
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Yang Liu,Xinyu Sun,Ying Wang,Shiqing Zhang,Fang Liu,Shaokai Ma,Jun Zhang,Ying Li,Yanming Xue,Chengchun Tang
Birnessite (δ-MnO 2 ), inspired by biological photosynthesis, holds promise as oxygen evolution reaction (OER) catalysts in water electrolysis for clean energy. Given that Mn 3+ serves as the active sites, various strategies have been employed to increase the Mn 3+ content to boost the OER activity. To surpass the limitations of the traditional adsorbate evolution mechanism (AEM), we have adopted an electrochemical reduction method to introduce metallic Ni and enrich oxygen vacancies onto δ-MnO 2 nanosheets. The resulting Ni/MnO 2 v /CC exhibits exceptional OER performance, with a reduction in overpotential by 190 mV (from 478 mV to 289 mV) at 10 mA cm −2 and a Tafel slope as low as 45 mV dec -1 , indicating accelerated catalytic activity. Experimental and theoretical analyses attribute this enhancement to a transition from the traditional AEM to lattice oxygen mechanism (LOM) mechanism. Moreover, the dual modification also enhances electronic conductivity, electrochemical surface area, and charge transfer ability of δ-MnO 2 . Our work offers a pathway to overcome conventional limitations in OER electrocatalysts, applicable not only to Mn-based catalysts but also to a range of other transition metal oxides.
研究领域:
能源材料
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电化学
·
纳米科学
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产品关联
DOI
高影响因子
JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2017
·
IF 4.233
Guangdi Nie,Xiaofeng Lu,Maoqiang Chi,Mu Gao,Ce Wang
Improving the conductivity and specific surface area of electrospun carbon nanofibers (CNFs) is beneficial to a rapid realization of their applications in energy storage field. Here, a series of one-dimensional C/MO x (M = Mn, Cu, Co) nanostructures are first prepared by a simple two-step process consisting of electrospinning and thermal treatment. The presence of low-valence MO x enhances the porosity and conductivity of nanocomposites to some extent through expanding graphitic domains or mixing metallic Cu into the CNF substrates. Next, the C/MO x frameworks are coated with MnO 2 nanosheets/nanowhiskers (C/MO x @MnO 2 ), during which process the low-valence MO x can partly reduce KMnO 4 so as to mitigate the consumption of CNFs. When used as active materials for supercapacitor electrodes, the obtained C/MO x @MnO 2 exhibit excellent electrochemical performances in comparison with the common CNFs@MnO 2 (CM) core-shell electrode due to the combination of desired functions of the individual components and the introduction of extra synergistic effect. It is believed that these results will provide an alternative way to further increase the capacitive properties of CNFs- or metal oxide-based nanomaterials and potentially stimulate the investigation on other kinds of C/MO x composite nanostructures for various applications.
研究领域:
材料科学
·
能源存储
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ACS Applied Energy Materials
·
2025
·
IF 5.5
Shenghao Zhao,Zhijiao Ji,Lu Hao,Zhangyou Wang,Jiawen Li,Fangge Cheng,Mansor Hussain,Jia Liu
Achieving high-efficiency electrooxidation of methanol (MOR) under low alkalinity is critical for the industrial application of direct methanol fuel cells. This challenge can be addressed by modulating the electron density of nanosized Pt particles via the support’s exchange effect. Herein, an electron-enriched Pt catalyst (Pt/Mn3O4) was successfully synthesized through the structural tuning of MnO2. The Pt/Mn3O4 catalyst exhibits a superior performance, delivering a mass activity of 1150 mA mgPt–1 in 0.1 M KOH with 4 M methanol, significantly outperforming commercial Pt/C (446 mA mgPt–1). The transfer of electrons from Mn3O4 to Pt was confirmed through X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and magnetic hysteresis loop analysis. Experimental and computational studies elucidate the nucleation mechanism of electron-enriched Pt, the source of active species (Pt–OH) for methanol oxidation, and the role of high-valence Mn. Furthermore, the spontaneous methanol decomposition on Pt/Mn3O4 and the corresponding active sites of dehydrogenation and CO oxidation were identified. Interference-free experiments revealed the deactivation mechanism of Pt/Mn3O4, underscoring the pivotal role of CO32– in the alkaline MOR.
研究领域:
材料科学
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电化学
·
催化反应
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2021
·
IF 13.273
Anqi Zhang,Rui Gao,Lingyuan Hu,Xiaogang Zang,Ru Yang,Shiyu Wang,Shuyun Yao,Zhiyu Yang,Haigang Hao,Yi-Ming Yan
Transition metal oxides with high theoretical capacity are known to show greatly limited energy and power density of electrochemical energy storage due to its sluggish charge transfer kinetics. Although oxygen vacancies at atomic level can efficiently regulate electronic configuration and ameliorate electrochemical performance, the construction of rich bulk oxygen vacancies is still a challenge. Here, rich oxygen vacancies were successfully introduced in bulk MnO 2 through complex induced chemical precipitation. Enhanced electrical conductivity and local electric-field formed around oxygen vacancies promote the charge transfer, remarkably enhancing capacitance and rate capability. Asymmetric supercapacitor of MnO 2 with rich bulk oxygen vacancies exhibits high energy density (54.2 Wh kg −1 ) and power density (3279.6 W kg −1 ), superior to most reported MnO 2 -based supercapacitor. Our strategy paves a way for the fine regulation of bulk electronic configuration and reaction kinetics.
研究领域:
材料科学
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电化学
·
能源存储
✓ 已验证
产品关联
DOI
高影响因子
International Journal of Applied Ceramic Technology
·
2024
·
IF 1.8
Guo-rong Ji,Ming Feng,Huilan Hao,Yunfeng Gao,Baoshun Zhu,Yu-ming Tian
In this study, varying amounts of MnO 2 up to 5 wt.% were added to magnesium aluminate spinel (MA) bodies using a solid-state sintering method at 1200–1600°C. The effect of MnO 2 addition on the phase composition, microstructure, distribution of elements, and ionic valence of MA was investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results showed that Mg 2+ ions in MA crystals were replaced by Mn 2+ ions, resulting in the formation of the (Mg 1- x Mn x )Al 2 O 4 solid solution. The distorted crystal structures promoted the sintering reactions, and the mechanical characteristics of MA were greatly improved by the solid solution strengthening process. When the additive amount of MnO 2 was 5 wt.% and the sintered temperature reached at 1600°C, excess manganese ions hardly dissolved into the lattice of MA. And these ions were only distributed at the grain boundaries of MgAl 2 O 4 , forming a “barrier” that hindered the migration and diffusion of particles, thereby suppressing the sintering process and weakening the mechanical strength of MA.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
DOI
高影响因子
SCIENCE OF THE TOTAL ENVIRONMENT
·
2022
·
IF 10.753
Ji-Ning Yang,Huan-Huan Yang,Ming-Shuang Niu,Hao Zhou,Xianliang Yi,Da-Lei Chang,Jingjing Zhan,Yang Liu
Under the background of indoor air formaldehyde decontamination , a freestanding ultra-light assembly was fabricated via ice-templating approach starting from MnO 2 nanoparticles and environmentally benign agar powder. The 3D composite of agar and MnO 2 (AM-3D) was comparatively studied with powdered counterparts (including pure MnO 2 and mixture of agar and MnO 2 ) and the 3D-structured agar for formaldehyde oxidation, and their physicochemical properties were examined with XRD , ATR, SEM, XPS, isothermal N 2 adsorption, ESR, Raman, CO-TPR and O 2 -TPD. For the single test of formaldehyde oxidation, the AM-3D catalyst exhibited 62.0%–67.0% removal percentage for ~400 mg/m 3 formaldehyde, which did not demonstrate significant advantage over the control samples. However, thanks to the porous 3D agar scaffold with large spatial volume that could promote a rapid gas-phase formaldehyde concentration reduction, and the strong interaction between the dispersed MnO 2 particles and agar substrate that could afford a large amount of reactive oxygen species to further oxidize the adsorbed formaldehyde, the AM-3D composite was a much better HCHO-to-CO 2 converter and possessed much more advantageous stability for repeated cycles of formaldehyde oxidation: even after ten cycles, there was still 41.7% of formaldehyde removed. Furthermore, the viable sunlight irradiation could easily restore the activity of the used AM-3D catalyst back to the level approaching that of the fresh one. Finally, reaction pathways were put forward via the infrared spectroscopic and ion chromatographic investigations on the surface intermediates of the spent materials.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）