Catalysis Science & Technology
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2022
·Vol. 12
·期 10
·3137-3147
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IF 6.177
Zhong-Ting Hu,Zi-Yan Jin,Si-Yan Gong,Xiuzhen Wei,Jia Zhao,Mian Hu,Jun Zhao,Zhong Chen,Zhiyan Pan,Xiaonian Li
Spinel ferrites with magnetic properties have great potential for the decontamination of aqueous systems due to their ease of recycling by magnetic separation. Herein, the purpose is to enhance ZnFe2O4 spinel properties in terms of magnetization and catalytic performance via Mn substitution into the crystal structure. Zn1−xMnxFe2O4 (x = 0–1) nanoclusters were successfully synthesized via an optimal hydrothermal process, in which additives (i.e., citric acid and ammonia) play key roles in inhibiting impurity phase formation via homogenizing the distribution of metal ions and slowing down the reaction rate. At a Zn/Mn ratio of 1 : 3, the nanocluster Zn0.25Mn0.75Fe2O4 (ZMF0.75) composed of nanoparticles with sizes ranging from 5 to 10 nm shows the highest saturation magnetization (Ms = 68 emu g−1, which is ∼5 times greater than that of ZnFe2O4) and the best catalytic performance, with >99% azoxystrobin (AZX) degradation in a Fenton-like system. Moreover, the findings unveiled that the balance of Zn and Fe occupation in the polyhedron centres in the spinel crystal is broken upon replacing Zn with Mn. In all probability, the Zn/Fe/Mn cross-occupation phenomenon is essential for enhancing the activity of Fe and Mn multivalent metal atoms. A plausible mechanism for the synergistic effect of multiple active sites in ZMF0.75 on the formation of HO˙ and HO2˙ radicals is proposed. This work proves that Mn-substituted ZnFe2O4 could be an efficient heterogeneous Fenton-like catalyst for EOC decontamination in aqueous systems with ease for recycling via magnetic separation.
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ELECTROCHIMICA ACTA
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2022
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IF 7.336
Tao Xu,Fanghui Du,Ling Wu,Zhongxu Fan,Lina Shen,Junwei Zheng
The urgent demands of developing Co-free materials for lithium ion batteries with high energy density for next generation electric vehicles have driven the attention of researches to LiNiO 2 stabilized by doping of common elements. Among those elements, manganese is usually used to stabilize cathode material crystal structures to achieve better electrochemical performances. However, the Li + /Ni 2+ cation disorder causing by Mn doping is greatly neglected of the effect on electrochemical behaviors. In order to elucidate the exact effect of Mn-doping, herein, we synthesize Mn-doped LiNiO 2 with extra low Mn content by using the solid-state element thermal interdiffusion strategy. Under calcination at high temperature, with the spherical species coated with Mn-containing gel as the precursor, Mn can be evenly doped into the framework of LiNiO 2 material. It is demonstrated that the small amount of Mn-doping can greatly stabilize both the crystal structure of LiNiO 2 and integrity of the secondary particles during the electrochemical cycling to provide the excellent electrochemical cycling performance and thermal stability of the materials. Nevertheless, the rate capability of the materials is strongly dependent on the amount of the doped Mn, due to the Li + /Ni 2+ cation mixing formed in the synthesis process and introduced in the electrochemical cycling. In the presence of a tiny quantity of the doped Mn, the enlarged crystal lattice would be favorable to the diffusion of the Li + ions in the crystal. However, serious Li + /Ni 2+ cation mixing of the materials with high content of the Mn-doping deteriorates the rate performance of the materials. Thus, in this case, the Mn content is optimized to be 4 mol%, endowing the material with an initial capacity of 202 mAh g −1 at 0.1 C, and a capacity retention of 85.41% after 200 cycles at 0.5 C. For the Mn-doped LiNiO 2 materials, it is suggested that to control the Li + /Ni 2+ cation mixing would be crucial for gaining the materials with superior electrochemical performance.
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ACS Applied Nano Materials
·
2022
·
IF 6.14
Xiaoshuo Zhang,Ziyi Zhang,Youyu Cao,Wenzhi Tang,Zhonghong Li
Excessive sulfite (SO32–) causes serious human health problems, making its detection highly valuable. In this work, a colorimetric sensor was presented for the detection of SO32– on the basis of Co–Mn mixed metal oxide (CoMn MMO) nanorods. CoMn MMOs composed of CoMn2O4 were uniformly dispersed among Co3O4 by calcining Co6(CO3)2(OH)8·H2O@CoMn2O4 nanorods in air, which had intrinsic oxidase-like activity. The synergistic introduction of CoMn2O4 promoted electron transfer in Co3O4, which not only prevented the aggregation problem but also increased the active sites, and the catalytic activity of the resulting CoMn MMO nanoenzyme was significantly enhanced. The obtained nanocomposites could catalyze the oxidation of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB with a quite low Michaelis–Menten constant (Km) of 0.042 mM and a quick Vmax of 0.85 × 10–8 M s–1 by generating a superoxide radical (·O2–). Based on the inhibitory effect of SO32– on the CoMn MMOs-TMB system, the proposed method allowed for SO32– detection with the linear concentration range from 1.56 to 15.58 μM and a limit of detection of 62.38 nM under optimal conditions. Combined with a smartphone chromaticity analysis app, we designed a portable and disposable agarose hydrogel test kit using the proposed system, which realized the on-site semiquantitative and visual detection of SO32– in food samples.
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Journal of Energy Chemistry
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2022
·
IF 13.599
Linfeng Fan,Yaxin Ji,Genxiang Wang,Zhifang Zhang,Luocai Yi,Kai Chen,Xi Liu,Zhenhai Wen
Electrolytic water splitting, as a promising route to hydrogen (H 2 ) production, is still confronted with the sluggish anodic oxygen evolution reaction (OER) and its less value-added O 2 production. Herein, we report a bifunctional electrode fabricated by in situ growth of Mn-doped CoSe 2 nanonetworks on carbon fiber cloth (Mn-CoSe 2 /CFC), which shows attractive electrocatalytic properties toward glycerol oxidation reaction (GOR) in alkali and hydrogen evolution reaction (HER) in acid. A flow alkali/acid hybrid electrolytic cell (fA/A-hEC) was then developed by coupling anodic GOR with cathodic HER with the Mn-CoSe 2 /CFC bifunctional electrode. Such fA/A-hEC enables a rather low voltage of 0.54 V to achieve 10 mA cm −2 , and maintain long-term electrolysis stability over 300-h operation at 100 mA cm −2 with Faraday efficiencies of over 99% for H 2 and 90% for formate production. The designed bifunctional electrode in such innovative fA/A-hEC device provides insightful guidance for coupling energy-efficient hydrogen production with biomass upgradation.
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SENSORS AND ACTUATORS B-CHEMICAL
·
2022
·
IF 9.221
Kun Yu,Guangyao Zhang,Huining Chai,Lijun Qu,Dan Shan,Xueji Zhang
Metal−organic frameworks (MOFs) have emerged as promising materials for smart sensing and imaging applications. Here, a novel micron-biscuit Mn(III)-based porphyrinic MOF is synthesized with the modulation of 4,4′-biphenyldicarboxylic acid (BPDC). The anisotropic growth of MOF is induced by the increased steric hindrance , yielding micron-biscuit Mn-TCPP(BPDC) MOF crystals. Mn(III), as a sealer, quenched the intrinsic fluorescence of porphyrin because of the ligand-to-metal charge transfer (LMCT) effect, and this disappeared fluorescence can be regularly restored and enhanced due to LMCT effect inhibition and release of free porphyrin derived from the water-induced two-stage ligand exchange (TSLE) between BPDC, porphyrin and water. The as-prepared MOF acts as an excellent “signal-on” luminescent water-sensing probe with low amount (2.5 μg/mL) that can efficiently realize the trace detection of water in various organic media with high sensitivity, especially in dimethyl sulfoxide (DMSO), the detection limit is as low as 0.04% (v/v). Moreover, Mn-TCPP(BPDC) was successfully used for sensing water content in real commercial samples. This MOF with the guest-induced TSLE not only provides inspiration for the design of new luminescent materials, but also widens the path for smart sensing.
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Inorganic Chemistry Frontiers
·
2022
·Vol. 9
·期 22
·5982-5993
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IF 7.779
Yifan Pan,Dongyan Gao,Yupeng Dang,Pengcheng Xu,Dandan Han,Changling Liu,Yen Wei,Yanru Yang
Metal–organic frameworks (MOFs) with bimetallic centers are considered as promising electrode materials for supercapacitors due to the large specific surface area and potential redox sites. In this work, the internal structure evolution, electron transfer in the metal center, and the mechanism of action of the Mn dopant to enhance conductivity in electrochemical processes are discussed. Density functional theory (DFT) calculations show that the introduction of Mn ions greatly reduces the band gap of the Ni-MOF and increases the carrier concentration, confirming the electron transfer process of electrons from Ni2+ to Mn2+ through the bridging oxygen. Therefore, the optimal NiMn-MOF produces an impressive specific areal capacity of 1.89 mA h cm−2 at 1 mA cm−2. Meanwhile, a hybrid supercapacitor (HSC) based on the NiMn-MOF electrode and activated carbon (AC) can output a high specific energy of 67.5 W h kg−1 at a specific power of 84.5 W kg−1 with excellent cycling stability (capacity retention of 94% after 10 000 cycles). Taking advantage of the high-energy storage properties of the NiMn-MOF//AC supercapacitor device, a solar power generation system is further integrated for self-powered portable electronic applications. This work broadens the applicability of activity prediction for bimetallic MOF electrode materials with high electrochemical performance.
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FUEL
·
2021
·
IF 6.609
Mengchang Zhou,Changsong Zhou,Dong Chen,Hao Wu,Zhen Zhang,Hongmin Yang,Wei Ruan,Yaming Zhou,Zengqiang Tan
Gaseous toluene, one of the volatile organic compounds, has aroused wide concerns in China due to its growing emissions and harmfulness. Herein, novel manganese decorated UIO-66 catalysts (Mn/UIO-66) were prepared by hydrothermal synthesis and applied to the vaporized hydrogen peroxide system for toluene removal. TEM, BET, XRD, ICP, and XPS were used to analyze the chemical and physical characteristics of Mn/UIO-66. A toluene removal efficiency of 82% with the 3-Mn/UIO-66 catalyst in the vaporized hydrogen peroxide system could achieved. The effects of different reaction conditions (reaction temperature, hydrogen peroxide concentration, and initial toluene concentration) on toluene removal were determined. The yield of hydroxyl radical in the Mn/UIO-66 catalyst combined with the hydrogen peroxide system was positively correlated with the Mn decorated ratio. Results suggested that the catalytic performance is related not only to the yield of hydroxyl radical but also to the catalyst specific surface. The intermediate products during toluene removal were analyzed by gas chromatography-mass spectrometry (GC–MS), and the possible reaction pathway of toluene removal was proposed.
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ACS Sustainable Chemistry & Engineering
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2021
·
IF 8.198
Weiquan Zhan,Yuan Yuan,Xin Yao,Bingqiao Yang,Feifei Jia,Changsheng Lin,José Luis Arauz-Lara,Shaoxian Song
Developing efficient materials for the extraction of gold(I) was pivotal for application of ammoniacal thiosulfate leaching technology. Mn-doped molybdenum disulfide (Mn-MoS2) spheres were fabricated by a facile hydrothermal route for photocatalytic reduction of the gold(I) thiosulfate complex ([Au(S2O3)2]3–) in this work. The experimental results exhibited that [Au(S2O3)2]3– was efficiently recycled in the form of gold nanoparticles by Mn-MoS2. The reduction capacity (936.9 mg/g) and rate (2.74 mg/(g min) in 300 min) was 1.5 and 2.72 times higher than that of MoS2, respectively. The inside photocatalytic reduction mechanism was studied by combining an experimental and first-principles approach. Outstanding reduction performance of [Au(S2O3)2]3– was attributed to the enhanced transfer of photoinduced electrons after Mn doping. In addition, S atoms in the Mn-S bond could well interact with Au(I), which slightly promoted the adsorption of [Au(S2O3)2]3– on Mn-MoS2. The discovery provided a promising strategy for the efficient extraction of gold(I) from thiosulfate leaching solutions.
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JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2021
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IF 8.128
Xianwei Bai,Lingqiang Meng,Ni Zhou,Jinju Zheng,Xue-Feng Yu,Paul K. Chu,Jun-Jun Xiao,Bingsuo Zou,Jia Li
Mn-doped perovskite nanocrystals have promised new optoelectronic applications due to their unique material properties . In the present study, Mn-doped perovskite nanocrystalline films were prepared in situ in a polymer matrix . The Mn-doped perovskite nanocrystals (PNCs) had good crystallinity and uniform size/spatial distributions in the polymer film . Bright dual-color emission and the long lifetime of the excited state of the dopant were observed from the host exciton and the Mn 2+ dopant, respectively. Furthermore, magnetism was observed in the optimal Mn 2+ concentration, implying that magnetic coupling was achieved in the Mn-doped perovskite lattice. The Mn-doped perovskite films also showed superior stability against moisture. To demonstrate the practicality of this composite film , a white light emitting device was fabricated by combining a single composite film with a blue light emitting diode ; the device showed a high-quality white light emission, and the Commission Internationale De L'Eclairage (CIE) chromaticity coordinate of the white light emitting diode (WLED) (0.361, 0.326) was close to the optimal white color index. In this single-layer WLED, self-absorption among the luminous multilayers in traditional white light emitting diodes can be avoided. The study findings revealed that Mn-doped perovskite nanocrystalline films have many exciting properties, which bodes well for the fundamental study and design of high-performance optoelectronic devices.
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PubMed
高影响因子
RSC Advances
·
2021
·Vol. 11
·期 46
·28949-28960
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IF 3.361
Ze Lv,Zhen Chen,Qiang Yu,Wei Zhu,Hongjun You,Bangyao Chen,Zhaoyi Zheng,Yuanyuan Liu,Qi Hu
PbO2–Co3O4–MnO2 electrodes, used in the electrowinning industry and in the degradation of organic pollutants, have demonstrated an elevated performance through macroscopic electrochemical measurements. However, few reports have investigated localized electrochemical performance, which plays an indispensable role in determining the essential reasons for the improvement of the modified material. In this study, the causes of the increase in electrochemical reactivity are unveiled from a micro perspective through scanning electrochemical microscopy (SECM), X-ray diffraction (XRD), Raman microscopy (Raman), and X-ray photoelectronic energy spectroscopy (XPS). The results show that the increase of electrochemical reactivity of the modified electrodes results from two factors: transformation of the microstructure and change in the intrinsic physicochemical properties. Constant-height scanning maps indicate that the electrochemical reactivity of the modified electrodes is higher than that of the PbO2 electrode on the whole and high-reactivity areas are orderly distributed, coinciding with the observations from SEM and XRD. Thus, one of the reasons for the improvement of the modified electrode performance is the refinement of the microscopic morphology. The other reason is the surge of the oxygen vacancy concentration on the surface of the coating, which is supported by XRD, Raman and XPS. This finding is detected by the probe approach curve (PAC), which can quantitatively characterize the electrochemical reactivity of a substrate. Heterogeneous charge transfer rate constants of the modified electrode are 4–5 times higher than that of the traditional PbO2 electrode. This research offers some insight into the electrochemical reactivity of modified PbO2 electrodes from a micro perspective.
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HYDROMETALLURGY
·
2021
·
IF 4.156
Luri Bao,Jingze Zhang,Jie Wu,Guotai Zhang,Yang Yang,Weiping Tang,Mei Xue
Owing to the increasing global demand for lithium, extraction of lithium from salt lake brine water has received considerable attention. In this study, the magnesium doping to produce Li 1.6 Mg x Mn 1.6-x O 4 (LMMO) was designed to overcome the limitation caused by the loss of Mn due to dissolution. The chemical and morphological properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The XRD results confirmed that the crystal structure of Li 1.6 Mn 1.6 O 4 was retained after Mg-doping. Scanning electron microscopy and energy-dispersive X-ray spectroscopy showed that LMMO has a flake-shaped structure and the Mg 2+ ions were uniformly distributed in the precursor. The doping of Mg 2+ led to the decrease of Mn 3+ content in the precursor, improving its structural stability. The adsorption capacity of LMMO-6% was 35.6 mg g −1 , which was greater than that of the undoped sample (33.2 mg g −1 ). After the tenth cycle, the dissolution loss of Mn in LMMO-6% was 0.55%, and it is smaller than that for lithium manganese oxide (0.94%). Results confirm that the structural stability was improved compared to undoped adsorbents. Moreover, batch adsorption experiments demonstrated the potential of the HMMO-6% adsorbent to be used for lithium adsorption from real salt lake brine.
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GEOCHIMICA ET COSMOCHIMICA ACTA
·
2021
·
IF 5.01
Jing Liu,Sayako Inoué,Runliang Zhu,Hongping He,Michael F. Hochella
It is recognized that different facets of minerals vary distinctively in their chemical reactivity with aqueous solutions. However, detailed molecular and atomistic understandings of these phenomena are relatively limited. This study investigated the interaction of aqueous Mn 2+ and dissolved oxygen on various facets of two morphology-types of iron oxide (hematite) nanocrystals. These interactions result in the oxidation of Mn(II) and heterogeneous growth of Mn(II)/Mn(III) and Mn(III) oxides. The nanoscale morphology and atomic structure of the manganese oxide products were characterized in detail. Our results, for the first time, directly demonstrate the facet-specific oxidation of Mn(II) and nucleation of Mn(II/III) oxides, followed by their epitaxial growth on hematite. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron diffraction measurements reveal the growth of MnO x nanowires on {1 1 3} of hematite nanoplates (HNP) and {0 1 2} facets of hematite nanocubes (HNC), while the basal {0 0 1} facets on the HNP particles do not produce precipitates. The average oxidation states of the MnO x on HNP and HNC determined using electron energy-loss spectroscopy (EELS) show that both Mn(II) and Mn(III) are present. The mineral composition and growth mechanisms of MnO x catalyzed by HNP and HNC are similar. High-resolution TEM analysis reveals the presence of both hausmannite and manganite on HNP and HNC. The crystallographic relationship between the heterogeneously formed manganite with hematite, which has not been reported before, proves that hematite provides reaction sites and can function as an atomic template for the formation of MnO x nanowires. These findings advance our understanding of the redox chemistry and heterogeneous growth of minerals as controlled by the surficial structure of the substrate mineral. This has important geochemical implications as the catalytic growth of less common, highly reactive phases like MnO x are known to be consequential in complex natural and anthropogenic environments.
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