Catalysis Science & Technology
·
2022
·Vol. 12
·期 8
·2426-2437
·
IF 6.177
Xinxin Zhang,Jiajun Dai,Jiageng Ding,Kok Bing Tan,Guowu Zhan,Jiale Huang,Qingbiao Li
Direct epoxidation of propylene (DEP) to propylene oxide (PO) with molecular oxygen is a very desirable reaction but remains a challenge due to the absence of efficient catalysts with high selectivity. The catalytic performance for direct epoxidation of propylene is well related to surface adsorbed electrophilic oxygen species. Herein, we prepared a series of Mn-doped La2CuO4 perovskites (LaMnxCu1−xO3) with adjustable valence electronic structure as selective catalysts to explore the impacts of catalyst intrinsic electronic structure evolution on the activation of molecular oxygen. Therein, LaMn0.5Cu0.5O3 performed the best with a PO selectivity of 74.2% at 150 °C. The characterization results and DFT calculations revealed that the excellent catalytic performance of LaMn0.5Cu0.5O3 might be ascribed to the change of molecular oxygen activation sites: from oxygen vacancy active sites on La2CuO4 to Cu active sites on LaMn0.5Cu0.5O3. Meanwhile, there was a synergistic interaction between manganese and copper affecting the electron density on Cu sites and ultimately modulating the activated states of surface adsorbed oxygen species. In addition, we employed crystal band theory to associate the oxygen vacancy density with the Cu valence state. This is important for people to understand the bulk electronic structure evolution rules caused by transition metal doping and to design catalysts efficiently for oxygen-based chemical reactions.
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Journal of Physical Chemistry C
·
2023
·
IF 3.7
Zhaolun Yang,Xi Yuan,Yusheng Song,Mingyan Chen,Ke Xing,Sheng Cao,Jinju Zheng,Jialong Zhao
Mn-doped CsPbBr3 perovskite nanoplatelets (NPLs) with multicolor emission have very promising applications in light-emitting devices. However, the effects of NPL thickness on the Mn2+ luminescence properties remain to be investigated. Herein, a series of Mn-doped CsPbBr3 NPLs and nanocubes with different Mn/Pb molar ratios were synthesized by a supersaturated crystallization method at room temperature. The incorporation of Mn2+ ions into CsPbBr3 perovskites is attributed to the formation of the L2[Pb1–xMnx]Br4 intermediate structure in the precursor. The excitonic peak is tuned from 437 to 488 nm and the morphology evolves from NPLs to nanocubes with an increasing Mn2+ ion doping concentration due to the excess Br– from MnBr2. The photoluminescence quantum yields (PL QYs) of NPLs/nanocubes were greatly enhanced, achieving the maximum PL QYs of 88.7% at the Mn/Pb molar ratio of 3/1. The PL lifetime of Mn2+ emission is tuned from 0.19 to 0.44 ms due to the passivation of defect states and morphology transformation. Temperature-dependent steady-state and time-resolved PL spectra revealed that deep defect states in the NPLs/nanocubes were significantly reduced as the thickness increased. The Mn-doped CsPbBr3 NPLs/nanocubes show great potential for application in white light-emitting diodes.
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CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Yong Suo,Quanwu Guo,Yutong Liao,Jianhong Luo
Inspired by the mechanical reciprocating movement, a novel active microchannel device (RCSM) utilizing segmented flow and cavity squeezing technique was designed for the enhanced extraction and separation of Mn (II). The experiment evaluated the separation efficiency of Mn (II) under different conditions from two aspects: static and movement states of the reciprocating plate, and the results showed that residence time was the main factor effecting the extraction efficiency. At the same time, the movement of reciprocating plate produced a cyclic flow between oil and aqueous phases, which effectively enhanced the mixing and internal mixing of the two phases, reduced the effective mass transfer distance, and increased the effective contact area. The thermodynamics calculations indicated that the additional enthalpy was generated by the movement of reciprocating plate. And the kinetics calculations indicated that inertial forces and interfacial tensions significantly acted in the formation, fragmentation, agglomeration, and mixing of oil ∼ aqueous phases droplets in the microchannel, ultimately leading to different results in the interface and fluid flow form of the oil ∼ aqueous phases. At both high and low flow rates, regular slug flows were observed at the outlet of the RCSM, and the fusion between adjacent slugs played a positive role in improving the efficiency of extraction. In addition, the total volume mass transfer coefficient (K L a) was calculated in this experiment to further reveal the mass transfer enhancement mechanism of RCSM. Compared with static experiments, dynamic experiments demonstrated stronger mass and heat transfer performance.
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ENVIRONMENTAL RESEARCH
·
2021
·
IF 6.498
Yanan Cai,Jing He
The release of Mn(II) occurs in the degradation of organic matters by manganese ore (MnO 2 ), resulting in a reduced efficiency. During the degradation of ciprofloxacin (CIP), in a biofilter, this paper put forward a novel method that similar to the geo-cycle of Mn (MnCS) on the Earth to regenerate MnO 2 . The freshly prepared MnO 2 was suitable for the use in the MnCS. It indicated that the mutual conversion between Mn(II), Mn(III), and Mn(IV) in the MnCS, which was driven by CIP and manganese oxidizing bacteria (MnOB), could maintain the activity of MnO 2 . The MnCS showed feasibility in the coexistence of ammonia or humic acid , and provided a kinetic degradation. The physicochemical features of MnO 2 before and after bio-regeneration were characterized by TEM , XRD, BET, and XPS. It was found that the morphological structure of MnO 2 became loose and the maximum peak of pore size distribution became smaller, but the increase of surface area, the change of Mn(III/IV) content, and the decrease of crystallinity favored the bio-regeneration process. Moreover, as a mediator in the MnCS, the group of MnOB was dramatically inhibited by CIP, and the bacterial community had changed significantly. The typical MnOB shared low abundance in the biofilter, while the rarely reported genera (e.g. Sphingomonas ) that related to the formation of Mn deposits appeared to be involved in the MnCS.
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SURFACE & COATINGS TECHNOLOGY
·
2021
·
IF 4.158
Yan Yan,Jiale Guo,Nuo Chen,Yuxin Song,Si Wu,Qi Zhang,Qiang Han,Ming Gao,Jinghai Yang,Jihui Lang
Mn-TiO 2 /carbon cloth (CC) membranes with various Mn doping concentrations have been synthesized by hydrothermal process for efficient oil-water separation. The prepared membranes with superhydrophilic in air and underwater superoleophobic have the excellent self-cleaning performance under visible light driven, and these performances are strongly influenced by Mn doping concentration. The separation efficiency of the membranes is above 98% even after 56 oil-water separation cycles for various oil-water mixtures due to the d-states hybridization of Mn ions. Importantly, the membranes also have the good mechanical performance, reusability, chemical durability, and even work in acid, alkali and salt environment. The aforementioned properties and the easily scale-up production technique ensure that the Mn-TiO 2 /CC membrane has a potential application in practical treatment of oil spillage clean-up and oily wastewater.
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Journal of Energy Storage
·
2021
·
IF 6.583
Jie Xu,Cuili Xiang,Songwen Fang,Luping Zhu,Fen Xu,Lixian Sun,Yongjin Zou,Jian Zhang
Supercapacitors, such as pseudocapacitors (PCs), are widely used because of their excellent electrochemical activity and capacitance; however, it is still challenging to fabricate PCs with high stability and good electrochemical properties. Therefore, suitable templates and transition metal composite materials should be selected for improving their performance. Binary transition metal sulfides exhibit excellent electrochemical performance owing to their rich valence, electrical conductivity, and abundant electrochemical active sites. In this study, we prepared porous Mn-Co-S nanospheres (MCSN) via the hydrothermal method using silica colloidal particles was as the template; to the best of our knowledge, this is the first study to synthesize MCSN. Results suggest that the MCSN composite exhibited excellent conductivity and enhanced stability owing to the porous structure formed by the vertical growth of MnS 2 -CoS 2 nanosheets on silica nanoparticles. The porous MCSN electrode showed an excellent specific capacitance of 1158 F g −1 at 1 A g −1 . Moreover, when coupled with an activated carbon (AC) positive electrode, the supercapacitor of MCSN//AC exhibited stability of 90.4% after 5000 cycles at 10 A g −1 (the specific energy of 34 W h kg −1 at 775 W kg −1 ). Given the results, we believe that the prepared MCSN material has potential application prospects for high-efficiency supercapacitors.
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JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2021
·Vol. 32
·期 10
·13430-13439
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IF 2.478
Kang Xiaoya,Ma Yingxia,Wang Jiawei,Shi Xiaofeng,Liu Binglu,Ran Fen
Metal organic frameworks (MOFs) have potential applications in the field of energy storage due to high specific surface area and rich porosity, and captured widely attention in recent years. In this work, nickel/manganese-based MOFs (Ni/Mn-MOFs) were successfully fabricated by solvothermal reaction using 1,4-phthalic acid as the organic ligand, nickel nitrate hexahydrate, and manganese nitrate tetrahydrate providing center metal ions. The Ni/Mn-MOFs were analyzed by scanning electron microscope, powder X-ray diffraction, and nitrogen absorption/desorption isotherm. The results indicate that the obtained Ni/Mn-MOFs have coral-like microstructures and hierarchical pores with a specific surface area of 380.8 m 2 /g and an average pore diameter of 13.6 nm. Subsequently, the Ni/Mn-MOFs were used as the electrode materials for supercapacitors, and the electrochemical properties were investigated in the three-electrode system using 6.0 M KOH aqueous solution as the electrolyte. The results show that the specific capacitances of the coral-like Ni/Mn-MOFs are 531.5 and 317.9 F/g at the current density of 0.5 and 5 A/g, respectively. And the capacitance retention is 67.7% after 2300 cycles at 5 A/g, which implies that the coral-like Ni/Mn-MOFs have higher specific capacitance and favorable cycle stability. The above results indicate that the coral-like Ni/Mn-MOFs facilitate the electrolyte infiltration and ions transportation.
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APPLIED CATALYSIS B-ENVIRONMENTAL
·
2021
·
IF 19.503
Zhe Chen,Xiaobin Liao,Congli Sun,Kangning Zhao,Daixin Ye,Jiantao Li,Gang Wu,Jianhui Fang,Hongbin Zhao,Jiujun Zhang
Constructing and excavating single atom catalysts with high-density active sites and long-life durability for energy storage and conversion devices still remain bestially challenges. In this paper, a novel dual-site electrocatalyst with atomically dispersed Fe/Mn-N x -C dual metal sites embedded in N-doped carbon matrix is successfully designed and synthesized, which exhibits a state-of-the-art oxygen reduction reaction (ORR) activity with a half-wave potential (E 1/2 ) of 0.88 V (vs. RHE) as well as a superior stability. Besides, the Fe/Mn-N x -C catalyst reaches a high power density of 208.6 mW cm −2 and a specific energy density of 825.5 W h kg -1 when this catalyst is employed in Zn-air battery, which is superior to most of the reported non-precious catalysts. Furthermore, theoretical DFT calculations reveal the excellent performance is induced through a synergic dual-site cascade mechanism, which overcomes the issue of low adsorption energy (E ads ) of *OH on Fe-N x site, followed by transfer of the *OH to adjacent Mn-N x sites. As a result, the first three steps during ORR more favored occur on the Fe-N x sites instead of the Mn sites to generate *OOH and *O intermediates due to the lower energy barriers. This mechanism is further approved by addition of methanol to verify the preferred adsorption of *OH on the Mn-N x site.
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JOURNAL OF MATERIALS SCIENCE
·
2021
·Vol. 56
·期 34
·19155-19164
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IF 4.22
Fan Xuhui,Wang Jing,Rao Yu,Zhao Lei,Zhu Kongjun
Dielectric ceramics have attracted ever-increasing interest in energy storage applications due to their high-power density and fast charge–discharge speed. In particular, AgNbO 3 -based antiferroelectric ceramics are considered potential substitutes for lead-based ceramics. AgNbO 3 ceramics sintered with fine hydrothermal-synthesized powders show the advantage of high breakdown strength. However, the fine grains lead to the decreased polarization, which harms the recoverable energy density. In this work, a little amount over-stoichiometrical WO 3 and MnO 2 were introduced to synergistically improve the polarization and dielectric breakdown strength of obtained AgNbO 3 ceramics. The dependences of structures and dielectric properties on WO 3 doping were explored. A maximum polarization of 49.4 μC/cm 2 and E b as large as 285 kV/cm were achieved in 0.1 wt % WO 3 and MnO 2 co-doped AgNbO 3 ceramic. The corresponding W rec reached 2.75 J/cm 3 , which was 1.3 times larger than that of pristine AgNbO 3 ceramics. Moreover, benign thermal stability with W rec = 2.2–2.7 J/cm 3 over 30–150 °C at 240 kV cm −1 was also achieved in 0.1 wt.% WO 3 and MnO 2 co-doped AgNbO 3 ceramics.
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Materials
·
2021
·Vol. 14
·期 9
·2238
·
IF 3.623
Xiaoming Cao,Liyuan Gu,Shike Hu,Aiman Mukhtar,Kaiming Wu
A lot of nanomaterials are using T1-T2dual mode magnetic resonance (MR) contrast agents (CAs), but multilayer nanowire (NW) with iron (Fe) and manganese (Mn) as T1-T2dual modal CAs has not been reported yet. Herein, we synthesized a Fe/Mn multilayer NW with an adjustable Fe layer, as T1-T2dual-mode CAs. The relaxation performance of Fe/Mn multilayer NW was studied at 1.5 T. Results show that, when the length of the Fe layer is about 10 nm and the Mn is about 5 nm, the r1value (21.8 mM−1s−1) and r2value (74.8 mM−1s−1) of the Fe/Mn multilayer NW are higher than that of Mn NW (3.7 mM−1s−1) and Fe NW (59.3 mM−1s−1), respectively. We predict that our Fe/Mn multilayer NW could be used as T1-T2dual mode MRI CAs in the near future.Keywords:dual modal;MRI;CAs;nanowire;relaxation
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Nanomaterials
·
2020
·Vol. 10
·期 9
·1745
·
IF 4.324
Ze Sun,Liuting Zhang,Nianhua Yan,Jiaguang Zheng,Ting Bian,Zongming Yang,Shichuan Su
Magnesium hydride (MgH2) has been considered as a potential material for storing hydrogen, but its practical application is still hindered by the kinetic and thermodynamic obstacles. Herein, Mn-based catalysts (MnCl2and Mn) are adopted and doped into MgH2to improve its hydrogen storage performance. The onset dehydrogenation temperatures of MnCl2and submicron-Mn-doped MgH2are reduced to 225 °C and 183 °C, while the un-doped MgH2starts to release hydrogen at 315 °C. Further study reveals that 10 wt% of Mn is the better doping amount and the MgH2+ 10 wt% submicron-Mn composite can quickly release 6.6 wt% hydrogen in 8 min at 300 °C. For hydrogenation, the completely dehydrogenated composite starts to absorb hydrogen even at room temperature and almost 3.0 wt% H2can be rehydrogenated in 30 min under 3 MPa hydrogen at 100 °C. Additionally, the activation energy of hydrogenation reaction for the modified MgH2composite significantly decreases to 17.3 ± 0.4 kJ/mol, which is much lower than that of the primitive MgH2. Furthermore, the submicron-Mn-doped sample presents favorable cycling stability in 20 cycles, providing a good reference for designing and constructing efficient solid-state hydrogen storage systems for future application.Keywords:hydrogen storage;MgH2;Mn-based catalysts;catalytic effect;reversibility
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MATERIALS CHEMISTRY AND PHYSICS
·
2020
·
IF 3.408
Tengyan Wu,Guokang Shen,Feng Ding,Duxin Li,Hongbin Zhong
In this study, the La doped Mn–Zn nanoferrites were synthesized through hydrothermal method , and then were used to activate persulfate for degrading azo dye the Direct Blue 15 (DB15). The structure and morphology of the as-prepared sample were characterized by X-ray Diffraction (XRD), Fourier Transformed Infrared Spectrometer (FTIR), Transmission Electron Microscopy (TEM) and Energy Dispersive Spectrometer (EDS). The results indicated that the La doped Mn–Zn ferrite was successfully synthesized in this study. Four absorption bands were observed in FTIR spectra and assigned to the corresponding site bonds. Mn 0.6 Zn 0.4 La x Fe 2- x O 4 was chosen as catalysts to activate persulfate (PS/Mn 0.6 Zn 0.4 La x Fe 2- x O 4 ) to decolorize the DB15. It was found that the DB15 was degraded effectively by PS/Mn 0.6 Zn 0.4 La x Fe 2- x O 4 systems. Furthermore, the influences of synthesized conditions (such as the temperature, holding time and doping content of La) of Mn 0.6 Zn 0.4 La x Fe 2- x O 4 on the DB15 decolorization were analyzed. The results indicated that the doping of La can significantly improve the DB15 degradation, 100% degradation of DB15 can be obtained by PS/Mn 0.6 Zn 0.4 La 0.09 Fe 1.91 O 4 within 15 min. The enhancement of synthesized holding time of Mn 0.6 Zn 0.4 La x Fe 2- x O 4 at 160 °C can also increase the DB15 decolorization, and the degradation rate of the DB15 reached almost 100% within 25 min when using Mn 0.6 Zn 0.4 La 0.05 Fe 1.95 O 4 synthesized at 160 °C for 13 h as catalyst.
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