COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
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2021
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IF 4.539
Zipeng Feng,Yanwei Sui,Zhi Sun,Jiqiu Qi,Fuxiang Wei,Yaojian Ren,Zhenzhen Zhan,Meihua Zhou,Dongmei Meng,Lijun Zhang,Lan Ma,Qun Wang
Developing cost-effective and binder-free bifunctional electrocatalysts to boost the hydrogen and oxygen evolution reactions are crucial for overall water splitting. In this work, three-dimensional hierarchical Mn-Co-P/NF electrodes on nickel foam are synthesized by electrodeposition and chemical vapor deposition (CVD) firstly. Provide an excellent and controllable synthesis method by controlling the electrodeposition time and phosphating temperature. The Mn-Co-P composite exhibits the characteristics of vertically grown porous nanosheets, which can effectively expose the active sites. Benefit from the rational design with in-situ growth of functional materials and the unique structure, the Mn-Co-P/NF presents excellent electrocatalytic activities and stability with lower overpotentials of 63 mV and 310 mV to deliver 10 mA cm −2 for hydrogen evolution reaction (HER) and 10 mA cm −2 for oxygen evolution reaction (OER), respectively. Moreover, when directly used as a positive electrode and a negative electrode to form an electrocatalytic device to complete the overall water splitting, Mn-Co-P/NF merely requires a small cell voltage of 1.70 V to obtain 20 mA cm −2 . This work offers a controllable method to design and synthesize highly efficient and stable transition metal phosphide catalysts for overall water splitting and other catalytic fields.
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GEOCHIMICA ET COSMOCHIMICA ACTA
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2021
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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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ACS Sustainable Chemistry & Engineering
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2021
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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
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WATER RESEARCH
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2021
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IF 11.236
Yuan Gao,Yang Zhou,Su-Yan Pang,Jin Jiang,Yong-Ming Shen,Yang Song,Jie-Bin Duan,Qin Guo
In recent years, the activation of persulfates (peroxydisulfate (PDS) and peroxymonosulfate (PMS)) via transition metal ions for contaminants degradation has received extensive attention in water treatment. There has been growing interest on the mechanism (radical versus non-radical pathway) of activation processes. Interestingly, in contrast to copper, iron or cobalt ions regarded as effective activators for persulfates, manganese ion (Mn(II)) is inefficient for persulfates activation. Inspired by the enhanced stability of manganese species by ligands, this study for the first time systematically investigated the Mn(II)/persulfates with different ligands as a novel oxidation technology. UV-vis spectrometry, chemical probing method and mass spectrometry were used to explore the reactive intermediate (free radical versus high-valent manganese species) therein. It was surprisingly found that the oxidation efficiency of Mn(II)/ligand/persulfates system was highly dependent on the nature of persulfates and ligands. Mn(II) chelated by amino ligands such as ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetate (NTA) could efficiently trigger the oxidation of contaminants (e.g., recalcitrant compounds nitrophenol, benzoic acid and atrazine) by PMS , suggesting a promising Mn(II)/ligand/PMS technology for environmental decontamination especially under manganese-rich conditions. High-valent Mn species (Mn(V)) but not free radicals was demonstrated to be the dominant reactive intermediate, where Mn(III) species played a vital role in Mn(V) generation. The formation of Mn(III) species was found to be affected by the reactivity of persulfates and the type of ligands, thus influencing its further oxidation to Mn(V) species. This study presents a new oxidation process based on the combination of PMS and Mn(II) complex and broadens the knowledge of persulfates activation as well as manganese chemistry for decontamination in water treatment.
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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
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2020
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IF 4.939
Li Wang,Lili Cui,Xin Ge,Nailin Yue,Xingquan He,Wei Zhang,Tewodros Asefa
Developing efficient nonprecious electrocatalysts that can drive the oxygen electrode reactions in zinc-air batteries (ZABs) is important but remains challenging. In this work, novel materials comprising Mn/Cu nanoclusters-grafted N-doped carbon nanotubes are synthesized by preparing and then pyrolyzing Mn/Cu polyphthalocyanine-encapsulated carbon nanotubes (CNTs), followed by treating the products with acidic solution. The materials are named CNTs@(Mn,Cu)PPc-T, where T denotes the pyrolysis temperature in °C, and they are demonstrated to serve as efficient oxygen electrode catalysts for zinc-air batteries (ZABs). Among them, the one synthesized at 900 °C, CNTs@(Mn,Cu)PPc-900, requires more positive onset and half-wave potentials for reduction of oxygen and a low overpotential for the evolution of oxygen. A rechargeable ZAB assembled with CNTs@(Mn,Cu)PPc-900 electrocatalyst delivers a high power density (158.5 mW cm −2 ) and displays an excellent stability in 200 cycles of charge/discharge (in over 33 h). Such performance is even superior to that of a ZAB containing the benchmark Pt/C + RuO 2 catalyst as an air cathode under identical testing condition.
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JOURNAL OF THE ELECTROCHEMICAL SOCIETY
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2020
·Vol. 167
·期 10
·104501
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IF 3.721
Shengliang Wei,Yuqing Miao
The Mn-doped Ni(OH)2 nanostructures were obtained by a simple ion-exchange hydrothermal method. The as-prepared materials were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) for their morphological, composition and structural properties. As a material for modified electrodes, electrochemical tests demonstrate that the methanol oxidation peak current density of Mn-doped Ni(OH)2 nanostructures reached 14.18 mA cm−2 at 0.596 V (vs Ag/AgCl) in NaOH electrolyte. Similarly, the Mn-doped Ni(OH)2 nanostructures also maintained good electrocatalytic stability during the term of 36,000 s. The improvement of electrochemical performance is related to the introduction of Mn element in Ni(OH)2. It may promote Ni in the Mn-doped Ni(OH)2 nanostructures to carry the lower electron density and the higher oxidation state which may be responsible for the better performance toward methanol oxidation.
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JOURNAL OF RARE EARTHS
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2020
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IF 3.104
Baohuai Zhao,Rui Ran,Liu Yang,Xiaodong Wu,Zhichun Si,Duan Weng
A series of La 1– x Ce x MnO 3+ δ ( x = 0, 0.05, 0.1, 0.2, and 0.3) perovskites and Mn–Ce mixed oxides were prepared. Their physico-chemical properties were systematically characterized and the NO oxidation activities of the catalysts were investigated. The La 0.9 Ce 0.1 MnO 3+ δ has the best activity among all of the catalysts, with a maximum NO conversion of 85% at 300 °C. The characterization results indicate that the doping of Ce improves the properties of the perovskites in terms of the specific surface area, the average valence state of Mn ions, the number of reactive oxygen species and the NO x desorption behaviors. The Mn–Ce mixed oxide calcined at 500 °C shows a similar NO oxidation activity with La 0.9 Ce 0.1 MnO 3+ δ . However, the activity of the mixed oxide obtained at 750 °C decreases a lot, which results from the loss of active sites and active oxygen species.
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RSC Advances
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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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Journal of Physical Chemistry C
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2021
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IF 4.126
Jonathan M. Wong,Jie Xu,Ruizhong Zhang,Kenneth Chu,Zhifeng Ding,Lijia Liu
Electrochemiluminescence (ECL) of Mn-doped CsPbCl3 perovskite quantum dot (MPQ) films was investigated for the first time. The electrochemical properties of the perovskite quantum dots are probed by cyclic voltammetry and spooling ECL spectroscopy. It has been discovered that the ECL of the MPQ/benzoyl peroxide coreactant system proceeds through two channels: an energy transfer process from the band-edge exciton to Mn2+, producing emission centered at 595 nm from Mn2+ d–d transition, and a second emission peak centered at 660 nm, which is of a surface-state origin. This observation is drastically different from the frequently reported photoluminescence (PL) of MPQ, which contains dual emission from the host and the dopant, respectively. ECL of the undoped CsPbCl3 (UPQ) was also investigated, and the presence of the 660 nm peak further supports our proposed surface-state emission scheme.
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FUEL
·
2021
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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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NANO
·
2019
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IF 1.293
Zhenping Liu,Xianfeng Wang,Jingzhou Hou,Danqun Huo,Changjun Hou
An innovative phosphorescence probe based on Mn-doped ZnS quantum dots (Mn:ZnS QDs) was developed for selective detection of chloramphenicol (CAP) via inner-filter effect (IFE). Mn:ZnS QDs were synthesized by water method and modified with L-Cysteine for better stability, and the average diameter of the nanometer particle was 3.8 nm. With the excitation wavelength at 289 nm, the strong phosphorescence of Mn:ZnS QDs can be emitted at 583 nm. The excitation spectrum of Mn:ZnS QDs was substantially overlapped with the absorption spectrum of the target CAP. The excited light of Mn:ZnS QDs can be absorbed partially by CAP when they coexist, the phosphorescence intensity decreased with the increasing concentration of CAP, and it has a good linear relationship. Under optimal conditions, the linear relational concentration range achieved four orders of magnitude from 25 to 1 . 2 × 1 0 5 ng ⋅ mL − 1 ( R 2 = 0 . 9 9 9 ), with a detection limit (LOD; S ∕ N = 3 ) down to 0.81 ng ⋅ mL − 1 . The simple, rapid and low cost IFE phosphorescent probe exhibited satisfactory recoveries ranging from 88.9% to 98.5% for CAP analysis in spiked honey, which shows a potential for routine screening of CAP in ensuring the food safety.
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