Mn 3s Research Articles

MnO@Mn2O3 nanocrystals embedded in biochar networks for sustainable anode of lithium-ion batteries

MnO is an alternative for commercial graphite as anode material for lithium-ion batteries (LIBs), if the issue of unstable performance caused by volume changes, poor conductivity, and changes in valence state of Mn is addressed. In this study, a series of nano MnO/biochar-containing composite materials were prepared with Mn(NO3)2, urea and pomelo peel as raw materials, via simple hydrothermal treatment and calcination, as anode materials for LIBs, where the biochar was used as inexpensive conductive medium and volume buffer. The electrochemical performance of the composite materials shows complicated correlation with the biochar contents, which associate with different carbonization temperatures. Elaborate characterizations with XRD, SEM, TEM, and Mn 2p, Mn 3s XPS spectra were conducted and jointly analyzed, which revealed that the surface of MnO nanocrystals undergoes different degrees of oxidation. The thickness of the surface amorphous Mn2O3 layer on the MnO nanocrystals influences the long-term electrochemical stability more significantly than the circumstances of biochar encapsulation, which was proved through cyclic voltammetry (CV) measurements. A composite material with moderate biochar content and thin layer of Mn2O3 coating on MnO nanocrystals will show more stable electrochemical performance. Based on this principle, one regulated composite material (MnOx/BC-650) gives an ultra-stable capacity of 446.9 mAh∙g−1 at 500 mA∙g−1 after 200 cycles. This study provides new insight for both revealing the true structure of manganese oxides and developing long-term stable MnO-containing anode materials for LIBs.

Improvement of CO Oxidation and CH4 Combustion by Pd and Pt Partial Substitution on LaMn0.5Cu0.5O3 Perovskite.

LaMn0.5Cu0.5O3 (LMC) as the parent perovskite and Pd- and Pt-doped LaMn0.5Cu0.5O3 catalysts (LMCPd and LMCPt) instead of Cu were synthesized in a new solid-state synthesis technique at a low temperature. Perovskite lattice formation of the LMC catalyst was successfully performed at 600 °C. All perovskites were investigated by X-ray diffraction, HRTEM, O2-TPD, H2-TPR, BET, and XPS analyses. The prepared perovskites were used as heterogeneous catalysts for CO oxidation and methane combustion reactions. The catalytic performance of the LMC catalyst was noticeably enhanced via Pd and Pt substitution instead of Cu. The enhancement in the mobility of lattice oxygen and specific surface area has triggered this catalytic performance improvement, which play an important role in CO oxidation and methane combustion. The Mn 2p and Mn 3s XPS spectra showed that by doping Pd and Pt in the LMC perovskite, Mn was affected in different states and the Mn 3s peaks were only observed in the LMCPt catalyst. XPS spectra of the LMCPd1 sample showed a high oxidation state of Pd3+ or Pd4+, from which it can be concluded that Pd was successfully incorporated into the LMC perovskite lattice. The H2-TPR profiles of the LMCPd and LMCPt perovskites revealed that the reduction peaks of Cu and Mn were shifted to lower temperatures by increasing Pd and Pt partial substitution due to the synergetic effect of the cation and the H2-spillover effect of palladium and platinum.

Electronic properties of MnO(110) film grown on Cu (111)

In this study, we investigated MnO thin films grown on Cu(111) using a soft x-ray and UV based spectroscopy, low energy electron diffraction (LEED), scanning tunneling (STM) and scanning transmission electron microscopy (STEM). MnO thin film assumes (110) preferential plane orientation organized in different spatial domains to better adapt to Cu(111) surface and an in-plane/out-of-plane lattice parameter variation up to 11% with respect to bulk counterpart originating a sizeable XLD signal at Mn L2,3 edges. The formation of oxidized Cu region during the MnO thin film growth is not avoidable due to the copper reactivity to oxygen and at the interface the coexistence of MnO islands alternated with Cu2O regions was observed by STM. Mn 2p and Mn 3s core level photoemission line shapes present a slight change in multiplet peak relative intensity with respect bulk MnO counterpart due to the role of Cu substrate in the core level relaxation process. The photon energy dependent photoemission spectra of valence band discriminate the MnO states and indicate a weak influence of the substrate once the film thickness is reduced to 1 nm. These findings open new route in the tuning oxide thin film properties.

Enhanced removal of organic matter from oxygen-pressure leaching solution by modified anode slime

Organic matter has become a typical harmful impurity, posing a serious problem and catastrophic effects in the hydrometallurgical extraction of zinc. The highly efficient and inexpensive method for the removal of organics from the leaching solution is of great practical significance for the efficient operation of zinc hydrometallurgy. For this reason, the removal of organic matter from oxygen-pressure leaching solution using modified anode slime was investigated by TOC analysis, FTIR spectroscopy, XRD, GCMS, and other characterization methods, and its mechanism was also discussed. The results show that the removal of organic matter using anode slime modified with sulfuric acid was significantly improved, and the removal of TOC reached 57.83% for anode slime modified at a temperature of 80 °C with a ratio of sulfuric acid to anode slime of 14 mL/100 g, which was more than 2.7 times that of untreated anode slime. The good removal effect of organic matter using the modified anode slime could be attributed to the transformation of inert α-MnO2 to active MnOOH by concentrated sulfuric acid-mediated modification. It was also found that the acid–solid ratio and temperature exhibited a significant effect on the modification of anode slime. The XPS analysis results of Mn 2p, Mn 3s, and O 1s, combined with the XRD patterns of the modified products indicated that the modification of anode slime led to the conversion of MnO2 in anode slime to MnOOH in the presence of H2SO4. However, MnO2 was further converted into high crystallinity MnOOH, even MnSO4 when the temperature exceeded 80 °C or the acid–solid ratio exceeded 18 mL/100 g, resulting in the decreased degradation performance for organic matter. The characterization results of FTIR spectroscopy and GCMS show that modified anode slime does not exhibit a degradation effect on all types of organic substances in leaching solution; however, it is very effective for some alcohols, olefins, and esters.

Photoelectron diffraction, multi-atom resonant photoemission, pioneered by Fadley

We discuss two important subjects pioneered by Fadley. As the first topic, we discuss the energy dependence of the intensity ratio observed in Mn 3s multiplet splitting excited from antiferromagnetic MnO, MnF2 and KMnF3. We apply the many-body scattering theory developed by Hedin in order to incorporate the extrinsic effects. We find that the extrinsic effects play an important role to explain the energy dependence of the branching ratio. Preliminary calculations show the smaller energy dependence than that observed. As the second topic we briefly discuss some features in multi-atom resonant photoemission (MARPE) based on the first principle quantum theory. Importance of the local symmetry around an emitter is stressed.

XPS on Mn0.95Dy0.05NiSb Heusler Alloy

"XPS results on Mn0.95Dy0.05NiSb Heusler alloy are presented. The compound is single phase with a C1b type cubic structure. All the experimental results suggest that the rare earth atoms entered in the lattice and they are not forming second phases. An exchange splitting of Mn 3s core-level spectrum of about 4.6 eV was shown, giving a direct evidence of the local magnetic moments on Mn sites. The Ni 3d states are giving the major contribution to the XPS valence band spectra. The Ni 3d satellite peak situated around 6 eV was attributed to the fact that the Ni 3d states in the valence band are not fully occupied. However, the Ni 3d band is almost full in this alloy and the Stoner criterion for the existence of a magnetic moment on Ni sites is no longer fulfilled. Keywords: Heusler alloys, X-ray photoelectron spectroscopy, valence band spectra. "

Operando leaching of pre-incorporated Al and mechanism in transition-metal hybrids on carbon substrates for enhanced charge storage

Operando leaching of pre-incorporated Al and mechanism in transition-metal hybrids on carbon substrates for enhanced charge storage

MnO2 nanomaterials functionalized with Ag and SnO2: An XPS study

The present study is devoted to the characterization of MnO2-Ag and MnO2-SnO2 nanocomposites of technological interest as gas sensors for food quality control and security applications. In particular, MnO2 nanomaterials were deposited on polycrystalline alumina substrates by plasma enhanced-chemical vapor deposition and functionalized with either Ag or SnO2 nanoparticles by means of radio frequency-sputtering. The target materials were investigated by a multitechnique approach, evidencing the successful formation of nanocomposites with tailored morphology, featuring an intimate contact of their components. Herein, the attention is dedicated to the characterization of system surface composition by x-ray photoelectron spectroscopy. Besides wide scan spectra, data obtained by the analysis of the C 1s, O 1s, Mn 2p, Mn 3s, Ag 3d, Sn 3d, and silver Auger signal spectral features are presented and critically discussed. The results highlight the occurrence of phase-pure MnO2 and SnO2 free from other Mn and Sn oxidation states and of appreciable silver surface oxidation in the target nanomaterials.

XPS characterization of Mn2O3 nanomaterials functionalized with Ag and SnO2

X-ray photoelectron spectroscopy was used to characterize the chemical composition and elemental states of bare and composite Mn2O3 (Mn2O3-Ag, Mn2O3-SnO2) nanomaterials. The target systems were prepared by the initial plasma enhanced-chemical vapor deposition of manganese oxides on alumina substrates, followed by annealing in inert atmospheres and functionalization with Ag and SnO2 by radio frequency-sputtering on the Mn2O3 surface. The survey scans of the fabricated samples, along with detailed spectra of the C 1s, O 1s, Mn 2p, Mn 3s, and, eventually, Ag 3d, Ag MVV, and Sn 3d regions, were collected and analyzed in detail. The obtained results revealed the formation of composite systems characterized by the presence of Mn2O3 free from other manganese oxides and pure SnO2, whereas appreciable Ag oxidation was observed. The O 1s photoelectron peaks could be fitted by means of two components related to lattice oxygen and to hydroxyl groups/oxygen species chemisorbed on surface O defects. The occurrence of the latter could exert a beneficial effect on the system functional behavior in gas sensing and electrocatalytic applications.

Electronic structure of CaMn1-xNbxO3 (x=0.02, 0.04, 0.06 and 0.08) perovskites. Self-organization of terminal layers

Electronic structure of niobium doped CaMn1-xNbxO3 (x = 0.02, 0.04, 0.06 and 0.08) powder and fresh chip manganites was studied by x-ray absorption near edge spectroscopy (XANES) at Mn K-edge, and by x-ray photoelectron spectroscopy (XPS) of Mn 3s -, Mn 2p -, O 1s -, Ca 2p- and Nb 3d-core levels. These XPS spectra for all the studied perovskites are very similar. The O 1s and Ca 2p spectra for powders differ from those for fresh chips because of the quick oxidation and carbonization of powder surface. The Mn 3s, Mn 2p and Nb 3d spectra for the powders and fresh chips are almost the same. According to Mn 3s spectra the formal valence of surface manganese ions is 3.82 for all studied oxides indicating the presence of oxygen vacancies in the samples. Niobium is in pentavalent state as evidenced by XPS measurements, but the negative chemical shift of the Nb 3d5/2 core level with respect to Nb2O5 oxide is observed. High similarity of the XPS spectra of the samples with different Nb doping is probably a result of the self-organization of terminal layers.

A zone-plate-based two-color spectrometer for indirect X-ray absorption spectroscopy.

X-ray absorption spectroscopy (XAS) is a powerful element-specific technique that allows the study of structural and chemical properties of matter. Often an indirect method is used to access the X-ray absorption (XA). This work demonstrates a new XAS implementation that is based on off-axis transmission Fresnel zone plates to obtain the XA spectrum of La0.6Sr0.4MnO3 by analysis of three emission lines simultaneously at the detector, namely the O 2p-1s, Mn 3s-2p and Mn 3d-2p transitions. This scheme allows the simultaneous measurement of an integrated total fluorescence yield and the partial fluorescence yields (PFY) of the Mn 3s-2p and Mn 3d-2p transitions when scanning the Mn L-edge. In addition to this, the reduction in O fluorescence provides another measure for absorption often referred to as the inverse partial fluorescence yield (IPFY). Among these different methods to measure XA, the Mn 3s PFY and IPFY deviate the least from the true XA spectra due to the negligible influence of selection rules on the decay channel. Other advantages of this new scheme are the potential to strongly increase the efficiency and throughput compared with similar measurements using conventional gratings and to increase the signal-to-noise of the XA spectra as compared with a photodiode. The ability to record undistorted bulk XA spectra at high flux is crucial for future in situ spectroscopy experiments on complex materials.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. III. LiNi0.6Co0.2Mn0.2O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated LiNi0.6Co0.2Mn0.2O2 powder obtained from Ecopro Company, Ltd. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.2Co0.05Mn0.1O0.7.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. IV. LiNi0.5Co0.2Mn0.3O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy (XAES) were used to analyze two lots of untreated LiNi0.5Co0.2Mn0.3O2 powder and one of the two lots of LiNi0.5Co0.2Mn0.3O2 powder recalcined in air at 750 °C obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals and show only minor sulfur contamination. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surfaces for the first lot, the first lot recalcined, and the second lot of LiNi0.3Co0.1Mn0.2O1.2, LiNi0.4Co0.1Mn0.3O1.5, and LiNi0.4Co0.1Mn0.2O1.3, respectively.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. VI. LiNi0.4Co0.2Mn0.4O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated LiNi0.4Co0.2Mn0.4O2 powder obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.5Co0.2Mn0.5O1.9.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. V. LiNi0.4Co0.3Mn0.3O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze untreated LiNi0.4Co0.3Mn0.3O2 powder obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.4Co0.2Mn0.3O1.6.

Lithium-based transition-metal oxides for battery electrodes analyzed by x-ray photoelectron spectroscopy. VII. LiNi0.33Co0.33Mn0.33O2

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy were used to analyze fresh LiNi0.33Co0.33Mn0.33O2 powder obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals and show carbon with only minor fluorine contamination. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surface of LiNi0.4Co0.1Mn0.7O2.0.

Modulating the electronic structure and pseudocapacitance of δ-MnO2 through transitional metal M (M = Fe, Co and Ni) doping

The experimental capacitance of manganese oxide (MnO2) is ordinarily less than 100 F/g due to their poor electronic conductivity and low structural stability. Herein, we demonstrate the design and synthesis of doped δ-MnO2 with enhanced electronic conductivity by the introduction of transitional metal Fe, Co and Ni. Structural characterizations shown that the Raman spectra of doped MnO2 has obviously blue shifted, as well as the separation values of Mn 3s XPS spectra has expanded, which indicate the transitional metal doping successfully changes the crystal lattice of δ-MnO2. The I-V measurements confirm that the electronic conductivity of MnO2 is significantly improved after doping. As a result, the Fe doped δ-MnO2 with a 0.5% doping amount displays the highest specific capacitance of 157 F/g at 0.5 A/g, by increasing 50.4% of the specific capacity than non-doped MnO2. Simultaneously, the Co doped δ-MnO2 exhibits the superb cycling stability (almost no degradation). Furthermore, the assembled 0.5% FeMO//AC, 1% CoMO//AC and 1% NiMO//AC asymmetric supercapacitor provide a specific energy densities of 30.3, 25.2 and 23.6 Wh/kg at a power density of 1000 Wh/kg. The excellent properties of as-prepared MnO2 are due to the enhanced conductivity after doping, which can ascribed to the forming of intermediate bands, or changing the intensity of valence band/conduction band as demonstrated by spin-polarized density functional (DFT) calculations. Thus, the current work will provide a pathway for the development of high-performance pseudocapacitive materials, as well as for other energy storage systems.

XPS investigation of F-doped MnO2 nanosystems fabricated by plasma assisted-CVD

Supported Mn(IV) oxide nanomaterials were prepared by plasma assisted-chemical vapor deposition from Ar/O2 plasmas starting from a fluorinated Mn(II) β-diketonate diamine adduct. Under the adopted conditions, the target compound served as a single-source molecular precursor for the obtainment of MnO2 nanosystems uniformly doped with fluorine. The overall F content in the target materials, composed of phase-pure β-MnO2, could be tailored as a function of the deposition temperature from 100 to 400 °C, a result of particular importance in view of photocatalytic and gas sensing applications. In the present study, attention is specifically devoted to the investigation of a representative specimen by means of x-ray photoelectron spectroscopy. Besides the wide scan spectrum, a detailed analysis of C 1s, O 1s, Mn 2p, Mn 3s, and F 1s photoelectron peaks is presented and discussed. The analyses reveal the formation of MnO2 free from other manganese oxides, with fluorine present in different chemical states, i.e., lattice F plus traces of precursor residuals at the system surface.

Investigation on the electrochemical performance of hausmannite Mn3O4 nanoparticles by ultrasonic irradiation assisted co-precipitation method for supercapacitor electrodes

ABSTRACTSpinel type manganese oxide (Mn3O4) nanoparticles were synthesized by ultrasonic irradiation assisted co-precipitation method using PEG and NaOH. The formation of tetragonal hausmannite phase (Mn3O4) with spinel structure was confirmed from XRD and FTIR studies. The average crystallite size of Mn3O4 nanoparticles was determined from Scherrer formula (39.9 nm) and Williamson–Hall relation (36.5 nm). The presence of elements, the overall oxidation state of manganese (Mn2+, Mn3+ and Mn4+) and chemical composition of these nanoparticles were determined from Mn 2p, Mn 3s and O 1s spectra using XPS. The spherically shaped morphology of these nanoparticles was analysed by SEM. The expected chemical composition of Mn3O4 nanoparticles was analysed by EDS. The electrochemical performance of these Mn3O4 nanoparticles was studied by CV, CP and AC impedance analysis. The maximum specific capacitance of Mn3O4 nanoparticles was found to be 296 F/g at a current density of 1 A/g2. Nyquist plot shows lower value of resistance that indicates the good electrical conductivity of the Mn3O4 electrode, which accounts for the improved electrochemical performance of the supercapacitors. Hence, the use of surfactant and the presence of ultrasonic irradiation in the synthesis process plays a dominant role in the electrochemical performance of Mn3O4 supercapacitors.

Mn3O4 thin films functionalized with Ag, Au, and TiO2 analyzed using x-ray photoelectron spectroscopy

In the present contribution, bare and composite Mn3O4 (Mn3O4-X, with X = Ag, Au, or TiO2) thin films were fabricated by a two-step vapor-phase route, consisting in: (1) chemical vapor deposition of Mn3O4 on Si(100) substrates starting from a fluorinated β-diketonate diamine Mn(II) complex; (2) introduction of silver, gold, or titania by means of radio frequency (RF)-sputtering. The obtained results evidenced the formation of phase-pure α-Mn3O4 thin films chemically modified with fluorine, which after RF-sputtering yielded Mn3O4-X nanocomposite systems with tailored properties. In this work, data obtained by x-ray photoelectron spectroscopy characterization of the surface chemical composition are presented and discussed for bare and functionalized Mn3O4 systems. In addition to wide scan spectra, particular attention is dedicated to the analysis of C 1s, O 1s, Mn 2p, Mn 3s, F 1s and, eventually, Ag 3d, Au 4d5/2, and Ti 2p core levels, as well as silver Auger signal. In the case of the Mn3O4-Au system, a quantification procedure aimed at circumventing problems arising from the overlap of Mn 2p/Au 4p1/2 and Mn 3s/Au 4f signals is proposed.