X-ray Photoelectron Spectroscopy Patterns Research Articles

Controlled synthesis of efficient novel Cr0.2Co2.8O4–MoO3 nanocomposites for high-performance O2-evolution and methanol oxidation in alkaline medium

The world of electrochemical devices is constantly pushing the boundaries to what's possible, and nanocomposites are becoming crucial electrocatalysts for enhancing electrochemical performance. In this study, the affect in electrochemical behaviour on altering constituent amount in the electrocatalysts has been discussed. For this we synthesized a novel Cr0.2Co2.8O4–MoO3 nanocomposites with varying constituent proportional amount using simple low-temperature route. The formation and the physicochemical properties have been investigated by Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Raman, Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) techniques. The XRD and XPS patterns confirms the nano crystalline structures and compositional difference in metal cations distribution respectively. Results from Cyclic Voltammetry (CV), Tafel experiments, Chronoamperometry and Electrochemical impedance Spectroscopy (EIS) shows the ratio of Cr0.2Co2.8O4 to MoO3 strongly affects the catalytic performance in both oxygen evolution and methanol oxidation reactions. The observed enhancement in electrocatalytic activity can be ascribed to the combined impact of the two materials facilitating the electron transfer process by increasing the number of active sites and thereby. Amongst different synthesized electrocatalysts the one with 1:4 composition exhibited not only the highest Specific activity of 2.5 × 103 mA cm−2/g at 700 mV towards OER but also retains maximum current showing their highest stability.

Preparation of Highly Stable DUT-52 Materials and Adsorption of Dichromate Ions in Aqueous Solution.

Highly stable DUT-52 materials were synthesized by the hydrothermal method and well-characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). In order to systematically study the adsorption of dichromate ions in aqueous solution by the DUT-52 materials, a single factor experiment, kinetic experiment, thermodynamic experiment, competition ion experiment, and material regeneration experiment were designed. Based on the H-bond interaction between the dichromate ions and the H atoms of a NDC2– ligand, the DUT-52 materials showed a maximum removal rate of 96.4% and a maximum adsorption capacity of 120.68 mg·g–1 with excellent selective adsorption and material regeneration. In addition, the process of adsorption of dichromate ions by the DUT-52 materials is in accordance with the pseudo second-order kinetics and Langmuir models, and the adsorption mechanism and the important role of the H-bond interaction were reasonably explained using the XPS pattern and theoretical calculation. Accordingly, DUT-52 can be regarded as a multifunctional material for efficiently removing dichromate ions from the wastewater.

In Situ Induced Surface Reconstruction of Single-Crystal Lithium-Ion Cathode Toward Effective Interface Compatibility.

LiNixCoyMn1-x-yO2 (x ≥ 0.5) layered oxide materials are generally considered as one of the most prospective candidates for lithium-ion battery (LIBs) cathodes due to their high specific capacity and working voltage. However, surface impurity species substantially degrade the electrochemical performance of LIBs. Herein, surface reconstruction from layered structure to disordered layer and rock-salt coherent region together with a uniform Li2CO3-dominant coating layer is first in situ constructed on the single-crystal LiNi0.5Co0.2Mn0.3O2 (NCM) material by a simple water treatment procedure. The unique surface structure is elucidated by Ar-sputtering-assisted X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (spherical aberration-corrected-scanning transmission electron microscopy (STEM), high-resolution transmission electron microscopy (HRTEM), and TEM). Meanwhile, neutron powder diffraction (NPD) indicates that the antisite defect concentration is mitigated in the treated materials. The modified samples display superior cycle stability with a capacity retention of up to 87.5% at 1C after 300 cycles, a high rate capacity of 151 mAh g-1 at 5C, an elevated temperature (45 °C) cycling property with 80% capacity retention (4.5 V), and improved full-cell performance with 91% after 250 cycles at 1C. Importantly, postmortem examination on the cycled cathodes by time-of-flight secondary-ion mass spectroscopy (TOF-SIMS), XPS, TEM, and X-ray diffractometer (XRD) pattern further demonstrate that these results are mainly attributed to the thin cathode electrolyte interface (CEI) film and low solubility of transition-metal ions. Therefore, this expedition provides an opportunity to construct an effective armor for the interface compatibility and stability of LIBs.

Effect of the Fluorine Substitution for –OH Group on the Luminescence Property of Eu3+ Doped Hydroxyapatite

In this study, different fluoridated hydroxyapatite doped with Eu3+ ion nanoparticles were prepared by the hydrothermal method. The relationship between luminescence enhancement of Eu3+ ions and a fluorine substitution ratio for hydroxyl group in hydroxyapatite was discussed. Moreover, the effect of fluorine substitution for a hydroxyl group on phase composition, crystallinity, and crystal size was studied. Phase composition and chemical structures were identified by X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) Spectroscopy analyses. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) patterns were performed to analyze the morphology and particle size. X-ray Photoelectron Spectroscopy (XPS) patterns were observed to analyze fluorine substitution for the hydroxyl group and chemical state of Eu3+ ions in fluoridated hydroxyapatite. The results of these experiments indicated that the samples with a different fluorine substitution ratio were prepared successfully by maintaining the apatite structure. With an increasing fluorine substitution ratio, the morphology maintained a rod-like structure but the aspect ratio tended to decrease. XPS patterns displayed that the fluorine replaced the hydroxyl group and brought environmental variation. The fluorine ions could affect the crystal field environment and promote luminescence conversion. There was a linear relationship between the fluorine substitution ratio and luminescence enhancement.

Automobile exhaust gas purification material based on physical adsorption of tourmaline powder and visible light catalytic decomposition of g-C3N4/BiVO4

Pure g-C3N4, g-C3N4/BiVO4, and g-C3N4/BiVO4/tourmaline powder composite photocatalytic materials were prepared via the methods of one-step calcination and bi-dispersion direct mixing, and their automobile exhaust gas purification efficiencies were tested. Four types of samples (g-C3N4, BiVO4, g-C3N4/BiVO4, and g-C3N4/BiVO4/tourmaline powder) were characterized using various methods, such as X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller analysis, Fourier transform infrared spectroscopy, ultraviolet–visible light-near infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). The test results showed that the photocatalysis composite exhibited the highest purification efficiency when the mass ratio of g-C3N4/BiVO4 was 2 and the load of tourmaline powder was 25 wt%. The hydrocarbon, CO, and NO purification rates of the g-C3N4/BiVO4/tourmaline powder were 1.73, 1.74, and 2.52 times higher than those of pure g-C3N4, respectively. It was concluded from the XPS patterns that the heterojunction formed by g-C3N4 and BiVO4 promoted the separation of electron-hole pairs and charge migration, which enhanced the photocatalytic degradation of exhaust gas under visible light. Moreover, tourmaline powder increased the physical adsorption capacities of the composite materials for automobile exhaust by releasing several negative ions, thus considerably increasing their decomposition efficiencies. This study is of immense significance to the management of urban automobile exhaust pollution.

Influence of benzotriazole on electroplated Cu films and interfacial microstructure evolution of solder joints

Benzotriazole (BTA), a nitrogen-containing heterocyclic compound, was employed as a leveler to prepare Cu film. During electroplating, the concentrations of BTA were 0, 10, 20, 50, and 100 ppm. After electroplating, the Cu substrates were soldered by dip soldering with Sn3.0Ag0.5Cu (SAC305) solder at 250 °C for 10 s, then isothermal aging was conducted at 180 °C up to 240 h. The electroplated Cu (EPC) films and solder joints were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and uniaxial micro-force test system. Experimental results showed that high concentration BTA (≥ 50 ppm) would lead to a reduction in the thickness of the EPC film. The surface roughness of the EPC film increased at first and then decreased with increasing BTA concentration. Additionally, the XPS patterns indicates that the Cu(I)-BTA complex could form on the copper surface. After soldering and thermal aging, for sample with low concentration of BTA (≤ 20 ppm), Cu–Sn intermetallic compound (IMC) was observed between the SAC305 solder and substrate. However, when the BTA concentration increased to 50 and 100 ppm. The Au coating and the Ni coating on the Kovar substrate would participate in interfacial reaction during the dip soldering process, resulting in the formation of single (Ni, Au, Cu)6Sn5 layer. The growth rate of the (Ni, Au, Cu)6Sn5 IMC was significantly lower than that of the Cu–Sn IMCs. Moreover, the incorporated impurities segregated and the doping of Au and Ni resulted in the decrease of shear strength at first and then increase as the BTA concentration increased.

MnO2 Nanowire-CeO2 Nanoparticle Composite Catalysts for the Selective Catalytic Reduction of NO x with NH3.

MnO x-based catalysts have been applied to the selective catalytic reduction of NO x with ammonia (NH3) owing to their high NO x removal efficiency and catalytic stability. In general, the fabrication of a variety of nanomaterials in a complex structure requires complicated processes, including heat treatment and a series of cleaning steps. In addition, MnO2 which has diverse polymorphs, exhibits different catalytic effects depending on its crystalline structure. Among them, synthesizing the ε-MnO2 phase, which functions as a nanocatalyst, has been the most difficult and has hardly been reported. Here, we report the synthesis of heterostructured composite nanocatalysts consisting of ε-MnO2 nanowires (NWs) and CeO2 nanoparticles (NPs) by applying pulsed currents sequentially. This method drastically simplifies the overall process compared to the conventional techniques. Through X-ray diffraction and transmission electron microscopy, it was confirmed that 2-3 nm of CeO2 NPs were formed on the surfaces of the ε-MnO2 NWs. The de-NO x efficiency of the nanocatalysts was analyzed in terms of content variation, specific surface area, and the elemental chemical state of the surface. A ceramic filter containing the nanocatalysts shows a high catalytic activity over the broad operating temperature range 100-400 °C. In the low-temperature region, ε-MnO2 plays a major role in determining the catalytic property, which is consistent with the Brunauer-Emmett-Teller (BET), H2 temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) results. On the other hand, in the high-temperature region, the efficiency increases gradually as the content of CeO2 increases. The H2 TPR, NH3-temperature-programmed desorption, and XPS patterns reveal why the composite exhibits such superior characteristics in the temperature range mentioned above.

CeVO4-coated LiNi0.6Co0.2Mn0.2O2 as positive material: towards the excellent electrochemical performance at normal and high temperature

The CeVO4-coated LiNi0.6Co0.2Mn0.2O2 (NCM 622) cathode materials are successfully synthesized by hydrothermal method. The structure, morphology and electrochemical properties of the surface modified NCM 622 materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and constant current charge and discharge test. The SEM images and XPS patterns show that nanosized CeVO4 layer is uniformly coated on the surface of NCM 622 active material. Furthermore, the electrochemical performance of all the CeVO4-coated NCM 622 samples are improved significantly. 3 wt% of CeVO4-coated NCM 622 cathode material exhibits specific capacity of 146.1 mAh g-1 and excellent capacity retention (89.63%) between 2.8 and 4.3 V after 100 cycles at elevated temperature (60 °C). The alternating current impedance and cyclic voltammetry tests show that the CeVO4 coating can reduce the electrode polarization and enhance the electrochemical activity of cathode materials.

Different oxidation routes for lattice oxygen recovery of double-perovskite type oxides LaSrFeCoO6 as oxygen carriers for chemical looping steam methane reforming

Double-perovskite type oxide LaSrFeCoO6(LSFCO) was used as oxygen carrier for chemical looping steam methane reforming (CL-SMR) due to its unique structure and reactivity. Two different oxidation routes, steam-oxidation and steam-air-stepwise-oxidation, were applied to investigate the recovery behaviors of the lattice oxygen in the oxygen carrier. The characterizations of the oxide were determined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR) and scanning electron microscopy (SEM). The fresh sample LSFCO exhibits a monocrystalline perovskite structure with cubic symmetry and high crystallinity, except for a little impurity phase due to the antisite defect of Fe/Co disorder. The deconvolution distribution of XPS patterns indicated that Co, and Fe are predominantly in an oxidized state (Fe3+ and Fe2+) and (Co2+ and Co3+), while O 1s exists at three species of lattice oxygen, chemisorbed oxygen and physical adsorbed oxygen. The double perovskite structure and chemical composition recover to the original state after the steam and air oxidation, while the Co ion cannot incorporate into the double perovskite structure and thus form the CoO just via individual steam oxidation. In comparison to the two different oxidation routes, the sample obtained by steam-oxidation exhibits even higher CH4 conversion, CO and H2 selectivity and stronger hydrogen generation capacity.

Effect of Mg Substitution in the Structural and Electrochemical Properties of Li2MnO3

The revolutionary concept of energy storage is constantly changing due to the increasing demand of high energy density devices. However, issues such as safety, high temperature performance, cost, and environmental concerns need to be addressed, especially for the high power applications. Among the cathode materials investigated, lithium manganese oxides have been exploited due to the abundance of Mn in earth, low toxicity and safety. In this family of oxides, Li2MnO3 possess monoclinic structure having c2/m space group symmetry with a layered arrangement of Li[Li1/3Mn2/3]O2, thus resembling the ideal layered structure of LiCoO2. Li2MnO3 is known to be electrochemically inactive due to the presence of Mn in tetravalent oxidation state. Substitutions of ions in the structure allow possible reduction of the valance state of manganese and electrochemically activating the material. In the present study, we investigated the electrochemical and structural properties of Li2MnO3at room temperature by partially substituting lithium with magnesium using the Pechini synthesis method. Li2MnO3, Li1.5Mg0.25MnO3, Li1.0Mg0.50MnO3 and Li0.5Mg0.75MnO3 compositions were prepared by the Pechini synthesis method. These substitutions were chosen balancing the charge of the cations. For the individual compounds the synthesis was carried out using lithium nitrate [LiNO3], manganese nitrate [Mn(NO3)2], magnesium nitrate [Mg(NO3)2•6H2O], ethylene glycol [C2H6O2] and citric acid [H3C6H5O7] as precursors materials.The molar ratio of M:CA:EG used was 1:1.2:1.2, where M is the sum of all metal ions. Stoichiometric ratios of the metals corresponding to each composition were measured and dissolved in deionized water (H2O) along with citric acid (CA), which behaves as a chelating reagent. The resulting compound was placed in an oven at 130oC for 24 h to complete the drying process, followed by annealing of the powder at 750oC for 8h in air to obtain desire phase. The final heat treated powder samples were mixed with polyvinylidenefloride (PVDF) and carbon black in the wt % ratio of 80:1010, respectively. A slurry paste was prepared using 1-methyl 2-pyrolidone as solvent and was coated on Al foil substrates to form a homogeneous layer. Electrodes were punched out for the fabrication of 2032 coin cells. Metallic Li was used as the counter electrode along with 1.2M LiPF6in EC:DMC (1:1) as electrolyte. The charge and discharge analysis was performed at 10mAh/g within a potential window of 2.0V- 4.8V. The structural phase formation of the materials and presence of any crystalline impurities in the compounds were studied with X-ray diffraction (XRD). Figure 1 shows XRD patterns for Li2MnO3, Li1.5Mg0.25MnO3, Li1.0Mg0.50MnO3 and Li0.5Mg0.75MnO3 synthesized at 7500C for 8h. The formation of single phase material was confirmed for Li2MnO3 and a combination of monoclinic/spinel phases (Li2-xMn1-yMgx+yO3+z) was observed for the Mg-substituted compounds. X-ray photoelectron spectroscopy (XPS) was used to study the valance state of the manganese ion after magnesium substitution. Figure 2 shows XPS pattern for Mn 2p of pristine and partially Mg-substituted samples. A shift to a lower binding energy is observed for Li1.0Mg0.50MnO3 and Li0.5Mg0.75MnO3, indicating a decrease in the tetravalent state of manganese. Therefore, an improvement in electrochemical cycling performance is expected. Preliminary results shown in Figure 3 indicate that partial Mg-substitution enhances the cycleability of Li2MnO3 and increase the capacity to ~90mAh/g. All the electrochemical performance of Li2MnO3, Li1.5Mg0.25MnO3, Li1.0Mg0.50MnO3 and Li0.5Mg0.75MnO3 cathodes will be presented in detail. Figure 1

Mechanism of Hg0 oxidation in the presence of HCl over a commercial V2O5–WO3/TiO2 SCR catalyst

Experiments were conducted in a fixed-bed reactor containing a commercial V2O5/WO3/TiO2 catalyst to investigate mercury oxidation in the presence of HCl and O2. Mercury oxidation was improved significantly in the presence of HCl and O2, and the Hg0 oxidation efficiencies decreased slowly as the temperature increased from 200 to 400°C. Upon pretreatment with HCl and O2 at 350°C, the catalyst demonstrated higher catalytic activity for Hg0 oxidation. Notably, the effect of pretreatment with HCl alone was not obvious. For the catalyst treated with HCl and O2, better performance was observed with lower reaction temperatures. The results showed that both HCl and Hg0 were first adsorbed onto the catalyst and then reacted with O2 following its adsorption, which indicates that the oxidation of Hg0 over the commercial catalyst followed the Langmuir–Hinshelwood mechanism. Several characterization techniques, including Hg0 temperature-programmed desorption (Hg-TPD) and X-ray photoelectron spectroscopy (XPS), were employed in this work. Hg-TPD profiles showed that weakly adsorbed mercury species were converted to strongly bound species in the presence of HCl and O2. XPS patterns indicated that new chemisorbed oxygen species were formed by the adsorption of HCl, which consequently facilitated the oxidation of mercury.

Electrochemical and Structural Properties of Rh Substituted Li2MnO3

Commercial realization of rechargeable Li-ion batteries has revolutionized portable electronic industry, especially microelectronics in recent years. However, issues such as safety, high temperature performance, cost, and environmental concerns need to be addressed, especially for high power applications. Among the cathode materials investigated, lithium manganese oxides have been exploited due to the abundance of Mn in earth, low toxicity and safety. In this family of oxides, Li2MnO3 possess monoclinic structure having c2/m space group symmetry with a layered arrangement of Li[Li1/3Mn2/3]O2, thus resembling the ideal layered structure of LiCoO2. Li2MnO3 is known to be electrochemically inactive due to the presence of Mn in tetravalent oxidation state. Substitutions of ions in the structure allow the reduction of the valance state of manganese, electrochemically activating the material. In the present study, we investigated the electrochemical and structural properties of Li2MnO3at room temperature by partially substituting Mn site with rhodium via the solid state synthesis method. Li2MnO3, Li2RhO3 and Li2Mn0.5Rh0.5O3 compositions were prepared by a solid state synthesis method. For the individual compounds the synthesis was carried out using lithium carbonate [Li2CO3], manganese oxide [MnO2] and rhodium chloride [RhCl3] as precursor materials. Stoichiometric ratios of the metals corresponding to each composition were measured and carefully ground using a pestle and mortar for 1 hour. The resulting mixture was calcined in air at a ramp rate of 100oC h-1 to a final temperature of 600oC for Li2CO3/MnO2, 850oC for Li2CO3/RhCl3 and 900oC for Li2CO3/MnO2/RhCl3.The final heat treated powder samples were mixed with polyvinylidenefloride (PVDF) and carbon black in the wt % ratio of 80:10:10, respectively. A slurry paste was prepared using 1-methyl 2-pyrolidone as solvent and was coated on Al foil substrates to form a homogeneous layer. Electrodes were punched out for the fabrication of 2032 coin cells. Metallic Li was used as the counter electrode along with 1.2M LiPF6in EC:DMC (1:1) as electrolyte. The charge and discharge analysis was performed at 10mAh/g within a potential window of 2.0V- 4.8V. The structural phase formation of the materials and presence of any crystalline impurities in the compounds were studied with X-ray diffraction (XRD). Figure 1 shows XRD spectra for Li2MnO3 600o C -8h, Li2Mn0.5Rh0.5O3 900o C -24h and Li2RhO3 850o C-24h. X-ray photoelectron spectroscopy (XPS) was obtained to study the valance state of the manganese ion after rhodium substitution. Figure 2 shows XPS pattern for Mn 2p of pristine and partially Rh-substituted samples. The Mn 2p1/2 and Mn 2p3/2 peaks for Li2MnO3 are 654.25eV and 642.50eV, respectively, being in agreement with those reported in literature [3]. A slightly shift to a lower binding energy is observed for Li2Mn0.5Rh0.5O3, indicating a decrease in the tetravalent state of manganese. Therefore, an improvement in electrochemical performance is expected. Preliminary results shown in Figure 3 indicate that partial Rh-substitution enhances the cycleability of Li2MnO3 and increases the capacity by 64mAh/g. Electrochemical performance of Li2MnO3, Li2RhO3 and Li2Mn0.5Rh0.5O3 cathodes will be presented in detail. Figure 1

Synthesis, Characterization and Electrochemical Performance for a Series of Al- Substituted Li2MnO3

Lithium manganese oxides have been exploited due to the abundance of Mn in Earth, low toxicity and safety. In this family of oxides, LiMnO2 and LiMn2O4 have shown promising electrochemical features, such as high discharge capacity and high operating voltage, respectively. However, these materials suffer from serious structural changes after certain number of cycles due to the presence of Mn3+, which is known to be a Jahn-Teller active ion [1]. Side reactions such as 2Mn3+ → Mn4+ + Mn2+, also lead to battery failure upon cycling, as Mn2+ is known to be soluble in non-aqueous electrolytes. Li2MnO3 belongs to the same family of oxide materials but is more stable due to the presence of Mn4+ instead of Mn3+ as in LiMnO2 or LiMn2O4. Li2MnO3 possess monoclinic structure having c2/m space group symmetry with a layered arrangement of Li[Li1/3Mn2/3]O2. The drawback of Li2MnO3 is the presence of Mn in +4 oxidation state, which makes the material electrochemically inactive. However, it can be made electrochemically active by extracting lithium and oxygen simultaneously from the structure by chemical or electrochemical means [2]. Electrochemical activation has been achieved after exposing the electrode to potentials higher than 4.5 V vs. Li0/Li+, which causes the partial removal of lithium and oxygen from the structure. This process leads to the rearrangement of the ions and hence vacancies in the host structure for the reversible intercalation of lithium. In the present study, we aim to improve manganese dissolution in Li2MnO3 using aluminum substitution at the Lithium site. Li2MnO3 and Al-substituted materials were prepared by sol-gel Pechini method. For the individual compounds the synthesis was carried out using lithium nitrate [LiNO3], manganese nitrate [Mn(NO3)2], aluminum nitrate [Al(NO3)3•9H2O], ethylene glycol [C2H6O2] and citric acid [H3C6H5O7] as precursors materials.The molar ratio of M:CA:EG used was 1:1.2:1.2, where M is the sum of all metal ions. Stoichiometric ratios of the metals corresponding to each composition were measured and dissolved in deionized water (H2O) along with citric acid (CA), which behaves as a chelating reagent. The resulting compound was placed in an oven at 130oC for 24 h to complete the drying process, followed by annealing of the powder at 750oC for 8h in air to obtain desire phase. The obtained powder samples were mixed with polyvinylidene (PVDF) and carbon black in the wt % ratio of 80 : 10 :10, respectively. Slurry was prepared using 1-methyl 2-pyrolidone as solvent and was coated on Al foil substrates to form a homogeneous electrode. Electrodes were punched out for the fabrication of 2032 coin cells, where Li was used as a counter electrode along with 1.2M LiPF6 in EC:DMC (1:1) as electrolyte. The charge and discharge analysis was performed using 10mAh/g within a potential window of 2.8V- 4.8V. The structural phase formation of the materials and presence of any crystalline impurities in the compounds were studied with X-ray diffraction (XRD). Figure 1 shows XRD spectra for (a) Li2MnO3, (b) 25% Li, (c) 50% Li and (d) 25% Li. Phase formation for the samples was obtained at 750C-8h without impurity. X-ray photoelectron spectroscopy (XPS) was obtained to study the valance state of the manganese ion after aluminum substitution. Figure 2 shows XPS pattern for Mn 2p of the samples. The Mn 2p1/2 and Mn 2p3/2 peaks for Li2MnO3 are 654.35eV and 642.55eV, respectively, being in agreement with those reported in literature [3]. A slightly shift to a lower binding energy is observed for 50% Li and 25% Li, indicating a decrease in the tetravalent state of manganese. Therefore, an improvement in electrochemical performance is expected. In the case of 75% Li, the Mn 2p peaks are shifted to the left, demonstrating a considerably increase in the binding energy which is indicative of a higher valance state. Preliminary results shown in Figure 3 indicate that Al-substitution for 75% of Lithium enhances the cycleability of Li2MnO3 and increase the capacity by 60mAh/g. Electrochemical performance of the pristine and Al-substituted cathodeswill be presented in detail.

Characterization of cerium dioxide nanoparticles prepared by supercritical water oxidation

CeO2 nanoparticles with high purity and crystallinity were prepared by a continuous supercritical water oxidation (SCWO) reaction. The phase composition, microstructure, and morphology of the prepared CeO2 particles were characterized by X-Ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), BET specific surface area (BET), and X-ray photoelectron spectroscopy (XPS). The size distribution of the particles is narrow with an average particle size between 10 and 13nm; the diameter decreased gradually as the Ce(NO3)3·6H2O concentration in the preparation increased. The BET results show an increase in the products׳ specific surface area as the Ce(NO3)3·6H2O concentration increased, with an average surface area of 48m2g−1. SEM micrographs reveal that the CeO2 particles are spherical, and that higher Ce(NO3)3·6H2O concentrations are conducive to the formation of smaller particles. However, excess Ce(NO3)3·6H2O caused serious agglomeration, due to the higher surface energy. XPS patterns indicate that Ce(III) was almost completely oxidized to Ce(IV) in the reaction, and that the binding capacity of Ce–O reduced gradually with increasing concentrations of Ce(NO3)3.

Effect of Al and Mg Doping on the Electrochemical Performance of Pure Li2MnO3

In the last three decades, lithium manganese oxides have been exploited as potential cathode materials for lithium ion batteries. In this family of oxides, LiMnO2 possess very high discharge capacity while LiMn2O4 possess high operating voltage. These materials suffer from serious structural change after certain number of cycles due to the presence of Mn3+ ion, which is known to be a Jahn-Teller active ion. Side reactions such as 2Mn3+ → Mn4+ + Mn2+, also lead to the battery failure upon cycling, as Mn2+ is known to be soluble in the non-aqueous electrolytes. Li2MnO3 belongs to the same family of oxide materials but is more stable due to the presence of Mn4+ instead of Mn3+ as in LiMnO2 or LiMn2O4. Li2MnO3 possess monoclinic structure having c2/m space group symmetry with a layered arrangement of Li[Li1/3Mn2/3]O2. Li2MnO3 is known to be electrochemically inactive because of the presence of Mn in +4 oxidation state which cannot be oxidized further. However, it can be made electrochemically active by extracting lithium and oxygen simultaneously from the structure by chemical or electrochemical means [1]. It has been reported that potentials higher than 4.5V causes the partial removal of Li and O from the structure leading to electrochemical activation[2]. This activation lead to the rearrangement of the ions and hence vacancies in the host structure for the reversible intercalation of Li. In the present study we aim to improve manganese dissolution in Li2MnO3using aluminum and magnesium doping at the Li site. Li2MnO3, LiAlMnO3 and LiMgMnO3 were prepared by sol-gel Pechini method. For the individual compounds the synthesis was carried out using lithium nitrate [LiNO3], manganese nitrate [Mn(NO3)2], aluminum nitrate [Al(NO3)3•9H2O], magnesium nitrate [Mg(NO3)2•6H2O], ethylene glycol [C2H6O2] and citric acid [H3C6H5O7] as precursors materials.The molar ratio of M:CA:EG used was 1:1.2:1.2, where M is the sum of all metal ions. Stoichiometric ratios of the metals corresponding to each composition were measured and dissolved in deionized water (H2O) along with citric acid (CA), which behaves as a chelating reagent. The resulting compound was placed in an oven at 130◦ C for 24 h to complete the drying process, followed by annealing of the powder at 750oC for 8h in air to obtain desire phase. The obtained powder samples were mixed with polyvinylidene (PVDF) and carbon black in the wt % ratio of 80 : 10 :10, respectively. Slurry was prepared using 1-methyl 2-pyrolidone as solvent and was spray coated on Al foil substrates to form a homogeneous electrode. Electrodes were punched out for the fabrication of 2032 coin cells, where Li was used as a counter electrode along with 1.2M LiPF6in EC:DMC (1:1) as electrolyte. The charge and discharge analysis was performed using 10mAh/g within a potential window of 2.0V-4.8V. The structural phase formation of the materials and presence of any crystalline impurities in the compounds was studied with X-ray diffraction (XRD). Figure 1 shows XRD spectra for (a)Li2MnO3, (b)LiAlMnO3 and (c)LiMgMnO3. Phase formation for the samples was obtained at 750C-8h. In the case of LiAlMnO3, the characteristic peak between 20-25 degrees vanishes, possibly due to the Mn site substitution by Al. X-ray photoelectron spectroscopy (XPS) were obtained to study the valance state of the manganese ion after aluminum and magnesium doping. Figure 2 shows XPS pattern for Mn 2p of the samples. The Mn 2p1/2 and Mn 2p3/2 peaks for Li2MnO3 are 654.15eV and 642.45eV, respectively, being in agreement with those reported in literature[3]. A slightly shift to the right is observed for LiAlMnO3 pattern, indicating a decrease in the tetravalent state of manganese. Therefore, an improvement in electrochemical performance is expected. In the case of LiMgMnO3 the Mn3/2 peak is shifted to the left, with an increase of approximately 0.1 eV, demonstrating a considerably increase in the binding energy indicative of a higher valance state. Preliminary results, shown in Figure 3, indicates that Al-doping enhances the cyclability of Li2MnO3and increase the capacity by 30mAh/g. The Mg-doped cells also have better cycle stability as compared to the pristine material, but the capacity faded by ~15mAh/g. Electrochemical performance of the pristine, Al-doped and Mg-doped cells will be presented in detail.

Structural and spectroscopic characteristics of terbium hydroxide/oxide nanorods and plates

Tb(III) complexes with morphologies of nanorods and plates were prepared by a hydrothermal method. Post-thermal treatment was then applied to obtain Tb(IV) oxides with the same morphologies. Their nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) crystallography, UV–vis absorption, FT-IR, Raman, X-ray photoelectron spectroscopy (XPS), and photoluminescence imaging spectroscopy. Strong photoluminescence signals between 470 and 720nm were attributed to the 5D4→7FJ (J =6, 5, 4, 3) transitions of Tb(III). The Tb(III) complex and Tb(OH)3 were found to be converted to Tb(IV) oxide upon thermal annealing at 700°C. The oxidation state of Tb(III) was changed to non-luminescent Tb(IV), as clearly evidenced by UV–vis absorption, change in sample color, XPS, photoluminescence and XRD patterns.

The fabrication and characterization of TiO2 nanospheres with high visible light photocatalytic activity by direct carbonization of block copolymer templates

Titanium dioxide nanospheres with visible light photocatalytic activity were synthesized via a sol–gel approach using an amphiphilic diblock copolymer, polystyrene-block-polyacrylic acid (PS-b-PAA), as template at room temperature in toluene. The morphology and crystal structure of synthesized TiO2 nanospheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD pattern of TiO2 nanospheres revealed the crystal transformation, resulting in the change of photocatalytic activity. The XPS pattern revealed the formation of Ti–O–C bonds upon carbonization, as a result of visible light absorption. The TiO2 nanospheres had diameters ranging from 200 to 500 nm. The photodegradation experiments showed that such TiO2 nanospheres had pronounced visible-light photocatalytic activity.

Further investigation of Ce0.9Sr0.1Cr0.5Fe0.5O3±δ as anode for solid oxide fuel cell fuelled with H2S

Ce0.9Sr0.1Cr0.5Fe0.5O3±δ as a potential anode for solid oxide fuel cell has been described in previous work, such as the conductivities in H2 and H2S, electrochemical properties and longevity of the cell with fuelled 3% H2 or 5% H2S, et al. In the further research, an interesting phenomenon is found that the mass increases when temperature rising over 680°C in TG–DTA. The reason is the formation of nitrides by the analysis of thermodynamics calculation. Therefore, the synthesized process is optimized to reduce and cool down in 100% H2 for avoiding forming nitrides. Then, the fluorite structure Ce0.9Sr0.1Cr0.5Fe0.5O4±δ (CSCFe) is obtained. Thermal expansion coefficient (TEC) shows that anode CSCFe and electrolyte Ce0.8Sm0.2O1.9 (SDC) have a good matching. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) are used to describe the electron changes of every element in CSCFe before and after cell test. The results indicate that some electrons transfer from Ce3+ to Fe3+, which causes the intensity of EPR weaker, and increases the electron conductivity of CSCFe. After the cell operating in 5% H2S, XPS patterns indicate that some lattice oxygen migrate from the bulk to the surface releasing oxygen vacancies. The triple phase boundary (TPB) of the reaction between H2S and O2− is magnified, and the efficiency of the single cell is enhanced. Compared the electrochemical properties of the cell which fluorite structure Ce0.9Sr0.1Cr0.5Fe0.5O4±δ as anode with previous perovskite structure Ce0.9Sr0.1Cr0.5Fe0.5O3±δ as anode, the results demonstrate that the former is more suitable as anode for SOFC fuelled with H2S due to more content of Ce3+ in the material.

Preparation and photocatalytic activity of La 3+ and Eu 3+ co-doped TiO 2 nanoparticles: photo-assisted degradation of methylene blue

Rare earth ions La 3+ and Eu 3+ co-doped TiO 2 photocatalyst (La-Eu/TiO 2) was prepared by sol-gel method, and characterized by various techniques such as X-ray diffraction (XRD), specific surface area and porosity (BET and BJH), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the La-Eu/TiO 2 was evaluated by the degradation of methylene blue (MB) under UV light irradiation. The catalyst had a relatively uniform particle diameter distribution in the range of 40–60 nm. When calcining at 600°C, the XRD patterns of La-Eu/TiO 2 indicated the anatase phase, while the XPS patterns showed the Ti 4+, La 3+ and Eu 3+ ions existence. The DRS spectra showed red shift in the band-gap transition. The experimental results of MB degradation demonstrated that the photocatalytic activity of La-Eu/TiO 2 was significantly enhanced due to better separation of photogenerated electron-hole pairs.

One-step synthesis of manganese dioxide/polystyrene nanocomposite foams via high internal phase emulsion and study of their catalytic activity

This paper is devoted to the preparation of manganese dioxide/polystyrene nanocomposite foams via a novel and facile one-step method using high internal phase emulsion as templates. Scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analyses (TGA) techniques were used to characterize the resulting composites. SEM measurements revealed the porous network structure, the average pore diameters ranged from 3.8 to 30.4 μm. The presence of manganese dioxide was identified by XPS pattern, XRD, pattern and FT-IR spectra of the resulting composites. The TGA thermograms showed that the maximum content of manganese dioxide in the nanocomposite foams reached about 15.5%. The applications of the nanocomposite in the oxidative degradation of methylene blue exhibited good catalytic activity in the presence of H2O2 as an oxidant.