O1s Binding Energy Research Articles

Adsorption removal of Co(II) from waste-water using graphene oxide

Graphene oxide (GO), having unique physicochemical properties, is widely used in various applications. GO prepared by a modified Hummer's method was characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and BET surface area analysis. The adsorption properties of the prepared GO towards Co(II) was elucidated by the batch adsorption method, indicating the maximum adsorption of Co(II) in a broad pH range of 5.0 to 8.0. The batch adsorption kinetics results suggest that the adsorption could be described as a rate-limiting pseudo-second-order process. To the adsorption equilibrium data applied the Langmuir, Freundlich and Temkin adsorption isotherm models for an evaluation of adsorption capacity and relevant mechanism. These results revealed that the adsorption was occurring through physical and chemical interactions between Co(II) and oxygen-containing surface functional groups, –C–O and –CO, and the π–π bonds electrons (–CC–, –CO) of GO. XPS (binding energy and shape of O1s and C1s) analysis of the GO material confirmed loading with Co(II). The maximum adsorption capacity was 21.28mg/g of Co(II) at pH5.5 and 298K with 1.0g/L GO, comparable to the reported adsorbents. Moreover, GO was precipitated upon loading with metal ions. Finally, the obtained results demonstrated the potential of the GO solid adsorbent for pre-concentration of trace heavy metals from waste effluents.

Insights into the Electronic Structure of the Oxygen Species Active in Alkene Epoxidation on Silver

Extensive density functional theory calculations of the O1s binding energies, adsorption energies, and the experimentally measured in situ X-ray photoelectron spectra of oxygen on silver are reported in an effort to clarify which species are present during ethylene epoxidation. We find that the O1s binding energy of an oxygen adatom increases near linearly with its adsorption energy due to the ionic nature of the Ag/O interaction. Thus, contrary to widespread assignments, a weakly bound oxygen adatom does not account for the electrophilic species with an O1s binding energy of 530 eV that is thought to be active in ethylene epoxidation. Instead, we show that the only species with O1s binding energies near 530 eV are covalently bound, which we find in our calculations, for example, when hydrogen or carbon are present.

Effect of substrate surface pretreatment and annealing treatment on morphology, structure, optical and electrical properties of sputtered ZnO films

ZnO films were deposited on glass substrates at room temperature by RF magnetron sputtering method. Prior to the deposition, the glass substrates were pretreated with Al target in Ar or Ar/O2 ambient by DC magnetron sputtering. After pretreatment, the glass substrate are still very transparent and no metallic luster. AFM shows that RMS has a very slight change. XPS shows that no Al–O bonds exist in ZnO films. Cauchy fitting model shows that no Al or Al2O3 thin layer is formed between thin film and glass substrate. However, the pretreatment forms some isolated Al or Al2O3 grains and changes the micro-structure of substrate slightly, which lead to different lattice, stress and properties of ZnO films. Interestingly, combining the pretreatment and annealing treatment, the sum of 2θ or lattice constant c between as-grown and annealed samples is equal. The average transmission of all samples is over 85% in the wavelength range of 400–1000nm. The band gap energies of all samples are in range of 3.23–3.26eV. According to PL, three main blue emission peaks located at about 437–438, 444 and 456nm were observed in the S1 and S2 with the pretreatment. However, the wavelength range of the blue peaks of S3 without pretreatment was observed to narrow down, and peaks are located at about 444, 450 and 456nm. The lowest resistivity and highest carrier concentration of S1 are 5.29∗10−5Ωcm and 3.9805∗1022cm−3 respectively. The conductivity of ZnO films can be converted from n-type to p-type by different substrate surface treatment. It is noteworthy that with the unit cell elongation along c-axis, compressive stress and mass difference between as-grown and annealed films increases, while refractive index and PL intensity decreases. The lattice constant c and compressive stress are mainly effect factors of thermal stability and optical properties of ZnO film. The binding energy (BE) of Zn2p3/2 and Zn2p1/2 of as-grown and annealed S1 are 1019.4 and 1019.3, and 1042.5 and 1042.4eV, respectively. The BEs of O1s of as-grown and annealed S1 are relatively low, 529.2 and 528.9eV, respectively.

Thermodynamic and spectroscopic properties of oxygen on silver under an oxygen atmosphere.

We report on a combined density functional theory and the experimental study of the O1s binding energies and X-ray Absorption Near Edge Structure (XANES) of a variety of oxygen species on Ag(111) and Ag(110) surfaces. Our theoretical spectra agree with our measured results for known structures, including the p(N× 1) reconstruction of the Ag(110) surface and the p(4 × 4) reconstruction of the Ag(111) surface. Combining the O1s binding energy and XANES spectra yields unique spectroscopic fingerprints, allowing us to show that unreconstructed atomic oxygen is likely not present on either surface under equilibrium conditions at oxygen chemical potentials typical for ethylene epoxidation. Furthermore, we find no adsorbed or dissolved atomic species whose calculated spectroscopic features agree with those measured for the oxygen species believed to catalyze the partial oxidation of ethylene.

Batch and column sorption of arsenic onto iron-impregnated biochar synthesized through hydrolysis

Iron (Fe)-impregnated biochar, prepared through a novel method that directly hydrolyzes iron salt onto hickory biochar, was investigated for its performance as a low-cost arsenic (As) sorbent. Although iron impregnation decreased the specific surface areas of the biochar, the impregnated biochar showed much better sorption of aqueous As (maximum sorption capacity of 2.16 mg g−1) than the pristine biochar (no/little As sorption capacity). Scanning electron microscope equipped with an energy dispersive spectrometer and X-ray diffraction analysis indicated the presence of crystalline Fe hydroxide in the impregnated biochar but no crystal forms of arsenic were found in the post-sorption biochar samples. However, large shifts in the binding energy of Fe2p, As3d, O1s and C1s region on the following As sorption indicated a change in chemical speciation from As(V) to As(III) and Fe(II) to Fe(III) and strong As interaction with oxygen-containing function groups of the Fe-impregnated biochar. These findings suggest that the As sorption on the Fe-impregnated biochar is mainly controlled by the chemisorption mechanism. Columns packed with Fe-impregnated biochar showed good As retention, and was regenerated with 0.05 mol L−1 NaHCO3 solution. These findings indicate that Fe-impregnated biochar can be used as a low-cost filter material to remove arsenic from aqueous solutions.

The poisoning and regeneration effect of alkali metals deposed over commercial V2O5-WO3/TiO2 catalysts on SCR of NO by NH3

In this study, commercial V2O5-WO3/TiO2 catalysts were deactivated by loading with alkali metals (K and Na). These catalysts were then regenerated by washing with either deionized water or 0.5 mol/L H2SO4 (through the ultrasonic-assisted method). The samples used in this research were characterized by NH3-temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). Results showed that Na2O and K2O doping can poison the V2O5-WO3/TiO2 catalyst and that the poisoning effect of Na2O was stronger than that of K2O. However, the Na2O-loaded sample was easier to regenerate than the K2O-loaded sample. The surfaces of catalysts can be sulfated by washing with dilute sulfuric acid because strong acid sites adhere to the catalyst surface. SO4 2− could also promote catalyst activity. As indicated by the NH3-TPD findings, the deposition of Na2O and K2O could also reduce the amount of desorbed ammonia and destabilize the acid sites, especially strong chemisorption sites. XPS results revealed that catalysts were deactivated by the decrease in the concentration of chemisorbed oxygen [the Oα/(Oα + Oβ) ratio]. In the Na2O-doped catalyst, much chemisorbed oxygen was lost (from 28.8 % to 10.6 %). However, the decrease in the Oα/(Oα + Oβ) ratio was less significant in the K2O-doped catalyst (from 28.8 % to 23.5 %). Nonetheless, the binding energies of O1s broadened with respect to both high and low energy. In particular, the binding energy of chemisorbed oxygen increased from 531.5 to 531.8 eV.

Enhanced photocatalytic activity of sulfated silica-titania composites prepared by impregnation using ammonium persulfate solution

Sulfate (SO42−) modified silica–titania (SiO2–TiO2) composite photocatalysts with different loadings of SO42− were prepared by a facile pore impregnating method using ammonium persulfate (NH4)2S2O8 solution. The surface parameters, structure, morphology, the adsorption ability of light, the binding energy of Ti2p and O1s, and the formation rate of OH radicals produced during the photocatalytic reaction process were characterized by the Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and terephthalic acid photoluminescence probing technique (TA-PL), respectively. The results reveal that sulfating of SiO2–TiO2 induces the shift of Ti2p and O1s, and increases the adsorption of rhodamine B on the sulfated photocatalysts and the formation rate of OH radicals produced during the photocatalytic reaction process. The photocatalytic activity of SO42−/SiO2–TiO2 for de-colorization of rhodamine B aqueous solution was evaluated. The result shows that when wt% of SO42− is 8.6%, SO42−/SiO2−TiO2 exhibits the best photocatalytic activity under ultraviolet light irradiation and the possible reason is discussed.

Density, Elasticity, and Stability Anomalies of Water Molecules with Fewer than Four Neighbors.

Goldschmidt-Pauling contraction of the H-O polar-covalent bond elongates and polarizes the other noncovalent part of the hydrogen bond (O:H-O), that is, the O:H van der Waals bond, significantly, through the Coulomb repulsion between the electron pairs of adjacent oxygen (O-O). This process enlarges and stiffens those H2O molecules having fewer than four neighbors such as molecular clusters, hydration shells, and the surface skins of water and ice. The shortening of the H-O bond raises the local density of bonding electrons, which in turn polarizes the lone pairs of electrons on oxygen. The stiffening of the shortened H-O bond increases the magnitude of the O1s binding energy shift, causes the blue shift of the H-O phonon frequencies, and elevates the melting point of molecular clusters and ultrathin films of water, which gives rise to their elastic, hydrophobic, highly-polarized, ice-like, and low-density behavior at room temperature.

Band-Bending at Buried SiO2/Si Interface as Probed by XPS

X-ray photoelectron spectroscopy is used to probe the photoinduced shifts in the binding energies of Si2p, O1s, and C1s of the SiO2/Si interfaces of a number of samples having oxide and/or thin organic layers on top of p- and n-Si wafers. Whereas the photoinduced shifts, in each and every peak related, vary from 0.2 to 0.5 eV for the p-type samples, the corresponding shifts are substantially smaller (<0.1 eV) for the n-type, regardless of (i) oxidation route (thermal or anodic), (ii) thickness of oxide layer, (iii) nature of organic layer, or (iv) color of three illuminating sources we have used. This leads us to conclude that these particular photoshifts reflect the charge state of the SiO2/Si interface, even in the case of a 20 nm thick oxide, where the interface is buried and cannot be probed directly by XPS.

Modified Carbon Papers as Electrode Materials of all-Vanadium Redox Flow Battery

ABSTRACTThe electrode materials for VRFB should possess higher electric conductivity, corrosion resistance and hydrophilic properties in sulfuric acid. The characteristics of the electrode materials affect the stability and the energy efficiency of VRFB. Carbon materials are the best suited for VRFB applications. In this study, the calcined treatment, acid treatment and ozone treatment were used to modify the surface of carbon papers. The redox reaction of [VO]2+/[VO2]+ on the modified carbon papers was evaluated by cyclic voltammetry (CV). The surface compositions of carbon materials were analyzed by X-ray photoelectron spectrometry (XPS). The experimental results reveal that three oxidative methods enhance the redox reaction of [VO]2+/[VO2]+. The calcined treatments and acid treatments also enhanced hydrolysis reaction. The mole ratio of O/C apparently increased, but the binding energy of C1s and O1s were not chemically shifted in the acid treatment. The intensity of binding energy of O1s, between 532 eV and 534 eV, apparently increased in the ozone and calcined treatments. The Ox treated samples were more hydrophilic than the Oz treated samples. In the Ox treated samples, the decrease of Rct value indicates that was contributed from the redox reaction of [VO]2+/[VO2]+ and hydrolysis reaction. It does not completely benefit the energy efficiency of VRFB. The 5 x 5 cm2 modified carbon papers were used as electrode materials in the VRFB. The voltage efficiency, coulomb efficiency and energy efficiency reached 93 %, 90 % and 83 %, respectively, at a current density of 12 mA．cm-2 at 0.8-1.8 V.

Adsorption of divalent metal ions from aqueous solutions using graphene oxide

The adsorptive properties of graphene oxide (GO) towards divalent metal ions (copper, zinc, cadmium and lead) were investigated. GO prepared through the oxidation of graphite using potassium dichromate was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FT-IR). The results of batch experiments and measurements by flame atomic absorption spectrometry (F-AAS) indicate that maximum adsorption can be achieved in broad pH ranges: 3-7 for Cu(II), 5-8 for Zn(II), 4-8 for Cd(II), 3-7 for Pb(II). The maximum adsorption capacities of Cu(II), Zn(II), Cd(II) and Pb(II) on GO at pH = 5 are 294, 345, 530, 1119 mg g(-1), respectively. The competitive adsorption experiments showed the affinity in the order of Pb(II) > Cu(II) ≫ Cd(II) > Zn(II). Adsorption isotherms and kinetic studies suggest that sorption of metal ions on GO nanosheets is monolayer coverage and adsorption is controlled by chemical adsorption involving the strong surface complexation of metal ions with the oxygen-containing groups on the surface of GO. Chemisorption was confirmed by XPS (binding energy and shape of O1s and C1s peaks) of GO with adsorbed metal ions. The adsorption experiments show that the dispersibility of GO in water changes remarkably after complexation of metal ions. After adsorption, the tendency to agglomerate and precipitate is observed. Excellent dispersibility of GO and strong tendency of GO-Me(II) to precipitate open the path to removal of heavy metals from water solution. Potential application of GO in analytical chemistry as a solid sorbent for preconcentration of trace elements and in heavy metal ion pollution cleanup results from its maximum adsorption capacities that are much higher than those of any of the currently reported sorbents.

Mesoporous Silica Sol-Gel as Catalyst for the Synthesis of Alkylpolyglucosides

The synthesis of alkylpolyglucosides involves condensation of decanol with dextrose in the presence of mesoporous silica sol-gel as a catalyst. In this study, mesoporous silica was produced using sol-gel technique by converting tetraethyl orthosilicate (TEOS) into silica. The mesoporous silica was characterized using BET surface area measurement and X-ray Photoelectron Spectroscopy surface analysis. The specific BET surface area was 794m2/g. From the XPS analysis, the Si2p binding energy is 103.7 eV while the O1s binding energy is 532.8eV indicating the formation of Si-O-Si bond which attributed to SiO2. Mesoporous silica has been found efficient to be solid catalyst for synthesis alkylpolyglucosides and easy to be separated. The reaction was carried out 8 hours at 110°C-120°C under vacuum condition. The mass determination of alkylpoluglucosides has been achieved by ESI LC-MS/MS (ToF) positive-mode giving a mass peak at m/z = 343.21 corresponding to [M++ of alkylmonoglucoside peak at retention time 11.0 min.

Density functional theory study of the vertical ionization energies of the valence and core electrons of cyclopentadiene, pyrrole, furan, and thiophene

The procedure abbreviated as ΔPBE0(SAOP)/et-pVQZ, based on density functional theory, was developed recently for the calculation of vertical ionization energies of the valence electrons of organic and other small molecules and succeeded in giving results with an average absolute deviation of 0.21 eV from experiment for a collection of 115 reliable test cases of nonperhalo molecules. The objective of this work is to add a number of test cases to the benchmark database. We chose the set of molecules cyclo-C4H4X, with X = CH2, NH, O, and S, previously studied by many workers both experimentally and theoretically. The results show that the ΔPBE0(SAOP)/et-pVQZ procedure is not only as good as ab initio methods such as SAC-CI, OVGF, and ADC(3) in performance, but also handles inner valence ionized cations more efficiently. Although the core-electron binding energies of the titled molecules have not been as well investigated theoretically, we apply the methods we developed in recent years to calculate the binding energies of C1s, N1s, O1s, S1s, and S2p, which compare well with available experimental data.

Origin of threshold voltage shift by interfacial trap density in amorphous InGaZnO thin film transistor under temperature induced stress

Effect of trap-density of amorphous InGaZnO thin film transistors (a-IGZO TFTs) were studied using different analysis of x-ray photoelectron spectroscopy (XPS) depth profile and density of states (DOSs). To change trap-densities systematically, rf-power was varied to cause different effect on the initial growth stage of a-IGZO layer grown on gate insulator. The interfacial trap-density was confirmed to be dominant effect on the performance and the threshold voltage shift of a-IGZO TFT by observing the variation of O1s binding energy from XPS. The relation between temperature stress induced and trap-density in deep level was investigated by analyzing DOSs.

Characterization of glasses based on basicity

Basicity is defined as an electron donating ability of a material, and hence, an oxide material containing oxide ions with high electron density is regarded to be in high basicity. It has been demonstrated that basicity can be evaluated by binding energy of core level electrons, which is measured by X-ray photoelectron spectroscopy. Based on the experimental results obtained from a large number of oxide glasses, correlations among basicity, O1s binding energy, structure and properties of glasses have been investigated. In the present paper, some of the research outcomes are introduced.

Thermal and Photoinduced Covalent Attachment of 3-Chloro-1-propanol on Si(100)-2×1

3-Chloro-1-propanol (HO−CH2−CH2−CH2−Cl) covalently binds onto Si(100)-2×1 through the thermal dissociation of the OH group to form Si−O−CH2−CH2−CH2−Cl surface intermediates, evidenced by the appearance of the Si−H stretching mode (2110 cm−1) and the retention of C−Cl stretching mode (654 cm−1) in the high-resolution electron energy loss spectroscopy (HREELS) spectrum of chemisorbed 3-chloro-1-propanol molecules and the chemical downshift of O1s binding energy (BE) in the X-ray photoelectron spectroscopy (XPS) study. The C−Cl bonds in the chemisorbed 3-chloro-1-propanol can be cleaved upon 193 nm irradiation, resulting in Si−O−CH2CH2CH2−CH2CH2CH2−O−Si through lateral diradical coupling. Upon covering the chemisorbed 3-chloro-1-propanol with physisorbed molecules, photoinduced diradical coupling between physisorbed and chemisorbed molecules was also evidenced, achieving the secondary attachment of 3-chloro-1-propanol on the Si surface and forming Si−O−CH2CH2CH2−CH2CH2CH2−OH.

Relationship between polymerization degree and cementitious activity of iron ore tailings

The aim of this study is to understand the relationship between the polymerization degree and cementitious activity of iron ore tailings. In light of the poor usage of iron ore tailings, stockpile samples from Tangshan were studied in terms of their ability to become cementitious materials. Compound thermal activation was used to improve the cementitious properties of the tailings, while analyzing methods, such as X-ray diffraction (XRD), infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectrometer (XPS), were employed to study the changes in phase and structure under different activation conditions. The results reveal clear relationships between the binding energies of Si2p and O1s, polymerization degree, and cementitious activity of iron ore tailings.

XPS characterization of sodium percarbonate granulated with sodium silicate

Granular sodium percarbonate has been characterized by X-ray powder diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The O1s binding energy for the solvating hydrogen peroxide molecules is 535.8 eV. Sodium percarbonate is stabilized by sodium silicate and polyphosphate.

A novel approach to prepare PBT nanocomposites with elastomer‐modified SiO2 particles

AbstractPoly(butylenes terephthalate) (PBT)/SiO2 nanocomposites with uniform dispersion, strong interfacial adhesion, and improved mechanical properties have been prepared by a novel approach. Ethylene‐methyl acrylate‐glycidyl methacrylate (E‐MA‐GMA) elastomer chains were first chemically grafted onto the surface of SiO2 nanoparticles. Fourier transform infrared spectra result shows that elastomer‐modified SiO2 nanoparticles exhibit absorption at 2963–2862 cm−1 of the stretching modes of CH, which suggests the reaction between the hydroxyl groups of SiO2 surface and epoxy groups of E‐MA‐GMA. And the binding energy of Si2p and O1s of the elastomer‐modified SiO2 shifts to lower binding energy, which further confirms the formation of SiOC bonds. This surface treatment allows SiO2 nanoparticles homogeneously dispersing in PBT matrix. The morphology with loose aggregates contains networked SiO2 particles with an interparticle distance ranging from 0 to 30 nm. As a result, the storage modulus and the tensile properties of PBT/E‐MA‐GMA‐SiO2 nanocomposites are higher than those of pure PBT and PBT with untreated SiO2. The incorporation of E‐MA‐GMA‐modified SiO2 particles increases the tensile strength and modulus to 58.4MPa and 2661MPa respectively, which is 8% and 16% higher than those of pure PBT. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers

Comparison of room-temperature multiferroics in Bi 4Fe 2TiO 12 film and bulk

It was reported that both dielectricity and magnetism at room temperature were appreciably improved in Bi 4Fe 2TiO 12 film compared with Bi 4Fe 2TiO 12 bulk. X-ray diffraction profiles reveal similar crystalline nature and random orientation of the two, but X-ray photoelectron spectroscopy (XPS) experiments indicate that it is 1.4 eV lower binding energy of core-state O1s in the film relative to that of the bulk, so the improvement of multiferroics in the film is attributed to oxygen vacancies and high fraction of interface. The results have promising applications in multifunctional integrated devices.