2p Energy Research Articles

Modulating Ti t2g Orbital Bonding in Dual‐Channeled TiO2/rGO Hybrid Architecture for Stable Photocatalytic Methanol to Hydrogen

AbstractCarbon materials are commonly integrated with TiO2 to achieve high carrier mobility and excellent photocatalytic performance, and the chemical bond between TiO2 − C is considered as a significant strategy to enhance efficiency. Nevertheless, few analyses have elucidated the formation mechanism of Ti3 + − C bonds and the underlying reasons for the performance enhancement. To address these issues, this study conducts an in‐depth investigation into the electronic structure of TiO2 − C and demonstrates that the charge in the nonbonding molecular orbital t2g of Ti3 + is transferred to the unoccupied 2p energy level of C through the formation of 1π and 2π bonds, i.e., (Ti 3dxz ‐ C 2py) and (Ti 3dxy ‐ C 2px). The hybridization of t2g‐2p orbitals endows the Ti3 + − C bond with higher carrier mobility and a stronger binding force, thereby contributing to stable photocatalytic H2 production. Inspired by this scenario, the NSTiO2/rGO hybrid architecture, featuring the {101}/{001} surface heterojunction and the Ti3 + − C interfacial chemical bond, has been constructed. As a result, the hybrid catalyst exhibited excellent photocatalytic cycling stability of and an H2 evolution rate of 33.4 mmolh−1g−1. This work proposes a strategy for designing efficient photocatalyst by regulating orbitals to achieve high‐performance photocatalytic methanol splitting.

Electronic structure of light-induced nitrosyl linkage isomers revealed by X-ray absorption spectroscopy at Ru L3,2-edges

X-ray absorption spectroscopy (XAS) is a powerful tool for examining changes of the electronic and molecular structure following light-induced excitation of a molecule. Specifically, this method can be applied to investigate the ground (GS, RuNO) and metastable states (MS1, RuON and MS2, Ruη2(NO)) of the nitrosyl ligand (NO), which differ in their coordination mode to the metal. In this work, we report for the first time experimental and theoretical (DFT) Ru L3,2-edge XA spectra for the octahedral complex trans-[RuNOPy4F](ClO4)2 (1, Py = pyridine) in both ground and metastable states. The transition from GS to MS1 using 420 nm light excitation leads to a significant downshift of the 2p → LUMO(+1) peaks by about 0.5–0.8 eV, attributed to the destabilisation of 2p orbitals and stabilization of LUMO(+1). Subsequent irradiation of MS1 at 920 nm produces isomer MS2, for which even greater stabilization of LUMO occurs, though without a significant change in 2p energy. The change in 2p energy is attributed to a variation in the charge on the Ru atom after NO isomerization, while LUMO(+1) stabilization is related to changes in the Ru(NO) bond length and the composition of this orbital.

Exploiting the Correlation between the 1s, 2s, and 2p Energies for the Prediction of Core-Level Binding Energies of Si, P, S, and Cl species.

The binding energies (BEs) of the 1s, 2s, and 2p core electrons of third-period elements (Si, P, S, Cl) were calculated using Hartree-Fock (HF) and B3LYP, BH&HLYP, and LC-BOP ΔSCF, and the shifted KS ΔSCF methods. Linear relationships between two BEs were derived and compared with the Auger parameter. The derived lines are essentially parallel, with only the intercepts differing. The difference in intercepts is due to the lack of electron correlation effects in HF and the self-interaction errors (SIEs) of the functional. The slope is the slope of the linear relationship between the chemical shifts. The straight lines between the 2s and 2p BEs also coincided with the Auger parameter lines, which have a slope of 1 by definition and an intercept being the difference between the 2s and 2p BEs. The shifted KS ΔSCF scheme compensates for SIEs, yielding equations that are approximately invariant. The calculated average gaps for the 2s and 2p BEs are 51.21 eV for Si, 57.48 eV for P, 63.85 eV for S, and 70.48 eV for Cl. The straight lines representing the relationships between the BEs of the 1s and 2s and 1s and 2p electrons are also parallel to each other in ΔSCF and converge into a single line in the shifted ΔSCF scheme. However, these lines are steeper than the Auger parameter line. The derived relationships can be used to predict unknown BEs, which we have applied to many molecules. The results are highly accurate, with mean absolute errors (MAEs) of less than 0.2 eV compared to experimental values.

An interpretation for the components of 2p 3/2 core level x-ray photoelectron spectra of the cations in some inverse spinel oxides

In an effort to reconcile the various interpretations for the cation components of the 2p 3/2 observed in x-ray photoelectron spectroscopy (XPS) of several spinel oxide materials, the XPS spectra of both spinel alloy nanoparticles and crystalline thin films are compared. We observed that different components of the 2p 3/2 core level XPS spectra, of these inverse spinel thin films, are distinctly surface and bulk weighted, indicating surface-to-bulk core level shifts in the binding energies. Surface-to-bulk core level shifts in binding energies of Ni and Fe 2p 3/2 core levels of NiFe2O4 thin film are observed in angle-resolved XPS. The ratio between surface-weighted components and bulk-weighted components of the Ni and Fe core levels shows appreciable dependency on photoemission angle, with respect to surface normal. XPS showed that the ferrite nanoparticles Ni x Co1−x Fe2O4 (x = 0.2, 0.5, 0.8, 1) resemble the surface of the NiFe2O4 thin film. Surface-to-bulk core level shifts are also observed in CoFe2O4 and NiCo2O4 thin films but not as significantly as in NiFe2O4 thin film. Estimates of surface stoichiometry of some spinel oxide nanoparticles and thin films suggested that the apportionment between cationic species present could be farther from expectations for thin films as compared to what is seen with nanoparticles.

Determining effects of doping lithium nickel oxide with tungsten using Compton scattering

X-ray Compton scattering experiments along with parallel first-principles computations were carried out on LiNiO2 to understand the effects of W doping on this cathode material for Li-ion batteries. By employing high-energy x rays exceeding 100 keV, an insight is gained into the fate of the W valence electrons, which are adduced to undergo transfer to empty O 2p energy bands within the active oxide matrix of the cathode. The substitution of W for Ni is shown to increase the electronic conductivity and to enhance the total magnetization per Ni atom. Our study demonstrates that an analysis of line shapes of Compton scattered x rays in combination with theoretical modeling can provide a precise method for an atomic level understanding of the nature of the doping process.

Band Structure Engineering Promotes Anionic Redox Reversibility of Cobalt-Free Li-Rich Layered Oxides Cathodes.

Li-rich layered oxides cathodes (LLOs) have prevailed as the promising high-energy-density cathode materials due to their distinctive anionic redox chemistry. However, uncontrollable anionic redox process usually leads to structural deterioration and electrochemical degradation. Herein, a Mo/Cl co-doping strategy is proposed to regulate the relative position of energy band for modulating the anionic redox chemistry and strengthening the structural stability of Co-free Li1.16Mn0.56Ni0.28O2 cathodes. The incorporation of Mo with high d state orbit and Cl with low electronegativity can narrow the band energy gap between bonding and antibonding bands via increasing the filled lower-Hubbard band (LHB) and decreasing the non-bonding O 2p energy bands, promoting the anionic redox reversibility. In addition, strong covalent Mo─O and Mn─Cl bonding further increases the covalency of Mn─O band to further stabilize the O2 n- species and enhance the reversible distortion of MnO6 octahedron. The strengthening electronic conductivity, together with the epitaxial structure Li2MoO4 facilitates the fast Li+ kinetics. As a result, the dual doping material exhibits enhanced anionic redox reversibility and suppressed oxygen release with increased cyclic stability and excellent rate performance. This strategy provides some guidance to design high-energy-density LLOs with desirable anionic redox reversibility and stable crystal structure via band structure engineering.

A Z-scheme heterojunction ZIF67/N, P-WO3 nanocomposite for photocatalytic degradation of levofloxacin

In this work, a ZIF67/N, P-WO3 (ZNPW) Z-scheme heterojunction was constructed by N, P-codoped WO3 (NPW), and ZIF67 and developed as a highly efficient photocatalyst for Levofloxacin (LFX) removal. A series of characterization measurements including FTIR, XRD, SEM, DRS, PL, and XPS are conducted to confirm the formation of the ZNPW. After optimization on the composition of WO3, NPW and ZIF67, the optimal ZNPW shows superior photocatalytic activity, yielding a higher removal efficiency of LFX ∼91.2% in 100 min than those of pure WO3 (9.4%), NPW (47.8%) and ZIF67 (14.3 %). Additionally, ZNPW exhibits remarkable stability and reusability for up to five consecutive runs. Reactive species scavenging experiments and ESR have revealed that the degradation of LFX is primarily facilitated by the generation of holes (h+) and hydroxyl radicals (·OH). Moreover, the degradation process of LFX was identified through an integrated LC-MS analysis and density functional theory computation of the Fukui indices. This process consists of three pathways: the opening of the piperazinyl ring, separation of piperazinyl and quinoline moieties, and cleavage of the pyridine ring on the quinoline moieties. The superior photocatalytic properties can be attributed to the N, P co-doping in the WO3 structure and the simultaneous coupling with ZIF67, leading to the formation of a heterojunction with a reduced band gap, efficient charge separation and transport, and a new N 2p and P 2p energy level. In conclusion, this study provides novel insights into designing high-efficiency antibiotics degradation using WO3-based Z-scheme heterojunction photocatalysts.

Characterization of the SIDDHARTA-2 Setup via the Kaonic Helium Measurement

The aim of the SIDDHARTA-2 experiment is to perform the first measurement ever of the width and shift induced by the strong interaction to the 2p→1s energy transition of kaonic deuterium. This ambitious goal implies a challenging task due to the very low X-ray yield of kaonic deuterium, which is why an accurate and thorough characterization of the experimental apparatus is mandatory before starting the data-taking campaign. Helium-4 is an excellent candidate for this characterization since it exhibits a high yield in particular for the 3d→2p transition, roughly 100 times greater than that of the kaonic deuterium. The ultimate goal of the work reported in this paper is to study the performances of the full experimental setup in view of the kaonic deuterium measurement. This is carried out by measuring the values of the shift and the width for the 3d→2p energy transition of kaonic helium-4, induced by the strong interaction. The values obtained for these quantities, for a total integrated luminosity of ∼31/pb, are ε2p=2.0±1.2(stat)±1.5(syst)eV and Γ2p=1.9±5.7(stat)±0.7(syst)eV. The results, compared to the value of the shift measured by the SIDDHARTA experiment ε2p=0±6(stat)±2(syst)eV, show a net enhancement of the resolution of the apparatus, providing strong evidence of the potential to perform the challenging measurement of the kaonic deuterium.

Research on reactivity evaluation and micro-mechanism of various solid waste powders for alkali-activated cementitious materials

Alkali-activated cementitious material (AACM) based on the utilization of solid waste is a new type of environmentally friendly inorganic material, which has the advantages of early strength, fast hardening, high strength, and better durability. The reactivity of solid waste powder is a key factor for its appropriate utilization in alkali-activated cementitious materials, necessitating a rational evaluation of its reactivity. The reactivity evaluation was conducted on various solid waste powders, including fly ash (FA), red mud (RM), recycled micro-powder (RMP), red brick powder (RBP), coal gangue powder (CGP), and cement kiln dust (CKD). The effects of NaOH concentration, weight ratio of water to solid waste powder (W/P) and curing humidity on the compressive strength were investigated，then the compressive strength under optimal conditions was determined based on response surface analysis. The compressive strength under optimal conditions was used to evaluate the reactivity of solid waste powders. Moreover, microscopic tests (e.g., XPS test, ICP test, and NMR test) were carried to evaluate the reactivity of the solid waste. The relative number of bridging oxygen (RBO) measured by the NMR method in conjunction with chemical composition analysis serves as an effective method for evaluating the reactivity of solid waste powders. The leaching rate of Silicon (Si) and Aluminum (Al) ions in the ICP method depended mainly on the NaOH concentration and the elemental content in the raw material. In addition, the binding energies of O1s, Si 2p, and Al 2p tested by the XPS method had no particular correlation with the compressive strength.

Investigation on the kinetics of a diode-pumped plasma-jet type metastable argon laser

Diode-pumped rare gas lasers (DPRGLs) have the potential for high-energy laser output with high beam quality. The metastable concentration >1014 cm−3 and pump intensity >10 kW/cm2 are required in developing high-power and efficient DPRGLs. However, the kinetics of 1s and 2p levels (Paschen notation) under these conditions is unclear yet, particularly regarding the adverse effects of interference energy levels (e.g., 1s4 and 2p1–2p8). This study addresses this gap by measuring the number densities of 1s and 2p levels in a diode-pumped plasma jet metastable argon laser. The experiment was conducted with a much higher number density of 1014 cm−3 and a higher pump intensity of 12 kW/cm2 than our previous works. The results indicate that the adverse effect of 1s4 accumulation could be partially compensated, and the relative population distribution of 2p energy levels remained unchanged. However, the high gas temperature (>1000 K) caused a significant negative impact of high 2p levels (2p1–2p8), and the air environment weakened the effect of He collision relaxation.

2D ZIF-67 derived V-doped CoP/NC nanosheets as efficient electrocatalysts for water splitting

The water splitting reaction to produce hydrogen is one of the most promising and cleanest ways to resolve the energy crisis. However, the preparation of efficient and stable electrocatalysts with low-cost remains challenging. In this work, the noble-metal free N-doped carbon (NC) incorporated V-doped cobalt phosphide (CoP) nanosheets on nickel foam (NF) (denoted as V-CoP-NC/NF) are prepared by using two-dimension zeolitic imidazolate framework (ZIF-67) as precursor followed by NaVO3 etching/doping and phosphorization. The V doping is found to be essential to enhance the electrochemical performance of CoP for water splitting. In particular, V5-CoP-NC/NF (V5 represents the concentration of NaVO3 for etching/doping is 5 mM) exhibits the highest hydrogen evolution performance in alkaline electrolyte, to achieve a current density of 10 mA cm−2, an overpotential of 119 mV (vs reversible hydrogen electrode) is required. X-ray photoelectron spectroscopy results show that the V doping significantly altered the binding energies of Co 2p, P 2p and N 1 s in V5-CoP-NC/NF, which is believed to facilitate the adsorption and dissociation of intermediates and accelerate interfacial charge transfer during hydrogen evolution reaction process. This work provides a simple route to prepare heteroatom doped CoP self-standing electrocatalysts for water splitting.

Mechanistic study on the depression of calcite by sodium hexametaphosphate in sodium oleate system

Sodium hexametaphosphate (NaHMP), a common depressant for calcium-containing minerals, is widely used in flotation practice. In this work, the depression mechanism of NaHMP on calcite was thoroughly investigated by using experiments and DFT calculations. Accordingly, the micro-flotation results revealed that NaHMP possessed noticeable depression effect on calcite, with the calcite recovery decreasing from 94.21% without NaHMP to 17.29% with NaHMP concentration of 1 mg/L at pH 8. The surface Zeta potential suggested that NaHMP could be strongly adsorbed on calcite, while no absorption band of hexametaphosphate was detected in the FTIR spectra of calcite treated by NaHMP, but a remarkable weakening of the absorption peak of sodium oleate (NaOL) was detected in the presence of NaHMP, which was also reflected in the XPS spectra. In addition, the significant chemical shifts in the binding energies of Ca 2p and P 2p electrons observed from the XPS high-resolution spectra suggested that the hexametaphosphate groups (HMP) were chemisorbed on calcite. DFT calculations further revealed that the sorption of HMP on calcite was more preferable than that of oleate ion (OL) in thermodynamics, which explained the beneficiation practice that NaOL was difficult to float calcite in the presence of NaHMP.

Defect Thermodynamic Modeling of Triple Conducting Perovskites (La,Ba)Fe1-xMxO3-δ for Proton-Conducting Solid-Oxide Cells

Density functional theory (DFT) based modeling was performed to investigate the defect energetics of the proton conducting oxides BaFe1-xMxO3-δ (with M=Zr, Y, and Zn at the B-site). High-throughput defect modeling was carried out to obtain the defect energetics ensembles as a function of B-site x (0 – 0.25) and oxygen δ (0 – 0.5) compositions for assessment of oxygen vacancy formation (Evac) and hydration reaction (Ehyd) energies in complex defect-dopant configurations. The modeling effort aims to elucidate the complex coupling among oxygen vacancies, the protons and metal dopants in various concentrations and their combined effect upon defect energetics in BaFe1-xMxO3-δ perovskite. This information complements the current experimental measurements with essential data related to the energetics of various defect configurations that can play a role in solid-oxide-cell (SOC) applications. Preliminary results among more than 3,000 configurations investigated are summarized in Figure 1. All calculations were performed with the Perdew-Burke-Ernzerhof (PBE) functional in charge neutral 2 × 2 × 2 perovskite supercells. An effective Hubbard Ueff correction of 4 eV was applied to the Fe 3d shell, with all the Fe atoms being in a high-spin state and having a ferromagnetic ordering. Stability analysis of each of the BaFe1-xMxO3-δ systems investigated at specified x and δ composition values reveals that the oxygen vacancy (VO) is energetically unfavorable when placed adjacent to the M dopant. Overall, the Fe-VO-Fe configurations are identified to be more stable than the Fe-VO-M and M-VO-M configurations, while one with a M-VO-M cluster arrangement is the least stable. Such a short-range ordering leads to the blocking of the oxygen vacancy migration toward the oxygen sites around the M dopant, whereas the proton hopping between the oxygens around the M dopants is energetically not hindered. Based on the stability of various defect-dopant configurations of the BaFe0.75M0.25O2.875 systems with or without hydration, it is revealed that the stability range of analogous configurations with varying dopant types can be an indicator of the defect-dopant ordering strength and can be correlated with the ionic radii of the dopants in the BaFe1-xMxO3-δ systems.Taking the energy of the most stable BaFe1-xMxO3-δ structures at various x and δ values analyzed as representative for the respective compositions, the corresponding derivations of the Evac and Ehyd energies as a function of δ (and x) are summarized in Figures 1(a) and 1(b), respectively. Overall, the results indicate a stronger oxygen non-stoichiometry (δ) dependence in the Evac values of the BaFeO3-δ and BaFe1-xMxO3-δ systems (M=Zr, Y, and Zn at x=0.125 and x=0.25), whereas the Ehyd data exhibit a much weaker δ dependence. This contrasting behavior in the δ dependences between Evac and Ehyd values may be attributed to the charge transfer characteristics of the oxygen vacancy formation reaction, which is associated with the Fe 3d and the O 2p energy levels of the materials at various δ values while the charge transfer involved in the hydration reaction is relatively minimal. The effect of dopant concentration (x) further shows an opposite trend in the Evac values vs. x with the dopant types, with an increase of Evac upon increasing the Zr doping concentration and a decrease of Evac upon increasing the Y and Zn doping content. Due to the strong oxygen non-stoichiometry dependence in the Evac values, the results indicate an increased proton affinity of the BaFe1-xMxO3-δ oxides. Further assessments of the Evac and Ehyd data on δ values and their impact upon the defect equilibria of the BaFe1-xMxO3-δ systems under the SOC operating conditions will be discussed. Disclaimer This project was funded by the U.S. Department of Energy, National Energy Technology Laboratory, in part, through a site support contract. Neither the United States Government nor any agency thereof, nor any of their employees, nor the support contractor, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Figure 1

Ce & F multifunctional modification improves the electrochemical performance of LiCoO2 at 4.60 V

Lithium cobalt oxide (LiCoO2) is proverbially employed as cathode materials of lithium-ion batteries attributed to the high theoretical capacity, and currently, it is developing towards higher cut-off voltages in the pursuit of higher energy density. However, it suffers from serious structural degradation and surface side reactions, in particular, at the voltage above 4.60 V, leading to rapid decay of the battery life. Taking into account the desirable oxygen buffering property and the fast ion mobility characteristic of cerium oxide fluoride, in this work, we prepared Ce & F co-modified LiCoO2 by using the precursors of Ce(NO3)3·6H2O and NH4F, and evaluated the electrochemical performance under voltages exceeding 4.60 V. The results indicated that the modified samples have multiphase heterostructure of surface CeO2−x and unique CeOF solid solution phase. At 3.0–4.60 V and 25 °C, the preferred sample LCO-0.5Ce-0.3F has a high initial discharge specific capacity of 221.9 mA h g−1 at 0.1 C, with the retention of 80.3% and 89.6% after 300 cycles at 1 and 5 C, comparing with the pristine LCO (56.4% and 22.6%). And at 3.0–4.65 V, its retention is 64.0% after 300 cycles at 1 C, versus 8.5% of the pristine LCO. Through structural characterizations and DFT calculations, it suggests that Ce4+ & F− co-doping suppresses the H3 to H1/3 irreversible phase transition, stabilizes the lattice structure, and reduces the redox activity of the lattice oxygen by modulating the Co 3d–O 2p energy band, consequently improving the electrochemical performance of LiCoO2 at high voltages.

Utilizing N-hydroxy-9-octadecenamide as a collector in flotation separation of bastnaesite and fluorite

Bastnaesite ((Ce,La,Pr,Nd)CO3F) is a significant light rare earth mineral found in nature, known for its fine-grained properties. Flotation is commonly employed for the recovery of fine-grained bastnaesite particles. Collectors serve as an essential flotation reagent that enhance the surface hydrophobicity of target minerals. A novel collector, N-hydroxy-9-octadecenamide (N-OH-9-ODA), was synthesised in this study. N-OH-9-ODA exhibits superior selectivity compared to the traditional collector oleic acid in the flotation separation of bastnaesite and fluorite. The experimental and computational results indicate that N-OH-9-ODA exhibits superior selectivity due to its higher adsorption affinity for bastnaesite surface compared to fluorite surface. The zeta potential and the binding energies of the Ce 3d peaks in the X-ray photoelectron spectrum (XPS) of bastnaesite surface exhibit significant shifts. Conversely, fluorite surface demonstrates minimal alterations in its zeta potential and the binding energies of the Ca 2p peaks in its XPS after its interaction with N-OH-9-ODA.

Effect of Nitrogen Doping on the Photocatalytic Properties of TiO2

AbstractA series of nitrogen‐doped TiO2 were prepared through a simple sol‐solvothermal method. The catalysts were characterized by BET, XRD, SEM‐EDS, Raman, XPS, FTIR, UV‐Vis, etc. The results show that N−TiO2 photocatalyst has a larger specific surface area, stable anatase phase, and narrow forbidden band energy (3.17–3.24 eV). The N‐doped TiO2 has more oxygen vacancies (OVs) than pure TiO2, as confirmed by results such as XPS and ESR. The photocatalytic evaluation results show that the decolorization of methyl orange reached 99.03 % over the 3 % N‐doped TiO2, which is 40 % higher than that of pure TiO2. Meanwhile, 3 % N‐doped TiO2 exhibited a faster MO mineralisation rate than TiO2. After repeatedly used for 5 times, the photocatalyst 3‐N−TiO2 still showed high activity in the degradation of MO. The improvement of the visible light performance of the N−TiO2 photocatalyst could be attributed to the introduction of N in TiO2 to generate new N 2p energy levels and rich OVs.

Analysis of the 2p-manifold population distribution in a diode-pumped metastable Ar laser.

The complex excited energy levels in the diode-pumped metastable Ar laser may induce harmful effects in laser cycling. Significantly, the influence of the population distribution in 2p energy levels on the laser performance is unclear yet. In this work, the absolute populations in all the 2p states were measured online by the simultaneous applications of tunable diode laser absorption spectroscopy and optical emission spectroscopy. The results showed that most atoms were populated to the 2p8, 2p9, and 2p10 levels while lasing, and the majority of the 2p9 population was efficiently transferred to the 2p10 level with the aid of helium, which was beneficial for the laser performance.

Plasma-Assisted N-Doped TiO2 Nanotube Array as an Active UV–vis Photoanode

This work shows the possibility of using plasma nitriding under ultra-high-vacuum conditions to introduce nitrogen into a titanium dioxide structure in the form of nanotubes with a diameter of about 110 nm. Nanotubes were produced by the anodic oxidation of Ti foil in a solution based on glycerine and water with the addition of ammonium fluoride at a voltage of 25 V. Based on experimental evidence obtained by X-ray photoelectron spectroscopy (XPS, in situ), it has been shown that alternating nitriding and annealing processes at 450 °C leads to formation of Ti-N-O, Ti-N, and Ti-O-N chemical bonds in the TiO2 crystal structure (anatase). The observed changes were identified as interstitial or substitutional admixtures or variations of these. The spectrophotometric and spectrophotoelectrochemical tests performed showed that the photoactivity of the photoanodes doped with nitrogen and annealed at 450 °C in the UV–vis range was significantly greater than that of the photoanodes without nitrogen. The highest maximum photocurrent density, of about 30.0 μA·cm–2 at a wavelength of λ = 350 nm, was obtained for the double-nitrided and once-annealed sample, where nitrogen was mainly incorporated in the interstitial positions in the TiO2 lattice. For the materials not nitrided as well as annealed only at 450 °C and pristine, the worse photoresponse was received at the levels of ∼16 and ∼0.2 μA·cm–2, respectively. The thermo-chemical treatment applied also effectively extended the operational range of the photoanodes toward visible light, where a wide maximum of light absorption was observed from ∼400 to ∼700 nm, with a maximum wavelength of 550 nm and an estimated bandgap energy of 2.5 eV. Our investigations confirmed that photoelectrochemical (PEC) performance for TiO2 NT-based photoanodes was achieved by the optimum annealing condition and concentration of nitrogen, where the narrowed bandgap was observed by generating a new N 2p energy level above the O 2p valence band. The following research techniques were used to identify the changes taking place in the materials produced: XPS spectroscopy, UV–vis spectroscopy, PEC measurements, X-ray diffraction structural measurements, and scanning electron microscopic observations.

Powdered and beaded zeolite A from recycled coal fly ash with modified iron (III) oxide-hydroxide for lead adsorptions

Lead is a highly toxic metal and bioaccumulation through food chain, so it causes human health effects. Thus, contaminated lead in wastewater is required to treat below the water quality standard. This study was to synthesize zeolite A powder (Z), zeolite A powder mixed iron (III) oxide-hydroxide (ZF), zeolite A beads (ZB), and zeolite A powder mixed iron (III) oxide-hydroxide beads (ZFB), characterize with various techniques, investigate their lead removal efficiencies by batch experiments, and study their adsorption patterns and mechanisms. All characterizations of Z have matched to the zeolite A standard (STD) which confirmed the ability to synthesize zeolite A. ZF had the highest specific surface area and smallest pore size than others, and they were mesoporous materials. Silicon, aluminum, and sodium were observed in all materials. The specific crystalline formation of zeolite A was found in all materials corresponding to the STD. Z was a cubic structure representing the specific zeolite A structure, and ZF, ZB, and ZFB had rough surfaces with presenting traces of cubic shapes confirmed being zeolite A. OH, Si or Al–O, and D4R were their main chemical functional groups, and Si–O–Fe was found in ZF and ZFB. In addition, –COOH was observed in ZB and ZFB. The binding energies of Na 1s, O 1s, Si 2p, and Al 2p were found in all materials, and Fe 2p3/2 and Fe 2p1/2 were observed in ZF and ZFB. In addition, Pb 4f7/2 and Pb 4f5/2 were detected after lead adsorptions. The point of zero charges of Z, ZF, ZB, and ZFB were 6.45, 8.65, 6.04, and 8.12. They could remove lead at 50 mg/L of more than 97.5 %. They corresponded to Langmuir and pseudo-second-order kinetic models. Moreover, they could reuse more than 5 cycles. Finally, ZFB is a good offer for real industrial applications.

Surface morphologies, chemical compositions and luminescent properties of ZnO thin films flattened by ion milling procedure

The luminescent properties of ZnO thin films have been developed to form a nanometric light source for an electron beam-excitation assisted optical microscope. Spatial uniformity of the electron-induced luminescence is important when using this luminescent ZnO film-based light source. In this work, ZnO thin film surfaces have been flattened using broad ion beam polishing with Ar+ ions at a grazing angle of incidence. Atomic force microscopy and electron microscopy confirmed transformation of needle-like ZnO surface structures into scale-like morphologies during ion irradiation. The root-square-mean roughness, corresponding to the height distribution decreased dramatically from 32 to 8 nm after 5 keV Ar+ ion irradiation for 60 min. X-ray photoelectron spectroscopy and Monte Carlo simulations revealed changes in the chemical state and lattice defects during ion irradiation. Positive shifts in the binding energies of the Zn 2p and O 1s spectra suggested preferential Zn atom sputtering and chemical composition change from oxygen-deficient to stoichiometric ZnO. The ultraviolet region luminescent intensity improved after ion irradiation for 60 min. Valence band electron redistribution was considered to influence the ZnO thin film’s luminescent properties. We propose that homogeneous luminescence over a specified area with flat surfaces can be accomplished by repeated short-duration ion irradiation.