X-ray Photoelectron Spectra Measurements Research Articles

Thermal and photochemical degradation of CsGeI3 and CsGeBr3: XPS and optical studies

The toxicity of complex lead halides significantly limits the commercialization and practical application of perovskite solar cells. In recent days, lead-free complex lead halides with a perovskite structure have become increasingly popular, among which germanium systems are the least studied. Here we present for the first time a systematic study of the thermal and photochemical stability of perovskite thin films of CsGeI3 and CsGeBr3. The measurements of optical absorbance and X-ray photoelectron spectra (XPS) of core levels and valence bands of Ge-based halide perovskites after light soaking and heat stress were thoroughly performed. It has been found the effect of thermal and photochemical degradation of Ge perovskites which is accompanied by reduction of I:Ge and Br:Ge ratios and appearance of tetravalent metal species fixed in XPS Ge 2p and Ge 3d spectra. The XPS O 1s measurements of irradiated and annealed Ge-based perovskites and their comparison with spectra of GeO2 have shown that formation of Ge4+-species is not due to metal oxidation but owing to defect-mediated hole-doping. While the Ge2+→Ge4+ process lowers the thermal and photochemical stability of Ge-based perovskites and limits their use in photovoltaics, the temperature induced hole doping is favorable for thermoelectric applications.

Efficient Spin-Adapted Implementation of Multireference Algebraic Diagrammatic Construction Theory. I. Core-Ionized States and X-ray Photoelectron Spectra.

We present an efficient implementation of multireference algebraic diagrammatic construction theory (MR-ADC) for simulating core-ionized states and X-ray photoelectron spectra (XPS). Taking advantage of spin adaptation, automatic code generation, and density fitting, our implementation can perform calculations for molecules with more than 1500 molecular orbitals, incorporating static and dynamic correlation in the ground and excited electronic states. We demonstrate the capabilities of MR-ADC methods by simulating the XPS spectra of substituted ferrocene complexes and azobenzene isomers. For the ground electronic states of these molecules, the XPS spectra computed using the extended second-order MR-ADC method (MR-ADC(2)-X) are in a very good agreement with available experimental results. We further show that MR-ADC can be used as a tool for interpreting or predicting the results of time-resolved XPS measurements by simulating the core ionization spectra of azobenzene along its photoisomerization, including the XPS signatures of excited states and the minimum energy conical intersection. This work is the first in a series of publications reporting the efficient implementations of MR-ADC methods.

Weak magnetic doping effect on the magnetic transition, magnetocaloric properties, and super-invar behavior in TbCo2Vx system

In this work, the V-doped effect on the magnetic transition and magnetocaloric properties have been studied systematically for TbCo2Vx (0 ≤ x ≤ 0.2) series. All samples were characterized by powder X-ray diffraction (XRD) as cubic structures (Fd-3 m) at room temperature. The Curie temperatures TC of TbCo2Vx decrease monotonically from 234 K (x = 0) to 214 K (x = 0.2) corresponding to a monotonically increasing value of lattice a. The slightly diminished magnetic saturation moment MS from 6.35 μB/f.u to 6.12 μB/f.u with the x value increasing indicates weak magnetic doping in this system, which can also be reflected in the slight decrease of the maximum values of magnetic entropy change (-ΔSM) from 6.23 J kg-1K−1 to 5.27 J kg-1K−1 (0–5 T). X-ray photoelectron spectrum (XPS) measurements confirm that the weak magnetic doping originates from the multivalences of V2+ and V4+, compared with other normally nonmagnetic V-doped cases reported before. Both the Banerjee criteria and rescaled magnetic entropy change lines deny the first-order transition in parent compound TbCo2 as reported recently. Almost zero thermal expansion near TC in TbCo2 with thermal expansion coefficient αl = -1.43 × 10-6 K−1 indicates weak magnetostriction, which is another experimental hint for second-order transition. The deviation of the critical exponents to Mean-field theory in TbCo2 implies some crystal defects and inhomogeneous polycrystalline distribution inside, which should also be a key point for the divergence of first-order and second-order transition in different samples of TbCo2 as reported before. Super-invar behavior with αl = 4.4 × 10-7 K−1 was found in the x = 0.2 component by macro-thermal expansion measurement.

Protecting Mg-sites from hydration by embedding magnesium-aluminium layered double hydroxide in halloysite and using as pickering catalysts in Baeyer-Villiger oxidation

A facile strategy was developed via thermal treatment to get hierarchically structured magnesium-aluminium layered double hydroxide (MgAl-LDH) selectively loaded on the inner and external surfaces of halloysite nanotubes, respectively. The loaded MgAl-LDH was found to have active centers for Baeyer-Villiger (BV) oxidation that was protected from hydration by embedding in halloysite lumens. The BV oxidation of cyclohexanone was observed to have better performance by using the halloysite impregnated MgAl-LDH (MgAl-LDH@Hal) as catalysts than that of external surface modified MgAl-LDH (MgAl-LDH@Hal600). A conversion 57.0% of cyclohexanone was achieved, and the yield of ε-caprolactone was 22.0% when the MgAl-LDH@Hal was used as catalysts. Density Functional Theory (DFT) calculations as well as high-resolution of X-ray photoelectron spectrum (XPS) measurements revealed the charge depletion occurred in the Mg-sites of sample MgAl-LDH@Hal in comparison with MgAl-LDH@Hal600, which benefited the activation of H2O2 oxidants, and thus assisting the BV reaction. The prepared composites were able to work as phase-transfer catalysts as Pickering emulsions in oxidation of cyclohexanone.

Graphene Film with a Controllable Microstructure for Efficient Electrochemical Energy Storage.

The agglomeration of graphene sheets and undesired pore size distribution usually lead to unsatisfactory electrochemical properties of reduced graphene oxide (RGO) film electrodes. Herein, crumpled exfoliated graphene (EG) sheets are adopted as the microstructure-regulating agent to tune the morphology and micro-/mesopore amounts with the aim of increasing active surface sites and ion transportation paths in electrodes. With the optimum ratio between EG and GO, the resulting 75%-EG/RGO shows significantly improved specific gravimetric capacitance (Cs) and rate capability when compared with pure RGO electrodes in a symmetrical supercapacitor system. Moreover, when coupling the 75%-EG/RGO cathode with a Zn anode to form a Zn ion hybrid supercapacitor (ZHS), the 75%-EG/RGO exhibits a much higher Cs of 327.39 F g-1 at 0.1 A g-1 and can maintain 91.7% capacitance after 8000 cycles. Systematic ex situ X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) measurements reveal that the charge storage mechanism is based on both reversible physical adsorption and dual ion uptake. Furthermore, the quasi-solid-state flexible ZHS also presents high capacitive performance and can maintain ∼100% capacitance under various bending states, demonstrating potential application in wearable electronics. This strategy opens up a new path for constructing high-performance graphene film electrodes.

The Stability of Hybrid Perovskites with UiO-66 Metal-Organic Framework Additives with Heat, Light, and Humidity.

This study is devoted to investigating the stability of metal-organic framework (MOF)-hybrid perovskites consisting of CH3NH3PbI3 (MAPbI3) and UiO-66 without a functional group and UiO-66 with different COOH, NH2,and F functional groups under external influences including heat, light, and humidity. By conducting crystallinity, optical, and X-ray photoelectron spectra (XPS) measurements after long-term aging, all of the prepared MAPbI3@UiO-66 nanocomposites (with pristine UiO-66 or UiO-66 with additional functional groups) were stable to light soaking and a relative humidity (RH) of 50%. Moreover, the UiO-66 and UiO-66-(F)4 hybrid perovskite films possessed a higher heat tolerance than the other two UiO-66 with the additional functional groups of NH2 and COOH. Tthe MAPbI3@UiO-66-(F)4 delivered the highest stability and improved optical properties after aging. This study provides a deeper understanding of the impact of the structure of hybrid MOFs on the stability of the composite films.

Spontaneous Enhancement of Power Conversion Efficiency in SnO2-Based Dye-Sensitized Solar Cells

Power conversion efficiency (PCE) of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based dye-sensitized solar cells (DSSCs) is reported to increase slowly over a period of days after their fabrication. Thus far, underlying processes involved in this slowly increasing phenomenon of PCE are not understood. In this article, we investigate the spontaneous enhancement of PCE in SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based DSSCs and the underlying mechanism by using the X-ray diffraction, the X-ray photoelectron spectra (XPS), electrochemical impedance spectrum, and first-principles calculations. The Sn 3d and O 1s binding energy are observed to shift toward low binding energy over time by the XPS measurements, and the ratio of O/Sn on the surface of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> increases from 1.9 to 2.1 implying the adsorption of oxygen atom on the surface of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Our first-principles calculation results confirm that a shift-up in the conduction band minimum of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> owing to its adsorption of oxygen atom. We, therefore, attribute the slowly increasing phenomenon of PCE to oxygen adsorption effect on the surface of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . This article gives a comprehensive understanding of the surface oxidation effect on the PCE enhancement in DSSCs and provides an effective way to fabricate DSSCs based on oxide semiconductors with good performance and long-time stability.

NASICON-Structured Na2VTi(PO4)3@C for Symmetric Aqueous Rechargeable Na-Ion Batteries with Long Lifespan

Mixed transition-metal ions NASICON-structured compounds are enabled simultaneously as cathode and anode for aqueous Na-ion batteries (ANIBs), simplifying the fabrication process and reducing manufacturing costs in practical applications. In this study, a mixed V³⁺/Ti⁴⁺ NASICON-structured Na₂VTi(PO₄)₃@C composite acts as a bifunctional electrode material of ANIBs, delivering excellent sodium storage performance including high reversible capacity (cathode: 52.4 mAh g–¹ at 1C, anode: 59.8 mAh g–¹ at 1C, 1C = 62 mA g–¹) and remarkable rate capability (cathode: 44.8 mAh g–¹ at 20C, anode: 52.9 mAh g–¹ at 20C), as well as long cycle life. Meanwhile, ex situ X-ray photoelectron spectra (XPS) measurements reveal that V⁴⁺/V³⁺ and Ti⁴⁺/Ti³⁺ oxidation/reduction couples are redox-active sites of NVTP@C cathode and anode, respectively. When NVTP@C assembled into symmetric ANIBs, a full cell achieves ultrahigh stability of over 2500 cycles at 10C, showing broad prospects in large-scale electric energy storage applications.

Magnetism and thermal stability of layered TiO2–MoS2

The magnetism and thermal stability of layered TiO2–MoS2(LTM) were investigated. Compared with layered TiO2(LT), the magnetization of LTM is reduced greatly. As verified by photoluminescence and X-ray photoelectron spectra measurements, the reduction of magnetization is related to the decreasing of oxygen vacancy and Ti3+. The temperature dependence of magnetism is only slightly different between LT and LTM, indicating that layer MoS2has very little contribution to magnetism. The thermal stability of LTM was studied by heating the sample in Ar atmosphere at different temperatures. The layered structure of LTM is destroyed by heating at 100 °C because the MoS2layer is changed into MoS2particles by heating at this temperature.

Tetracycline removal from aqueous solution using zirconium-based metal-organic frameworks (Zr-MOFs) with different pore size and topology: Adsorption isotherm, kinetic and mechanism studies

The adsorptive removal of tetracycline (TC) was studied with three types of zirconium-based metal–organic frameworks (Zr-MOFs), UiO-66, NU-1000 and MOF-525. The adsorption kinetics best fitted with the pseudo-second-order kinetic model and the adsorption equilibrium was rapidly reached within 40 min on UiO-66 and NU-1000, and 120 min on MOF-525. The adsorption isotherms best fitted with Sips model, and the maximum Sips adsorption capacities of TC on UiO-66, NU-1000 and MOF-525 were 145 mg·g−1, 356 mg·g−1 and 807 mg·g−1 respectively, which were much higher than common adsorbents. The X-ray photoelectron spectra measurements and the influence of pH suggested that the π-π interaction played a crucial role during the adsorption. Pore characteristics and topology of MOFs showed great effect on adsorption performance. The cages whose size match well with TC helped MOF-525 to get highest adsorption amount per surface area among MOFs we studied. The proper topology of NU-1000 contributed to its high adsorption rate. River water was also used to confirm the excellent adsorptive performance of these three Zr-MOFs in practical application. These results might aid us to comprehend the adsorption of TC on Zr-MOFs and expand the application of Zr-MOFs in water treatment for removal of emerging contaminants.

The Electronic States of Copper Oxides Photoactive Layers Prepared by Electrodeposition followed by Annealing

The copper oxides are best performing metal oxide materials regarding solar energy conversion, and due to their abundance, scalability, ease of fabrication and subsequently being low-cost, Cu2O and CuO have attracted extensive attraction. In this research, Cu2O layers were electrodeposited on Ga:ZnO (GZO) and annealed to form directly-stacked GZO/Cu2O/CuO. The external quantum efficiency (EQE) of the devices was evaluated which demonstrated peculiar negative regions around 500 nm besides the typical 410 nm originating from the Cu2O. Reversed bias voltages were applied to investigate the changes, and along with the disappearance of negative regions, a peak around 550 nm and an absorption edge at 850 nm appeared, which increased with the increment of bias voltage. To elucidate the mechanism, the electronic states were investigated by x-ray photoelectron spectra (XPS). Species identification was also successful which showed the presence of CuO on the topmost layer and the underlying Cu2O, which was difficult to analyze by XRD due to its thinness. The schematics of the band-alignments were drawn based on the calculations from the XPS measurements. The conduction band of the Cu2O appeared elevated, which contributed to the speculated two-way flow of the charge when illuminated, and explains the appearance of the negative EQE regions. The charge transportation was successfully controlled and aligned when bias voltages were applied, which caused the disappearance of negative regions and the appearance of the absorption edge of the CuO.

Impact of surface chemistry and pore structure on water vapor adsorption behavior in gas shale

To determine the effects of surface chemistry and the pore structure of shale on water vapor adsorption behavior, water vapor isothermal adsorption experiments were performed with untreated and 15 wt% H2O2 treated shale samples from Longmaxi Formation, Sichuan Basin, China. Additionally, low-pressure N2 ad-/desorption, X-ray diffraction, and X-ray photoelectron spectra measurements were conducted to analyze the pore structure, mineral composition, and functional groups in shale pore surfaces, respectively. The results show that when relative humidity ranged from 0 to 1, water vapor adsorption occurred through primary adsorption sites (monolayer adsorption) and secondary adsorption sites (multi-layer adsorption and capillary condensation). Adsorption by the primary sites was directly related to the number and type of oxygen-containing functional groups and pore size. Furthermore, compared with C–C/C–H and C-O, the functional groups of COO– and C = O/O-C-O provided more adsorption sites. A smaller pore size resulted in more water vapor adsorbed at the primary adsorption sites. The adsorption at secondary sites is not affected by the surface chemical properties; rather, it is directly related to pore volume. Additionally, a larger pore volume results in increased water vapor adsorbed by the secondary adsorption sites. These findings contribute to a better understanding of the primary water distribution in the multiscale pore structure of shale and accurate evaluation of the amount of gas in place.

Superoxide-Triggered Luminol Electrochemiluminescence for Detection of Oxygen Vacancy in Oxides.

Oxygen vacancy is known to act as a reactive center in oxides to produce radicals. Currently, X-ray photoelectron spectra (XPS) become a unique spectral tool for analyzing oxygen vacancy based on the differences in atomic number ratios between metal ions and lattice oxygen. In this work, it was found that the superoxide radical (O2•-)-luminol electrochemiluminescence (ECL) intensity linearly increases with increasing the oxygen vacancy concentrations of TiO2 samples coated on the electrodes. An experimental study of the mechanism demonstrates that an increase in oxygen vacancy concentrations could lead to an increase in the generation of O2•-, resulting in an increase in the O2•--related luminol ECL signals. Accordingly, we have developed a rapid and simple O2•--luminol ECL platform to detect oxygen vacancy in TiO2 samples, based on the relationship between O2•- generation and oxygen vacancy. The proposed ECL platform exhibits good reproducibility and stability through the parallel ECL measurements. Moreover, the feasibility is verified by analyzing the oxygen vacancy concentrations in different TiO2 samples with varying the Co, Cr, Fe, and N doping concentrations. The oxygen vacancy concentrations obtained by the proposed ECL method could match well with those obtained by conventional XPS measurements. Our successful construction of the ECL platform will significantly promote the development of the oxygen vacancy detection in oxides and deepen the understanding of the relationship between oxygen vacancy and radicals.

Improved Direct Current Electrical Properties of Crosslinked Polyethylene Modified with the Polar Group Compound.

To suppress space charge accumulation and improve direct current (DC) electrical properties of insulation materials, crosslinked polyethylene modified with 2-(4-benzoyl-3-hydroxyphenoxy) ethyl acrylate (XLPE/BHEA) containing polar functional groups was prepared by melt blending. The gel content, thermal elongation, tensile strength, elongation at break, elasticity modulus, differential scanning calorimetry (DSC) and X-ray photoelectron spectra (XPS) measurement results demonstrated that the BHEA could slightly enhance the crosslinking of polyethylene (PE) and affect the mechanical properties and crystallization of XLPE, and the BHEA molecule was not easy to precipitate from XLPE after the crosslinking process. XLPE modified with 3.0 phr (parts per hundreds by weight) BHEA could effectively suppress space charge accumulation, reduce DC conduction and improve DC breakdown strength of XLPE at a higher temperature. Deeper traps were introduced in XLPE/BHEA composites due to the polar functional groups in BHEA, which could raise the potential charge injection barrier and reduce the charge carrier number and mobility to suppress space charge accumulation and reduce the conduction current density.

Thin NiFeCr-LDHs nanosheets promoted by g-C3N4: a highly active electrocatalyst for oxygen evolution reaction

NiFeCr layered double hydroxides (NiFeCr-LDHs) supported on graphitic carbon nitride (g-C3N4) hybrids (NiFeCr-LDHs/g-C3N4) are synthesized and used as an electrocatalyst for oxygen evolution reaction (OER) in alkaline media. Effect of g-C3N4 on the structure and OER performance of NiFeCr-LDHs are investigated in detail. g-C3N4 can promote the formation of thin NiFeCr-LDHs nanosheets, thereby enhancing both the number of active sites and OER activity. X-ray photoelectron spectra measurements confirm the electronic interaction between g-C3N4 and NiFeCr-LDHs nanosheets. The OER performance of NiFeCr-LDHs/g-C3N4 hybrids highly relates to the weight ratio of g-C3N4 to NiFeCr-LDHs. When the weight ratio of g-C3N4 to NiFeCr-LDHs is 5%, the corresponding electrocatalyst shows the best OER activity. The component optimized NiFeCr-LDHs/g-C3N4 hybrids display the overpotential of ∼223 mV at 10 mA cm−2 and Tafel slope of 89 mV dec−1 for OER in 1 M KOH solution, which is better than that of pristine NiFeCr-LDHs, bare g-C3N4, and commercial RuO2.

Growth and photocatalytic behavior of transparent reduced GO–ZnO nanocomposite sheets

Reduced graphene oxide–zinc oxide (rGO–ZnO) nanocomposites were grown on solid substrates by rapid thermal treatment of Langmuir–Blodgett transferred GO–Zn composite sheets in oxygen ambient. The changes induced by uptake of Zn2+ ions and subsequent thermal treatment on surface morphology, micro-structure, composition and optical properties of composite sheets were investigated by atomic force microscopy, high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared (FT-IR) and Raman measurements. The morphological features of composites are practically independent of subphase Zn concentration and are largely determined by the temperature of rapid thermal treatment. FT-IR results indicate the presence of zinc carboxylate in composites and HR-TEM results confirm the formation of ZnO nanoparticles upon subsequent oxidation. XPS and Raman measurements show that rapid thermal treatment in oxygen ambient results in decrease of carbon-oxygen functional groups and increase in graphitic carbon content leading to the reduction of GO in the composites. The average optical transmittance of rGO–ZnO composites in the visible region is found to be ∼87%. Photocatalytic studies carried out on methylene blue (MB) overlayer coated rGO–ZnO composites show reduction in concentration of MB with increasing duration of UV irradiation. The transparent two-dimensional rGO–ZnO composite solid state structures thus facilitate efficient adsorption and degradation of MB molecules, without any composite aggregation.

Octadecylamine degradation through catalytic activation of peroxymonosulfate by Fe[sbnd]Mn layered double hydroxide

A kind of heterogeneous catalyst, FeMn layered double hydroxide (Fe-Mn-LDH), was fabricated by coprecipitation process and used as PMS activator to degrade a novel organic pollutant octadecylamine (ODA). And the X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microcopy (TEM), Mapping and X-ray photoelectron spectra (XPS) measurements were utilized to characterize the fresh and used Fe-Mn-LDH. After a serious of degradation experiments, it was clearly to see that the activator possessed excellent activation property for PMS and was capable of removing 85% ODA (10 mg·L−1) within 25 min obviously higher than pure PMS. Moreover, the effect of some elements (such as PMS consumption, catalyst consistence and initial pH value), different reaction system and catalyst repeatability on ODA degradation were also explored. And by identification of main radical experiment, SO4— and HO were both confirmed the primary radicals. What's more, extra anion and nature organic matter (NOM) addition experiment displayed that NOM, NO3— and CO32— perform a negative effect on ODA degradation but Cl— could promote it. In addition, repeated experiments and metal leaching after degradation showed good stability of Fe-Mn-LDH. Finally, based on the XPS and Gas Chromatography-Mass Spectrometer (GS-MS) technology, the possible degradation mechanism and pathway were proposed.

Pyridine-based additive optimized P3HT:PC61BM nanomorphology for improved performance and stability in polymer solar cells

Photovoltaic (PV) performance of bulk heterojunction polymer solar cells (BHJ PSCs) highly depends on the optoelectronic properties of the photoactive layer. In this regard, additives (solvent or solid) are considered as one of the versatile methods and key morphology directing agents for solution processed PV devices. Herein this contribution, we rationally utilize a new kind of pyridine-based solid additives (2-hydroxypyridine (2-DHP) and 2,4-dihydroxypyridine (2,4-DHP)) to manipulate and engineer the nanomorphology of the poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) photoactive system, that can influence the optoelectronic properties for enhanced performance in BHJ PSCs. The optical, electrical, morphological, surface, structural characteristics of the fabricated BHJ PSCs were systematically examined. The atomic force microscopy and X-ray photoelectron spectra measurements confirmed the structural reorganization, phase separation of polymer and fullerene domains resulting in the formation of well-ordered blend in the additive based devices. BHJ PSCs fabricated with P3HT:PC61BM:2-DHP and P3HT:PC61BM:2,4-DHP yielded a best power conversion efficiency (PCE) of 4.35% and 3.58%, respectively, which in contrast outperformed than the PCE obtained from P3HT:PC61BM device (3.01%). The remarkably improved performance for P3HT:PC61BM:2-DHP can be attributed to the enhanced short-circuit current density induced by the morphology optimization. Additionally, the devices fabricated with the solid additives (2-DHP and 2,4-DHP) exhibited improved air-stability due to the oxygen insensitivity of the functional groups present in the chosen additives. The pyridine and hydroxyl groups in 2-DHP and 2,4-DHP possibly form the intermolecular interactions with the photoactive components (P3HT/PC61BM), contribute to the morphology optimization and subsequent PV performance enhancement in BHJ PSCs. It is believed that our findings can inspire and trigger further advanced research toward the design and development of stable and highly efficient BHJ PSCs by rationally choosing low-cost solid additives.

Construction of surface lattice oxygen in metallic N−CuCoS1.97 porous nanowire for wearable Zn−air battery

Abstract Achieving high activity and stability oxygen evolution reaction (OER) catalysts to optimize the efficiency of metal−air battery, water splitting and other energy conversion devices, remains a formidable challenge. Herein, we demonstrate the metallic porous nanowires arrays with abundant defects via nitrogen and copper codoped CoS1.97 nanowires (N−CuCoS1.97 NWs). The N−CuCoS1.97 NWs can serve as an excellent OER self-supported electrode with an overpotential of 280 mV (j = 10 mA cm−2) and remarkable long-term stability. The X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectrum (XPS) measurements confirmed the surface lattice oxygen created on the N−CuCoS1.97 NWs during OER. Then, the density function theory (DFT) results evident that lattice oxygen constructed surface of N−CuCoS1.97 NWs has more favorable OER energetic profiles and absorption for reaction intermediate. More importantly, the flexible and wearable Zn−air battery fabricated by the N−CuCoS1.97NWs shows excellent rechargeable and mechanical stability, which can be used in portable mobile device.

Removal of atrazine by photoelectrocatalytic process under sunlight using WN-codoped TiO2 photoanode

The present study was focused on the degradation of Atrazine (ATZ) and major by-products (DEA, DIA, DEDIA and ATZ-OH) from water by photoelectrocatalytic (PEC) oxidation process under solar light. The undoped TiO2, sub-stoichiometric TiO2 (TiO2−x) and codoped TiO2 (TiO2:WN) photoanodes were prepared by means of a radio frequency magnetron sputtering (RF-MS) deposition process. The X-ray photoelectron spectra (XPS) analysis shows that the N and W atoms were incorporated into the O and Ti lattice sites of TiO2 respectively (case of TiO2:WN film), while the XPS measurements of the TiO2−x films composition was determined to be TiO1.9. The UV–Vis transmittance spectra shows that in the case of the TiO2:WN films, the presence of nitrogen and tungsten improve the optical response of TiO2 under visible range compare to the presence of oxygen vacancies in to the TiO2−x films. The experimental results under solar light with an initial concentration of ATZ (100 µg L−1) show that after 180 min of treatment, the degradation of ATZ were 34.98%, 68.57% and 94.33% using TiO2, TiO2−x and TiO2:WN photoanodes, respectively. These results of ATZ degradation proved that TiO2:WN photoanode was more photoactive under solar light. The evolution by-products of ATZ under sunlight show that the principal mechanism of ATZ degradation was the oxidation of alkyl side chain and dealkylation.