X-ray Photospectroscopy Research Articles

Photodegradation of Polyethersulfone (PES), Polyvinylidene Fluoride (PVDF) and Polymethyl Methacrylate (PMMA) Microplastics via a Metal Organic Framework Namely ZIF-8/ZnO/C

The aim of this study was to photodegrade the Polyethersulfone (PES), Polyvinylidene fluoride (PVDF) and Polymethyl methacrylate (PMMA) microplastics using Zeolitic imidazolate framework-8/Zinc oxide/Carbon (ZIF-8/ZnO/C) nanocomposite generated under laboratory conditions. The produced nanocomposite was analysed using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Photo Spectroscopy (XPS), Scanning Electron Microscope (SEM), Diffuse reflectance UV-vis spectra (DRS) and Electron Spin Resonance (ESR) analyses. The maximum PES, PVDF and PPMA photodegradation yields were 99%, 98%, and 96%, respectively, at 1 mg/l ZIF-8/ZnO/C nanocomposites (NCs) concentration, 1000 mg/l microplastics concentration, at pH = 10.0, at a temperature and photodegradation time of 40°C and 20 min, under oxic conditions at a sunlight intensity of 80 W/m<sup>2</sup> and a photon yield of 16. The XRD analysis showed the generation of ZIF-8/ZnO/C, while the FTIR analysis indicated the ZnO, C, and ZIF-8.

Electrical properties of acetone imprinted hematite nanomaterials doped with Pd & Ag for gas sensing and simulation of their wireless devices

This article presents a novel technique for wireless hydrothermally improved gas sensor devices enhanced by molecular imprinting technique (MIT) for hematite nanomaterials with the existence of acetone using different ratios (10 %, 15 %, and 25 %) as well as doping with palladium/ silver to detect the imprinted gas. α-Fe2O3 are characterized utilizing field emission scanning electron microscope (FESEM), photoluminescence, Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photo-spectroscopy (XPS), and High-Resolution Transmission Electron Microscopy (HRTEM), Thermogravimetric Analysis (TGA) and utilizes Brunauer-Emmett-Teller (BET) to ascertain their shape, optical properties, and values for surface area and thermal characteristics, respectively. Depending on the preparation conditions, non-regular cubes and rods have typical particle sizes ranging from 25 to 120 nm, acetone imprinted and doped with palladium sample (Ap) offers smaller particles than acetone imprinted sample (A15) making adsorption easier. Where XRD showed all diffraction peaks for α-Fe2O3 as well as XPS authorized the oxidation state, also FTIR showed the characteristic peaks of the stretching mode Fe-O which indicates the formation of α-Fe2O3. Lower defects for (Ap) as it has the highest intensity of 176.15 a.u. in the photoluminescent spectrum, for TGA analysis results explain that pure sample has more thermal stability and lower weight loss. Six hematite films are fabricated using the spin coating technique where acetone molecules are presented during the synthesis process of the nanomaterials to imprint their shapes on the surface of hematite. By measuring the response of the gas sensors and their electrical properties, the I-V curve for Ap showed a rectifying behavior and its shunt resistance (Rsh) is higher than series resistance (Rs) which ensures a high response of (115 %). To develop a wireless gas sensor COMSOL Multiphysics software 5.3(a) software is used for the simulation of three devices model by depositing a layer by specified dimensions of hematites (A15, As, and Ap) with their different electrical conductivities on the surface of rectangular patch antenna by showing geometry, the microstrip patch antenna bandwidth, resonant frequency, scattering parameters, and radiation patterns in the E-plane and 3-D far-field pattern and directivity is calculated also, Sp gives improved reflection coefficient, gain quality factor and directivity due to its high electrical conductivity.

Synthesis of Sn-ZnO nanostructures on MgO by hybrid pulsed laser ablation and RF magnetron sputtering tandem system for CO gas-sensing application

An exceptional method of incorporating Sn ions into Zinc Oxide (ZnO) using a tandem system of Pulsed Laser Deposition (PLD) and Radio-Frequency Magnetron Sputtering (RFMS) to synthesize and functionalize ZnO nanostructures is demonstrated in this study for gas-sensing application. The RFMS power was varied up to 50 W to sputter a pure Sn metal target, while simultaneously or successively growing ZnO nanostructures on a templated MgO < 0001 > substrate and on an Au-plated Al2O3 gas sensor, via PLD process at the substrate temperature of 700 °C in 100–500 millitorr oxygen/argon gas background. The morphologies of the grown Sn-ZnO nanostructures were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and X-ray Diffraction (XRD), and while their chemical/oxidation states and optical properties were analyzed by X-ray photospectroscopy (XPS) and photoluminescence (PL), respectively. For simultaneous deposition, the resulting (0002)-dominated 2D grain-like ZnO nanostructures were influenced by the interaction of the dynamic PLD plasma with static RFMS plasma at different powers. For successive growth, at 50 W-RF power, a remarkable increase in the sensor response to 50-ppm carbon monoxide (CO) gas was observed at 250 °C, which could be attributed to the creation of more adsorption sites in the Sn-ZnO depletion region caused by the replacement of some Zn sites with Sn ions in the ZnO matrix. This study, therefore, exhibits the viability of this hybrid system to design, synthesize, and functionalize Sn-ZnO nanomaterials, either by simultaneous/successive deposition, for gas-sensing applications.

In-Situ Synthesis of CuO/TiO2 Nanocomposite Onto Amine Modified Cotton Fabric for Antibacterial Durability and UV Protection

ABSTRACT In this research work, we explore antibacterial activity and the UV-protection of cotton fabric functionalized with copper oxide-titanium dioxide nano composites particles (CuO+TiO2 NCPs). Cotton fabrics (Cot) were treated with L-methionine (Am) and functionalized with bimetallic CuO+TiO2 NCPs by pad and rolling technique. Cu(NO3)2 and titanium isopropoxide (TIP) were used as sources of Cu(OH)2 and TiO2 colloid respectively, which were then converted into CuO and TiO2 nanoparticles (NPs) for making antibacterial and UV-protective cotton. The method yielded a crystallite size of CuO and TiO2 NPs of 18.09 and 32.5 nm, respectively. FTIR, Raman spectroscopy, High-resolution scanning electron microscopy-Energy dispersive Spectroscopy (HRSEM), (EDS), X-ray photo spectroscopy (XPS), thermal gravimetric analysis (TGA), and XRD were used to analyze the functional group, morphology, chemical composition, thermal stability and crystalline structure of the functionalized cotton fabric samples. The results showed that an esterification reaction occurred between Am and OH in cotton fabric, which further enhanced the binding of NCPs. AmCot-CuO+TiO2 NCPs exhibit outstanding antibacterial activity against gram-positive S. aureus and gram-negative E. coli. The UV protection factor (UPF) for AmCot-CuO+TiO2 NCPs reached 50+; thus, multifunctional cotton fabrics with excellent antibacterial and anti-ultraviolet properties were obtained.

Mechanical Behavior of Selective Laser Melting (SLM) Parts with Varying Thicknesses in a Saline Environment under Different Exposure Times.

A promising method for additive manufacturing that makes it possible to produce intricate and personalized parts is selective laser melting (SLM). However, the mechanical properties of as-corroded SLM parts are still areas of concern. This research investigates the mechanical behavior of SLM parts that are exposed to a saline environment containing a 3.5% NaCl solution for varying lengths of time. The exposure times chosen for this study were 10 days, 20 days, and 30 days. The results reveal that the tensile strength of the parts is significantly affected by the duration of exposure. Additionally, the study also examined the influence of porosity on the corrosion behavior of the parts. The analysis included studying the mass loss of the parts over time, and a regression analysis was conducted to analyze the relationship between exposure time and mass loss. In addition, the utilization of scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS) techniques yielded valuable insights into the fundamental mechanisms accountable for the observed corrosion and mechanical behavior. It was found that the presence of corrosion products (i.e., oxide layer) and pitting contributed to the degradation of the SLM parts in the saline environment. This research emphasizes the importance of considering part thickness in the design of SLM components for corrosive environments and provides insights for enhancing their performance and durability.

CuMOF@Faujasite nanocomposite as a novel catalyst for hydrogen production

Energy production is one of the most crucial issues presently attracting global attention. In this work, a CuMOF@Faujasite nanocomposite was synthesized and utilized as a novel efficient catalyst for hydrogen production. The produced composite was first characterized using X‐ray diffraction (XRD), Fourier‐ transform infrared (FT‐IR), thermogravimetric analysis (TGA), and differential scanning calorimetry. Surface properties were analyzed via nitrogen adsorption–desorption isotherms. All characterization results revealed the formation of a pure and well‐defined crystalline phase, with a high specific surface area (SBET) of 286 m2/g (SBET of Faujasite is 35 m2/g). Moreover, the morphology and compositional analysis of the nanocomposite were assured through the scanning (SEM) and transmission (TEM) electron microscope and X‐ray photospectroscopy (XPS). SEM and TEM images revealed sponge‐like spheres that are related to Faujasite besides small spherical particles related to CuBDC MOF. XPS analysis revealed a low content of CuMOF in the nanocomposite. The catalytic activity of the nanocomposite was tested for the dehydrogenation of NaBH4. The impact of NaBH4 concentration, weight of the catalyst, and the reaction temperature on NaBH4 hydrolysis was investigated. A hydrogen generation rate (HGR) of 484 mLmin−1 g−1 at 30 °C was achieved using 50 mg of the catalyst and 0.05 mol/l of NaBH4 owing to the high specific area and the selective active sites for such hydrolytic reaction. The kinetic analysis of the activity data indicates the first‐order behavior at low concentrations of NaBH4. Furthermore, at concentrations ≥0.065 mol L−1, zero‐order kinetics was predominant. The time needed for completion of the hydrolysis reaction was found to be decreased (~20 min) by increasing the catalyst mass as well as NaBH4 concentration or even by elevating the reaction temperature (~4 min at 60 °C). The activation energy was estimated; it was found to be 70.5 KJ mol−1. Ultimately, our catalyst showed a reasonable rate of hydrogen production, as compared to others reported earlier.

Synergetic and anomalous effect of CNTs in the sulphide‐based binary composite for an extraordinary and asymmetric supercapacitor device

AbstractCarbon nanotubes (CNTs) have attained great interest from researchers due to their excellent electrical conductivity, vast surface area, and good chemical stability. In this work, the sulphide‐based composite Ag2S@ZnS was synthesized using the hydrothermal method and was doped with CNTs in various weight percentage ratios. The structural and morphological characteristics of the samples were evaluated by employing X‐ray diffractometry (XRD), X‐ray photo spectroscopy (XPS), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, and thermogravimetric analysis (TGA), while cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) were also executed for their electrochemical characterization. The performance of the Ag2S@ZnS electrode was enhanced after the doping of CNTs because of their synergistic effect. An extraordinary specific capacity (Qs) of 946.5 Cg−1 (262.91 mAh g−1) was exhibited by Ag2S@ZnS with 50% CNTs doping (Ag2S@ZnS/CNT‐50%), which is significantly greater than the reference samples. Furthermore, an asymmetric supercapacitor was designed and assessed for its electrochemical properties. The specific capacity of the asymmetric supercapacitor reached 148.62 Cg−1 (41.28 mAh g−1). The device showed improved stability and retained the 87% initial capacity after 5000 cycles. The energy and power densities were found to be 33.02 Wh kg−1 at 639.98 W kg−1, respectively, with a high value of coulombic efficiency of 92%. The device succeeded in acquiring a higher power density of 3200 W kg−1 for an energy density of 4 Wh kg−1. These astonishing results provide opportunities to design high‐performance electrode materials for extraordinary energy storage devices.

Synthesis of CuxO/Ag nanoparticles on exfoliated graphene: application for enhanced electrochemical detection of H2O2 in milk

In this paper, a novel composite is constructed as a non-enzymatic hydrogen peroxide (H2O2) sensor by liquid-phase exfoliation method, which is composed of copper oxide, cuprous oxide and silver nanoparticles doped few-layer-graphene (CuxO/Ag@FLG). Its surface morphology and composition were characterized by scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS), and its H2O2 sensing performances include catalytic reduction and quantitative detection were studied with electrochemical methods. Our sensor had a high sensitivity of 174.5 μA mM−1 cm−2 (R2 = 0.9978) in an extremely wide range of concentrations from 10 μM to 100 mM, a fast response (about 5 s) and a low limit of detection (S/N = 3) of 2.13 μM. The sensor exhibits outstanding selectivity in the presence of various biological interference, such as dopamine, ascorbic acid, uric acid, citric acid, etc. In addition, the constructed sensor continued 95% current responsiveness after 1 month of storage further points to its long-term stability. Last but not least, it has a good recovery rate (90.12–102.00%) in milk sold on the open market, indicating that it has broad application possibilities in the food industry and biological medicine.

Novel ternary g-C3N4/Zn2SnO4/MoS2 nanocomposites for improved visible light photodegradation of tetracycline

The development of highly effective photocatalysts with a visible light response is a primary goal in the photocatalysis field. In this work, a novel ternary g-C3N4/Zn2SnO4/MoS2 nanocomposite was prepared by hydrothermal method and the prepared catalyst exhibited efficient photocatalytic activity towards tetracycline (TC). Different techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photo spectroscopy (XPS), and UV–Vis spectroscopy, were used to examine the structural, morphological, electronic and optical characteristics of the prepared catalysts. The obtained ternary composite exhibited efficient photodegradation of TC with a degradation rate of 0.0526 min−1 which is ∼2.5 fold higher than pristine samples. Furthermore, the optimum catalyst shows good recycle stability and hydroxyl radicals and super oxide radicals were the key active species in TC degradation. The current study offers a new perspective on developing highly effective, recyclable photocatalysts for removing aqueous pollutants.

One-step synthesis of ultrafine silver-decorated polyaniline nanowire arrays for trace analysis of sulfamethoxazole

Sulfamethoxazole (SMX), a broad-spectrum antibiotic, has potential risk of ecological damage and human health, due to its over-dosage utilization and wanton discharge. It is desirable to develop a highly sensitive sensor for the rapid and accurate determination of SMX to evaluate the environmental risk of antibiotics. Herein, an ultrafine Ag nanoparticles-decorated polyaniline nanowire arrays (AgNPs-PANI-NAs) were successfully formed on the carbon nanofibers (AgNPs-PANI-NAs@CNF) by in-situ one-step redox reaction. The PANI wire length around CNFs and the AgNPs amount were conveniently tuned by adjusting Ag+ concentration. The conductivity and electrochemical activity of the AgNPs-PANI-NAs@CNF were significantly improved. With AgNPs-PANI-NAs@CNF as sensing material, the resultant AgNPs-PANI-NAs@CNF modified glassy carbon electrode (AgNPs-PANI-NAs@CNF/GCE) presented a super-high electrochemical response to the oxidation of SMX by strong interaction of SMX with the sensing interface. A wide linear range (1 nM ∼ 10 μM) was achieved with an ultra-low detection limit (80 pM, S/N>3). The chronocoulometry measurement proved that the adsorption capacity of SMX at AgNPs-PANI-NAs@CNF/GCE was significantly enhanced, thus improving the sensitivity of SMX detection. The related reaction mechanism and strong interaction of SMX with AgNPs-PANI-NAs were demonstrated by X-ray photo spectroscopy and ultraviolet-visible spectroscopy characterization. This work provides a novel strategy of constructing high-performance sensing materials for pollutants analysis in environmental waters.

Wide light-harvesting AgZnGaS3 quantum dots as an efficient sensitizer for solar cells

In this work, Silver, Zinc, Gallium, and Sulfur based AgZnGaS3(AZGS) QDs were synthesized with a colloidal hot injection method and it is loaded onto the surface of TiO2 nanofibers. The morphological and structural properties of the AZGS QDs and QDs sensitized TiO2 were examined by X-ray diffraction, X-ray photo spectroscopy, High-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy studies. The optical properties were examined by using absorption and emission spectra studies. These results showed that the synthesized QDs have a bandgap of 2.1 eV and their average lifetime is 67.75 ns. There is no alteration found in the crystal structure of TiO2 when AZGS QDs are loaded onto TiO2 nanofibers (AZGS/TiO2) surface. A solar cell is fabricated with AZGS/TiO2-based photoanode and analyzed by ac-impedance and photovoltaic performance. Its photoconversion efficiency was estimated to be 3.81%.

Study on Aluminum Corrosion in Lithium Perchlorate-Based Super-Concentrated Electrolyte Solution

For realizing sustainable world, Lithium-ion batteries are required to have higher energy density. Aluminum metal have been dominantly used as a current collector of positive electrode. A mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) containing 1 mol dm-3 Lithium hexafluorophosphate (LiPF6) has been used as an electrolyte solution, however, aluminum corrosion may occur due to this electrolyte solution under high voltage condition. On the other hand, super-concentrated electrolyte solution (SCES), which consists of only two or three times as much solvent as lithium salt, has been attracting attention as a new electrolyte solution of Lithium-ion battery. Motsumoto et al. proposed that aluminum corrosion was remarkably suppressed in lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-based SCES. However, the electrolyte solution containing fluorine has the problem which is the dissolution of the active material due to the decomposition product of the electrolyte solution．In the present work, we investigated aluminum corrosion in the lithium perchlorate (LiClO4)-based SCES as a fluorine-free solution.The LiClO4 based SCES was prepared by dissolving LiClO4 into DMC as the molar ratio of 1 : 2. For comparison, DMC solution containing 1 mol dm-3 LiClO4 was also prepared. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were measured. X-ray photospectroscopy (XPS) was performed to evaluate the decomposition product on the aluminum electrode. Anodic current of the dilute electrolyte solution is observed at 3.9 V vs. Li/Li+. By contrast, in the LiClO4 based SCES, the anodic current is less than 100 µA cm-2 when polarized to 6 V vs. Li/Li+. In the dilute electrolyte solution, the ClO4 - anion is decomposed to form Cl-, which promotes aluminum corrosion. By contrast, the SCES has high oxidative stability, suggesting that the liquid structure of the SCES differ from that of the dilute electrolyte solution. two intense peaks appear at 196 and 198 eV in in XPS spectra of Cl 2p for the aluminum surface after LSV measurement in the dilute electrolyte solution. On the other hand, a weak peak is observed at approximately 199 eV in XPS spectra of Cl 2p for the aluminum surface after LSV measurement in the SCES. This result suggests that the ClO4 - anion is not decomposed in the SCES.

Unusual synthesis of nanostructured Zn-MOF by bipolar electrochemistry in ionic liquid-based electrolyte: Intrinsic alkaline phosphatase-like activity

Metal-organic frameworks (MOFs) as a unique class of multifunctional materials have increasingly attracted interest. So, the development of available and straightforward strategies for the synthesis of MOFs reminds challenging. Here, we developed an indirect bipolar electrodeposition method to construct a novel and fine nanostructured Zn-MOF on the indium tin oxide (ITO) surface. The room temperature ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) is used as an electrolyte, zinc sulfate (monohydrate) as the source of metal ion, and 1,3,5 benzenetricarboxylic acid (BTC) as an organic ligand. The synthesized MOF was characterized by scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy (EDAX), grazing Incidence X-ray Diffraction (GIXRD), atomic force microscopy (AFM), X-ray photo spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. Furthermore, we have explored the structure of Zn-BTC MOF and their enzyme cofactor's similarity to alkaline phosphatase mimics in aqueous solutions. The proposed MOF nanostructures have been investigated as a promoter for hydrolysis of sodium para-nitrophenylphosphate (PNPP) to para-nitrophenol (PNP) and inorganic phosphate.

Novel millet husk crop-residue based thermoplastic composites: Waste to value creation

The objective of the current research endeavor is to explore the potential of novel natural lignocellulosic crop-residue fibers (husk) extracted from the finger millet (Eleusine coracana) and barnyard millet (Echinochloa frumentaceae). The extracted finger millet husk (FMH) and barnyard millet husk (BMH) were characterized for their physical (extractive and density), chemical (X-ray photo spectroscopy and Fourier transform infrared spectroscopy), thermal (Thermo-gravimetric analysis), and morphological (X-ray diffraction and Scanning electron microscopy) behavior. The major objective was to explore their potential in the development of thermoplastic composites. Thermal kinetics of the fibers were studied with Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models. After fiber characterization, the composites were developed using injection molding process and characterized for mechanical, thermal, and morphological behavior. In the end, the flammability properties of the developed composites were investigated with Thermo-gravimetric analysis, UL-94 Horizontal burning, and Limiting Oxygen Index testing. Chemical constituent analysis reveals higher cellulosic and lower lignin content of FMH (cellulose; 38.01% and lignin; 16.25%) than BMH (cellulose; 34.5% and lignin; 21.31%). Thermal kinetics shows higher activation energy (Ea) for BMH (207.17 kJ/mol) than FMH (129.82 kJ/mol) as per the FWO model. BMH reinforced composites offer higher thermal stability and flame resistance than FMH reinforced composites, while FMH reinforced composites show higher mechanical properties than BMH reinforced composites. Overall, both husks show the potential to be used in developing thermoplastic composites.

3DOM Cerium Doped LaCoO3Bifunctional Electrocatalysts for the Oxygen Evolution and Reduction Reactions

AbstractA bifunctional oxygen evolution reaction and oxygen reduction reaction (OER/ORR) electrocatalyst, macroporous cerium‐doped LaCoO3, was designed based on a dual strategy that included (1) constructing a three‐dimensionally ordered macroporous (3DOM) structure to increase the electrochemical surface area and (2) varying amount of cerium substitution from 0.02 to 0.15 mole fraction of the A site to alter the intrinsic activity of LaCoO3. The catalytic activity of 3DOM La0.95Ce0.05CoO3(3DOM LCCO‐0.05) is significantly improved over that of the unmodified LaCoO3, with the OER overpotential to reach 10 mA cm−2lowered by 190 mV, the ORR limiting current density doubled, and the OER‐ORR potential gap reduced by 220 mV to 1.07 V. This enhanced activity is attributed to the increased electrochemical surface area and specific activity, as evidenced by the greater double‐layer capacitances and the lower charge transfer resistances determined by electrochemical impedance spectroscopy (EIS). Furthermore, X‐ray diffraction (XRD) and X‐ray photospectroscopy (XPS) results reveal that these enhanced OER/ORR activities are possibly related to the transformation of the cobalt(III) spin state from low to intermediate or high‐spin, and the increasing amount of surface oxygen species and oxygen vacancies.

Mitigating iron-induced catalytic wear in monocrystalline diamond tools using two-dimensional (2D) materials

Diamond tools are known to wear rapidly during the machining of ferrous materials because of the catalytic effect of iron on diamond graphitization. This work aims to perform a relative comparison of the wear mitigation efficacy of candidate two-dimensional (2D) materials, viz., graphene oxide (GO), hexagonal boron nitride (hBN), molybdenum disulfide (MoS 2 ) and tungsten disulfide (WS 2 ), when used as cutting fluid additives during diamond turning of steel. The 2D material suspensions (0.15 wt.%) are first characterized for their hydrodynamic diameter distributions. Multi-pass turning studies are then conducted using monocrystalline diamond tools. Tool wear, cutting forces and surface roughness are used as the comparison metrics. Overall, graphene oxide has the highest reduction in tool wear (60 %) over the baseline case. It is followed by hexagonal boron nitride, tungsten disulfide and molybdenum disulfide that offered 52 %, 45 % and 38 % wear reduction, respectively, over the baseline case. Overall, hBN provides the best combination of low tool wear, low cutting forces and low surface roughness. The tool wear mitigation efficacy of the materials can be explained in terms of their specific chemical/physical interactions at the iron-diamond interface. X-ray Photo Spectroscopy (XPS) measurements reveal a clear correlation between the tool wear trends and strength of the graphitic carbon/carbide signals obtained on the machined surfaces. XPS measurements in the B1s and S2p regions shed light on the chemical reactions responsible for the performance of hBN, WS 2 and MoS 2 . The unique surface chemistries of the resulting surfaces offer the potential of a rich exploration landscape for downstream applications.

Effect of Ni particle size on the production of renewable methane from CO2 over Ni/CeO2 catalyst

Production of ‘renewable Methane’ has attracted renewed research interest as a fundamental probe reaction and process for CO2 utilization through potential use in C1 fuel production and even for future space exploration technologies. CO2 methanation is a structure sensitive reaction on Ni/CeO2 catalysts. To precisely elucidate the size effect of the Ni metal center on the CO2 methanation performance, we prepared 2%Ni/CeO2 catalysts with pre-synthesized uniform Ni particles (2, 4 and 8 nm) on a high surface area CeO2 support. Transmission electron microscopy (TEM) and ambient pressure X-ray photo spectroscopy (AP-XPS) characterization have confirmed that the catalyst structure and chemical state was uniform and stable under reaction conditions. The 8 nm sized catalyst showed superior methanation selectivity over the 4 and 2 nm counterparts, and the methanation activity in term of TOF is 10 times and 70 times higher than for the 4 and 2 nm counterparts, respectively. The DRIFTS studies revealed that the larger Ni (8 nm particles) over CeO2 efficiently facilitated the hydrogenation of the surface formate intermediates, which is proposed as the rate determining step accounting for the excellent CO2 methanation performance.

One-step plasma deposited thin SiO x C y films for corrosion resistance of low carbon steel

Tetraethyl orthosilicate (TEOS) was used as a chemical precursor to deposit ultra-thin SiO x C y plasma polymer films onto mild steel surfaces for preventing the corrosion process. The structure–property relationships of the coatings were evaluated by X-ray Photo Spectroscopy (XPS), X-Ray Diffraction (XRD), Fourier Transform InfraRed spectroscopy (ATR-FTIR) and Energy Dispersive X-ray spectroscopy (EDX) completed with Scanning Electron Microscopy (SEM). The SEM micrographs confirmed a pinhole-free surface morphology of the low-pressure deposited plasma polymer films. The TEOS molecules become fragmented in the plasma by numerous collisions with energy-rich electrons and heavier particles. Recombination of fragments and condensation onto the steel substrate is responsible for the formation of organic SiO containing plasma polymer layers. Such thin layers consist of predominantly SiO x structures. Their properties are determined largely by the gap distance between the two samples used as electrodes in the plasma. The efficiency of the corrosion-protecting coating was compared with uncoated samples. The corrosion protection was determined by exposure of samples to 3.5% NaCl aqueous solutions. For this purpose, polarization and Electrochemical Impedance Spectroscopy (EIS) were used to monitor the corrosion. The optimal gap distance between the electrodes was determined for corrosion protection. The best protective efficiency reached more than 97% of the total protection as measured at room temperature.

Polypyrrole Hollow Microspheres with Boosted Hydrophilic Properties for Enhanced Hydrogen Evolution Water Dissociation Kinetics

The water dissociation step (H2O + M + e- → M - Hads + OH-) is a crucial one toward achieving high-performance hydrogen evolution reaction (HER). The application of electronic conducting polymers (ECPs), such as polypyrrole (PPy), as the electrocatalyst for HER is rarely reported because of their poor adsorption energy per water molecule, which hinders the Volmer step. Herein, we strongly enrich PPy hollow microspheres (PPy-HMS) with attractive HER activity by enhancing their hydrophilic properties through hybridization with good water affinity SiO2. The as-prepared PPy-coated SiO2 (PPy@SiO2-HMS) achieves a current density of 10 mA cm-2 at -123 mV, which is lower than that of pristine PPy-HMS (-192 mV). Raman and X-ray photospectroscopy analyses reveal that the enhanced HER catalytic capability can be attributed to the strong electronic couplings between PPy and SiO2, and this improves the adsorption energy per water molecule and in turn accelerates the water dissociation kinetics on PPy. This work highlights the potential application of low-cost ECPs as promising electrocatalysts for water electrolysis.

Application of iron-biochar composite in topsoil for simultaneous remediation of chromium-contaminated soil and groundwater: Immobilization mechanism and long-term stability

This study was aimed to prove the effectiveness and practicability of an integrated technology for simultaneous remediation of Cr-contaminated soil and groundwater. The remediation system was built by pumping Cr-contaminated groundwater into top contaminated soil round after round, enabling the pre-applied iron-biochar composite (Fe-BC) in topsoil to stabilize Cr from both groundwater and soil. Immobilization ability and mechanism of Cr in soil were explored by toxicity characteristic leaching procedure test, scanning electron microscopy-elemental mapping, and X-ray photo spectroscopy. Hydrus-1D software was used to examine the long-term stability of immobilized Cr in soil. Results showed that Fe-BC-amended soil could remove about 71% Cr from contaminated groundwater. Meanwhile, Cr from both groundwater and soil was simultaneously immobilized in topsoil, leachability of Cr in which was reduced by over 81%. The immobilization of Cr in soil was attributed to the reduction of Cr(VI) into Cr(III) to form stable CrxFe(1−x)(OH)3. After remediation, the average transport rate of Cr in the soil profile was only 0.420 cm y−1 along with the local rainfall. Our study demonstrated that integrated technology could effectively remove Cr from groundwater and stabilize Cr in soil and the simultaneous remediation target for both soil and groundwater reached.