Co3O4–Ag photocatalysts for the efficient degradation of methyl orange

In this paper, a series of Co₃O₄–Ag photocatalysts with different Ag loadings were synthesized by facile hydrothermal and in situ photoreduction methods and fully characterized by XRD, SEM, TEM, FTIR spectroscopy, XPS, UV-vis and PL techniques. The catalysts were used for the degradation of methyl orange (MO). Compared with the pure Co₃O₄ catalyst, the Co₃O₄–Ag catalysts showed better activity; among these, the Co₃O₄–Ag-0.3 catalyst demonstrated the most efficient activity with 96.4% degradation efficiency after 30 h UV light irradiation and high degradation efficiency of 99.1% after 6 h visible light irradiation. According to the corresponding dynamics study under UV light irradiation, the photocatalytic efficiency of Co₃O₄–Ag-0.3 was 2.72 times higher than that of Co₃O₄ under identical reaction conditions. The excellent photocatalytic activity of Co₃O₄–Ag can be attributed to the synergistic effect of strong absorption under UV and visible light, reduced photoelectron and hole recombination rate, and decreased band gap due to Ag doping. Additionally, a possible reaction mechanism over the Co₃O₄–Ag photocatalysts was proposed and explained.

A novel Co₃O₄–Ag catalyst covered on the Ni foam substrate was synthesized via facile hydrothermal and in situ photoreduction methods for the efficient degradation of methyl orange.     

Comparison of Fe2TiO5/C photocatalysts synthesized via a nonhydrolytic sol–gel method and solid-state reaction method

Fe₂TiO₅/C photocatalysts were synthesized by a solid-state reaction method (Fe₂TiO₅/C_(S)) and nonhydrolytic sol–gel (NHSG) method (Fe₂TiO₅/C_(N)), where C was introduced by external carbon and in situ carbon sources, respectively. The Fe₂TiO₅/C_(N) photocatalyst with in situ carbon has much better photocatalytic degradation efficiency than that of Fe₂TiO₅/C_(S) synthesized by doping external carbon. The superiorities of in situ carbon were demonstrated by SEM, EDS, BET and photoelectrochemical analysis. Compared with Fe₂TiO₅/C_(S) using external carbon as a carbon source, Fe₂TiO₅/C_(N) with in situ carbon exhibits more uniform elemental distribution, much larger surface area, higher photocurrent density and lower resistivity of interfacial charge transfer. The results show that the introduction of in situ carbon via the NHSG method more easily promotes the separation of photogenerated electron–hole pairs, owing to the uniformity of the carbon element, thereby improving the photocatalytic activity of the photocatalyst.

Two different methods were used to prepare Fe₂TiO₅/C photocatalysts, demonstrating the superiorities of in situ carbon introduced by a NHSG method.     

Superconducting properties and non-isothermal crystallization kinetics of a Bi2Sr2CaCu2O8+δ (Bi2212) superconductor prepared by the Pechini sol–gel method

Bi2212 superconductors with crystallization treatments at different temperatures were prepared by the Pechini sol–gel method, and their structural, thermal and transport properties were investigated. The X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) results revealed the high purity and sheet crystal structures of the prepared samples. The non-isothermal crystallization kinetics and process of the Bi2212 superconductor were characterized and analyzed by differential scanning calorimetry (DSC) and Jeziorny and Mo methods, respectively. The results showed that both the Jeziorny and Mo methods were well suitable for describing the non-isothermal crystallization process of the Bi2212 superconductor prepared by the Pechini sol–gel method. The Avrami exponent (n = 2) confirmed the two-dimensional sheet growth mechanism of the Bi2212 superconductor. In addition, the non-isothermal crystallization kinetic parameter Z_c increased with the increase in cooling rate. The crystallization parameter F(T) also increased with the increase in crystallinity, and the F(T) values were calculated to be 4.79 and 42.66 when the crystallinity values were 20% and 90%, respectively, indicating that for the Bi2212 superconductor, it was harder to crystallize at relatively larger crystallinity. Furthermore, the transport properties of the samples were greatly improved after the cooling crystallization process. Sample J3 had the highest onset of the superconducting transition T_(c,onset) of 80.1 K, which was higher than the 73.1 K value determined for sample J0. Also, sample J2 had the best zero resistivity superconducting transition temperature T_(c,zero) value of 70.1 K, which was higher than the value of 63.2 K for sample J0. The maximum calculated J_c value was 7.62 × 10⁴ A cm⁻² at 2 K for sample J2, which was higher than the 4.70 × 10⁴ A cm⁻² value determined for J0.

Bi2212 superconductors with crystallization treatments at different temperatures were prepared by the Pechini sol–gel method, and their structural, thermal and transport properties were investigated.     

Photoluminescence and afterglow of Dy3+ doped CaAl2O4 derived via sol–gel combustion

With doping concentration varying from 0.1 to 5.0 mol%, a series of Dy³⁺ doped calcium aluminate (CaAl₂O₄:Dy³⁺) phosphors were synthesized via a sol–gel combustion technique. The phase, morphology, photoluminescence (PL), afterglow, and thermoluminescence (TL) glow curves of CaAl₂O₄:Dy³⁺ were investigated by means of X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, PL spectroscopy, afterglow spectroscopy, and TL dosimetry, respectively. It is found that: (i) oxygen vacancies and Dy³⁺ work as two independent sets of luminescence centers of PL for CaAl₂O₄:Dy³⁺; (ii) Dy³⁺ works as the luminescence center of afterglow for CaAl₂O₄:Dy³⁺; (iii) the afterglow of CaAl₂O₄:Dy³⁺ lasts for about 115 min at the optimal doping concentration of around 0.8 mol%; and (iv) multiple traps, which are sensitive to doping concentration, are present in CaAl₂O₄:Dy³⁺. The PL and afterglow mechanisms of CaAl₂O₄:Dy³⁺ are discussed to reveal the processes of charged carrier excitation, migration, trapping, detrapping, and radiative recombination in CaAl₂O₄:Dy³⁺.

A systematic investigation into the photoluminescence and afterglow mechanisms of trivalent Dy ion doped CaAl₂O₄.     

Annealing atmosphere effect on the resistive switching and magnetic properties of spinel Co3O4 thin films prepared by a sol–gel technique

Spinel Co₃O₄ thin films were synthesized using a sol–gel technique to study the annealing atmosphere effect on resistive switching (RS) and magnetic modulation properties. Compared with oxygen and air annealed Pt/Co₃O₄/Pt stacks, the nitrogen annealed Pt/Co₃O₄/Pt stack shows optimal switching parameters such as a lower forming voltage, uniform distribution of switching voltages, excellent cycle-to-cycle endurance (>800 cycles), and good data retention. Improvement in switching parameters is ascribed to the formation of confined conducting filaments (CFs) which are composed of oxygen vacancies. From the analysis of current–voltage characteristics and their temperature dependence, the carrier transport mechanism in the high-field region of the high resistance state was dominated by Schottky emission. Besides, temperature dependent resistance and magnetization variations revealed that the physical mechanism of RS can be explained based on the formation and rupture of oxygen vacancy based CFs. In addition, multilevel saturation magnetization under different resistance states is attributed to the variation of oxygen vacancy concentration accompanied with the changes in the valence state of cations. Results suggested that using a nitrogen annealing atmosphere to anneal the thin films is a feasible approach to improve RS parameters and enhance the magnetic properties of Co₃O₄ thin film, which shows promising applications to design multifunctional electro-magnetic coupling nonvolatile memory devices.

The resistive switching and magnetic properties can be enhanced by controlling oxygen vacancies via the annealing atmosphere effect.     

Effect of unmelted lime on the element distribution behavior on a CaO–SiO2–MgO–Al2O3–FeO–CaF2(–Cr2O3) slag

In this study, a CaO–SiO₂–Al₂O₃–MgO–FeO–CaF₂(–Cr₂O₃) slag was chosen according to the compositions of the stainless steel slag for industrial production, and a CaO block was added to the molten slag after the synthetic slag was fully melted. The influences of unmelted lime on the distribution of elements and the structure of product layers at the lime/slag boundary, particularly the existing state of chromium oxide in the chromium-bearing stainless steel slag, were deeply discussed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and FactSage 7.1. The experiment results indicated that when the unmelted lime existed in the CaO–SiO₂–Al₂O₃–MgO–FeO–CaF₂ slag system, two product layers of periclase (MgO) and dicalcium silicate (Ca₂SiO₄) at the boundary of the CaO block were formed. However, when the CaO block was added in the CaO–SiO₂–Al₂O₃–MgO–FeO–CaF₂–Cr₂O₃ stainless steel slag, besides MgO and Ca₂SiO₄ product layers, needle-shaped calcium chromite (CaCr₂O₄) was also precipitated around the CaO block. Moreover, a small amount of Cr dissolved in the periclase phase. Eh–pH diagrams showed that the CaCr₂O₄ and MgO phase unstably existed in a weak acid aqueous solution. Therefore, the existence of unmelted lime in the stainless steel slag could enhance the leachability of chromium.

The effect of unmelted lime on the distribution of elements and structure of product layers in CaO–SiO₂–MgO–Al₂O₃–FeO–CaF₂(–Cr₂O₂) stainless steel slag and the action of unmelted lime phase mechanism in experimental slags was conducted.     

Removal of aqueous Hg(ii) by thiol-functionalized nonporous silica microspheres prepared by one-step sol–gel method

It is well known that thiol-functionalized silica (SiO₂-SH) can be used as an effective adsorbent for the removal of Hg(ii) from water. Studies in this field have focused on porous silica gels and mesoporous silicas that have large surface area and pore volume, while nonporous silica particles are seldom reported. This work aims to investigate the Hg(ii) adsorption properties of nonporous SiO₂-SH microspheres prepared by a simple one-step sol–gel method. The effects of pH, initial concentration of Hg(ii) and temperature on the adsorption properties of the SiO₂-SH microspheres were studied via batch adsorption experiments. The maximum adsorption capacity for Hg(ii) at 293 K calculated from the Langmuir equation was 377.36 mg g⁻¹. The adsorption kinetics and equilibrium data were well-fitted to the pseudo-second-order model and the Langmuir isotherm model, respectively.

The adsorption properties of nonporous SiO₂-SH microspheres prepared by a one-step sol–gel method for Hg(ii) in water were studied.     

Green and facile sol–gel synthesis of the mesoporous SiO2–TiO2 catalyst by four different activation modes

The most environmentally friendly protocol for obtaining mesoporous SiO₂–TiO₂ catalysts has been sought. Water has been employed as a green solvent, the energy input has been minimized, and three further principles (1, 3, and 12) of Green Chemistry have been considered. Four different modes for promoting the reaction have been comparatively evaluated, namely near-infrared and microwave electromagnetic irradiations, ultrasound, and traditional mantle heating. Brunauer–Emmett–Teller (BET) analyses of the catalysts produced revealed that the non-conventional activation modes afforded both large surface areas (335–441 m² g⁻¹) and smaller crystal sizes (7.2–15.3 nm) than the mantle heating process. These modes also generated the catalysts in shorter reaction times than traditional mantle heating, 10–30 min versus 3 h, with anatase as the sole crystalline phase. The photocatalytic degradation of 4-chlorophenol has been carried out to assess the catalytic efficiencies of the hybrid materials. The catalyst synthesized with microwave assistance showed the best mineralization activity (97%), followed by those prepared with ultrasound, near-infrared, and mantle heating. The materials have been extensively characterized by FTIR, XRD, DRS-UV/Vis, SEM, ²⁹Si MAS NMR, and BET analyses. To the best of our knowledge, this is the first such comparative assessment of green energetic alternatives in developing a sol–gel process.

The most environmentally friendly protocol for obtaining mesoporous SiO₂–TiO₂ catalysts has been sought.     

Novel mesoporous Co3O4–Sb2O3–SnO2 active material in high-performance capacitive deionization

Capacitive deionization (CDI), as an emerging eco-friendly electrochemical brackish water deionization technology, has widely benefited from carbon/metal oxide composite electrodes. However, this technique still requires further development of the electrode materials to tackle the ion removal capacity/rate issues. In the present work, we introduce a novel active carbon (AC)/Co₃O₄–Sb₂O₃–SnO₂ active material for hybrid electrode capacitive deionization (HECDI) systems. The structure and morphology of the developed electrodes were determined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer–Emmett–Teller (BET)/Barrett–Joyner–Halenda (BJH) techniques, as well as Fourier-transform infrared (FT-IR) spectroscopy. The electrochemical properties were also investigated by cyclic voltammetry (CV) and impedance spectroscopy (EIS). The CDI active materials AC/Co₃O₄ and AC/Co₃O₄–Sb₂O₃–SnO₂ showed a high specific capacity of 96 and 124 F g⁻¹ at the scan rate of 10 mV s⁻¹, respectively. In addition, the newly-developed electrode AC/Co₃O₄–Sb₂O₃–SnO₂ showed high capacity retention of 97.2% after 2000 cycles at 100 mV s⁻¹. Moreover, the electrode displayed excellent CDI performance with an ion removal capacity of 52 mg g⁻¹ at the applied voltage of 1.6 V and in a solution of potable water with initial electrical conductivity of 950 μs cm⁻¹. The electrode displayed a high ion removal rate of 7.1 mg g⁻¹ min⁻¹ with an excellent desalination–regeneration capability while retaining about 99.5% of its ion removal capacity even after 100 CDI cycles.

Capacitive deionization (CDI), as an emerging eco-friendly electrochemical brackish water deionization technology, has widely benefited from carbon/metal oxide composite electrodes.     

A modified random network model for P2O5–Na2O–Al2O3–SiO2 glass studied by molecular dynamics simulations

We investigated the short- and medium-range structural features of sodium aluminosilicate glasses with various P₂O₅ (0–7 mol%) content and Al/Na ratios ranging from 0.667 to 2.000 by using molecular dynamics simulations. The local environment evolution of network former cations (Si, Al, P) and the extent of clustering behavior of modifiers (Na⁺) is determined through pair distribution function (PDF), total correlation function (TDF), coordination number (CN), Q_xⁿ distribution and oxygen speciation analysis. We show that Al–O–P and Si–O–Al linkage is preferred over other connections as compared to a random model and that Si–O–Si linkage is promoted by the P₂O₅ addition, which is related to structural heterogeneity and generates well-separated silicon-rich and aluminum–phosphorus-rich regions. Meanwhile, due to the relatively high propensity of Al to both Si and P, heterogeneity can be partly overcome with high Al content. A small amount of Si–O–P linkages have been detected at the interface of separated regions. Clustering of Na⁺ is also observed and intensified with the addition of P₂O₅. Based on the simulated structural information, a modified random network model for P₂O₅-bearing sodium aluminosilicate glass has been proposed, which could be useful to optimize the mobility of sodium ions and design novel functional glass compositions.

(A) A modified structural model proposed for P₂O₅-bearing sodium aluminosilicate glasses. (B) Degree of preferred connection (DPC) of different T–O–T network linkage for LAP, MAP and HAP glass compositions with various P₂O₅ content.     

Gas phase dehydration of glycerol to acrolein over WO3-based catalysts prepared by non-hydrolytic sol–gel synthesis

Solid acid catalysts based on WO₃–SiO₂ and WO₃–ZrO₂–SiO₂ were prepared by one-pot non-hydrolytic sol–gel method and tested in the gas phase glycerol dehydration to acrolein. Their structural and textural characteristics were determined by X-ray diffraction (XRD), N₂ adsorption, X-ray energy dispersive spectroscopy (XEDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Their acid characteristics were studied by both temperature programmed desorption of ammonia (NH₃-TPD) and FTIR of adsorbed pyridine. Under our operating conditions, all the catalysts were active and selective in the transformation of glycerol to acrolein, which was always the main reaction product. The high selectivity to acrolein is achieved on catalysts presenting a higher proportion of Brønsted acid sites. In addition, the role of oxygen in the feed on catalytic performance of these catalysts is also discussed.

Active and selective W–Si–(Zr)–O catalysts for glycerol dehydration to acrolein have been successfully prepared by non-hydrolytic sol gel method.     

Comparative photocatalytic activity of sol–gel derived rare earth metal (La,Nd, Sm and Dy)-doped ZnO photocatalysts for degradation of dyes

Rare earth metal doping into semiconductor oxides is considered to be an effective approach to enhance photocatalytic activity due to its ability to retard the electron–hole pair recombination upon excitation. Herein, we report the synthesis of different rare earth metal (La, Nd, Sm and Dy)-doped ZnO nanoparticles using a facile sol–gel route followed by evaluation of their photocatalytic activity by studying the degradation of methylene blue (MB) and Rhodamine B (RhB) under UV-light irradiation. Different standard analytical techniques were employed to investigate the microscopic structure and physiochemical properties of the prepared samples. The formation of the hexagonal wurtzite structure of ZnO was established by XRD and TEM analyses. In addition, the incorporation of rare earth metal into ZnO is confirmed by the shift of XRD planes towards lower theta values. All metal doped ZnO showed improved photocatalytic activity toward the degradation of MB, of which, Nd-doped ZnO showed the best activity with 98% degradation efficiency. In addition, mineralization of the dye was also observed, indicating 68% TOC removal in 180 min with Nd-doped ZnO nanoparticles. The influence of different operational parameters on the photodegradation of MB was also investigated and discussed in detail. Additionally, a possible photocatalytic mechanism for degradation of MB over Nd-doped ZnO nanoparticles has been proposed and involvement of hydroxyl radicals as reactive species is elucidated by radical trapping experiments.

In this study, we compared the photocatalytic activity of sol–gel derived rare earth metal (La, Nd, Sm and Dy)-doped ZnO photocatalysts by studying the degradation of MB and RhB under UV light irradiation.     

Study of resistance performance of Al2O3–ZnO–Y2O3 thermal control coating exposed to vacuum-ultraviolet irradiation

As deep space exploration moves farther and farther away, thermal control coating of the in-orbit spacecraft will suffer a serious vacuum-ultraviolet radiation environment, which seriously threatens the reliability of the spacecraft in orbit. Therefore, it is important to improve the vacuum-ultraviolet resistance performance of the thermal control coating. In this work, the inorganic Al₂O₃–ZnO–Y₂O₃ thermal control coating was in situ fabricated on a 6061 aluminum alloy surface by PEO technology, and its vacuum-ultraviolet resistance performance was investigated. The results show that the Al₂O₃–ZnO–Y₂O₃ thermal control coating has a good resistance performance to vacuum-ultraviolet radiation, which is mainly because the large extinction coefficients of the ZnO and Y₂O₃ materials in the ultraviolet band are conducive to improving the ultraviolet resistance performance. Furthermore, the life prediction model of the Al₂O₃–ZnO–Y₂O₃ thermal control coating shows that its Δα_s value first slightly increases and then tends to be stable with the increase of ultraviolet irradiation time from 0 ESH to 25 000 ESH, and the maximum variation of Δα_s is about 0.0536. This work provides a material basis and technical support for the thermal control system of spacecraft with long life and high reliability.

The Al₂O₃–ZnO–Y₂O₃ thermal control coating in situ fabricated by PEO technology, shows a good resistance performance to vacuum-ultraviolet radiation. Further, its life prediction model at vacuum-ultraviolet irradiation is preliminarily established.     

2-Nitrophenol sensor-based wet-chemically prepared binary doped Co3O4/Al2O3 nanosheets by an electrochemical approach

Herein, the wet-chemical process (co-precipitation) was used to prepare nanosheets (NSs) of Co₃O₄/Al₂O₃ in an alkaline medium (pH ∼ 10.5). The synthesized NSs were totally characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV/vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). The synthesized NSs were deposited onto a glassy carbon electrode (GCE) to prepare a very thin layer with a conducting binder for detecting 2-nitrophenol (2-NP) selectively by a reliable electrochemical method. The proposed chemical sensor exhibits good sensitivity (54.9842 μA μM⁻¹ cm⁻²), long-term stability, and enhanced chemical response by electrochemical approaches. The resultant current is found to be linear over the concentration range (LDR) from 0.01 nM to 0.01 mM. The estimated detection limit (DL) is equal to 1.73 ± 0.02 pM. This study introduces a potential route for future sensitive sensor development with Co₃O₄/Al₂O₃ NSs by an electrochemical approach for the selective detection of hazardous and carcinogenic chemicals in environmental and health care fields.

This potential research work introduces a route of future sensitive sensor development with Co₃O₄/Al₂O₃ NSs by electrochemical approach to selective detection of hazardous and carcinogenic chemicals in environmental and health care fields.     

Photocatalytic activity of Ni0.5Zn0.5Fe2O4@polyaniline decorated BiOCl for azo dye degradation under visible light – integrated role and degradation kinetics interpretation

Herein, we demonstrated the excellent improvement in photocatalytic degradation performance of BiOCl upon facile heterogeneous decoration with an integrated Ni_0.5Zn_0.5Fe₂O₄@polyaniline nanocomposite for an organic pollutant, methyl orange dye (MO), under visible light irradiation. The physico-chemical nature of the heterogeneous nanocomposite was characterized by XRD, FTIR, HRTEM-EDX and XPS analyses. The tuning of the band gap and optical sensitivity of BiOCl using Ni_0.5Zn_0.5Fe₂O₄@polyaniline were measured by DRS, PL and EIS techniques. To validate the transformation of the BiOCl photocatalyst to a visible light active photocatalyst due to the incorporation of Ni_0.5Zn_0.5Fe₂O₄@polyaniline and to gain insight into the origin of the synergistic effect for dye degradation by the heterostructured nanocomposite, we explored the effects of process parameters such as catalyst dosage, initial dye concentration, pH and the presence of inorganic anions on the extent of photo degradation. To get more details about reaction kinetics, a kinetic model using non-liner regression analysis was developed and the validity of the model was tested by comparing the experimental values with the calculated data. Based on the intermediate product formation, identified by GC-MS, a probable degradation pathway and a mechanism based on the electrochemical behaviour of the developed catalyst and trapping experiments were also proposed.

The photocatalytic activity of BiOCl is tuned through heterogeneous decoration with an integrated Ni_0.5Zn_0.5Fe₂O₄@polyaniline. The outstanding degradation capacity, effects of parameters on degradation kinetics and a kinetic model using regression analysis is reported.     

Structure,thermostability and magnetic properties of cubic Ce2−xTi2O7 pyrochlore obtained via sol–gel preparation

Lanthanum-based titanates have been attracting considerable interest by virtue of their structural operability and hence diverse physical properties. The preparation of lanthanum-based titanates with novel crystal structure is a fascinating task. In this work, we report the preparation of a cubic Ce_2−xTi₂O₇ pyrochlore using the sol–gel method. The crystal structure, thermostability and magnetism were studied via the temperature dependence of X-ray powder diffraction, X-ray photoelectron spectroscopy and magnetization measurements. It has been revealed that the as-prepared Ce_2−xTi₂O₇ pyrochlore possesses a cubic symmetry (space group: Fd$\bar{3}$m), however there is an 18(1)% vacancy of Ce ions in the as-prepared samples. No distinct phase transition and thermal expansion anomaly were observed in the investigated temperature range from 300 K to 700 K. Intriguingly, lattice defects may favor the transformation of Ce valence from +3 to +4 and an unusual weak magnetic ordering state emerged up to 400 K. The persistence of magnetism at such high temperatures is rare and mysterious for cerium titanates. Our findings provide the possibility of adjusting the crystal structure and magnetic properties of cerium titanates, anticipated to the development of lanthanum-based oxides.

We report a novel cubic Ce_2−xTi₂O₇ compound prepared via the sol–gel method. There is an 18% vacancy of Ce ions in the as-prepared samples. The lattice defects may favor the transformation of Ce valence from +4 to +3, and a weak magnetic ordering state emerges up to 400 K.     

Facile solvothermal preparation of Fe3O4–Ag nanocomposite with excellent catalytic performance

Functional nanocomposites demonstrate excellent comprehensive properties and outstanding characteristics for numerous applications. Magnetic nanocomposites are an important type of composite materials, due to their applications in optics, medicine and catalysis. In this report, a new Fe₃O₄-loaded silver (Fe₃O₄–Ag) nanocomposite has been successfully synthesized via a simple solvothermal method and in situ growth of silver nanowires. The silver nanowires were prepared via the reduction of silver vanadate with the addition of uniformly dispersed Fe₃O₄ nanoparticles. Structural and morphological characterizations of the obtained Fe₃O₄–Ag nanocomposite were carried out using many characterization methods. As a new composite catalyst, the synthesized magnetic Fe₃O₄–Ag nanocomposite displayed a high utilization rate of catalytically active sites in catalytic reaction medium and showed good separation and recovery using an external magnetic field. The facile preparation and good catalytic performance of this Fe₃O₄–Ag nanocomposite material demonstrate its potential applications in catalytic treatment and composite materials.

A new Fe₃O₄–Ag nanocomposite was prepared via solvothermal method, demonstrating potential application in catalytic degradation of wastewater treatment and composite materials.     

Photocatalytic degradation of ethylene by Ga2O3 polymorphs

In this work, we fabricated four different Ga₂O₃ polymorphs, namely, α-, β-, γ-, δ-Ga₂O_3, and investigated their photocatalytic activities by the degradation of ethylene under ultraviolet (UV) light irradiation. Owing to the more positive valence band, all these Ga₂O₃ polymorphs are more photocatalytic reactive than P25 during the degradation of ethylene. The normalized photocatalytic ethylene degradation rate constants of the as-prepared Ga₂O₃ polymorphs follow the order: α-Ga₂O₃ > β-Ga₂O₃ > γ-Ga₂O₃ > δ-Ga₂O₃, which is mainly determined by the position of VBM and the crystallinity of the samples. Among these Ga₂O₃ polymorphs, γ-Ga₂O₃, with the highest surface area, exhibits the highest activity during photocatalytic ethylene degradation, and the degradation rate constant is almost 10 times as that of P25. Furthermore, with the most positive CBM, γ-Ga₂O₃ produces the least CO. These attributes are beneficial for ethylene degradation during post-harvest storage of fruits and vegetables, which makes γ-Ga₂O₃ a potential candidate for practical photocatalytic ethylene degradations.

In this work, we fabricated four different Ga₂O₃ polymorphs, namely, α-, β-, γ-, δ-Ga₂O_3, and investigated their photocatalytic activities by the degradation of ethylene under ultraviolet (UV) light irradiation.     

Novel green manufacture of metallic aluminum coatings on carbon steel by sol–gel method

Industrial processes for fabricating hot-dipping aluminum coatings on carbon steels involve problems related to equipment complexity, environmental issues and high energy consumption. To address these problems, a novel method for manufacturing metallic aluminum coating on carbon steel Q235 at room temperature by sol–gel method was developed in this work. Both the single-layer coating (47 μm) and the double-layer coating (97 μm) specimens were prepared by spraying some aqueous silica sol slurries containing spherical and flaky micro metallic aluminum powders on the steel surface at room temperature and then drying them at 50 °C. When the two coating specimens were heated at 500 °C for 10 h, heated double-layer specimens were thus obtained. It was found that the double-layer and the heated double-layer specimens didn''t rust at all after being soaked in aerated 3.5 wt% NaCl for 30 days. The shielding effect of the compact top coating was the main anticorrosion mechanism of the double-layer coating based on some electrochemical impedence spectroscopies and potentiodynamic polarization curves. Both coatings comprised only one metallic Al phase based on XRD. A very small quantity of Al₂O₃ phase appeared only after heating both coating specimens at 500 °C in the air for 10 h. In both cases the coatings didn''t crack at all after being heated at 500 °C in the air for 15 h by SEM observation and the oxidation rates of the steel substrates under these conditions were reduced by over 72% owing to the presence of the coatings. The average adhesive strengths of the single-layer and double-layer Al coatings were 12.06 MPa and 11.23 MPa, respectively, which were much larger than the corresponding value (max 8 MPa) of an ordinary anti-rusting epoxy coating on Q235 steel. Compared to the conventional hot-dipping aluminum or aluminized process, this novel method eliminates all the high temperature processes and thus saves a lot of energy, eliminates the use of all hazardous fluorides or chlorides and explosive H₂, avoids the formation of the voids inside aluminized coating, reduces the hot-dipped Al coating defects, can be applied for the steel plates with over 0.8 mm thickness, and can be applied in situ to repair damaged Al or Zn coatings.

The novel double-layer specimen of Al coating had the ability to resist simulated seawater corrosion for 30 days and air oxidation at 500 °C for 15 h.     

Effects of calcination temperatures on the structure–activity relationship of Ni–La/Al2O3 catalysts for syngas methanation

A series of Ni–La/Al₂O₃ catalysts for the syngas methanation reaction were prepared by a mechanochemical method and characterized by thermogravimetric analysis (TG-DTA), X-ray fluorescence (XRF), X-ray diffraction (XRD), N₂ adsorption–desorption, H₂ temperature-programmed reduction (H₂-TPR), and X-ray photoelectron spectroscopy (XPS). The calcination temperatures (350–700 °C) had significant impacts on the crystallite sizes and interactions between NiO and Al₂O₃. The catalyst calcined at 400 °C (cat-400) showed a 12.1% Ni dispersion degree and the maximum bound state of NiO (54%) through the Gaussian fitting of H₂-TPR. Cat-400 also achieved the highest CO conversion, CH₄ selectivity and yield. Cat-400 exhibited good stability and catalytic activity in a lifetime testing of 200 h. The deactivation of cat-400 was mainly caused by carbon deposition according to the data from XRD, TG-DTG and XPS.

Calcination temperature affects the existing types of NiO, and the influence of the three NiO types on the catalytic activity of samples is bound type ≫ free type > combined type.