Formation of arsenic clusters in InAs nanowires with an Al2O3 shell

An in-depth understanding of thermal behavior and phase evolution is required to apply heterostructured nanowires (NWs) in real devices. The intermediate status during the vaporization process of InAs NWs in an Al₂O₃ shell was studied by conducting quenching during in situ heating experiments, using a transmission electron microscope. The formation of As clusters in the amorphous Al₂O₃ shell was confirmed by analyzing the high-angle annular dark field images and energy-dispersive X-ray spectra. The As clusters existed independently in the shell and were also observed at the end of the InAs pieces obtained after quenching. The formation process of the As clusters was demonstrated from a theoretical perspective. Moreover, an ab initio molecular dynamics simulation (AIMD) was conducted to study the atomic and molecular behaviors.

InAs nanowires were broken into pieces after the quenching process; some of the pieces were composed only of As.     

Recycling the CoMo/Al2O3 catalyst for effectively hydro-upgrading shale oil with high sulfur content and viscosity

Hydrotreatment is an effective upgrading technology for removing contaminants and saturating double bonds. Still, few studies have reported the hydro-upgrading of shale oil, with unusually high sulfur (13200 ppm) content, using the CoMo/Al₂O₃ catalyst. Here we report an extensive study on the upgrading of shale oil by hydrotreatment in a stirred batch autoclave reactor (500 ml) for sulfur removal and viscosity reduction. From a preliminary optimization of the reaction factors, the best-operating conditions were 400 °C, an initial H₂-pressure of 5 MPa, and an agitation rate of 800 rpm, a catalyst-to-oil ratio of 0.1, and a reaction time of 1 h. We could achieve a sulfur removal efficiency of 87.1% and 88.2% viscosity reduction under the optimal conditions. After that, the spent CoMo/Al₂O₃ was repeatedly used for subsequent upgrading tests without any form of pre-treatment. The results showed an increase in the sulfur removal efficiency with an increase in the number of catalyst runs. Ultimately, 99.5–99.9% sulfur removal from the shale oil was achieved by recycling the spent material. Both the fresh and the spent CoMo/Al₂O₃ were characterized and analyzed to ascertain their transformation levels by XRD, TEM, TG, XPS, TPD and N₂ adsorption analysis. The increasing HDS efficiency is attributed to the continuing rise in the sulfidation degree of the catalyst in the sulfur-rich shale oil. The light fraction component in the liquid products (IBP–180 °C) was 30–37 vol% higher than in the fresh shale oil. The product oil can meet the sulfur content requirement of the national standard marine fuel (GB17411-2015/XG1-2018) of China.

The CoMo/Al₂O₃ catalyst was used to upgrade shale oil. Sulfur removal was increased on the spent catalyst. The transition of oxidic Mo-species into active phase MoS₂ was observed with recycling. The high sulfidation degree of the CoMo/Al₂O₃ suppressed deactivation by coking.     

Continuous selective deoxygenation of palm oil for renewable diesel production over Ni catalysts supported on Al2O3 and La2O3–Al2O3

The present study provides, for the first time in the literature, a comparative assessment of the catalytic performance of Ni catalysts supported on γ-Al₂O₃ and γ-Al₂O₃ modified with La₂O₃, in a continuous flow trickle bed reactor, for the selective deoxygenation of palm oil. The catalysts were prepared via the wet impregnation method and were characterized, after calcination and/or reduction, by N₂ adsorption/desorption, XRD, NH₃-TPD, CO₂-TPD, H₂-TPR, H₂-TPD, XPS and TEM, and after the time-on-stream tests, by TGA, TPO, Raman and TEM. Catalytic experiments were performed between 300–400 °C, at a constant pressure (30 bar) and different LHSV (1.2–3.6 h⁻¹). The results show that the incorporation of La₂O₃ in the Al₂O₃ support increased the Ni surface atomic concentration (XPS), affected the nature and abundance of surface basicity (CO₂-TPD), and despite leading to a drop in surface acidity (NH₃-TPD), the Ni/LaAl catalyst presented a larger population of medium-strength acid sites. These characteristics helped promote the SDO process and prevented extended cracking and the formation of coke. Thus, higher triglyceride conversions and n-C₁₅ to n-C₁₈ hydrocarbon yields were achieved with the Ni/LaAl at lower reaction temperatures. Moreover, the Ni/LaAl catalyst was considerably more stable during 20 h of time-on-stream. Examination of the spent catalysts revealed that both carbon deposition and degree of graphitization of the surface coke, as well as, the extent of sintering were lower on the Ni/LaAl catalyst, explaining its excellent performance during time-on-stream.

Highly selective and stable Ni supported on La₂O₃–Al₂O₃ catalyst on the deCO/deCO₂ reaction paths for the production of renewable diesel.     

ALD Al2O3 gate dielectric on the reduction of interface trap density and the enhanced photo-electric performance of IGO TFT

The amorphous indium gallium oxide thin film transistor was fabricated using a cosputtering method. Two samples with different gate dielectric layers were used as follows: sample A with a SiO₂ dielectric layer; and sample B with an Al₂O₃ dielectric layer. The influence of the gate dielectrics on the electric and photo performance has been investigated. Atomic layer deposition deposited the dense film with low interface trapping density and effectively increased drain current. Therefore, sample B exhibited optimal parameters, with an I_on/I_off ratio of 7.39 × 10⁷, the subthreshold swing of 0.096 V dec⁻¹, and μ_FE of 5.36 cm² V⁻¹ s⁻¹. For ultraviolet (UV) detection, the UV-to-visible rejection ratio of the device was 3 × 10⁵, and the photoresponsivity was 0.38 A W⁻¹ at the V_GS of −5 V.

The amorphous indium gallium oxide thin film transistor was fabricated using a cosputtering method.     

The effects of Bi2O3 on the selective catalytic reduction of NO by propylene over Co3O4 nanoplates

Bi₂O₃/Co₃O₄ catalysts prepared by the impregnation method were investigated for the selective catalytic reduction of NO by C₃H₆ (C₃H₆-SCR) in the presence of O₂. Their physicochemical properties were analyzed with SEM, XRD, H₂-TPR, XPS, PL and IR measurements. It was found that the deposition of Bi₂O₃ on Co₃O₄ nanoplates enhanced the catalytic activity, especially at low reaction temperature. The SO₂ tolerance of Co₃O₄ in C₃H₆-SCR activity was also improved with the addition of Bi₂O₃. Among all catalysts tested, 10.0 wt% Bi₂O₃/Co₃O₄ achieved a 90% NO conversion at 200 °C with the total flow rate of 200 mL min⁻¹ (GHSV 30 000 h⁻¹). No loss in its C₃H₆-SCR activity was observed at different temperatures after the addition of 100 ppm of SO₂ to the reaction mixture. These enhanced catalytic behaviors may be associated with the improved oxidizing characteristics of 10.0 wt% Bi₂O₃/Co₃O₂. XRD results showed that Bi₂O₃ entered the lattice of Co₃O₄, resulting in the formation of lattice distortion and structural defects. H₂-TPR results showed that the reduction of Co₃O₄ was promoted and the diffusion of oxygen was accelerated with the addition of Bi₂O₃. XPS measurements implied that more Co³⁺ formed on the 10.0% Bi₂O₃/Co₃O₂ catalysts. The improved oxidizing characteristics of the catalyst with the addition of Bi₂O₃ due to the synergistic effect of the nanostructure hybrid, thus enhanced the C₃H₆-SCR reaction and hindered the oxidization of SO₂. Therefore, the 10.0% Bi₂O₃/Co₃O₄ catalyst exhibited the highest NO conversion and strongest SO₂ tolerance ability.

Bi₂O₃/Co₃O₄ catalysts prepared by the impregnation method were investigated for the selective catalytic reduction of NO by C₃H₆ (C₃H₆-SCR) in the presence of O₂.     

A study on the high efficiency reduction of p-nitrophenol (4-NP) by a Fe(OH)3/Fe2O3@Au composite catalyst

Precious metal nanometric catalysts are widely used in the removal of harmful substances. In the process of synthesis and catalytic reaction, it is particularly important to study green and simple synthesis methods and high catalytic efficiency. In this paper, a green one-step method was used to synthesize the Fe(OH)₃/Fe₂O₃@Au composite catalyst, in which Au was single atom-dispersed. The removal of 4-nitrophenol (4-NP), a typical dangerous chemical widely existing in factory waste gas, waste water and automobile exhaust gas, was catalysed by Fe(OH)₃/Fe₂O₃@Au. The catalytic performance of Fe(OH)₃/Fe₂O₃@Au with different synthesis conditions (different amounts of MES, NaBH₄, FeSO₄, Au and Pt) on the 4-NP reduction reaction were systematically studied. Finally, the stability and recyclability of Fe(OH)₃/Fe₂O₃@Au composite nanocatalyst were investigated thoroughly.

The process of the catalytic reduction of 4-nitrophenol based on single atom-dispersed Au loaded with ultrathin Fe(OH)₃/Fe₂O₃ nanosheets.     

Synthesis of Bi2O3/g-C3N4 for enhanced photocatalytic CO2 reduction with a Z-scheme mechanism

Bi₂O₃/g-C₃N₄ nanoscale composites with a Z-scheme mechanism were successfully synthesized by high temperature calcination combined with a hydrothermal method. These synthesized composites exhibited excellent photocatalytic performance, especially the 40 wt% Bi₂O₃/g-C₃N₄ composite, which produced about 1.8 times the CO yield of pure g-C₃N₄. The obtained products were characterized by X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and so on. Characterization results revealed that Bi ions had well covered the surface of g-C₃N₄, thus restraining the recombination of electron–hole pairs and resulting in a stronger visible-light response and higher CO yield. In addition, the electron transfer process through the Z-scheme mechanism also promoted the photocatalytic activity.

Bi₂O₃/g-C₃N₄ composites were synthesized and used in photocatalytic reduction of CO₂ with a Z-scheme mechanism.     

Effects of calcination and reduction temperature on the properties of Ni-P/SiO2 and Ni-P/Al2O3 and their hydrodenitrogenation performance

A series of SiO₂-supported and γ-Al₂O₃-supported nickel phosphides were prepared by temperature-programmed reduction (TPR) with different calcination and reduction temperatures. The prepared catalysts were characterized by XRD, BET, H₂-TPR, CO titration and HRTEM. The crystal phase and CO uptake content were influenced by calcination and reduction temperature. The catalytic performance of various catalysts was tested in quinoline hydrodenitrogenation and exhibited considerable differences. The quinoline HDN activity of SiO₂-supported nickel phosphides decreases with increase of calcination and reduction temperature. In contrast to SiO₂-supported samples, the ability to remove nitrogen of γ-Al₂O₃-supported samples increases with reduction temperature.

XRD patterns of different SiO₂-supported nickel phosphides reduced at (a) 560 °C, (b) 650 °C, (c) 750 °C and different γ-Al₂O₃-supported nickel phosphides reduced at (d) 560 °C, (e) 650 °C, (f) 750 °C.     

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.     

Experimental study on viscosity reduction of heavy oil by hydrogen donors using a cavitating jet

Cavitating jet technology is used to change the quality and to reduce the viscosity of heavy oil because bubble collapse can cause extreme conditions such as high pressure and temperature. The experimental study on the viscosity reduction of heavy oil using a cavitating jet was performed through a self-designed experimental system for heavy oil viscosity reduction by a cavitating jet. Tetrahydronaphthalene was used as the hydrogen donor, and after adding different amount of tetrahydronaphthalene, the viscosity change of the heavy oil was studied before and after treatment by the cavitation jet. The experimental results show that cavitating jet technology can be used to improve the quality and reduce the viscosity of heavy oil, and the addition of tetrahydronaphthalene can effectively reduce the viscosity of heavy oil. With the increase in the amount of tetrahydronaphthalene added, the viscosity reduction effect on the heavy oil improved, and the viscosity reduction rate increased. When a certain amount of tetrahydronaphthalene was added, the viscosity of the heavy oil decreased gradually and plateaued with the increase in the cycles of cavitation jet treatment. The addition of tetrahydronaphthalene can dilute the heavy oil and effectively reduce the viscosity and improve the quality of heavy oil by providing active hydrogen to close the macromolecular hydrocarbon free radicals generated by the cavitation effect.

Cavitating jet technology is used to change the quality and to reduce the viscosity of heavy oil because bubble collapse can cause extreme conditions such as high pressure and temperature.     

Microstructure of interface regions and mechanical properties of Ti/Al 2O 3 and Ti-alloy/Al 2O 3 joints for dental implants

Titanium and alumina are very well suited as constituents of dental metal/ceramic implants because of their excellent biocompatibility and their special chemical and mechanical properties which can be exploited to tailor composite implant structures. However, prior attempts to join pure titanium without any intermediate layer to alumina ceramic led to unsatisfactory results mainly due to thermal expansion mismatch between both materials. Therefore we used recently developed Ti alloys containing 30%wt Ta or 40%wt Nb for manufacturing dental implants. Moreover, we studied two alternative methods to join pure titanium with alumina using intermediate layers to reduce internal stresses within the joint caused by thermal expansion mismatch. We examined the interface region of these joints by metallographic, mechanical, analytical, and electron microscopy methods. Additionally, a comparison of the properties of the hitherto investigated types of joints with a view of their applicability in dental implants is given. Promising results were obtained for Ti/alumina joints with Nb interlayers. The studies are continuing.     

Y3Al5O12:Ce nanoparticles made by ionic-liquid-assisted particle formation and LiCl-matrix-treated crystallization

Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce) nanoparticles were prepared by a two-step approach including ionic-liquid-assisted particle formation and LiCl-matrix-treated crystallization. Subsequent to particle formation in [MeBu₃N][N(SO₂CF₃)₂] as the ionic liquid (MeBu₃N: tributylmethylammonium; N(SO₂CF₃)₂: bis(trifluoromethanesulfonyl)imide), the as-obtained amorphous precursor nanoparticles were crystallized in a LiCl matrix (600 °C, 1 h). The resulting YAG:Ce nanoparticles are well crystallized and exhibit a diameter of about 40 nm. They show bulk-like luminescence and a quantum yield of 51(±3)%. The selected Y : Al ratio and temperature profile turned out to be optimal for the synthesis strategy in terms of particle size and luminescence properties although minor amounts of CeO₂ remained. The YAG:Ce nanoparticles can be easily redispersed in the liquid phase and embedded in polymers such as polyester. The course of the reaction and the properties of the nanoparticles are characterized by electron microscopy, dynamic light scattering, infrared spectroscopy, X-ray powder diffraction, and fluorescence spectroscopy.

Y₃Al₅O₁₂:Ce³⁺ nanoparticles were prepared by a two-step approach (mean size: 40 nm; quantum yield: 51%) and embedded in polyester.     

Incorporation of Al2O3, GO,and Al2O3@GO nanoparticles into water-borne epoxy coatings: abrasion and corrosion resistance

Nano-Al₂O₃ particles and graphene oxide (GO) nanosheets were modified by 3-aminopropyltriethoxysilane (KH550), and then dispersed in epoxy resin, and finally modified-Al₂O₃/epoxy, modified-GO/epoxy and modified-Al₂O₃@GO/epoxy composite coatings were prepared on steel sheets by the scraping stick method. The microstructure, phase identification, surface bonding and composition of the nanoparticles were characterized by SEM, XRD, FT-IR, and Raman spectroscopy, respectively. The hardness of the coating was assessed by the pencil hardness method. The abrasion resistance of the coating was tested by a sand washing machine. The corrosion resistance of the coating was assessed using salt spray, a long-period immersion test, potentiodynamic polarization curves and electrochemical impedance spectra. With the addition of a small amount of nanoparticles, the dispersion of nanoparticles in the epoxy resin was good. When the content of nano-Al₂O₃ particles was equal to 1.5 wt%, the particles in the epoxy exhibited the best dispersion and stability. However, the GO and Al₂O₃@GO nanofillers in the epoxy resin exhibited poor dispersion and stability. The hardness, abrasion and corrosion resistance of the composite coatings were improved with the addition of a small amount of nanoparticles, but the performance began to decline after exceeding a certain content range of the nanoparticles. A relatively good abrasion resistance for the coatings was obtained when the content of Al₂O₃, GO and Al₂O₃@GO after modification was 1.5 wt%, 0.2 wt% and 0.4 wt%, respectively. The corrosion resistance of the coatings doped with nano-Al₂O₃ particles was better than that of the coatings incorporating GO nanosheets and Al₂O₃@GO hybrids. The corrosion mechanism of the composite coatings in 3.5 wt% NaCl solution was addressed and studied.

Nano-Al₂O₃ particles and graphene oxide (GO) nanosheets were modified by 3-aminopropyltriethoxysilane (KH550), and then dispersed in epoxy resin, and finally modified-Al₂O₃/epoxy, modified-GO/epoxy and modified-Al₂O₃@GO/epoxy composite coatings were prepared on steel sheets by the scraping stick method.     

Development of a thermally stable Pt catalyst by redispersion between CeO2 and Al2O3

For catalytic systems consisting of Pt as the active component and CeO₂–Al₂O₃ as the support material, the metal–support interaction between the Pt and CeO₂ components is widely applied to inhibit aggregation of Pt species and thus enhance the thermal stability of the catalyst. In this work, a highly thermostable Pt catalyst was prepared by modifying the synthesis procedure for conventional Pt/CeO₂/Al₂O₃ (Pt/Ce/Al) catalyst, that is, the CeO₂ component was introduced after deposition of Pt on Al₂O₃. The obtained CeO₂/Pt/Al₂O₃ (Ce/Pt/Al) catalyst exhibits significantly different aging behavior. During the hydrothermal aging process, redispersion of Pt species from the surface of Al₂O₃ to the surface of CeO₂ occurs, resulting in a stronger metal–support interaction between Pt and CeO₂. Thus, the formed Pt–O–Ce bond could act as an anchor to retard aggregation of Pt species and help Pt species stay at a more oxidative state. Consequently, excellent reduction capability and superior three-way catalytic performance are acquired by Ce/Pt/Al-a after hydrothermal aging treatment.

Ce/Pt/Al undergoes redispersion of Pt upon hydrothermal aging, resulting in higher dispersion and consequently superior three-way catalytic performance of Ce/Pt/Al-a.     

A new approach to improve the electrochemical performance of ZnMn2O4 through a charge compensation mechanism using the substitution of Al3+ for Zn2+

ZnMn₂O₄ and Zn_1−xAl_xMn₂O₄ were synthesized by a spray drying process followed by an annealing treatment. Their structural and electrochemical characteristics were investigated by SEM, XRD, XPS, charge–discharge tests and EIS. XPS data indicate that the substitution of Al³⁺ for Zn²⁺ causes manganese to be in a mixed valence state by a charge compensation mechanism. Moreover, the presence of this charge compensation significantly improves the electrochemical performance of Zn_1−xAl_xMn₂O₄, such as increasing the initial coulombic efficiency, stabilizing the cycleability as well as improving the rate capability. The sample with 2% Al doping shows the best performance, with a first cycle coulombic efficiency of 69.6% and a reversible capacity of 597.7 mA h g⁻¹ after 100 cycles. Even at the high current density of 1600 mA g⁻¹, it still retained a capacity of 558 mA h g⁻¹.

This work reports the nonequivalent substitution of ZnMn₂O₄. This is a new approach to improve the electrochemical performance of ZnMn₂O₄ through a charge compensation mechanism using the substitution of Al³⁺ for Zn²⁺.     

Combined experimental and computational study of Al2O3 catalyzed transamidation of secondary amides with amines

Amides are the most extensively used substances in both synthetic organic and bioorganic chemistry. Unfortunately, the traditional synthesis of amides suffers from some important drawbacks, including low atom efficiency, high catalyst loading, separation of products from the reaction mixture and production of byproducts. Al₂O₃ is an amphoteric catalyst that activates the carbonyl carbon of the secondary amide group and helps the C–N cleavage of the reactant amide group by attacking the N–H hydrogen. By using the concepts of amphoteric properties of Al₂O₃, amides were synthesized from secondary amides and amines in the presence of triethylamine solvent. Several aliphatic and aromatic amines were used for the transamidation of N-methylbenzamide in the presence of the Al₂O₃ catalyst. Moreover, using the Gaussian09 software at the DFT level, HUMO, LUMO and the intrinsic reaction coordinates (IRCs) have also been calculated to find out the transition state of the reaction and energy. In this study, five successful compounds were synthesized by the transamidation of secondary amides with amines using a reusable Al₂O₃ catalyst. The catalyst was reused several times with no significant loss in its catalytic activity. The products were purified by recrystallization and column chromatography techniques. This catalytic method is effective for the simultaneous activation of the carbonyl group and N–H bond by using the Al₂O₃ catalyst.

Amides are the most extensively used substances in both synthetic organic and bioorganic chemistry.     

Non-scrambling of hydrogen in NH4+(H2O)3 clusters

We have measured the metastable decay of protonated, ammonia-doped, deuterated water clusters produced in an electrospray source, d_n-NH₄⁺(H₂O)₃, n = 0–6. The mass spectra show a very strong odd–even effect, consistent with a low degree of scrambling of the hydrogen bound to water and to the ammonia. The relative evaporation rate constant for light water was almost twice the one for heavy water, with the rate for mixed protium–deuterium water molecule intermediate between these two values.

We have measured the metastable decay of protonated, ammonia-doped, deuterated water clusters produced in an electrospray source, d_n-NH₄⁺(H₂O)₃, n = 0–6.     

Enhanced performance of chemical looping combustion of methane with Fe2O3/Al2O3/TiO2 oxygen carrier

Iron-based oxygen carriers supported on alumina or alumina/titania were prepared and evaluated for chemical looping combustion of methane. The reduction conversion of Fe₂O₃/Al₂O₃ and Fe₂O₃/Al₂O₃/TiO₂ particles was markedly increased with increasing inlet concentration and was slightly enhanced by elevated operating temperatures. According to the shrinking core model, the mass transfer coefficients (k_g) of Fe₂O₃/Al₂O₃ and Fe₂O₃/Al₂O₃/TiO₂ reduction with methane are found to be 0.07 and 0.12 mm s⁻¹. Complete combustion of methane is almost achieved for experiments conducted with Fe₂O₃/Al₂O₃ and Fe₂O₃/Al₂O₃/TiO₂ operated as the Fe₂O₃/CH₄ molar ratio reached about 5.4 and 4.4, respectively. Carbon deposition during methane combustion was avoided by using Fe₂O₃/Al₂O₃/TiO₂ as an oxygen carrier. More heat was generated for the combustion of methane by Fe₂O₃/Al₂O₃/TiO₂ oxygen carriers because methane more fully reacted with the Fe₂O₃ contained in the Fe₂O₃/Al₂O₃/TiO₂ oxygen carriers.

The effect of Fe₂O₃/CH₄ molar ratio on fuel and oxygen carrier conversion for methane combustion in the moving bed.     

Photocatalytic activity of Ag/Al2O3–Gd2O3 photocatalysts prepared by the sol–gel method in the degradation of 4-chlorophenol

The photocatalytic activity in the degradation of 4-chlorophenol (4-ClPh) in aqueous medium (80 ppm) using 2.0 wt% Ag/Al₂O₃–Gd₂O₃ (Ag/Al–Gd-x; where x = 2.0, 5.0, 15.0, 25.0 and 50.0 wt% of Gd₂O₃) photocatalysts prepared by the sol–gel method was studied under UV light irradiation. The photocatalysts were characterized by N₂ physisorption, X-ray diffraction, SEM, HRTEM, UV-Vis, XPS, FTIR and fluorescence spectroscopy. About 67.0% of 4-ClPh was photoconverted after 4 h of UV light irradiation using Ag/γ-–Al₂O₃. When Ag/Al–Gd-x photocatalysts were tested, the 4-ClPh photoconversion was improved and more than 90.0% of 4-ClPh was photoconverted after 3 h of UV light irradiation in the materials containing 15.0 and 25.0 wt% of Gd₂O₃. Ag/Al–Gd-25 was the material with the highest efficacy to mineralize dissolved organic carbon, mineralizing more than 85.0% after 4 h of UV light irradiation. Silver nanoparticles and micro-particles of irregular pentagonal shape intersected by plane nanobelts of Al₂O₃–Gd₂O₃ composite oxide were detected in the Ag/Al–Gd-25 photocatalyst. This material is characterized by a lowest recombination rate of electron–hole pairs. The low recombination rate of photo-induced electron–hole pairs in the Ag/Al–Gd-x photocatalysts with high Gd₂O₃ contents (≥15.0 wt%) confirmes that the presence of silver nanoparticles and microparticles interacting with Al₂O₃–Gd₂O₃ composite oxide entities favors the separation of photo-induced charges (e⁻ and h⁺). These materials could be appropriate to be used as highly efficient photocatalysts to eliminate high concentrations of 4-ClPh in aqueous medium.

Ag/Al₂O₃–Gd₂O₃ showed high efficacy to photodegradate 4-chlorophenol, the strong interaction between silver nano-particles and micro-particles and Al₂O₃–Gd₂O₃ entities favors the decrease in the recombination rate.     

N-doped graphene/CoFe2O4 catalysts for the selective catalytic reduction of NOx by NH3

In this paper, CoFe₂O₄/graphene catalysts and N-doped graphene/CoFe₂O₄ (CoFe₂O₄/graphene-_N) catalysts were prepared using the hydrothermal crystallization method for the selective catalytic reduction of NO_x by NH₃. The results of the test showed that CoFe₂O₄/graphene catalysts exhibited the best denitrification activity when the loading was at 4% and the conversion rate of NO_x reached 99% at 250–300 °C. CoFe₂O₄/graphene-_N catalysts presented a better denitrification activity at low temperature than CoFe₂O₄/graphene catalysts, and the conversion rate of NO_x reached more than 95% at 200–300 °C. The intrinsic mechanism of CoFe₂O₄/graphene-_N catalysts in promoting SCR activity was preliminarily explored. The physicochemical properties of the samples were characterized using XRD, TEM, N₂ adsorption, XPS, NH₃-TPD, and H₂-TPR. The results indicated that nitrogen doping can improve the dispersion of CoFe₂O₄, and it also increased the acidic sites and the redox performance conducive to improving the denitrification activity of the catalysts. In addition, CoFe₂O₄/graphene-_N catalysts demonstrated a better resistance to water and sulfur than CoFe₂O₄/graphene catalysts.

N-doped graphene/CoFe₂O₄ presented better denitrification activity than CoFe₂O₄/graphene due to the more uniform distribution of CoFe₂O₄ and acidic sites etc.