Mixing-calcination Method Research Articles

In2O3[sbnd]Co3O4 p-n heterojunction sensors: Comparison of efficient interfaces and gas sensing enhancement mechanism through two strategies

The fabrication of heterostructure has been considered as a great potential to improve the gas sensing performances due to its flexible features at the interface. The p-n heterojunction composites with Co3O4 modified In2O3 were synthesized through physical mixing calcination process and hydrothermal method for the effectiveness comparison as gas sensors for detecting of ethanol. The morphology, microstructure, and surface element state of the heterojunction materials were investigated. Furthermore, the forbidden band width and the active oxygen species were analyzed on account of the efficient interface for the heterojunction materials. The gas response of heterojunction sensor by the physical mixing calcination method exhibits an outstanding response of 5585 towards 100 ppm of ethanol gas, which was about 10 times higher than that by two-step hydrothermal method. Moreover, it shows improved adsorption and desorption kinetics with response time of 8 s and 15 s, respectively at the operating temperature of 280 °C. It also reveals a distinct selectivity to ethanol with better reproducibility, the humidity-dependent stability and ambient retention over a period of 30 days with rendering 94 %. Combined with the in-situ infrared diffuse reflection spectrum analysis and Hall effect test from the perspective of catalytic and electrical properties, we inferred the gas sensing enhancement mechanism involved in In2O3Co3O4 p-n heterojunction with the design of proof-of-concept demonstration by surface modification, which could provide an approach to explore the effect of heterojunction interface through the variable method.

Practical liquid phase mixing-calcination synthesis of Nb5+ doped SrTiO3 nanoparticles with elevated photocatalysis

The mediocre photocatalytic activity and unpractical preparation methods of SrTiO3 have restricted its practical application as a photocatalyst. Herein, a practical liquid phase mixing-calcination method was designed to synthesize Nb5+ doped SrTiO3 (Nb-SrTiO3) with remarkably elevated photocatalytic activity. Nb-SrTiO3 nanoparticles were synthesized by mixing Sr(NO3)2, NbCl5 and tetrabutyl titanate in deionized water (DW), evaporating the solvent (DW) and calcining the evenly mixed precursors at 700 °C for 4 h. The as-synthesized Nb-SrTiO3 exhibited a photocatalytic activity 4.2 times that of SrTiO3 in the reduction of Cr(VI) under Xenon lamp irradiation. Moreover, Nb-SrTiO3 showed a rather good photocatalytic stability. Nb5+ doping can decrease the particle size and promote the photogenerated carrier separation and transfer of SrTiO3, thereby contributing to heightened photocatalytic activity of Nb-SrTiO3.

A morphological decoration of g-C3N4/ZrO2 heterojunctions as a visible light activated photocatalyst for degradation of various organic pollutants

Rational decoration of heterojunctions with photocatalytic activity under visible light has received tremendous attentions in the last decade. In particular, fine tuning the morphologies of the components of heterojunction is of great importance that can determine the efficiency of the designed photocatalyst. In this work, various graphitic carbon nitride (g-C3N4)/zirconium dioxide (ZrO2) heterojunctions were successfully synthesized via a solution mixing-calcination method using different morphologies of g-C3N4 (nanosheet and particle) and ZrO2 (nanosphere, nanorod, and nanosheet). The properties of as-designed heterojunction photocatalysts were characterized by XRD, TGA, FTIR, TEM, AFM, XPS, BET, DRS, PL, EIS, PR, and HPLC. All the designed heterojunctions showed weaker photoluminescence compared to each of components, indicating the efficient charge transfer between g-C3N4 and ZrO2, and delayed electron-hole pairs recombination process. Among the six designed heterojunctions, the highest photocatalytic activity was observed in the 2D/2D heterojunction with efficient •O2- production, which was due to higher surface area, good integration of nanosheets morphologies, existence of abundant high-rate charge transfer nanochannels and better separation efficiency of electron-hole pairs in this heterojunction. This research indicates that right selection of morphology of the nanomaterials for designing photocatalysts plays an important role in realizing efficient heterojunctions nanomaterials.

Enhanced photocatalytic activity of novel \u03b1-Bi2O3@g-C3N4 composites for the degradation of endocrine-disrupting benzophenone-3 in water under visible light

The commonly used benzophenone-3 (BP-3) as ultraviolet filter ingredients is an endocrine-disrupting chemical that has received particular attention owing to its environmental ubiquity, and it poses a threat to aquatic biota and human health. In this study, novel α-Bi2O3@g-C3N4 nanocomposites with different α-Bi2O3 contents and enhanced photocatalytic activity were synthesized by a mixing calcination method. The as-synthesized photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, N2 adsorption/desorption isotherm analysis, electrochemical impedance spectroscopy, photoluminescence spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. The 1 wt% α-Bi2O3@g-C3N4 composite exhibited the highest rate constant of 0.42 h-1 for photocatalytic degradation of BP-3, which was up to 6.3 times higher than that of g-C3N4 (0.07 h-1). The enhanced photocatalytic activity might be due to the enhanced separation of photogenerated electron-hole (e--h+) charge pairs and suppression of e--h+ recombination. Scavenging experiments suggested that •OH, h+ and •O2- worked together in the α-Bi2O3@g-C3N4 photocatalytic process. The EPR spectra demonstrated that the α-Bi2O3@g-C3N4 composites generated considerably more •O2- and •OH than g-C3N4. Finally, cyclic degradation experiments showed the reusability of 1 wt% α-Bi2O3@g-C3N4 for BP-3 removal.

When C3N4 meets BaTiO3: Ferroelectric polarization plays a critical role in building a better photocatalyst

Photogenerated electrons (e−) and holes (h+) easily undergo fast recombination in many semiconductors, limiting the further improvement of its photocatalytic efficiency. To solve this bottleneck problem, graphitic C3N4 was used to group tetragonal-phase BaTiO3 ferroelectric and successfully constructed the g-C3N4/BaTiO3 heterojunction via a facial mixing-calcination method. These composites exhibited an extraordinary improvement under visible-light irradiation, achieving a “1 + 1>2” performance compared with their single pristine components. It is because the formation of double-transfer structure promotes the fast transfer of photo-induced charge carriers in g-C3N4/BaTiO3 composites. Synergy between the two materials, especially the ferroelectric polarization, plays a key role in facilitating the spatial separation of photo-excited e−/h+ pairs and improving the photocatalytic efficiency.

Characterization and competitive benzene hydrogenation activity of nickel supported on SBA-15/LxOy (L = Zn, Ti, W) composites in an aromatic mixture

SBA-15/metal oxide composites were prepared by the mixing-calcination method and the nickel phase was impregnated by the wet impregnation method. The textural and structural properties of catalysts were characterized with scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray fluorescence, UV–visible diffuse reflectance spectra, and nitrogen adsorption–desorption analysis. Ni/composite materials were used for competitive hydrogenation of benzene in the range of 403–463 K and ambient pressure. It is found that the reaction kinetics follows the pseudo-first-order kinetic for hydrogen. Activity data demonstrated that the highest activity and the best selectivity were obtained for Ni/SBA-15/TiO2 (> 93%) at 403 K, and nickel supported over SBA-15/W2O (> 73%) at 403 K.

Enhanced visible-light responsive photocatalytic activity of Bi25FeO40/Bi2Fe4O9 composites and mechanism investigation

Pure Bi25FeO40, Bi2Fe4O9, and different weight ratios of Bi25FeO40/Bi2Fe4O9 composite photocatalysts have been synthesized via a hydrothermal process combined with a mixing-calcination method and evaluated as visible-light responsive catalyst for the degradation of Rhodamine B (RhB). All the as-prepared samples have been characterized by a range of techniques including X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), UV–vis absorption spectra (DSR), Field Emission Scanning Electron Microscope (FE-SEM), Transmission electron microscope (TEM) and High-resolution TEM (HRTEM). The XRD, FT-IR, TEM and HRTEM results confirm that the composite only consists of Bi25FeO40 and Bi2Fe4O9. In the Bi25FeO40/Bi2Fe4O9 composites, closely contacted interfaces have been observed. Compared with the single-phase Bi25FeO40 and Bi2Fe4O9, Bi25FeO40/Bi2Fe4O9 composites exhibit enhanced visible-light responsive photocatalytic activities. The photocatalytic efficiency of optimized Bi25FeO40/Bi2Fe4O9 composite with Bi2Fe4O9 weight ratio of 30% is about 8.8 and 6.2 times higher than that of pure Bi25FeO40 and Bi2Fe4O9, respectively. On the basis of electronic energy-band structure analysis, the active species trapping experiments and the electrochemical impedance spectrum (EIS) performance, a heterojunction-type charge transfer mechanism interpreting the enhanced photocatalytic activities of the composite are proposed and discussed. In addition, the effects of different Bi25FeO40/Bi2Fe4O9 weight ratios and their geometry architecture on photocatalytic activities are also thoroughly discussed.

A Facile Method to Construct MXene/CuO Nanocomposite with Enhanced Catalytic Activity of CuO on Thermal Decomposition of Ammonium Perchlorate.

In this work, a mixing-calcination method was developed to facilely construct MXene/CuO nanocomposite. CuO and MXene were first dispersed in ethanol with sufficient mixing. After solvent evaporation, the dried mixture was calcinated under argon to produce a MXene/CuO nanocomposite. As characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectra (XPS), CuO nanoparticles (60–100 nm) were uniformly distributed on the surface and edge of MXene nanosheets. Furthermore, as evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), the high-temperature decomposition (HTD) temperature decrease of ammonium perchlorate (AP) upon addition of 1 wt% CuO (hybridized with 1 wt% MXene) was comparable with that of 2 wt% CuO alone, suggesting an enhanced catalytic activity of CuO on thermal decomposition of AP upon hybridization with MXene nanosheets. This strategy could be further applied to construct other MXene/transition metal oxide (MXene/TMO) composites with improved performance for various applications.

Enhanced visible-light-driven photocatalytic activities of Bi2Fe4O9/g-C3N4 composite photocatalysts

A series of Bi2Fe4O9/g-C3N4 composite photocatalysts are prepared via a facile mixing-calcination method. The crystal structures of composites are investigated by X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). The Field Emission Scanning Electron Microscope (FE-SEM) in combination with Energy Dispersive X-ray Spectroscopy (EDS) mapping analysis and Transmission Electron Microcopy (TEM) images illustrate the uniform distribution of constituent elements and clear interface between Bi2Fe4O9 and g-C3N4 component. The visible-light-driven photocatalytic rates of Rhodamine B over Bi2Fe4O9/g-C3N4 composites increase and then decrease with the increase of g-C3N4 content. The effects of Bi2Fe4O9/g-C3N4 weight ratios on photocatalytic performance are thoroughly discussed. Meanwhile, the active species trapping experiments and the electrochemical impedance spectra as well as the electronic energy-band structure estimation analysis demonstrate that the photocatalytic mechanism for Bi2Fe4O9/g-C3N4 composites is ascribed to the Z-scheme. In addition, the recyclability and stability experiments of the composite are also studied.

Novel, Facile and Swift Technique for Synthesis of CeO2 Nanocubes Immobilized on Zeolite for Removal of CR and MO Dye

CeO2/zeolite nanocomposite was successfully prepared by the mixing-calcination method. The structural characteristics of photocatalyst were investigated by XRD, SEM, TEM and EDX. Photocatalytic degradation experiments were carried out with varying amounts of the CeO2/zeolite, the ratio of 3:1 (CeO2/zeolite) was exhibited excellent photocatalytic activity towards dye degradation. Synergistic effect of CeO2/zeolite played a key role in photocatalytic degradation. The main reactive oxygen species was determined by trapping experiments. Additionally, the recyclability was tested up to the fourth cycle. The CeO2/zeolite nanocomposite is a promising photocatalyst for removing trace and unprocessed organic contaminants in the industrial dye waste water treatment. The efficiency of CeO2/zeolite nanocomposite offers a potential economical route to degrade organic contaminants and recovering photocatalyst simultaneously.

Enhanced visible light photocatalytic activity of CeO2/alumina nanocomposite: Synthesized via facile mixing-calcination method for dye degradation

In this present study, an effort has been made to novel CeO2/alumina nanocomposite photocatalyst was fabricated through mixing-calcination method. The XRD, IR, SEM, TEM, EDX and XPS results designated that these synthesized materials are formed effectively. The photocatalytic results for the degradation of dye solution indicate that the most dynamic ratio is CeO2:Al2O3 (2.5:1) under visible light irradiation. The photocatalytic degradation was made under dark and in the presence of light to establish the photocatalytic efficiency of the synthesized photocatalyst. The improved performance of CeO2/alumina nanocomposite is attributed to the separation efficiency of photo-induced charge carriers and it inhibit charge recombination. The major active species are determined by radical scavengers trapping experiments were revealed that superoxide radical (O2−) and hydroxyl radical (OH) are playing a vital role in the degradation of dye solution. The stability of catalyst was confirmed by consecutive runs of CeO2/alumina nanocomposite.

2D graphitic-C3N4 hybridized with 1D flux-grown Na-modified K2Ti6O13 nanobelts for enhanced simulated sunlight and visible-light photocatalytic performance

Novel 1D/2D hybrid Na-K2Ti6O13/g-C3N4 heterojunction photocatalysts with enhanced simulated sunlight and visible-light photocatalytic performance have been successfully fabricated using a facile mixing–calcination method.

Enhanced photocatalytic activity of g-C3N4 via modification of NiMoO4 nanorods

A novel NiMoO4/g-C3N4 composite with heterojunction structure was prepared via a simple mixing–calcination method and used as a photocatalyst for rhodamine B (RhB) degradation and hydrogen generation under visible light irradiation. Multiple techniques, such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy, were applied to investigate the physical and photo properties of the catalysts. Results indicated that the synthesized NiMoO4/g-C3N4 composite can produce hydrogen 4.4 times faster than pure g-C3N4 under visible light irradiation. When the composite was applied in photodegradation of RhB, it was found that the introduction of NiMoO4 nanorods into g-C3N4 can promote the photoabsorption performance and the adsorption of RhB, both of which benefit the photocatalytic reaction. Nevertheless, more important is the formed heterojunction between NiMoO4 and g-C3N4 efficiently retards the recombination of electron-hole pairs, which subsequently significantly promotes the photocatalytic activity. The degradation rate of the optimal NiMoO4/g-C3N4 reaches 0.044min−1, which is 4.0 times that of pure g-C3N4. The proposed mechanism for the enhanced visible-light photocatalytic activity of NiMoO4/g-C3N4 composite is further evidenced by photoluminescence spectroscopy and photocurrent experiments.

Novel Fe2(MoO4)3/g-C3N4 heterojunction for efficient contaminant removal and hydrogen production under visible light irradiation

Novel Fe2(MoO4)3/g-C3N4 composites were synthesized by a facile mixing-calcination method. The photocatalytic activity of the Fe2(MoO4)3/g-C3N4 hybrid was evaluated via RhB degradation and H2-production under visible light irradiation. Results indicated that the Fe2(MoO4)3/g-C3N4 binary composite exhibited excellent photocatalytic activity. The optimal hybrid could produce hydrogen 6.6 times faster than pure g-C3N4 from water-methanol solution under visible light irradiation. For the photocatalytic degradation of RhB, it showed a degradation rate of 0.070min−1, which was 7.8 times higher than that of pure g-C3N4. Moreover, the composite showed high stability and extensive adaptability in degradation of other organic pollutants. The N2 physical absorption measurement and UV–visible diffuse reflection spectroscopy suggested that the coupling of Fe2(MoO4)3 increased the BET specific surface area and visible light absorption, both of which favored the photocatalytic reaction. However, the main reason of the enhanced activities were attributed to the interfacial transfer of photogenerated electrons and holes between Fe2(MoO4)3 and g-C3N4, leading to the effective charge separation in the composite, which were evidenced by photoluminescence spectroscopy and photocurrent analysis. This work may provide some useful information for the future design and practical application of multifunctional hybrids photocatalysts in water purification.

Preparation, characterization, and photocatalytic activity of CdV2O6 nanorods decorated g-C3N4 composite

Novel CdV2O6/g-C3N4 hybrid system was synthesized by a facile mixing-calcination method. The photocatalytic test indicated that the decoration of CdV2O6 nanorods on g-C3N4 can significantly promote the photocatalytic activity in RhB degradation under visible light. The optimal CdV2O6/g-C3N4 sample exhibited a degradation rate of 0.041min−1, which is 4.5 times higher than that of pure g-C3N4. Various techniques including N2 adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy were applied to investigate the origin of the enhanced photoactivity of CdV2O6/g-C3N4. The results indicated that the enhanced activities were mainly attributed to the interfacial transfer of photogenerated electrons and holes between CdV2O6 and g-C3N4, leading to the effective charge separation in the composite, which were evidenced by photoluminescence spectroscopy and photocurrent analysis. This work may provide some useful information for the future design and practical application of multifunctional hybrids photocatalysts in water purification.

Synthesis of g-C3N4/CeO2 nanocomposites with improved catalytic activity on the thermal decomposition of ammonium perchlorate

Novel g-C3N4/CeO2 nanocomposites were synthesized through a simple mixing-calcination method. The structure, morphology and composition of g-C3N4/CeO2 nanocomposites were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), as well as X-ray photoelectron spectroscopy (XPS). The results indicated that CeO2 nanoparticles with a diameter of 50–100nm were uniformly loaded on the surface of g-C3N4. Furthermore, the catalytic effect of our prepared novel g-C3N4/CeO2 nanocomposites on the thermal decomposition of ammonium perchlorate (AP) was investigated by utilizing thermogravimetric and differential thermal analyses (TG-DTA). Compared with pure g-C3N4 and CeO2, the g-C3N4/CeO2 nanocomposites were proved to catalyze the thermal decomposition of AP more effectively. Upon addition of g-C3N4/CeO2 nanocomposites, the high weight-loss decomposition temperature of AP was decreased by up to 74.6°C, which is quite more than that upon the addition of pure g-C3N4 and CeO2. The proposed mechanism demonstrated that this situation was presumably attributed to a synergistic effect between g-C3N4 and CeO2.

Fabrication and characterization of hollow CdMoO4 coupled g-C3N4 heterojunction with enhanced photocatalytic activity

This research was designed for the first time to investigate the activities of CdMoO4/g-C3N4 heterojunction in photocatalytic degradation of rhodamine B (RhB) and converting CO2 to fuels. The composite was synthesized via a simple mixing-calcination method and characterized by various techniques including Brunauer–Emmett–Teller method (BET), X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and electrochemical method. The results showed that the introduction of CdMoO4 to g-C3N4 exerted little effect on the property of light absorption, but resulted in an increase in the BET surface area, which was beneficial for the adsorption of RhB. More importantly, formation of a hetero-junction structure between CdMoO4 and g-C3N4 significantly promoted the separation of electron–hole pairs and ultimately enhanced the photocatalytic activity. The optimal CdMoO4/g-C3N4 composite could degrade RhB 6.5 times faster than pure g-C3N4 under visible light irradiation. Meanwhile, the composite showed a CO2 conversion rate of 25.8μmolh−1gcat−1, which was 4.8 and 8.1 times higher than those of g-C3N4 and P25, respectively, under simulated sunlight irradiation. This work might represent an important step in simultaneous environmental protection and energy production by g-C3N4 based materials.

Visible-light-induced blue MoO3–C3N4 composite with enhanced photocatalytic activity

Composite photocatalyst of blue MoO3/g-C3N4 (denoted as MoO3–C3N4) was prepared by a simple mixing-calcination method. The obtained MoO3–C3N4 composite contains a low amount of molybdenum blue and shows remarkably enhanced absorption of visible light and high efficiency for the degradation of methylene blue dye (MB) under visible light. The enhancement of visible light photocatalytic activity in MoO3–C3N4 is attributed to the synergetic effect: (i) the strong and wide absorption of visible light, (ii) the high separation and easy transfer of photogenerated electron–hole pairs at the heterojunction interfaces derived from the match of band position between the g-C3N4 and MoO3.

Synthesis of BiVO4-g-C3N4 composite photocatalyst with improved visible light-induced photocatalytic activity

The novel visible light-induced carbon nitride (g-C3N4) and BiVO4 composite photocatalysts were obtained through a simple mixing-calcination method. The physical and photophysical properties of the BiVO4-g-C3N4 composites were investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, UV-vis diffuse reflection spectroscopy, high-resolution transmission electron microscopy (HRTEM), photoluminescent (PL) spectroscopy, and BET surface area measurements. Photocatalytic oxidation ability of the prepared samples was examined by studying the degradation of rhodamine B (RhB) as a target pollutant under visible-light irradiation. The composite photocatalysts exhibited an enhanced photocatalytic performance in degrading RhB. The optimal g-C3N4 content of the composite photocatalysts was determined for the photodegradation activity. The improved photocatalytic activity of the as-prepared composite photocatalyst may be attributed to the enhancement of photo-generated electron-hole separation at the interface.

G-C3N4 modified Bi2O3 composites with enhanced visible-light photocatalytic activity

Novel g-C3N4 modified Bi2O3 (g-C3N4/Bi2O3) composites were synthesized by a mixing-calcination method. The samples were characterized by thermogravimetry (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (DRS), photoluminescence (PL) and photocurrent-time measurement (PT). The photocatalytic activity of the composites was evaluated by degradation of Rhodamine B (RHB) and 4-chlorophenol (4-CP) under visible light irradiation (>400nm). The results indicated that the g-C3N4/Bi2O3 composites showed higher photocatalytic activity than that of Bi2O3 and g-C3N4. The enhanced photocatalytic activity of the g-C3N4/Bi2O3 composites could be attributed to the suitable band positions between g-C3N4 and Bi2O3. This leads to a low recombination between the photogenerated electron–hole pairs. The proposed mechanism for the enhanced visible-light photocatalytic activity of g-C3N4/Bi2O3 composites was proven by PL and PT analysis.