One-step Sol-gel Method Research Articles

Engineering Ni/SiO2 catalysts for enhanced CO2 methanation

The CO2 methanation is an important process in coal-to-gas, power-to-gas and CO2 removal for spacecraft. Recently, metal-organic framework (MOF) derivatives have been demonstrated as high-performance catalysts for CO2 upgrading processes. However, due to the high costs and low stability of MOF derivatives, it still remains challenge for the development of alternative synthesis methods avoiding MOF precursors. In this work, we present the sol-gel method for loading Ni-MOF to silica support in two-steps. Upon modifying the procedure, a more simplified one-step sol-gel method has been developed. Furthermore, the obtained Ni/SiO2 catalyst still exhibits great catalytic performance with a CO2 conversion of 77.2% and considerable CH4 selectivity of ~100% during a stability test for 52 h under a low temperature of 310 °C and high GHSV of 20,000 mL·g−1·h−1. Therefore, this work provides a ground-breaking direct strategy for loading MOF derived catalysts, and might shed a light on the preparation of highly dispersed Ni/SiO2 catalyst.

Synthesis of Au/Co9S8 composite aerogels by one-step sol–gel method as hydrogen evolution reaction electrocatalysts

The development of effective electrocatalysts for hydrogen evolution reaction (HER) with a high performance and low-cost is greatly desirable to meet the increasing demands for sustainable energy. In this work, we herein demonstrate Au nanoparticles (NPs)-coupled Co9S8 (Au/Co9S8) aerogels with a porous feature and high surface area via a simple sol–gel approach. Besides, the as-prepared complexes are supposed to generate synergistic effect to greatly promote the HER electrocatalysis in an alkaline electrolyte. The improved electric conductivity of the resulting composite can accelerate the HER kinetics. Notably, the as-prepared Au/Co9S8-10 aerogel displays a good electrocatalytic property for HER with an overpotential of 35 mV at 10 mA cm−2 and a small Tafel slope of 64 mV dec−1. The porous architecture not only improves the contact area at interfaces but also allows faster mass transportation during electrochemical process. Furthermore, the catalyst declares a promising electrochemical stability over 40 h of continuous HER catalysis with only 6% loss of its initial activity. Hence, this work offers a guiding strategy for synthesizing nanostructured earth abundant electrocatalyst with an enhanced HER performance.

Characterization of nio-bczy as composite anode prepared by a one-step sol-gel method

A high polarization resistance (Rp) at intermediate temperature (500–800°C) operation has become one of the major challenges in the development of proton-conducting fuel cells (PCFCs). Rp is the resistance of the cell that contributes by the electrodes parts which are anode and cathode as well as their interfacial components. The present study focused on the NiO-Ba(Ce0.6Zr0.4)0.9Y0.1O3-δ (NiO-BCZY) composite anode and its interfacial parts where the oxidation process takes place. The NiO-BCZY with a ratio of 50:50 was prepared by a sol-gel method and characterized by X-Ray Diffractometer (XRD), Field Emission Scanning Electron Microscopy/Energy Dispersive X-ray (FESEM/EDX), and Electrochemical Impedance Spectroscopy (EIS). At calcination temperature of 1100°C, NiO and BCZY oxides can preserve their phases to form composite anode as proven by XRD analysis. Morphology of the composite anode as observed by FESEM was spherical with particle size in the range of 30-70 nm. XRD analysis showed the formation of Ni-BCZY after undergoing reduction process under wet H2:N2 (10%:90%). As confirmed by the EIS data, the increased conductivity of the composite anode in wet H2:N2 (10%:90%) indicates that the NiO in the composite anode was reduced to Ni metal. The fabricated NiO-BCZY composite anode has shown a good potential to be a promising anode in PCFC application.

Precursor effect on the Fe-doped cryptomelane (Fe-OMS-2) prepared via one-step sol-gel route as heterogeneous Fenton catalyst for degradation of methylene blue

The pristine cryptomelane (OMS-2) and Fe-OMS-2 (1%, 5%, and 10%) have been successfully synthesized by a one-step sol-gel method and characterized by XRD, SEM, BET surface area and AAS. The incorporation of Fe (III) within the structure of OMS-2 leads to an increase in surface area, pore-volume, and catalytic activity for the degradation of methylene blue (MB) and a decrease in the content of K+ and average of pore diameter. The catalytic test indicated that the catalytic activity of Fe-OMS-2 1% is considerably higher that of pure OMS-2. The highest degradation of MB is 93.5% achieved using Fe-OMS-2 1% after 120 minutes of degradation time, the initial concentration of MB of 20 ppm, the catalyst concentration of 0.125 mg and the H2O2 volume of 15 mL. The enhanced catalytic activities of Fe-OMS-2 compared to pristine OMS-2 for catalytic degradation of MB are associated with an increase in surface area, pore-volume, and smaller particle size. The results from catalytic studies imply that the metal doping is an effective strategy to enhance the catalytic activities of OMS-2 for degradation of MB.

Superoxide anion: Critical source of high performance antibacterial activity in Co-Doped ZnO QDs

In this paper, Co-doped ZnO quantum dots (QDs) with smaller lateral size and high stability were prepared via a simple and one-step sol-gel method. We found that Co-doped ZnO QDs could more effectively absorb visible light and motivate the separation efficiency of photogenerated electrons and holes, resulting in the over yield production of superoxide anion (.O2-) and hydroxyl radical (.OH) under environmental condition. As a result, the antibacterial activity of Co-doped ZnO QDs was drastically improved than that of bare ZnO QDs, and the superoxide radicals mediated oxidative stress plays a dominant role in the antibacterial mechanism. Besides, controllable construction of smaller size Co-doped ZnO QDs was favoured for the contact between the nanoparticles and bacteria, thus significantly decreased the transmission path of ROS and Zn2+, causing the markedly enhanced antibacterial activities.

Pseudo core-shell LaCoO3@MgO perovskite oxides for high performance methane catalytic oxidation

Magnesia modified LaCoO3 was prepared by a facile one-step sol-gel method and used for removal of dilute methane. Compared with the conventional doping technique, the obtained LaCoO3@MgO-x exhibits pseudo core-shell structure and shows superior catalytic activity. The methane conversion exceeds 90% at 532 °C on LaCoO3@MgO-0.1, while only 60% of methane is conversed using the doped perovskite LaCo0.9Mg0.1O3. The high catalytic performance of LaCoO3@MgO-0.1 is mainly attributed to the adjustment of surface acid-base properties by the MgO shell structure. According to density functional theory (DFT) calculation, the methane is more likely to be adsorbed and cracked on LaCoO3@MgO-0.1. The in situ DRIFTS shows that CH3–O–CH3 intermediate specie is formed. The pseudo core-shell structure also enhances the stability and the LaCoO3@MgO-0.1 maintains high activity after working for 100 h. The above results demonstrate that surface modification by magnesia is an effective strategy for improving LaCoO3 catalytic performance.

Photocatalytic degradation of nonylphenol ethoxylate and its degradation mechanism

Photocatalyst TiO2@g-CQDs were prepared by one-step sol-gel method using tetrabutyl titanate, anhydrous ethanol, hydrochloric acid and graphite carbon quantum dots and characterized by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), UV–visible diffuse reflectance spectra (UV-DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic degradation of nonylphenol ethoxylate (NPE10O) by TiO2@g-CQDs and the degradation path of NPE10O by time-of-flight mass spectrometry (TOF-MS) were investigated. In addition, the photocatalytic mechanism of TiO2@g-CQDs was discussed in detail and the major active species were identified. The results showed that when the doping amount of g-CQDs is 5%, the amount of TiO2@g-CQDs is 0.1 g·L−1, the initial concentration of NPE10O is 50 mg·L−1, and the power of the light source is 500 W, the degradation efficiency of NPE10O can reach 100% at 60 min, which indicates TiO2@g-CQDs have excellent photocatalytic properties. TOF-MS showed that NPE10O was mainly degraded by nonylphenol polyethoxycarboxylate (NPExC) and carboxylated alkyl oxidation products of nonylphenol ethoxy (CAyPEC) intermediates during photocatalytic degradation. Trapping experiment of active species demonstrated that OH is the major active component for photocatalytic degradation of contaminant.

Facile Fabrication of Lilium Pollen-like Organosilica Particles.

Organosilica particles with a novel lilium pollen-like morphology were synthesized by a one-step sol-gel method. The hydrolysis and co-condensation of vinyltrimethoxysilane (VTMS) and tetraethoxysilane (TEOS) took place in an aqueous medium with ammonia as the catalyst. The growth process of the organosilica particles was tracked by scanning electron microscopy (SEM). The bulk and surface composition of the lilium pollen-like organosilica particles were characterized by solid-state 29Si nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. In addition, bowl-like, golf ball-like, and walnut kernel-like organosilica particles could also be obtained by changing the concentration of ammonia, the amount of silane precursors, or the reaction medium. This study provides a facile method to prepare nonspherical organosilica particles with controllable morphologies.

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.

Structural and optical properties of macroporous Ag@TiO2 thin films prepared by a facile one-step sol–gel method

A principle of obtaining macroporous Ag@TiO2 thin films by a template-free method in the frame work of sol–gel is developed. The macroporous structure is constructed by photo polymerization induced phase separation (PIPS) method, and the reduction of Ag+ to Ag0 is induced by ultraviolet irradiation at the same time. The achieved macroporous Ag@TiO2 films are well interconnected and crack free with an average pore size in the range 350–440 nm. Increasing Ag concentration results in the enhancement of extinction coefficient and reduction of refractive index, which are found to be consistent with absorbance and transmittance observations. In addition, Ag concentration causes red shift in absorbance which in turn decreases the band gap energy. These results may add important insight into developing high-performance materials for visible light activities.

Transparent and robust SiO2/PDMS composite coatings with self-cleaning

ABSTRACTIn recent years, people have paid increasing attention to improving the durability of highly transparent superhydrophobic surfaces. In this work, we first synthesized a superhydrophobic silica powder by using a one-step sol–gel method and then compounded it with Polydimethylsiloxane. After spin-coating on the glass surface, a transparent superhydrophobic glass with a high water contact angle (158°) was acquired. In the visible region (400–800 nm), the transmittance of the coated glass substrate was higher than 80%. Moreover, the obtained coating can maintain stable superhydrophobicity after undergoing treatment from −15 to 450°C and under extreme environmental conditions, such as strong acidity and alkalinity. In addition, the coating can maintain excellent superhydrophobicity even after exposure to a large amount of water flow impact.

Effect of chromium doping on Na3V2(PO4)2F3@C as promising positive electrode for sodium-ion batteries

Cr-doped Na3V2(PO4)2F3@C samples, obtained by a one-step sol-gel method, are studied as cathode materials for sodium-ion batteries. Their structural and morphological properties induced by Cr incorporation are determined by powerful solid-state techniques including X-ray diffraction, electron microscopy, and Raman and XPS spectroscopies. Galvanostatic tests reveal the beneficial effects of low-level Cr doping in Na3V2(PO4)2F3, mainly improving the kinetic response of the electrode materials at the highest studied rates. These results are correlated to low cell internal resistances and cell polarization between charge and discharge. Eventually, a full sodium-ion cell is essayed as a proof of concept to evidence the reliability of these cathode materials in practical conditions.

Decoration of MoO3 nanoparticles by MWCNTs driven visible light for the reduction of Cr(VI)

A simple one-step sol-gel method was used to prepare mesoporous molybdenum oxide using a F127 triblock copolymer structure-directing agent for the first time. MoO3@MWCNT nanocomposites with 1%, 2%, 3%, and 4% weight MWCNT were prepared using the impregnation method. MoO3 and MoO3@MWCNT nanocomposites were analyzed to identify their physical and chemical properties. The TEM results showed that MoO3 has a nanoparticle shape, and MoO3 nanoparticles were well dispersed on the surface of MWCNTs. The bandgap of the MoO3 sample can be adapted by adjusting the weight percent of MWCNTs. Additionally, the band gap of MoO3 was reduced by the addition of MWCNTs and improved their photocatalytic reduction of chromium (VI) under visible light. Finally, MoO3@MWCNT nanocomposites were used to reduce chromium (VI) beyond the loss of photocatalytic performance, which means they have high photocatalytic stability.

Novel Two-Dimensional Carbon-Chromium Nitride-Based Composite as an Electrocatalyst for Oxygen Reduction Reaction.

For future pollution-free renewable energy production, platinum group metal (PGM)-free electrocatalysts are highly required for oxygen reduction reaction (ORR) to avoid all possible Fenton reactions and to make fuel cell more economical. Therefore, in this study, to overcome traditional electrocatalyst limitations, we applied facile method to synthesize robust mesoporous CrN-reduced graphene oxide (rGO) nanocomposite with MnO (thereafter, Cr/rGO composite with MnO) as an electrocatalyst by efficient one-step sol-gel method by ammonolysis at 900°C for 9 h. Synthesized porous structures of Cr/rGO nanocomposite with MnO have the highest estimated surface area of 379 m2·g−1, higher than that of the carbon black (216 m2·) support, and almost uniform pore size distribution of about 4 nm. The Cr/rGO nanocomposites with MnO exhibit enhanced electrocatalytic ORR properties with estimated high half-wave potential of 0.89 V vs. the reversible hydrogen electrode (RHE) and current density of 5.90 mA·cm−2, compared with that of benchmark 20% Pt/C electrode (0.84 V, 5.50 mA·cm−2), with noticeable methanol tolerance and significantly enhanced stability in alkaline media. Hence, the Cr/rGO nanocomposites with MnO showed superior performance to 20 wt.% Pt/C; their half-wave potentials were 50 mV high, and the limiting current density was 0.40 mA·cm−2 high. In alkaline anion exchange membrane fuel cell (AAEMFC) setup, this cell delivers a power density of 309 mW·cm−2 for Cr/rGO nanocomposite with MnO, demonstrating its potential use for energy conversion applications. The nanosized Cr/rGO metallic crystalline nanocomposites with MnO gave a large active surface area owing to the presence of rGO, which also has an effect on the charge distribution and electronic states. Hence, it may be the reason that Cr/rGO nanocomposites with MnO, acting as more active and more stable catalytic materials, boosted the electrocatalytic properties. The synergistic consequence in nanosized Cr/rGO composite with MnO imparts the materials' high electron mobility and thus robust ORR activity in 0.1 M of KOH solution. This potential method is highly efficient for synthesis of large-scale, non-noble-metal-based electrocatalytic (NNME) materials (i.e., Cr/rGO nanocomposite with MnO) on the gram level and is efficient in preparing novel, low-cost, and more stable non-PGM catalysts for fuel cells.

La2Zr2O7/rGO synthesized by one-step sol-gel method for photocatalytic degradation of tetracycline under visible-light

In this study, La2Zr2O7/rGO (LZO/rGO) composite photocatalyst was prepared by a one-step sol-gel method, which achieved synthesis of LZO and reduction of GO simultaneously. LZO/rGO-3 (dosage of GO: 0.5 g) was well-crystallized and had the specific surface area of 16.5 m2/g which was higher than that of LZO (9.4 m2/g). Moreover, the introduction of rGO improved the surface microstructure and slightly reduced the band gap (LZO/rGO-3: 2.42 eV), expanding the light absorption range. Tetracycline (TC) was chosen as the target contaminant to assess photocatalytic activity in visible-light. The removal rate and constant of reaction rate (kapp) of LZO/rGO-3 was 82.1% and 0.3097 min−1 after 40 min, which was significant higher than that of LZO (57.8% and 0.1741 min−1). In addition, the TC degradation follows pseudo-first-order kinetic and shows thestability after five cycling experiments. The enhanced photocatalytic activity was mainly due to two aspects. Firstly, the improved surface appearance provided more adsorption and reaction sites. Secondly, the rGO as co-catalyst (electron trap) reduced the recombination of electron-hole pairs, and further promoted production of active substances. The photocatalytic mechanism was proposed coupled with analysis of energy structure, active substances and degradation pathways, indicating that h+, 1O2, O2− and H2O2 were the main active substances in TC photocatalytic degradation, and the generation of 1O2 was of vital importance.

Designed synthesis of microstructure and defect-controlled Cu-doped ZnO–Ag nanoparticles: exploring high-efficiency sunlight-driven photocatalysts

Cu-doped ZnO nanoparticles composited with Ag were synthesized by a one-step sol-gel method in this work, aiming at highly photocatalytic activity and possible application under sunlight (especially near ultraviolet and visible light regions, 300–760 nm) irradiation. Scanning electron microscopy (SEM) shows that the introduction of Cu inhibits particle aggregation. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) reveal that Zn(Cu)O–Ag nanoparticles (CZA NPs) are composed of metallic Ag (Ag0) and Zn(Cu)O nanocrystals; while at the Cu concentration of higher than 2%, a few CuO nanocrystals appear. Transmission electron microscopy (TEM) results evidenced the well-defined formation of Zn(Cu)O–Ag and/or CuO–ZnO–Ag heterojunctions. UV–vis spectra display that the visible absorption of the samples is obviously enhanced after the Cu introduction. At a low Cu doping level (0.2%) and moderate Cu concentration (3%–5%), the blue and green photoluminescence (PL) emission strength of the samples becomes very weak in comparison to other samples, indicative of the high separation of photogenerated electron-hole pairs. Reasonably, the higher photocatalytic degradation (complete degradation of methylene blue (MB) and methyl orange (MO) within 40 min under the simulated sunlight irradiation) are achieved in these cases: low Cu doping level (0.2%) and moderate Cu concentration (3%–5%) in CZA NPs. Further, we checked the effects of other factors on the photocatalytic degradation for possible application. Our results suggest that one well-designed composite type such as element-doped Zn(M)O–Ag nano-heterojunction or complicated metal oxide–ZnO–Ag nanocomposites possessing suitable band structures for the separation and utilization of photo-generated carriers, will remarkably improve the photocatalytic performance of nano-ZnO under sunlight irradiation.

Tourmaline-Modified FeMnTiO x Catalysts for Improved Low-Temperature NH3-SCR Performance.

Low temperature NH3 selective catalytic reduction (NH3-SCR) technology is an efficient and economical strategy for cutting NO x emissions from power-generating equipment. In this study, a novel and highly efficient NH3-SCR catalyst, tourmaline-modified FeMnTiO x is presented, which was synthesized by a simple one-step sol-gel method. We found that the amount of tourmaline has an important impact on the catalytic performance of the modified FeMnTiO x-based catalysts, and the NO x conversion exceeded 80% from 160 to 380 °C with the addition of 5 wt % tourmaline. Compared with the pure FeMnTiO x, the catalytic efficiency at a temperature below 100 °C was increased by nearly 18.9%, and the operation temperature window was broadened significantly. The enhanced catalytic performance of the FeMnTiO x catalyst was mainly attributed to the small spherical nanoparticles structure around the tourmaline powders, resulting in the increased content of Mn3+, Mn4+, and chemical oxygen on the catalytic surface. These as-developed tourmaline-modified FeMnTiO x materials have been demonstrated to be promising as a new type highly efficient low temperature NH3-SCR catalyst.

CO<SUB align="right">2 adsorption performances of amine hybrid silica aerogels synthesised via in-situ polymerisation of hybrid precursors

Amine hybrid silica aerogels (AHSAs) were synthesised via a one-step sol-gel method under room temperature, using N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPTES) and tetraethyl orthosilicate (TEOS) as precursors. AHSAs with different amine loadings were synthesised by changing the TEOS/AEAPTES ratio. The specific surface area decreases with amine loading. The highest CO2 adsorption capacity was achieved when the amine loading was 11.90 mmol/g. The corresponding CO2 adsorption capacities with simulated air (417 ppm CO2), 1% CO2 and flue gas (9.68% CO2) are 1.86, 3.78 and 5.51 mmol/g, respectively. The amine efficiency of AHSA is up to 0.32. The as-prepared sorbent shows excellent cycle stability. The CO2 adsorption kinetics were also discussed.

One-Step Synthesis of Nonspherical Organosilica Particles with Tunable Morphology

A one-step sol-gel method was developed to synthesize nonspherical organosilica particles with tunable morphology. The morphology of organosilica particles can be tuned from spherical to golf ball-like or bowl-like through varying the molar ratio of tetraethoxysilane (TEOS) to vinyltrimethoxysilane (VTMS) in the precursors. The morphology and interior structure of the organosilica particles were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The effect of ammonia concentration on the morphology of organosilica particles was investigated. The growth process of golf ball-like and bowl-like particles was tracked by SEM in detail, and the formation mechanism of nonspherical organosilica particles was also proposed.

Ternary semiconductor metal oxide blends grafted Ag@AgCl hybrid as dimensionally stable anode active layer for photoelectrochemical oxidation of organic compounds: Design strategies and photoelectric synergistic mechanism.

The development of ultra-efficient, sustainable, and easily accessible anode with relative non-precious semiconducting metal oxides is highly significant for application in the practical treatment of organically polluted water. Herein, we report SnO2, TiO2, and Ag2O ternary semiconductor metal oxide blend grafted Ag@AgCl hybrids, prepared with the one-step sol-gel method and applied as a dimensionally stable anode (DSA)-active layer on a SnO2-Sb/Ti electrode. Factors affecting crystal formation, including the presence or absence of O2 during calcination, the calcination temperature, and Ag@AgCl additive dosage were discussed. The micromorphology, phase composition, and photoelectrochemical activity of the newly designed anode were comprehensively characterized. The optimized preparation, which yielded a solid-solution structure with flat and smooth surface and well-crystallized lattice configuration, occurred in the absence of O2 during calcination at 550 ℃ with an Ag@AgCl additive dosage of 0.2 g in the sol-gel precursor. The newly designed DSA displayed improved electrocatalysis (EC) and photoelectrical catalysis (PEC) capacity. The phenol and its TOC removal efficiency reached 90.65% and 58.17% for 10 mA/cm2 current density with a metal halide lamp in 3 h. The lifespan was four times that of SnO2-Sb/Ti electrode. This proposed DSA construction strategy may support improved EC and PEC reactivities toward the decomposition of organic pollutants.