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The LaCo0.94Pt0.06O3 catalyst is reduced under 5% H2/Ar in different temperatures to get Pt/LaCoO3 with high catalytic activity for soot oxidation. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR), O2-TPD and TGA were used to study the physicochemical properties of the catalyst. SEM and TEM results indicate that Pt nanoparticles (

NixMn3−xO4 and NixMn3−xO4/T (T represents tourmaline) catalysts with a double-layer hollow structure were prepared by a rigid template method for low-temperature selective catalytic reduction of NOx with NH3 (NH3-SCR). The catalytic activity and SO2 tolerance performance of NixMn3−xO4 catalyst were enhanced by the addition of 2 wt% tourmaline. The results showed the addition of tourmaline could affect the growth, shell thickness and redox property of the NixMn3−xO4 catalysts. The relative contents of Mn4+ and surface chemical oxygen were also increased by the addition of tourmaline, which were beneficial for improving the SCR activity, the catalyst showed 100% NO conversion in a low-temperature range of 125–240 °C. The mechanism of SCR reaction and SO2 tolerance were analyzed by In-situ DRIFTS. The SCR reaction process mostly follows Langmuir–Hinshelwood (L–H) mechanisms. The primary NOx adsorption materials on NixMn3−xO4/T catalyst were nitrate bidentate and bridge nitrate, which was not affected by SO2, and it had excellent SO2 tolerance at 150 ℃.

In this work, the Ag loaded Ce-based catalyst was synthesized (by the sol-gel method) and its performance was studied by TG, H2-TPR, XRD, SEM, TEM, BET and XPS. The results show that Ag nanoparticles be successfully loaded onto the CeO2 surface and the relative content of Ag nanoparticles is about 10.22 wt.% close to the theoretical value (10%). XPS shows that Ag nanoparticles induce a great number of oxygen vacancies in the CeO2 lattice through the electronic transfer, and H2-TPR indicates that the Ag-assisted CeO2 catalyst exhibits a better reduction performance and Ag nanoparticles can promote O- transform into O2-. The catalytic activity for soot oxidation was studied by TG under air atmosphere and the activity was found to be obviously enhanced when Ag nanoparticles be load on the surface of CeO2 (T10 = 386 °C, T90 = 472.5 °C, Tm = 431 °C). The reaction mechanism was also presented and O 2 - species is regarded as the determinant factor for the catalytic activity.

Present paper deals with the preparation (by sol-gel method) and characterization (by H2-TPR, XPS, XRD, IR, SEM, TEM) of the Pt substituted LaMn1-xPtxO3 (x = 0,0.05,0.1,0.2,0.3) perovskite oxides and their activities towards the diesel soot oxidation at simulated atmosphere. The results show platinum enters the perovskite crystal structure when x＜0.1. With the increase of platinum doping amount, the oxygen vacancy concentration on the catalyst surface increases, and H2-TPR shows that the low-temperature oxidation-reduction performance of the catalyst is improved with the increase of platinum doping amount. Catalytic oxidation of soot was studied under tight contact with soot/catalyst ratio of 1/10 under a flow rate of air at 100 ml/min. LaMn0.8Pt0.2O3 perovskite catalyst was found to give the best result for soot oxidation with the light off temperatures T10 = 339 °C, T50 = 370 °C, T90 = 405 °C. The might reaction mechanism is also presented.

Developing an efficient catalyst for oxygen evolution reaction (OER) is one of the most effective ways to cope with the energy crisis. Here, we report a simple method to prepare A-site deficiency SrxCo0.8Fe0.2O3−δ (x = 0.9, 0.95, 1) perovskites by sol-gel. XRD、SEM and XPS are used to characterize structure and element valence of catalysts. The introduction of A-site deficiency results in the expansion of lattice expansion due to the increase of oxygen vacancies and optimization of eg occupancy of B-site transition metal, which greatly improves the OER activity of catalysts. Among them, Sr0.95Co0.8Fe0.2O3−δ (S0.95CF) exists the best activity. Besides, after the durability test, an unusual activation process with enhanced OER activity was observed for all the prepared perovskites. This work highlights the importance of tailoring A-site deficiency of perovskites as a valid strategy to improve OER activity.

In this study, a series of perovskite oxides LaCo1−xPtxO3−δ (x = 0, 0.02, 0.04, 0.06, and 0.08) were prepared by the citric acid–ethylenediaminetetraacetic acid (CA–EDTA) complexing sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Then, the samples were investigated as OER and HER bifunctional electrocatalysts in alkaline media. Compared with other catalysts, LaCo0.94Pt0.06O3−δ had good stability and presented more activity at a lower overpotential of 454 mV (at 10 mA cm−2), a lower Tafel slope value of 86 mV dec−1 and a higher mass activity of 44.4 A g−1 for OER; it displayed a lower overpotential of 294 mV (at −10 mA cm−2), a lower Tafel slope value of 148 mV dec−1 and a higher mass activity of −34.5 A g−1 for HER. The improved performance might depend on a larger ECSA, faster charge transfer rate and higher ratio of the highly oxidative oxygen species (O22−/O−). Furthermore, the eg orbital filling of Co approaching 1.2 in the B site might play a leading role.

Hollow silica spheres possessing excellent mechanical properties were successfully prepared through a layer-by-layer process using uniform polystyrene (PS) latex fabricated by dispersion polymerization as template. The formation of hollow SiO2 micro-spheres, structures and properties were observed in detail by zeta potential, SEM, TEM, FTIR, TGA and nitrogen sorption porosimetry. The results indicated that the hollow spheres were uniform with particle diameter of 1.6 μm and shell thickness of 150 nm. The surface area was 511 m2/g and the pore diameter was 8.36 nm. A new stationary phase for HPLC was obtained by using C18-derivatized hollow SiO2 micro-spheres as packing materials and the chromatographic properties were evaluated for the separation of some regular small molecules. The packed column showed low column pressure, high values of efficiency (up to about 43 000 plates/m) and appropriate asymmetry factors.

In this paper, a new concept of calibration hold-up time was defined. On the basis of the concept, a novel method was proposed to predict retention times in temperature programmed (isothermal) under constant flow and constant pressure mode each other, and the method also researched in simultaneous pressure and temperature programmed. The prediction results show that average relative errors are 1.33% (0.64%) in temperature programmed (isothermal) under constant pressure mode by using isothermal dates in constant flow mode, and the other way around, average relative errors are 0.62% (−0.62%). For simultaneous pressure and temperature programmed, retention times were predicted by using isothermal dates in constant flow and constant pressure mode, average relative errors are −0.24% and −0.16%; and retention times were predicted by using isothermal dates directly, average relative errors are −0.62%.

Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NOx. The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCe0.25Zr0.75/TiO2 at high temperature, while Bronsted acid sites are more important than Lewis acid sites at low temperature. For the NH3+NO+O2 co-adsorption, NH3 species occupy most of activity sites on CuCe0.25Zr0.75/TiO2 catalyst, and mainly exist in the forms of NH4 + (at low temperature) and NH3 coordinated (at high temperature), playing a crucial role in the NH3-SCR process. Two different reaction routes, the L-H mechanism at low temperature ( 200°C), are presented for the SCR reaction over CuCe0.25Zr0.75/TiO2 catalyst.

Witnessed by X-ray powder diffraction (XRD), Raman, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies, BiVO4 nanofibers and porous nanostructures were successfully fabricated by electrospinning method using NH4VO3 and Bi(NO3)3 as starting materials. Polyvinylpyrrolidinone (PVP) was used to tune the viscosity and spinnability of the electrospinning sol. The slow decomposition and combustion of PVP matrix prevented rapid crystal growth of BiVO4 nanostructures leading to considerably small crystallite size (approximately 19.1–28.3 nm) with less surface defects after two hours calcination at varying temperatures. This paid great tributes to the superior visible light photocatalytic activity when compared to the submicron sized BiVO4 prepared in the absence of PVP.

Perovskite oxide is a potential alternative to precious metal oxides like IrO2 and RuO2 as electrocatalysts in the oxygen evolution reaction (OER), mostly for its cost-effectiveness and adequate stability. However, the low catalytic activity in the OER limits its practical application. This paper deals with the preparation of perovskite oxides (by the sol-gel method) with enhanced electrocatalytic activity through selective dissolution of A-site cations of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF) in order to tune the A-site cation deficiency. Additionally, a thorough investigation of the catalysts’ OER performance was performed in a 0.1 mol⋅L−1 KOH solution. Based on the results of XRD, SEM, TEM, XPS and ICP-AES, it can be concluded that selective dissolution of Sr cations on A-sites can be achieved using a HNO3 etching remaining the perovskite structure. The OER catalytic activity of LSCF can be effectively promoted after acid etching for 6 h, which can be attributed to the higher surface area (BET result) and ratio of the high oxidative oxygen species (O2−/O−) and surface oxygen species (OH−/O2). Moreover, the LSCF catalysts maintains an appropriate electrochemical stability after acid etching. Our work offers a simple but effective way to modify the perovskite surface so as to boost the OER performance.

In-situ modification is studied in this work on LaCo1-xPtxO3 for soot oxidation. A series of perovskite catalysts LaCo1-xPtxO3 (by sol-gel method) are modified with 30% H2O2. XRD, TEM, SEM, BET, XPS, Raman, in-situ DRIFTS, H2-TPR and TGA are used to investigate physicochemical properties of catalysts. TGA results show that all doped catalysts have a lower temperature of soot conversion, especially LaCo0.94Pt0.06O3 (T50 = 437 °C). The T50 of the catalyst with modification by H2O2 solution decreases at least 20 °C compared with the doped catalysts. A highly symmetrical structure and an obvious amorphous layer about 3–5 nm are observed in the modified catalysts. According to the XPS study, the symmetrical structure benefits to the movement of oxygen vacancy thus catalyst captures more adsorbed oxygen (about 95%). And the amorphous surface could adsorb more oxygen species. In addition, all catalysts show excellent aging resistance performance. The reaction mechanism of catalyst for soot oxidation is presented in the end.

Porous biomorphic La0.9K0.1CoO3 catalysts were fabricated by the bio-templating method using tailored pinewood as the template and La0.9K0.1CoO3 sol as the precursor. The specimens were characterized by SEM, TEM, XRD, FT-IR, EDX, and N2-adsorption techniques. SEM and TEM results proved that the biomorphic cellular morphology of the initial pinewood structure was retained after heat treatment. The XRD and FT-IR results suggested a perovskite-type crystal structure for the microcellular catalysts. The generated catalysts possessed a relatively high surface area (147.97 m2 g−1) and porosity with a mean pore size of approximately 4–25 μm. The catalytic activity for the combustion of diesel soot was tested by a technique using a temperature-programmed reaction. The biomorphic La0.9K0.1CoO3 exhibited better catalytic activity for diesel soot combustion at low temperature than the La0.9K0.1CoO3 powders prepared from the same precursor sol due to enhanced contact efficiency between the soot and the catalysts, and the value of T10 was about 340 °C.

Three-dimensionally ordered macroporous (3DOM) SiOC was successfully fabricated on a cordierite monolith inner wall of a polystyrene (PS) sphere template through a colloidal crystal templating (CCT) method (named as 3DOM SiOC/cordierite). And perovskite-type LaCoO3 (LCO) mixed metal oxides, prepared by a facile sol–gel process, were coated onto the wall of the 3DOM SiOC/cordierite by a simple impregnation-sintering approach (named as LCO/3DOM SiOC/cordierite). The morphological and physicochemical properties studies indicate that the 3DOM structure has excellent connectivity, a large specific surface area, and applicable pore size. And the 3DOM structure plays an important role in preventing aggregation of the targeted catalyst particles, improving the contact condition between catalysts and soot as well as enhancing the reducibility of the LCO. The subsequent investigation on the catalytic performance of the 3DOM samples for diesel soot combustion shows that the 3DOM texture offers the catalyst a lower soot combustion temperature than a conventional catalyst, and the LCO/3DOM SiOC/cordierite reduces the combustion temperature even further while avoiding the rise of back-pressure effectively as well.

Graphical abstract: The Cu–Ce{sub 0.25}–Zr{sub 0.75}/TiO{sub 2} catalyst exhibited excellent SCR activity at 165–450 °C within the range of exhaust temperatures of diesel engines. - Highlights: • Cu–Ce{sub x}–Zr{sub 1−x}/TiO{sub 2} catalysts were prepared by a wet impregnation method. • The property for NH{sub 3}-selective catalytic reduction of NO{sub x} were investigated. • The Ce/Zr molar ratio had effects on the performance of Cu–Ce–Zr/TiO{sub 2} catalysts. • The Cu–Ce{sub 0.25}–Zr{sub 0.75}/TiO{sub 2} sample exhibited 100% NO{sub x} conversion between 165 °C and 450 °C. • The factors that govern the activity enhancement were extensively investigated. - Abstract: Copper–cerium–zirconium catalysts loaded on TiO{sub 2} prepared by a wet impregnation method were investigated for NH{sub 3}-selective catalytic reduction of NO{sub x}, aiming to study the effects of the Ce/Zr molar ratio on the performance of Cu–Ce–Zr/TiO{sub 2} catalysts. The Cu–Ce{sub 0.25}–Zr{sub 0.75}/TiO{sub 2} sample exhibited nearly 100% NO{sub x} conversion over a wide temperature range (165–450 °C), which is strikingly superior to that of Cu/TiO{sub 2} (210–389 °C) within the range of exhaust temperatures of diesel engines. The factors that govern the activity enhancement were extensively investigated by using a series of characterization techniques, namely X-ray diffraction (XRD), transmission electron microscopy (TEM),more » X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H{sub 2}-TPR). The results showed that the addition of zirconium and/or cerium refined the copper dispersion, prevented copper crystallization and partially incorporated the copper ions into the zirconia (ceira) lattice, which led to enhance the redox abilities of Cu–Ce–Zr/TiO{sub 2} catalysts.« less

La 1− x Ce x Mn 1− y Co y O 3 catalysts were prepared by the “glucose method”. The structures and physico-chemical properties for these catalysts were characterized using X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR), H 2 -temperature-programmed reduction (H 2 -TPR) and O 2 -tempreature-programmed desorption (O 2 -TPD). Results showed that cerium substitution at the A-site in LaMnO 3 produced a CeO 2 phase. The cobalt can be introduced into the B-site in La 0.8 Ce 0.2 MnO 3 at any substitution ratio because of the similar ionic radii between cobalt and manganese. The catalytic activity for soot combustion in air was evaluated using a TG/DTA analyzer. Cerium substitution at A-site enhances the catalytic activity, while cobalt substitution at B-site inhibits the catalytic activity. The activation energy for soot combustion was calculated using the Horowitz method. The activation energy for non-catalytic soot combustion was 164.1 kJ mol − 1 . The addition of catalysts decreased the activation energy by about 26–63 kJ mol − 1 . Among the applied catalysts, Ce20Mn exhibited the lowest activation energy (101.1 kJ mol − 1 ).

Based on the enlightenment from the crystallization behavior of polymer, a novel retention equation constructed with only three pairs of isothermal retention data was proposed to predict retention times in temperature programmed gas chromatography (TPGC). The new retention equation worked beautifully in both the single- and the multiple-ramp temperature-programmed modes, yielding the average absolute relative errors of 0.65% for single-ramp TPGC across all the 18 analytes in 3 temperature programmed experiments and 0.30% for multiple-ramp TPGC across all the 8 analytes in 6 temperature programmed experiments tested in this work. Moreover, to compare with the new retention equation systematically and thoroughly, another 13 retention equations determined by two or three parameters were derived from a universal formula ln k = a0 + a1/T + a2/T2 + a3 ln T + a4T + a5T2 as a combination of the relationships between ln k and T with reference to four widely used retention equations in publications. Calculated by these 14 retention equations with the same experimental data, the absolute relative errors of prediction retention times for single-ramp TPGC mode were compared by means of statistical analysis. At a very high significance level of 1%, statistical evidences of paired t-test strictly implied that the new retention equation yielded the best prediction results among all of the 14 retention equations. In addition, remarkably, among the 13 retention equations, three seldom used in publications retention equations also worked nicely, yielding satisfactory average absolute relative errors of 0.78%, 0.81% and 0.84% for single-ramp TPGC.

A serials of La1−xCexMnO3 (x = 0, 0.2, 0.4, 0.6 and 0.8) catalysts have been prepared via a sol-gel process using citric acid as a chelating agent. The phase composition and morphology of the catalysts are characterized by XRD, SEM and TEM. La1−xCexMnO3/γ-Al2O3/cordierite catalyst has also been prepared by immersion process using cordierite honeycomb ceramic as carrier and γ-Al2O3 as support agents. The effect of Ce-doping on the structure of perovskite and catalytic property of methane combustion is explored. The results show that with the increase of Ce substitution, the crystal structure of perovskite changes from the tetragonal system to the orthorhombic system and when the x is equal to 0.2, the catalytic property in methane combustion is the best.

Barium-ferrite-containing glass ceramic fibers were successfully prepared by the combination of a sol–gel process and electrospinning technique using basic iron formate, barium acetate and boric acid as the starting materials. After leaching of barium borate matrix, pure phase BaFe12O19 fibers were obtained. The relationship of aged time and viscosity of the precursor solution was studied and the results showed that the viscosity corresponding to the spinnable state was 1–4 Pa s. The morphology, structure and magnetic properties of the obtained fibers were characterized with scanning electron microscopy, transmission electron microscopy, fourier transform infrared spectroscopy, thermo gravimetric analysis–differential scanning calorimetry, vibrating sample magnetometer. The X-ray diffraction results indicate that only the M-type Ba-ferrite and Ba-borate exist. The fibers had rough surface and hollow structure with the diameter no more than 1 μm. The fibers were composed of 40 nm BaFe12O19 nanoparticles embedded in the borate matrix. The coercivity and saturation magnetization of the synthesized fibers were 4,106.9 Oe and 17.8 emu/g, respectively.

Perovskite-type La1–xKxCoO3 and LaCo1–yFeyO3 catalysts were prepared and characterized by nitrogen sorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Catalytic activity for the simultaneous removal of NOx and soot was investigated using temperature-programmed reactions. For the La1–xKxCoO3 series, the introduction of K ions into the A-site caused the enhancement of Co valence state, which was beneficial to improving the catalytic activity. Excess K ions produced a Co3O4 phase adhering to the perovskite crystals, but the rhombohedral perovskite structure was well-maintained. In contrast, the B-site could be substituted by Fe ions with the doping ratio changing from null to 0.5, and no secondary phases were detected. With increasing K substitution, NOx conversion in the La1–xKxCoO3 series showed a declining trend after an initial ascent. The Co3O4 particles produced at high K content were re...

The BaFe12O19 nanoparticles with different morphologies including plates, lamella, and rods have been prepared from a facile thermal pyrolysis of citrate precursors obtained from a spray-drying process. The additives and thermal history affect the morphology of BaFe12O19 nanopartilces. The lattice parameter values vary with the particle morphology especially for lattice parameter c, and the value is 23.235, 23.187, and 23.344 A corresponding to lamella, nanorod, and plate, respectively. The coercivity value of the lamella, nanrod, and plate is 4579, 3115, and 3974 Oe.

La0.9K0.1CoO3 perovskite type oxide fibers have been prepared by a sol−gel process combined with electrospinning procedure. The reactions during the calcination process of fibers have been tracked ...

A sol‐gel‐related solvothermal process is developed to prepare iron oxide fibers. Continuous iron oxide gel fiber was drawn from spinnable sol using ferric alkoxide as the precursor, and hollow hematite fiber was obtained after the gel fiber was treated by hydroncarbon thermal reaction. The as‐prepared hollow fiber was several millimeters in length, 4∼15 µm in outer diameter, and ∼3 µm in wall thickness. Substituting the hydrocarbon with triethylamide, Fe3O4 solid fiber composed of nanorods can be obtained. Incubated at 200°C in air for only 1 hour, Fe3O4 was oxidated to γ‐Fe2O3 fiber. Possible mechanisms involved in formation of these nanostructured iron oxide fibers also are discussed.

A series of complex oxide La1−x Ce x CoO3 catalysts was synthesized at a low temperature through a combustion process, in which x is among 0, 0.1, 0.2, 0.4 and 0.6 corresponding to the quantity of La3+ partial substitution by Ce4+. The catalysts were characterized for phase composition using chemical analysis and X-ray diffraction. The catalytic activity of the catalysts in removal of NO x , total hydrocarbon (THC) and particulate matter (PM) from diesel exhaust gases were examined in detail using temperature-programmed reaction technique. The results show that after partial substitution of La3+ with Ce4+, the oxygen vacancy concentration increases significantly and a Co3+-Co2+ system is formed. Consequently, the catalytic activity in the removal of THC and NO x is significantly improved. But for the PM, the effect is not so obvious. The possible catalytic mechanism for this was presented. It is also worth noting that the doped catalysts showed good stability.

Hollow zinc ferrite fibers have been prepared via a facile citrate sol-gel process using Fe(OH)(HCOO)2 prepared in laboratory and Zn(CH3COO)2⋅2H2O as the original materials. The obtained hollow fibers were flexible and handlable with the outer diameter being 1–4 μm and the wall thickness less than 1 μm, and the fiber wall were made up of nanoparticles about 50 nm. Rheological behaviour of the precursor sol was tracked by Rheometer. The development of the gel fibers to zinc ferrite fibers was studied by IR, TG and XRD. Morphology observation of the fibers was given on SEM and TEM.

Continuous iron oxide gel fibers were prepared by the sol–gel method using ferric alkoxide and acetic acid as starting materials and alcohol as solvent, and continuous hollow α-Fe2O3 fibers produced after the gel fibers were heat treated at 400 °C for 1 h. The outer diameter of the α-Fe2O3 fibers is between 4–10 µm and the wall thickness is 1–2 µm, in which the α-Fe2O3 particle size is about 100 nm. 2-Methoxyethanol and acetic acid played important roles in the formation of the spinnable sol and the possible mechanism for the formation of the hollow α-Fe2O3 fibers was discussed in detail. The hollow α-Fe fibers could be obtained by reducing the as-prepared α-Fe2O3 fibers under hydrogen flow and the α-Fe particle size increased to ∼150 nm.

Zinc ferrite gel fibers were prepared from the sol precursor by the electrospinning method, and the ZnFe2O4 polycrystalline nanofibers were obtained upon calcination of the gel fibers. The obtained ZnFe2O4 nanofibers composed of 20–30 nm nanocrystals were about one hundred to several hundred nanometers in diameter. The materials have been characterized by means of SEM, TEM, XRD, TGA, and IR techniques.

Copper catalysts prepared using two kinds of supports (BaTiO3 and Fe2O3@BaTiO[Formula: see text] have been tested for soot combustion. Perovskite-type oxide BaTiO3 shows excellent properties as support but has small specific surface area. Fe2O3@BaTiO3 core/shell microspheres, as improved support of BaTiO3 support, were fabricated by a hydrothermal-annealing approach. Fe2O3@BaTiO3 support has large specific surface area, which optimizes the contact condition of the gas-soot-catalyst three-phase reaction. Due to the Cu-Fe2O3@BaTiO3 interaction, the redox properties of copper are improved. Soot combustion is tested under O2 gas flow and NOx/O2 gas flow, and Fe2O3@BaTiO3 supported copper catalyst (Cu/Fe2O3@BaTiO[Formula: see text] all shows higher catalytic activity and CO2 selectivity than BaTiO3 supported copper catalyst (Cu/BaTiO[Formula: see text].