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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.

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.

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.

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.

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.

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.