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A series of nitrogen-doped CoAlO (N-CoAlO) were constructed by a hydrothermal route combined with a controllable NH 3 treatment strategy. The effects of NH 3 treatment on the physico-chemical properties and oxidation activities of N-CoAlO catalysts were investigated. In comparison to CoAlO, a smallest content decrease in surface Co3+ (serving as active sites) while a largest increased amount of surface Co2+ (contributing to oxygen species) are obtained over N-CoAlO/4h among the N-CoAlO catalysts. Meanwhile, a maximum N doping is found over N-CoAlO/4h. As a result, N-CoAlO/4h (under NH 3 treatment at 400°C for 4 hr) with rich oxygen vacancies shows optimal catalytic activity, with a T 90 (the temperature required to reach a 90% conversion of propane) at 266°C. The more oxygen vacancies are caused by the co-operative effects of N doping and suitable reduction of Co3+ for N-CoAlO/4h, leading to an enhanced oxygen mobility, which in turn promotes C 3 H 8 total oxidation activity dominated by Langmuir-Hinshelwood mechanism. Moreover, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) analysis shows that N doping facilities the decomposition of intermediate species (propylene and formate) into CO 2 over the catalyst surface of N-CoAlO/4h more easily. Our reported design in this work will provide a promising way to develop abundant oxygen vacancies of Co-based catalysts derived from hydrotalcites by a simple NH 3 treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

• In 2 O 3 phase in In 2 O 3 /Co 3 O 4 can be regulated via altering citric acid content in the impregnation process. • With the help of Co0, h-In 2 O 3 is partially transformed into c-In 2 O 3 during reaction reconstruction. • c-In 2 O 3 has stronger interaction with metal Co0 than h-In 2 O 3. • More oxygen vacancies are formed in c-In 2 O 3 /Co 3 O 4 while stronger CO adsorption ability is achieved in h-In 2 O 3 /Co 3 O 4. • CO 2 conversion and methanol selectivity are directly related to the In 2 O 3 crystal phase for In 2 O 3 /Co 3 O 4. In 2 O 3 /Co 3 O 4 catalysts with various crystal structure of In 2 O 3 were successfully prepared by means of regulating the amount of citric acid, and were applied for CO 2 hydrogenation to methanol to understand the structure-activity relationship. With the increase of citric acid content in the impregnation process, hexagonal In 2 O 3 (h-In 2 O 3) is gradually transformed into cubic In 2 O 3 (c-In 2 O 3). The interaction and electron transfer between c-In 2 O 3 and Co 3 O 4 are stronger than those between h-In 2 O 3 and Co 3 O 4. In the In 2 O 3 /Co 3 O 4 catalysts prepared with citric acid, phase transformations were observed under reaction conditions of 4 MPa and 300 °C. Initially, h-In 2 O 3 transitions into c-In 2 O 3. Concurrently, there is a transformation of In 2 O 3 and Co 3 O 4 into metallic cobalt (Co0) and the compound Co 3 InC 0.75. Except for h-In 2 O 3 /Co 3 O 4 containing mixed h-In 2 O 3 and c-In 2 O 3 , In 2 O 3 in all other catalysts exists in the form of c-In 2 O 3. Owing to stronger interaction between c-In 2 O 3 and Co0, dissociated hydrogen atoms diffuse more easily from the metallic Co0 to c-In 2 O 3 to produce more oxygen vacancies, accompanied with the formation of more inactive Co 3 InC 0.75 (70 wt% for c-In 2 O 3 /Co 3 O 4 vs 58 wt% for h-In 2 O 3 /Co 3 O 4). However, h-In 2 O 3 /Co 3 O 4 has stronger adsorption ability of CO to improve methanol selectivity. Thus, it can be observed that the CO 2 conversion and methanol selectivity of the catalyst are directly related to the In 2 O 3 crystal phase for In 2 O 3 /Co 3 O 4 catalysts. To be specific, h-In 2 O 3 /Co 3 O 4 has the higher selectivity of methanol, while c-In 2 O 3 /Co 3 O 4 exhibits the higher conversion of CO 2 and methanol space-time yield. [Display omitted] [ABSTRACT FROM AUTHOR]

Co3O4 nanoparticles-assembled microrods (Mic-Co3O4) were successfully synthesized with the precursor of Co-BTC (BTC = 1,3,5-benzenetricarboxylic acid) and applied for efficient propane (C3H8) oxidation. It shows a higher reaction rate of 4.14 μmolC3H8 gcat−1 s−1 at 250 °C, when it is only 1.18 μmolC3H8 gcat−1 s−1 obtained over Co3O4 nanoparticles (Np-Co3O4) via direct calcination of cobalt nitrate. Moreover, Mic-Co3O4 remains the original morphology of Co-BTC MOF, and the keeping pores enhance the microrod rigidity, hindering nanoparticles growth and thus resulting in superior thermal stability. After 12 h of durability test at 500 °C, the size of Mic-Co3O4 nanoparticles increases slightly from 62 to 70 nm, whereas it is from 97 to 130 nm for Np-Co3O4. Meanwhile, the calcination of Co-BTC precursor can induce large amounts of surface Co2+, favoring activation of adsorptive oxygen species. This can promote oxygen mobility, which is helpful for total propane oxidation. [ABSTRACT FROM AUTHOR]

Abstract: Bismuth titanates (BTs) can be fabricated by electrospinning combined with calcination at different temperatures. BiOCl/Bi2Ti2O7 nanorod heterostructures were obtained at 500 °C. They possess excellent photocatalytic efficiency and stability for tetracycline hydrochloride (TC‐HCl) degradation under simulated solar light. The excellent catalytic activity is predominantly attributed to the heterostructure between BiOCl and Bi2Ti2O7, which accelerates the separation of photogenerated carriers while the narrow band gap of Bi2Ti2O7 enhances solar energy utilization. On the basis of energy band engineering, scavenger tests, and LC‐HRMS analysis, a possible degradation pathway of TC‐HCl and photocatalytic mechanism were proposed. Our work can predict a facile route for achieving high photocatalytic performance of Bi2Ti2O7‐based materials in the application of TC‐HCl degradation. [ABSTRACT FROM AUTHOR]

Ag/AgCl composite as an alternative visible-light photocatalyst has attracted extensive interests; however, the high charge carrier recombination rate and short-term photocatalytic durability limit their practical application. In the present work, TiO 2 hollow nanofibers (ELTiO 2 ) grafted Ag/AgCl is fabricated via electrospinning-precipitation method. Compared with Ag/AgCl and Ag/AgCl-SGTiO 2 (sol-gel synthetized TiO 2 ), 2.89 and 1.59-fold enhancement in the photodegradation rate toward MO is observed over Ag/AgCl-ELTiO 2 under visible light irradiation. The enhancement of photocatalytic activity is mainly attributed to the higher content of the exposed AgCl {1 1 1} facet, which is beneficial for the separation of photogenerated carriers and accounts for more active sites. Moreover, Ag/AgCl-ELTiO 2 shows better photostability than bare Ag/AgCl. [ABSTRACT FROM AUTHOR]

The chelating effect of COO− and the electrostatic repulsive force of −OH groups in BP contribute to low temperature synthesis of LaCoO 3. [Display omitted] • Bamboo-mediated biosynthesis LaCoO 3 can be achieved at 550 °C. • COO- groups were utilized as bridging bidentate ligands to chelate metal ions. • High specific surface area, good oxygen mobility, large acid sites are obtained. • Excellent thermal stability and good resistance against H 2 O and CO 2 are observed. A pure phase of LaCoO 3 perovskite was low-temperature synthesized via a novel bamboo-mediated sol-gel route, which can meanwhile regulate Co species and oxygen vacancies of the catalyst by pretreatment of bamboo powder (BP). In the absence of BP, segregated phases of La 2 O 3 and Co 3 O 4 were found. Characterization results reveal that COO- in BP performs as a complexing agent to chelate metal ions, while the −OH groups can promote the dispersion of precursors in the formed sol solution. On the other hand, chelation effect together with bio-reduction of organic carbon is in charge of large content of bulk Co2+ in LaCoO 3 , resulting in high amounts of oxygen vacancies that are helpful for total propane oxidation. However, Na+ and K+ species originated from BP easily lead to the formation of carbonate species on the catalyst surface, playing a negative role in propane oxidation activity. Thus, an optimum pretreatment under acid solution (pH = 1) is adopted to address the above issue. As a result, BP-1-mediated (BP pretreated under pH = 1 solution) biosynthesis of LaCoO 3 exhibits a significantly high reaction rate of 3.78 μmol C3H8 g−1·s−1 at 300 °C. Moreover, the obtained catalyst delivers excellent thermal stability against 5 vol% H 2 O and 5 vol% CO 2. [ABSTRACT FROM AUTHOR]

• MnO 2 nanoparticles were encapsuled in spheres of Ce-Mn solid solution. • The package structure of catalyst shows superior activity of toluene oxidation. • Synergistic effect between the shell material and cavity nanoparticles is crucial. • The shell contributes to high water resistance and thermal stability. The high-efficient catalyst is critical for volatile organic compounds (VOCs) catalytic oxidation. MnO 2 nanoparticles encapsuled in spheres of Ce-Mn solid solution (package structure) are controllable designed and applied for the catalytic oxidation of toluene, a representative of VOCs. Our study indicates that the obtained Ce 1 Mn 2 (molar ratio of Ce:Mn = 1:2) catalyst displays much better toluene oxidation activity than pristine MnO 2 and CeO 2. Meanwhile, the shell of Ce-Mn solid solution contributes to superior thermal stability and resistance against 5 vol% H 2 O. The synergistic effect between two oxides is maximized by the package structure, giving rise to high BET surface area, good reducibility and fast oxygen mobility, which in turn leads to the outstanding catalytic performance in Ce 1 Mn 2. Additionally, in situ DRIFTS results indicate that intermediate species COO and O CH(O) are found during the catalytic oxidation of toluene over Ce 1 Mn 2 , which is mainly dominated by MvK mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • The chelation of –NH 2 to metal ions enhances the formation of small Co 3 O 4 particles. • N doping regulates the valence states of Co and oxygen vacancies. • The presence of Brønsted and Lewis acid sites promotes the adsorption of C 8 H 8. • The oxidation reactions are mainly dominated by the Mars-van Krevelen mechanism. • Good C 8 H 8 oxidation activity, thermal stability and water-resistance are achieved over CS/Co 3 O 4 -W. In this study, a Co 3 O 4 catalyst is synthesised using the chitosan-assisted sol–gel method, which simultaneously regulates the grain size, Co valence and surface acidity of the catalyst through a chitosan functional group. The complexation of the free –NH 2 complex inhibits particle agglomeration; thus, the average particle size of the catalyst decreases from 82 to 31 nm. Concurrently, Raman spectroscopy, hydrogen temperature-programmed reduction, electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy experiments demonstrate that doping with chitosan N sources effectively modulates Co2+ to promote the formation of oxygen vacancies. In addition, water washing after catalyst preparation can considerably improve the low-temperature (below 250 °C) activity of the catalyst and eliminate the side effects of alkali metal on catalyst activity. Moreover, the presence of Brønsted and Lewis acid sites promotes the adsorption of C 8 H 8. Consequently, CS/Co 3 O 4 -W presents the highest catalytic oxidation activity for C 8 H 8 at low temperatures (R 250 °C = 8.33 μmol g−1 s−1, WHSV = 120,000 mL hr−1∙g−1). In situ DRIFTS and 18O 2 isotope experiments demonstrate that the oxidation of the C 8 H 8 reaction is primarily dominated by the Mars–van Krevelen mechanism. Furthermore, CS/Co 3 O 4 -W exhibits superior water resistance (1- and 2- vol% H 2 O), which has the potential to be implemented in industrial applications. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: A series of electrospun LaCoO3 perovskites derived from CoX2 (X = CH3COO–, NO3–) were prepared and investigated for total propane oxidation. It is shown that pure rhombohedral perovskite LaCoO3 from Co(CH3COO)2 can be obtained at a relatively low temperature, 400 °C, benefitting from the complexation effect of CH3COO–. On the other hand, CH3COO– can accelerate the complete decomposition of polymer. The low‐temperature process can protect LaCoO3 nanoparticles from growing up. As a result, Co(CH3COO)2‐derived catalysts exhibit better propane oxidation activity than the ones suffered the same thermal treatment by using Co(NO3)2. XPS and H2‐TPR analysis provide that there is subtle change in Co3+/Co2+ on bulk/surface of Co(CH3COO)2‐derived catalysts prepared at different temperatures, giving rise to similar propane oxidation activities. Moreover, the result of cyclic stability test over 400 °C obtained catalyst shows little deactivation, demonstrating a good thermal stability. Our study can provide a feasible route for energy‐saving synthesis of LaCoO3 catalyst applied in the catalytic oxidation of volatile organic compounds (VOCs). [ABSTRACT FROM AUTHOR]

[Display omitted] • Co species are active sites for C 3 H 8 oxidation despite Pt loading. • Coaxial electrospinning anchors Pt on both surface and bulk phase. • Coaxial electrospun Pt/LaCoO 3 gives the best C 3 H 8 oxidation activity. • Surface Pt favors Co3+ → Co2+ while bulk Pt accelerates Co2+ → Co0+. • Redox property and lattice oxygen mobility are crucial. The effect of location sites of platinum (Pt) nanoparticles on LaCoO 3 support for complete catalytic oxidation of propane (C 3 H 8) was investigated. Pt nanoparticles were anchored on the surface, bulk and surface/bulk of LaCoO 3 by using three different loading methods: incipient-wetness impregnation, single-needle electrospinning and coaxial electrospinning, respectively, followed by a simple 300 °C H 2 reduction process. The obtained catalysts were systematically characterized. It turns out that one step synthesis of coaxial electrospun Pt/LaCoO 3 nanotubes with both surface and bulk Pt species exhibits a relatively more efficient catalytic activity, where surface Pt favors the reduction of Co3+ to Co2+ and bulk Pt accelerates that of Co2+ to Co0. Meanwhile, Co species are active sites for C 3 H 8 oxidation despite Pt loading, but the enhanced redox property and oxygen mobility upon Pt loading are crucial for the Mars-van Krevelen mechanism obeyed total C 3 H 8 oxidation. Additionally, good thermal stability is found over coaxial electrospun Pt/LaCoO 3 , removing propane at a temperature of 450 °C over 48 h without a significant decrease in propane conversion. The addition of water vapor has a little inhibition effect on the catalytic activity under the reaction condition. Such route of Pt anchoring will provide an effective means for designing highly efficient perovskite based catalysts with low precious loadings for total oxidation reaction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sequential thermal annealing in He, O 2 , and H 2 achieves well Pt dispersion. • Good interaction between metallic Pt and LaCoO 3 nanorods is realized. • Rapid Co3+/Co2+ cycle is decisive for Mars-van Krevelen mechanism obeyed oxidation. • Good oxidation activity, thermal stability and water resistance are observed. • "Circulation" in situ FTIR technology is first applied to detect the intermediates. Abstract In the present work, 0.29 wt% Pt/LaCoO 3 nanorods with high Pt dispersion were prepared by using high surface area of electrospun LaCoO 3 nanorods (31 m2/g) as the support, and the physicochemical properties are correlated with the propane oxidation activities. It is demonstrated that sequential thermal annealing in He, O 2 , and H 2 can achieve well Pt dispersion and good interaction between metallic Pt and LaCoO 3 nanorods. The latter leads to a good reducibility and high oxygen mobility, resulting in a rapid redox cycle of Co3+/Co2+. It mainly contributes to the good propane oxidation activity following the Mars-van Krevelen mechanism for Pt/LaCoO 3 -He + O 2 + H 2. Meanwhile, it exhibits good thermal stability and water resistant. Additionally, a unique "circulation" in situ FTIR technology was developed to detect the intermediate species for the weak interaction of propane with Pt/LaCoO 3. [ABSTRACT FROM AUTHOR]

A one-dimensional (1D) core-shell of Co-Ce oxide has been prepared by multifluidic coaxial electrospinning method and evaluated for the total oxidation of propane (C 3 H 8). Activity and morphological characterizations show that the CeO 2 @Co 3 O 4 nanofiber catalyst, of which the core is CeO 2 and the shell is Co 3 O 4 , exhibits excellent oxidation activity. The exposed Co 3 O 4 grown on the outside of the fibers can rapidly react with C 3 H 8 while CeO 2 with high oxygen storage capacity in the inside is conductive to the enhanced oxidation rate. Besides, the continuous grain boundary provides a fast mass transfer channel for lattice oxygen, and rich oxygen vacancies favor the mobility of active oxygen species. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) confirms that the CeO 2 @Co 3 O 4 catalyst have a faster rate of C 3 H 8 adsorption and better oxidation activity with respect to the counterpart using a single-needle electrospinning method. Moreover, the CeO 2 @Co 3 O 4 catalyst displays excellent thermal stability, and strong resistance against 5 vol% H 2 O and 5 vol% CO 2 at both 300 and 400 °C. Our strategy can give some new insights into morphological engineering to promote active oxygen mobility via the construction of one-dimensional core-shell of metal oxides for catalytic oxidation of VOCs. ga1 • CeO 2 @Co 3 O 4 nanofibers were prepared by multifluidic coaxial electrospinning. • Co 3 O 4 shell rapidly reacts with C 3 H 8 while CeO 2 core enhances oxygen migration. • Continuous grain boundary provides a fast mass transfer channel for lattice oxygen. • Abundant oxygen vacancies favor the mobility of active lattice oxygen. • Superior oxidation activity, thermal stability and H 2 O/CO 2 resistance were obtained. [ABSTRACT FROM AUTHOR]