Tubular g-C3N4/carbon framework for high-efficiency photocatalytic degradation of methylene blue.

The preparation of high-efficiency, pollution-free photocatalysts for water treatment has always been one of the research hotspots. In this paper, a carbon framework formed from waste grapefruit peel is used as the carrier. A simple one-step chemical vapor deposition (CVD) method allows tubular g-C3N4 to grow on the carbon framework. Tubular g-C3N4 increases the specific surface area of bulk g-C3N4 and enhances the absorption of visible light. At the same time, the carbon framework can effectively promote the separation and transfer of charges. The dual effects of static adsorption and photodegradation enable the g-C3N4/carbon (CNC) framework to quickly remove about 98% of methylene blue within 180 min. The recyclability indicates that the tubular g-C3N4 can stably exist on the carbon framework during the photodegradation process. In the dynamic photocatalytic test driven by gravity, roughly 77.65% of the methylene blue was degraded by the CNC framework. Our work provides an attractive strategy for constructing a composite carbon framework photocatalyst based on the tubular g-C3N4 structure and improving the photocatalytic performance.

Synthesis of sub-micrometric SAPO-34 by a morpholine assisted two-step hydrothermal route and its excellent MTO catalytic performance.

SAPO-34 with a sub-micrometer crystal size was synthesized by a double hydrothermal treatment employing cost-effective morpholine as a structure directing agent, which presented an enhanced catalytic lifetime (nearly 3 times the conventional one) in the reaction of methanol to olefins with a higher light olefin selectivity (total selectivity of 97.1%). Detailed studies of the sample after different time intervals in the second crystallization with and without additional morpholine were carried out, which offered insight into crystal degradation and re-crystallization phenomena. The samples with different morpholine concentrations during the second hydrothermal treatment were also prepared, in which the sample with 80% MOR aqueous solution exhibited the smallest crystal size and the longest MTO lifetime. Furthermore, the investigation on the additional amount of mother liquor (from the first crystallization) required for the second crystallization showed that the presence of half the amount of the mother liquor (nutrients) could give us the required results effectively.

CTAB-assisted size controlled synthesis of SAPO-34 and its contribution toward MTO performance.

SAPO-34 shows higher light olefin selectivity in the reaction of methanol to olefin (MTO), but its small pore system implies diffusion limitations to bigger molecular products and results in coking too. To inhibit these limitations, sub-micrometric sized SAPO-34 crystallites were successfully synthesized by a facile surfactant-assisted hydrothermal synthesis route, in which cetyltrimethylammonium bromide (CTAB) was used as a crystal growth inhibitor (CGI). It was found that the crystal size changes in the V shape with the increase in the amount of CTAB. The sub-micrometric sized sample (SP-0.02CTAB) was obtained when the molar ratio of CTAB to Al2O3 was 0.02 in a precursor gel. The SP-0.02CTAB catalyst presents excellent performance for the MTO reaction with 97.8% C2-C4 selectivity and 3 times longer lifetime than the conventional SAPO-34 sample (SP-Conv), which is attributed to its much higher surface area and enhanced acidity derived from the formation of the sub-micrometric sized crystallites. Further study about the appropriate time of CTAB addition demonstrates that CTAB can play its role as a crystal growth inhibitor effectively, only when it is added at the very initial stage of the crystallization process.

Cellulose nanofiber induced self-assembly of zinc oxide nanoparticles: Theoretical and experimental study on interfacial interaction.

In-depth understanding of interfacial behavior between biopolymer and semiconductor metal oxides is crucial to developing potential applications of their composites. A structure-ordered cellulose/zinc oxide composite was synthesized and systematically examined by a relativistic density functional theory. The prepared composite shows a hierarchical structure. ZnO nanoparticles of around 30 nm in size are found to uniformly grow along the cellulose fiber, which together construct the primary-structure unit. Associated with experimental characterizations, calculations unravel that the electrostatic attraction between cellulose and ZnO is the main driving force to form the primary structure and the subsequent electron transfer from cellulose to ZnO enhances their interfacial interaction; moreover, an exothermic process was computed. The interfacial interaction is mainly contributed by Zn-Oc (Oc denotes the cellulose oxygen atom), which is intrinsically of a dative bond; the interaction was calculated between -1.39 and -1.83 eV in strength and dominated by orbital attractions.

Soot Combustion over Nanostructured Ceria with Different Morphologies.

In this study, nano-structure ceria with three different morphologies (nanorod, nanoparticle and flake) have been prepared by hydrothermal and solvothermal methods. The ceria samples were deeply characterized by XRD, SEM, TEM, H2-TPR, XPS and in-situ DRIFTS, and tested for soot combustion in absence/presence NO atmospheres under loose and tight contact conditions. The prepared ceria samples exhibit excellent catalytic activities, especially, the CeO2 with nanorod (Ce-R) shows the best catalytic activity, for which the peak temperature of soot combustion (Tm) is about 500 and 368 °C in loose and tight contact conditions, respectively. The catalytic activity for Ce-R is higher than that of the reported CeO2 catalysts and reaches a level that of precious metals. The characterization results reveal that the maximal amounts of adsorbed oxygen species on the surface of the nanostructure Ce-R catalyst should be the crucial role to decide the catalytic soot performance. High BET surface area may also be a positive effect on soot oxidation activity under loose contact conditions.

Preparation of Pd supported on La(Sr)-Mn-O Perovskite by microwave Irradiation Method and Its Catalytic Performances for the Methane Combustion.

In this work, a series of palladium supported on the La0.8Sr0.2MnO3.15 perovskite catalysts (Pd/LSM-x) with different Pd loading were prepared by microwave irradiation processing plus incipient wetness impregnation method and characterized by XRD, TEM, H2-TPR and XPS. These catalysts were evaluated on the lean CH4 combustion. The results show that the Pd/LSM-x samples prepared by microwave irradiation processing possess relative higher surface areas than LSM catalyst. The addition of Pd to the LSM leads to the increase in the oxygen vacancy content and the enhancement in the mobility of lattice oxygen which play an important role on the methane combustion. The Pd/LSM-3 catalysts with 4.2wt% Pd loading exhibited the best performance for CH4 combustion that temperature for 10% and 90% of CH4 conversion is 315 and 520 °C.

Preparation of hollow CuO@SiO2 spheres and its catalytic performances for the NO + CO and CO oxidation.

The hollow CuO@SiO2 spheres with a mean diameter of 240 nm and a thin shell layer of about 30 nm in thickness was synthesized using an inorganic SiO2 shell coating on the surface of Cu@C composite that was prepared by a two-step hydrothermal method. The obtained hollow CuO@SiO2 spheres were characterized by ICP-AES, nitrogen adsorption-desorption, SEM, TEM, XRD, H2-TPR, CO-TPR, CO-TPD and NO-TPD. The results revealed that the hollow CuO@SiO2 spheres consist of CuO uniformly inserted into SiO2 layer. The CuO@SiO2 sample exhibits particular catalytic activities for CO oxidation and NO + CO reactions compared with CuO supported on SiO2 (CuO/SiO2). The higher catalytic activity is attributed to the special hollow shell structure that possesses much more highly dispersed CuO nanocluster that can be easy toward the CO and NO adsorption and the oxidation of CO on its surface.

Transesterification of Tributyrin and Dehydration of Fructose over a Carbon-Based Solid Acid Prepared by Carbonization and Sulfonation of Glucose.

A series of carbon-based sulfonated solid acid (CS) catalysts can be prepared through a facile method of direct simultaneous carbonization and sulfonation of d-glucose with concentrated sulfuric acid without a hydrothermal process. Temperature is a key factor in obtaining CS catalysts with higher amounts of -SO3 H acid sites. The transesterification of tributyrin with methanol and the dehydration of fructose to 5-hydroxymenthylfurfural (5-HMF) are investigated over the CS catalysts. The CS-150 catalyst, which is the CS catalyst prepared at 150 °C, shows much higher catalytic activity to give a tributyrin conversion of 99.4 %. The yield of methyl butyrate is 97.2 % and a remarkably high yield of 5-HMF (93 %) can be obtained efficiently; these yields result from the high acid density of -SO3 H. Good linearity is displayed between the total acid density and yield of methyl butyrate/5-HMF. The CS-150 catalyst has high stability and good recyclability for the dehydration of fructose.

Effects of surface oxygen vacancies on photophysical and photochemical processes of Zn-doped TiO2 nanoparticles and their relationships.

In this paper, TiO(2) nanoparticles doped with different amounts of Zn were prepared by a sol-gel method and were mainly characterized by means of X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and surface photovoltage spectrum (SPS). The effects of surface oxygen vacancies (SOVs) of Zn-doped TiO(2) nanoparticles on photophysical and photocatalytic processes were investigated along with their inherent relationships. The results show that the SOVs easily bind photoinduced electrons to further give rise to PL signals. The SOVs can result in an interesting sub-band SPS response near the band edge in the TiO(2) sample consisting of much anatase and little rutile, except for an obvious band-to-band SPS response. Moreover, the intensities of PL and SPS signals of TiO(2), as well as the photocatalytic activity for degrading phenol solution, can be enhanced by doping an appropriate amount of Zn. These improvements are mainly attributed to the increase in the SOV amount. It can be suggested that the SOVs should play an important role during the processes of PL, surface photovoltage, and photocatalytic reactions, and, for the as-prepared TiO(2) samples doped with different amounts of Zn by thermal treatment at 550 degrees C, the larger the SOV amount, the stronger the PL and SPS signal, and the higher the photocatalytic activity.