LaFe0.8Co0.15Cu0.05O3 Supported on Silicalite-1 as a Durable Oxygen Carrier for Chemical Looping Reforming of CH4 Coupled with CO2 Reduction.

Chemical looping reforming of CH4 coupled with CO2 reduction is a novel technology for the utilization of CH4 and CO2. Here, we report a durable and outstanding LaFe0.8Co0.15Cu0.05O3/S-1 oxygen carrier at lower operating temperature to efficiently convert CH4 and utilize CO2. LaFe0.8Co0.15Cu0.05O3 showed a high CH4 reaction rate (7.0 × 10-7 mol·(g·s)-1), CO selectivity (84.2%), and CO yield (0.045 mol·g-1) at 800 °C. However, the reactivity of LaFe0.8Co0.15Cu0.05O3 reduced quickly with the redox cycles. The introduction of Silicalite-1 promoted the performance of the LaFe0.8Co0.15Cu0.05O3 perovskite oxygen carrier during the redox cycles. It can be attributed to the fact that under heat treatment, the LaFe0.8Co0.15Cu0.05O3 particles grew along the edge of Silicalite-1 and the LaFe0.8Co0.15Cu0.05O3 nanoparticles were homogeneously dispersed on the Silicalite-1 surface, which improved the thermal stability and reactivity of the oxygen carrier. In addition, the interface between Silicalite-1 and LaFe0.8Co0.15Cu0.05O3 nanoparticles also played important roles because the porous structure of Silicalite-1 could reduce the mass transfer restriction of the interface. In addition, Silicalite-1 also possessed high CH4 and CO2 adsorption selectivity, leading to higher reactivity.

Ultra-Fine CeO2 Particles Triggered Strong Interaction with LaFeO3 Framework for Total and Preferential CO Oxidation.

Interactions between the active components with the support are one of the fundamentally factors in determining the catalytic performance of a catalyst. In contrast to the comprehensive understanding on the strong metal-support interactions (SMSI) in metal-based catalysts, it remains unclear for the interactions among different oxides in mixed oxide catalysts due to its complexity. In this study, we investigated the interaction between CeO2 and LaFeO3, the two important oxygen storage materials in catalysis area, by tuning the sizes of CeO2 particles and highlight a two-fold effect of the strong oxide-oxide interaction in determining the catalytic activity and selectivity for preferential CO oxidation in hydrogen feeds. It is found that the anchoring of ultra-fine CeO2 particles (<2 nm) at the framework of three-dimensional-ordered macroporous LaFeO3 surface results in a strong interaction between the two oxides that induces the formation of abundant uncoordinated cations and oxygen vacancy at the interface, contributing to the improved oxygen mobility and catalytic activity for CO oxidation. Hydrogen spillover, which is an important evidence of the strong metal-support interactions in precious metal catalysts supported by reducible oxides, is also observed in the H2 reduction process of CeO2/LaFeO3 catalyst due to the presence of ultra-fine CeO2 particles (<2 nm). However, the strong interaction also results in the formation of surface hydroxyl groups, which when combined with the hydrogen spillover reduces the selectivity for preferential CO oxidation. This discovery demonstrates that in hybrid oxide-based catalysts, tuning the interaction among different components is essential for balancing the catalytic activity and selectivity.

A novel magnetic MIL-101(Fe)/TiO2 composite for photo degradation of tetracycline under solar light.

A novel magnetic MIL-101(Fe)/TiO2 composite was synthesized for photo degradation of tetracycline (TC) under solar light. The composite was characterized by XRD, TGA, SEM, TEM, EDS, BET, FTIR, XPS, VSM, ESR, and PL. The resultant composite was environment friendly material, which exhibited high TC degradation efficiency and excellent reusability. In the meantime, it could be separated easily from TC solution by using magnet, which would save significant time and cost of preparation and degradation, having broad prospect in application. Using 1 g L-1 magnetic MIL-101(Fe)/TiO2 at pH = 7, 92.76% degradation efficiency was achieved under solar light irradiation in 10 min for 20 mg L-1 TC. Further experiments indicated that TiO2 introduced in the composite played an important role in the degradation process, which could be activated by the UV light in solar light to generate large amount of O2- and OH radicals. The degradation efficiency of TC in this paper was significantly higher than other research papers reported in last three years. This study put forward new magnetic Fe-based metal-organic frameworks (MOFs)/TiO2 composite for degrading pharmaceutical wastewater.

DFT insights into oxygen vacancy formation and CH4 activation over CeO2 surfaces modified by transition metals (Fe, Co and Ni).

The effects of transition metal (Fe, Co and Ni) modification (adsorption, insertion and substitution) of CeO2 surfaces on oxygen vacancy formation and CH4 activation are studied on the basis of first principles calculations. The results indicate that the hollow, O-O-bridge and Ce-O-bridge sites are the most stable sites for Fe, Co and Ni atom adsorption on the CeO2(111) surface, and the double O-bridge, O-top and double O-bridge sites are the corresponding most favorable sites for the CeO2(110) surface. Most of the configurations that are generated by the transition metal modification of CeO2(111) and (110) surfaces are accompanied by the reduction of Ce4+ to Ce3+. Based on the calculated subsurface (SS) and sublayer (SL) oxygen vacancies of the CeO2(111) surface, the results show that the substitution of transition metals on the CeO2(111) surface can promote SS oxygen vacancy formation spontaneously, whereas the most stable adsorption of transition metal Fe and Ni atoms on the CeO2(111) surface can promote SL oxygen vacancy formation spontaneously. For the CeO2(110) surface, the substitution of transition metals can facilitate plain (P) and spilt (S)-type oxygen vacancy formation spontaneously. With respect to CH4 activation, the results show that Co atom substitution on the CeO2(110) surface can greatly facilitate the first C-H bond activation step, with an energy barrier of 0.783 eV and a reaction energy of 0.229 eV. However, Co atom substitution on the CeO2(110) surface with P and S-type oxygen vacancies is not conducive to C-H activation. The obtained results could provide new insights into the structural features of transition metal-modified CeO2 at the atomistic level, leading to the more efficient design of oxygen carriers and the optimization of the activation pathways of methane over this type of catalyst.