N-doped CoAl oxides from hydrotalcites with enhanced oxygen vacancies for excellent low-temperature propane oxidation

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-Co AlO catalysts were investigated.In comparison to CoAlO,a smallest content decrease in surface Co^(3+)(serving as active sites)while a largest increased amount of surface Co^(2+)(contributing to oxygen species)are obtained over N-Co AlO/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℃ for 4 hr)with rich oxygen vacancies shows optimal catalytic activity,with a T90(the temperature required to reach a 90% conversion of propane)at 266℃.The more oxygen vacancies are caused by the co-operative effects of N doping and suitable reduction of Co^(3+) for NCoAlO/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.

Template preparation of twisted nanoparticles of mesoporous silica

Optical isomers of N-lauroyl-L-（Or-D-） alanine sodium salt {C12-L-（Or-D-）AIaS} surfactants were used for the preparation of mesoporous silica nanoparticles with a twisted hexagonal rod-like morphology. Thermogravimetric analysis （TGA） was used to determine the temperature for template removal. Circular dichroism （CD） spectra of the surfactant solution with various compositions illustrated the formation and supramolecular assembly of protein-like molecular architecture leading to formation of twisted nanopar- ticles. Scanning electron microscopy （SEM）, high-resolution transmission electron microscopy （HRTEM） and X-ray powder diffraction （XRD） patterns of these as-synthesized mesoporous silica confirmed that the twisted morphology of these nanoparticles was closely related to the supramolecular-assembled complex of amino acid surfactants.