Pore structure analysis of PFSA/SiO_2 composite catalysts from nitrogen adsorption isotherms

The perfluorosulfonic acid （PFSA）/SiO2 composite catalysts were prepared by sol-gel method. Differences concerning pore structure analysis of PFSA/SiO2 catalysts were discussed on the basis of nitrogen adsorption. Their surface area and pore size distributions were evaluated by Brunauer-Emmett-Teller （BET） and Barrett-Joyner-Halenda （BJH） methods, respectively. The nitrogen adsorption-desorption isotherms associated with adsorption hysteresis of PFSA/SiO2 catalysts were analyzed in detail. The adsorption isotherms of PFSA/SiOe catalysts belonged to Type IV isotherms accompanied by hysteresis loops of Type H1 for PFSA/SiO2 catalysts with content of 5%, 13% and 20% PFSA （PFSA-5, PFSA-13 and PFSA-20）, and the hysteresis loop of Type H2 for PFSA/SiO2 catalyst with 40% PFSA content （PFSA-40）. It indicated that PFSA-5, PFSA-13 and PFSA-20 catalysts had narrow pore size distributions and the well-defined cylindrical pores, while PFSA-40 catalyst had wide pore size distribution and inkbottle-like pores. The pore structure of PFSA-40 catalyst from the analysis of the hysteresis loop was not in agreement with that from BJH method. As an emendation for evaluation of pore size distributions of PFSA/SiOz catalysts, the comparison plots method was introduced, which was helpful to evaluate the pore structure of PFSA/SiO2 catalysts more factually.

Nanorattle Au@PtAg encapsulated in ZIF-8 for enhancing CO2 photoreduction to CO

Imidazolate-based ZIF-8 catalysts M@ZIF-8 (M = Au NR, Au@Ag NR, or Au@PtAg NRT;NR = nanorod, NRT = nanorattle), were assembled. Au NRs acted as the core for the epitaxial growth of the Ag shell, and oxidative etching of Au@Ag NRs led to Au@PtAg NRTs with K2PQI4 aqueous soluti on. All metal nano rods (MNRs) and metal nano rattles (MNRTs) were well dispersed and fully en capsulated in ZIF-8. Au @ PtAg NRTs encapsulated in ZIF-8 could lead to enhanced stability and selectivity for catalytic applications, combining the advantages of ZIF-8 (tailorable porosity) with the high surface area and improved optical sensitivity of rod-shaped NRTs. The catalyst Au @ PtAg@ZIF-8 exhibited efficient catalytic activity and CO selectivity for the gas-phase photoreduction of CO2 with H2O.

Polymer-nanoinorganic particles composite membranes: a brief overview

Polymer-nanoinorganic particles composite membranes present an interesting approach for improving the physical and chemical,as well as separation properties of polymer membranes,because they possess character-istics of both organic and inorganic membranes such as good permeability,selectivity,mechanical strength,ther-mal stability and so on.The preparations and structures of polymer-nanoinorganic particles composite membranes and their unique properties are reviewed.

Nanocable catalysts MTe(M=Pt,PtCu)@UIO-67 for CO2 conversion

Zr-based metal–organic framework nanocable catalysts comprising MTe(M=Pt,PtCu)@UIO-67 resembling"sugarcoated haws on a stick"were assembled.Ultrathin Te nanowires with diameters of about 8.48 nm served as a sacrificial template for the epitaxial growth of an outer M(Pt or PtCu)to obtain cable cores comprising MTe nanowires with good dispersity,which were then successfully encapsulated in the center of a monodisperse MTe@UIO-67 cable nanostructured catalyst.Transmission electron microscopy(TEM),scanning electron microscopy(SEM),powder X-ray diffraction(XRD)and energy dispersive X-ray(EDX)element mapping were used to investigate the morphology,structure and composition of the nanocable catalysts.Six types of catalysts were synthesized,and all of the catalysts demonstrated superior product selectivity to CO for reverse water-gas shift(RWGS)reaction.Especially,the morphology and dispersion of PtCuTe@UIO-67 nanocable catalyst can be maintained to some extent after catalysis at high temperature,and PtTe@UIO-67 catalyzed CO2 conversion was achieved with 99.86%CO selectivity.