The synthesis and precise structural characterization of highly ordered three-dimensional close-packed cage-type mesoporous silica is reported. The siliceous mesoporous material is proven to be commensurate with the face-centered-cubic Fm3m symmetry in high purity by a combination of experimental and simulated powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. The cage-type calcined samples were additionally characterized by nitrogen physisorption. The aqueous synthesis method to prepare large cage mesoporous silica with cubic Fm3m structure is based on the use of EO106PO70EO106 triblock copolymer (F127) at low HCl concentrations, with no additional salts or organic additives. Here, emphasis is put on the low HCl concentration regime, allowing the facile thermodynamic control of the silica−triblock copolymer mesophase self-assembly. Further, simple application of hydrothermal treatments at various temperatures ranging from 45 to 150 °C enables the tailoring of the mesopore diameters and apertures. The combination of experimental and simulated XRD patterns and TEM images is confirmed to be a very powerful means for the accurate elucidation of the structure of new mesoporous materials.

Exceptional control of the phase behavior of highly ordered large pore mesostructured silica (with the choice of Fm3m, Im3m or p6mm symmetry) is achieved using a triblock copolymer (EO(106)PO(70)EO(106)) and butanol at low acid concentrations.

Nitrogen containing mesoporous carbon obtained by the pyrolysis of graphene oxide (GO) wrapped ZIF-8 (Zeolitic Imidazolate Frameworks-8) micro crystals is demonstrated to be an efficient catalyst for the oxygen reduction reaction (ORR). ZIF-8 synthesis in the presence of GO sheets helped to realize layers of graphene oxide over ZIF-8 microcrystals and the sphere-like structures thus obtained, on heat treatment, transformed to highly porous carbon with a nitrogen content of about 6.12% and surface area of 502 m/g. These catalysts with a typical micromeso porous architecture exhibited an onset potential of 0.88Vvs RHE in a four electron pathway and also demonstrated superior durability in alkaline medium compared to that of the commercial Pt/C catalyst. The N-doped porous carbon derived from GO sheathed ZIF-8 core-shell structures could therefore be employed as an efficient electrocatalyst for fuel cell applications.

No abstract

In recent years, there has been an everincreasing demand for liquid-fueled energy carriers, including direct ethanol fuel cells and direct formate fuel cells. Current research on liquid fuel cells is focused on the exploration of new, durable, and highly efficient non-platinum based electrocatalysts with long-term stability. In this research, bimetallic palladium−cobalt (Pd−Co) nanoalloys were investigated as bifunctional anode catalysts with enhanced efficiency and stability toward the direct electrooxidation of ethanol and formate in alkaline medium. X-ray diffraction, transmission electron microscopy−energy-dispersive spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy were employed for the in-depth characterization of the nanocatalysts synthesized by a modified polyol reduction process in triethylene glycol medium. Electrochemical analysis via cyclic voltammetry and chronoamperometry revealed improved electrocatalytic activity and excellent stability in alkaline medium toward the anodic oxidation of liquid fuels: ethanol (ethanol oxidation reaction, EOR) and formate (formate oxidation reaction, FOR). Excellent mass activity values as high as 3.7 A mg −1 and 3.2 A mg −1 were observed for the as-made Pd 2.3 Co/C and PdCo/C electrocatalyst samples, respectively, during EOR. In addition, enhanced FOR activity and high durability were observed for the Pd 2.3 Co/C catalyst compared to that of Pd/ C prepared in a similar manner. The superior electrochemical activities for the prepared bimetallic catalysts compared to monometallic Pd/C is related to the reduced poisoning on the catalyst surface, induced by the synergistic effect and an altered Pd electronic structure by the incorporation of Co.

A one-dimensional morphology comprising nanograins of two metal oxides, one with higher electrical conductivity (CuO) and the other with higher charge storability (CoO), is developed by electrospinning technique. The CuO-CoO nanocomposite nanowires thus formed show high specific capacitance, high rate capability, and high cycling stability compared to their single-component nanowire counterparts when used as a supercapacitor electrode. Practical symmetric (SSCs) and asymmetric (ASCs) supercapacitors are fabricated using commercial activated carbon, CuO, CoO, and CuO-CoO composite nanowires, and their properties are compared. A high energy density of ∼44 Wh kg at a power density of 14 kW kg is achieved in CuO-CoO ASCs employing aqueous alkaline electrolytes, enabling them to store high energy at a faster rate. The current methodology of hybrid nanowires of various functional materials could be applied to extend the performance limit of diverse electrical and electrochemical devices.

A facile method for designing and synthesizing nanostructured carbon particles via ultrasonic spray pyrolysis of a self-organized dual polymer system comprising phenolic resin and charged polystyrene latex is reported. The method produces either hollow carbon particles, whose CO2 adsorption capacity is 3.0 mmol g(-1), or porous carbon particles whose CO2 adsorption capacity is 4.8 mmol g(-1), although the two particle types had similar diameters of about 360 nm. We investigate how the zeta potential of the polystyrene latex particles, and the resulting electrostatic interaction with the negatively charged phenolic resin, influences the particle morphology, pore structure, and CO2 adsorption capacity.

No abstract