Pt nanoparticles entrapped in ordered mesoporous carbons:An efficient catalyst for the liquid-phase hydrogenation of nitrobenzene and its derivatives

Pt nanoparticles entrapped in ordered mesoporous CMK-3 carbons with p6mm symmetry were prepared using a facile impregnation method, and the resulting materials were characterized using X-ray diffraction spectroscopy, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The Pt nanoparticles were highly dispersed in the CMK-3 with 43.7% dispersion. The Pt/CMK-3 catalyst was an effective catalyst for the liquid-phase hydrogenation of nitrobenzene and its derivatives under the experimental conditions studied here. The Pt/CMK-3 catalyst was more active than commercial Pt/C catalyst in most cases. A highest turnover frequency of 43.8 s-1 was measured when the Pt/CMK-3 catalyst was applied for the hydrogenation of 2-methyl-nitrobenzene in ethanol under optimal conditions. It is worthy of note that the Pt/CMK-3 catalyst could be recycled easily, and could be reused at least fourteen times without any loss in activity or selectivity for the hydrogenation of nitrobenzene in ethanol.

A facile template approach for the synthesis of mesoporous Fe3C/Fe-N- doped carbon catalysts for efficient and durable oxygen reduction reaction

Facile synthetic approaches toward the development of efficient and durable nonprecious metal catalysts for the oxygen reduction reaction （ORR） are very important for commercializing advanced electrochemical devices such as fuel cells and metal-air batteries. Here we report a novel template approach to synthesize mesoporous Fe-N-doped carbon catalysts encapsulated with Fe3C nanoparticles. In this approach, the layer-structured FeOCI was first used as a template for the synthesis of a three- dimensional polypyrrole （PPy） structure. During the removal of the FeOCI template, the Fe^3＋ can be absorbed by PPy and then converted into Fe3C nanoparticles and Fe-N-C sites during the pyrolyzing process. As a result, the as-prepared catalysts could exhibit superior electrocatalytic ORR performance to the commercial Pt/C catalyst in alkaline solutions. Furthermore, the Zn-air battery assembled using the mesoporous carbon catalyst as the air electrode could surpass the commercial Pt/C catalyst in terms of the power density and energy density.

Controlled Synthesis of Porous Carbon Nanostructures with Tunable Closed Mesopores via a Silica-Assisted Coassembly Strategy

Controllable fabrication of mesoporous carbon nanoparticles(MCNs)with tunable pore structures is of great interest,due to the remarkable effect of pore structure on electrochemical performance of the materials.However,it has remained a major challenge.Here,we demonstrate the controlled synthesis of MCNs with tunable closed pore structures via a silica-assisted coassembly strategy,which employs polystyrene-block-poly(ethylene oxide)diblock copolymers as soft template,phenolic resol and tetraethyl orthosilicate as carbon and silica precursors,respectively.Through simply varying the sequential cross-linking of the silica and carbon precursors or the copolymer composition,novel MCNs with alluring spherical,hollow-hoop-structured,or yolk-shell-like closed mesopores are tunably prepared.In particular,serving as cathode materials of lithium-sulfur batteries,the resultant silica-hybridized MCNs with the exceptional hollow-hoop mesopores and a moderate sulfur-loading content of 46 wt%exhibit top-level electrochemical performance.This study opens an avenue for tunable construction of mesoporous particles with closed pores and provides clues for the effect of pore geometry on the electrochemical performance of porous cathode materials for lithium-sulfur batteries.