Ordered Mesoporous Platinum@Graphitic Carbon Embedded Nanophase as a Highly Active, Stable, and Methanol-Tolerant Oxygen Reduction Electrocatalyst

Highly ordered mesoporous platinum@graphitic carbon (Pt@GC) composites with well-graphitized carbon frameworks and uniformly dispersed Pt nanoparticles embedded within the carbon pore walls have been rationally designed and synthesized. In this facile method, ordered mesoporous silica impregnated with a variable amount of Pt precursor is adopted as the hard template, followed by carbon deposition through a chemical vapor deposition (CVD) process with methane as a carbon precursor. During the CVD process, in situ reduction of Pt precursor, deposition of carbon, and graphitization can be integrated into a single step. The mesostructure, porosity and Pt content in the final mesoporous Pt@GC composites can be conveniently adjusted over a wide range by controlling the initial loading amount of Pt precursor and the CVD temperature and duration. The integration of high surface area, regular mesopores, graphitic nature of the carbon walls as well as highly dispersed and spatially embedded Pt nanoparticles in the mesoporous Pt@GC composites make them excellent as highly active, extremely stable, and methanol-tolerant electrocatalysts toward the oxygen reduction reaction (ORR). A systematic study by comparing the ORR performance among several carbon supported Pt electrocatalysts suggests the overwhelmingly better performance of the mesoporous Pt@GC composites. The structural, textural, and framework properties of the mesoporous Pt@GC composites are extensively studied and strongly related to their excellent ORR performance. These materials are highly promising for fuel cell applications and the synthesis method is quite applicable for constructing mesoporous graphitized carbon materials with various embedded nanophases

A Versatile Kinetics-Controlled Coating Method To Construct Uniform Porous TiO₂ Shells for Multifunctional Core–Shell Structures

The development of a simple and reproducible route to prepare uniform core@TiO₂ structures is urgent for realizing multifunctional responses and harnessing multiple interfaces for new or enhanced functionalities. Here, we report a versatile kinetics-controlled coating method to construct uniform porous TiO₂ shells for multifunctional core–shell structures. By simply controlling the kinetics of hydrolysis and condensation of tetrabutyl titanate (TBOT) in ethanol/ammonia mixtures, uniform porous TiO₂ shell core–shell structures can be prepared with variable diameter, geometry, and composition as a core (e.g., α-Fe₂O₃ ellipsoids, Fe₃O₄ spheres, SiO₂ spheres, graphene oxide nanosheets, and carbon nanospheres). This method is very simple and reproducible, yet important, which allows an easy control over the thickness of TiO₂ shells from 0 to ∼25, ∼45, and ∼70 nm. Moreover, the TiO₂ shells possess large mesoporosities and a uniform pore size of ∼2.5 nm, and can be easily crystallized into anatase phase without changing the uniform core–shell structures

Controllable Synthesis of Ordered Mesoporous Mo₂C@Graphitic Carbon Core–Shell Nanowire Arrays for Efficient Electrocatalytic Hydrogen Evolution

Mo₂C is a possible substitute to Pt-group metals for electrocatalytic hydrogen evolution reaction (HER). Both support-free and carbon-supported Mo₂C nanomaterials with improved HER performance have been developed. Herein, distinct from prior research, novel ordered mesoporous core–shell nanowires with Mo₂C cores and ultrathin graphitic carbon (GC) shells are rationally synthesized and demonstrated to be excellent for HER. The synthesis is fulfilled via a hard-templating approach combining in situ carburization and localized carbon deposition. Phosphomolybdic acid confined in the SBA-15 template is first converted to MoO₂, which is then in situ carburized to Mo₂C nanowires with abundant surface defects. Simultaneously, GC layer (the thickness is down to ∼1.0 nm in most areas) is controlled to be locally deposited on the Mo₂C surface because of its strong affinity with carbon and catalytic effect on graphitization. Removal of the template results in the Mo₂C@GC core–shell nanowire arrays with the structural properties well-characterized. They exhibit excellent performance for HER with a low overpotential of 125 mV at 10 mA cm^–2, a small Tafel slope of 66 mV dec^–1, and an excellent stability in acidic electrolytes. The influences of several factors, especially the spatial configuration and relative contents of the GC and Mo₂C components, on HER performance are elucidated with control experiments. The excellent HER performance of the mesoporous Mo₂C@GC core–shell nanowire arrays originates from the rough Mo₂C nanowires with diverse active sites and short charge-transfer paths and the ultrathin GC shells with improved surface area, electronic conductivity, and stabilizing effect on Mo₂C

Interface Tension-Induced Synthesis of Monodispersed Mesoporous Carbon Hemispheres

Here we report a novel interface tension-induced shrinkage approach to realize the synthesis of monodispersed asymmetrical mesoporous carbon nanohemispheres. We demonstrate that the products exhibit very uniform hemispherical morphology (130 × 60 nm) and are full of ordered mesopores, endowing them high surface areas and uniform pore sizes. These monodispersed mesoporous carbon hemispheres display excellent dispersibility in water for a long period without any aggregation. Moreover, a brand new feature of the mesoporous carbon materials has been observed for the first time: these monodispersed mesoporous carbon hemispheres show excellent thermal generation property under a NIR irradiation