Hollow Macroporous Core Research Articles

Synthesis of mesoporous hollow polypyrrole spheres and the utilization as supports of high loading of Pt nanoparticles

In this paper, mesoporous hollow polypyrrole spheres (MHPS) are prepared via a chemical polymerization from pyrrole using silica spheres as hard templates. The MHPS possesses a hierarchical structure with hollow macroporous core in combination with mesoporous shell and a high surface area (117.5m2g−1) and pore volume (0.34cm3g−1). And this material is applied to support Pt nanoparticles to form Pt/MHPS catalyst via a simple chemical reduction method by using formic acid as reducing agent for methanol oxidation reaction (MOR). In the Pt/MHPS, the Pt nanoparticles in mean diameter of ∼3.6nm are uniformly dispersed on the shells of the hollow polypyrrole spheres. The resulting Pt/MHPS shows a higher specific electrochemically active surface area (ECSA), improved activity and poisoning tolerance for MOR compared with the carbon black (Vulcan XC-72R)-supported Pt catalyst.

Hierarchical CuO–TiO2 Hollow Microspheres for Highly Efficient Photodriven Reduction of CO2 to CH4

In this study, a scalable one-pot template-free synthesis strategy was employed to fabricate CuO-incorporated TiO2 hollow microspheres in large scale. The as-prepared hollow spherical TiO2 nanoparticles possess unique structural characteristics, namely, large surface area and a hierarchical nanoarchitecture composed of a hollow macroporous core connected with large mesopores in the shell. The large surface area provides a great number of surface active sites for the reactant adsorption and reaction whereas the hierarchical nanoarchitecture enables fast mass transport of reactant and product molecules within the porous framework. In addition, the hollow macroporous core–mesoporous shell nanostructure favors multilight scattering/reflection, resulting in enhanced harvesting of exciting light. Furthermore, the incorporated CuO clusters work efficiently as a cocatalyst to improve the photocatalytic activity. As a result, the CuO-incorporated TiO2 hollow microsphere catalyst demonstrates much higher photocatal...

Well-dispersed platinum nanoparticles supported on hierarchical nitrogen-doped porous hollow carbon spheres with enhanced activity and stability for methanol electrooxidation

Hierarchical nitrogen-doped porous hollow carbon spheres (HNPHCS) with porous-thin mesoporous shell and hollow macroporous core structure have been prepared via in-situ oxidation polymerization method using polyaniline as the precursor. After carbonization at 900 °C, the average diameter of HNPHCS is ca. 140 nm with shell thickness of ∼1 nm. Pt nanoparticles with high dispersion and small size have been successfully deposited on the HNPHCS by a microwave-assisted polyol process to synthesize Pt/HNPHCS catalyst. The obtained samples are characterized by physical characterization and electrochemical measurements. Electrochemical studies reveal that the prepared Pt/HNPHCS catalyst possesses notably higher catalytic activity and CO-tolerance, and better stability toward methanol electrooxidation in comparison with Pt/nitrogen-doped porous carbon and the commercial Pt/C catalysts. It is likely that enhanced catalytic properties of the Pt/HNPHCS could be due to the high dispersion of small Pt nanoparticles, the presence of nitrogen species, developed porous-thin mesoporous shell and hollow macroporous core structure of support HNPHCS. As a result, the as-developed Pt/HNPHCS present attractive advantages for the application in fuel cell electrocatalyst.

Smart synthesis of hollow core mesoporous shell carbons (HCMSC) as effective catalyst supports for methanol oxidation and oxygen reduction reactions

The present paper describes an easy and quick synthesis of hollow core mesoporous shell carbon (HCMSC) simply templated from unpretreated solid core mesoporous shell silica using a cheap precursor like sucrose. Physical characterizations showed uniform spherical carbon capsules with a hollow macroporous core of ca. 305- and 55-nm-thick mesoporous shell, forming a well-developed 3-D interconnected bimodal porosity. High specific surface area and large pore volume were also confirmed, suggesting the obtained HCMSC as a promising catalyst support. HCMSC-supported Pt (nominal 20 wt.%) with an average Pt particle size of 1.9 nm was synthesized by wet impregnation, and a signal of strong interaction between carbon support and platinum was confirmed by X-ray photoelectron spectroscopy. In cyclic voltammetry and linear sweep voltammetry tests, the Pt/HCMSC electrode showed significantly higher electrocatalytic activity for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) if compared with commercial Pt/Vulcan catalyst. The durability tests by cyclic voltammetry showed for the Pt/HCMSC a lower electrochemical active surface area loss than the commercial one in acidic solution. All the primary tests suggested that the Pt/HCMSC, due to its particular structure and the high dispersion of noble metal particles, is a promising catalyst for fuel cell applications, for MOR and ORR.

Fabrication of hollow core carbon spheres with hierarchical nanoarchitecture for ultrahigh electrical charge storage

A simple and reproducible sol–gel synthesis strategy was developed to fabricate hollow core carbon spheres (HCCSs) with hierarchical nanoarchitecture through the hydrolysis, self-assembly and co-condensation of bis-[3-(triethoxysilyl)propyl]disulfide (TESPDS) and octadecyltrimethoxysilane (C18TMS). This synthesis route allows one to fabricate thioether-bridged organosilica (TBOS) with tailored spherical structure and particle size which can be further converted to HCCS upon calcination under N2 flow. It is assumed that hydrophobic octadecyl chains of hydrolyzed C18TMS first form a micelle-like self-assembly structure with hydrophilic trihydroxysilyl groups as heads, and a reactive core is then expanded by the base-catalyzed co-condensation of TESPDS and/or C18TMS over the C18TMS self-assembly structure. The organic moieties of TESPDS and C18TMS not only serve as a porogen during the formation of TBOS but also as a carbon precursor for transformation of TBOS into HCCS during the carbonization. Due to its unique hierarchical nanostructure composed of hollow macroporous core and meso/microporous shell, which facilitates fast mass transport, along with large surface area for electrical charge storage, the HCCS for the first time exhibits ultrahigh specific capacitance and energy, good cycling performance and rate capability.

Incorporating Hierarchical Nanostructured Carbon Counter Electrode into Metal-Free Organic Dye-Sensitized Solar Cell

Hierarchical nanostructured carbon with a hollow macroporous core of ca. 60 nm in diameter in combination with mesoporous shell of ca. 30 nm in thickness has been explored as counter electrode in metal-free organic dye-sensitized solar cell. Compared with other porous carbon counterparts such as activated carbon and ordered mesoporous carbon CMK-3 and Pt counter electrode, the superior structural characteristics including large specific surface area and mesoporous volume and particularly the unique hierarchical core/shell nanostructure along with 3D large interconnected interstitial volume guarantee fast mass transport in hollow macroporous core/mesoporous shell carbon (HCMSC), and enable HCMSC to have highly enhanced catalytic activity toward the reduction of I(3)(-), and accordingly considerably improved photovoltaic performance. HCMSC exhibits a V(oc) of 0.74 V, which is 20 mV higher than that (i.e., 0.72 V) of Pt. In addition, it also demonstrates a fill factor of 0.67 and an energy conversion efficiency of 7.56%, which are markedly higher than those of its carbon counterparts and comparable to that of Pt (i.e., fill factor of 0.70 and conversion efficiency of 7.79%). Furthermore, HCMSC possesses excellent chemical stability in the liquid electrolyte containing I(-)/I(3)(-) redox couples, namely, after 60 days of aging, ca. 87% of its initial efficiency is still achieved by the solar cell based on HCMSC counter electrode.

Hierarchical nanostructured hollow spherical carbon with mesoporous shell as a unique cathode catalyst support in proton exchange membrane fuel cell

Hierarchical nanostructured spherical carbon with hollow macroporous core in combination with mesoporous shell has been explored to support Pt cathode catalyst with high metal loading in proton exchange membrane fuel cell (PEMFC). The hollow core-mesoporous shell carbon (HCMSC) has unique structural characteristics such as large specific surface area and mesoporous volume, ensuring uniform dispersion of the supported high loading (60 wt%) Pt nanoparticles with small particle size, and well-developed three-dimensionally interconnected hierarchical porosity network, facilitating fast mass transport. The HCMSC-supported Pt(60 wt%) cathode catalyst has demonstrated markedly enhanced catalytic activity toward oxygen reduction and greatly improved PEMFC polarization performance compared with carbon black Vulcan XC-72 (VC)-supported ones. Furthermore, the HCMSC-supported Pt(40 wt%) or Pt(60 wt%) outperforms the HCMSC-supported Pt(20 wt%) even at a low catalyst loading of 0.2 mg Pt cm(-2) in the cathode, which is completely different from the VC-supported Pt catalysts. The capability of supporting high loading Pt is supposed to accelerate the commercialization of PEMFC due to the anticipated significant reduction in the amount of catalyst support required, diffusion layer thickness and fabricating cost of the supported Pt catalyst electrode.

Controllable Synthesis of Hierarchical Nanostructured Hollow Core/Mesopore Shell Carbon for Electrochemical Hydrogen Storage

Hierarchical nanostructured hollow core/mesopore shell carbon (HN-HCMSC) represents an innovative concept in electrochemical hydrogen storage. This work deals with physical characteristics and electrochemical hydrogen storage behavior of the HN-HCMSCs, produced by a replica technique using solid core/mesopore shell (SCMS) silica as template. HN-HCMSCs with various core sizes and/or shell thicknesses have been fabricated through the independent control of the core sizes and/or shell thicknesses of the SCMS silica templates. The superb structural characteristics of the HN-HCMSCs including large specific surface area and micropore volume, and particularly well-developed three-dimensionally interconnected hierarchical nanostructure (hollow macroporous core in combination with meso-/microporous shell), provide them with great potential for electrochemical hydrogen storage. A discharge capacity up to 586 mAh/g, corresponding to 2.17 wt % hydrogen uptake, has been demonstrated in 6 M KOH for the HN-HCMSC with a core size of 180 nm and a shell thickness of 40 nm at a discharge rate of 25 mA/g. Furthermore, the HN-HCMSC also possesses excellent cycling capacity retainability and rate capability.

Hollow core/mesoporous shell carbon as a highly efficient catalyst support in direct formic acid fuel cell

Spherical carbon capsules with a hollow macroporous core of ca. 260nm and a ca. 40nm thick mesoporous shell were explored for the first time as an anode catalyst support in direct formic acid fuel cell (DFAFC). Hollow core/mesoporous shell carbon (HCMSC) possesses fantastic structural characteristics such as uniform particle size, well-developed three-dimensionally interconnected bimodal porosity, and large specific surface area and pore volume, which are highly desired for a catalyst support in low temperature fuel cells. HCMSC-supported Pt50Ru50 (60wt.%) has exhibited almost two times the power density that delivered by the commonly used catalyst support carbon black Vulcan XC-72 supported one, suggesting that the HCMSC is a highly efficient anode catalyst support in DFAFC.

Hollow Macroporous Core/Mesoporous Shell Carbon with a Tailored Structure as a Cathode Electrocatalyst Support for Proton Exchange Membrane Fuel Cells

Well-tailored spherical carbon capsules with a hollow macroporous core of ca. 280 nm and a ca. 40 nm thick mesoporous shell were synthesized and explored for the first time as cathode catalyst support in proton exchange membrane fuel cells (PEMFC). The unique structural characteristics of hollow core/mesoporous shell (HCMS) carbon including high specific surface area, large pore volume, uniform particle size, and well-developed three-dimensionally interconnected bimodal porosity make it an ideal candidate as catalyst support for low-temperature fuel cells. Considerable improvements in electrocatalytic activity toward oxygen reduction reactions and in fuel cell performance have been achieved by Pt(20 wt %) supported on the HCMS carbon (HCMSC) when compared with its counterpart, Pt supported on commonly used commercially available catalyst support carbon black Vulcan XC-72 (VC), suggesting that the HCMSC is an excellent and much more efficient cathode catalyst support than VC for PEMFC application.

Synthesis of new nanostructured carbon materials using silica nanostructured templates by Korean research groups

In this review, we summarise recent advances on the synthesis of various nanoporous carbon materials using nanostructured silica templates. In particular, we will focus on the research activities in Korea for the last seven years. Many nanoporous carbons having variable pore sizes and pore structures have been synthesised using appropriate nanostructured silica materials as templates. The synthetic procedure for nanoporous carbons through mesostructured silica templates involves infiltration of carbon precursor into the template, its carbonisation, and subsequent template removal. Nanoporous carbons with high pore volumes and uniform pore sizes have been produced using silica sol nanoparticles and related nanostructured materials as templates. Mesoporous carbons with several different pore structures have been synthesised using mesoporous silica materials such as MCM-48, HMS, SBA-15 and MSU as templates. Mesocellular carbon foams have been synthesised using mesocellular silicate foam as templates. Ordered mesoporous carbons with graphitic pore walls were synthesised using soft-carbon source which can be converted to highly ordered graphite at high temperature. Carbon capsules with hollow macroporous core and mesoporous shell structures were synthesised using silica spheres with solid core and mesoporous shell structures. Using the bimodal mesoporous silica composed of 30~40 nm sized nanoparticles with 3.5 nm mesopores as a template, bimodal mesoporous carbon was synthesised. Ordered mesoporous carbon materials were synthesised through a simple direct synthetic method using as-synthesised silica/surfactant nanocomposites. Some of these nanoporous carbon materials were successfully used as adsorbents for bulky pollutants and methane gas and electrodes for supercapacitors and fuel cells.

Template synthesis of nanostructured silica with hollow core and mesoporous shell structures

Silica capsules with hollow macroporous core–mesoporous shell (HCMS) were synthesized through template-assisted replication of submicrometer-size polystyrene spheres as templates. The silica mesoporous shell exhibited highly ordered hexagonal structure as confirmed by X-ray diffraction pattern and TEM image. The pore diameter and BET surface area of this sample were found to be 2.1 nm and 1387 m 2 /g, respectively.

Spherical carbon capsules with hollow macroporous core and mesoporous shell structures as a highly efficient catalyst support in the direct methanol fuel cell

Carbon capsules with hollow core and mesoporous shell (HCMS) structures were used as a support material for Pt(50)-Ru(50) catalyst, and the catalytic performance of the HCMS supported catalyst in the direct methanol fuel cell was described; the HCMS carbon supported catalysts exhibited much higher specific activity for methanol oxidation than the commonly used E-TEK catalyst by about 80%, proving that the HCMS carbon capsules are an excellent support for electrode catalysts in DMFC.

Synthesis and characterization of spherical carbon and polymer capsules with hollow macroporous core and mesoporous shell structures

The synthesis and characterization of spherical carbon hollow capsules with mesoporous shell (HCMS) structures is reported. Silica spheres with sub-micrometer sized solid cores and mesoporous shell (SCMS) structures were used as templates in the synthesis. The resulting carbon capsules inversely replicated the morphology of the silica template and had uniform pores with a narrow pore size distribution centered at 3 nm. The carbon capsules exhibited a BET surface area of >1000 m 2/g and a total pore volume of >1.0 cm 3/g. The diameter of the hollow core and the mesoporous shell thickness of the carbon capsules could easily be controlled using appropriate SCMS silica materials as templates. Using a similar synthetic procedure, hollow poly(divinylbenzene) capsules were also synthesized.

Nanostructured Carbon Capsules with Hollow Core/Mesoporous Shell Structure

AbstractCarbon capsules with hollow macroporous core/mesoporous shell were synthesized using sacrificial submicrometer-size solid core/mesoporous shell (SCMS) silica spheres as templates. Size of the hollow macroporous core and thickness of the mesoporous shell can be easily controlled by the choice of silica spheres and the amount of TEOS/C18-TMS mixture, respectively.