Academic literature on the topic 'Mesoporous carbon nitride'

The influence of different borazinic precursors on mesoporous boron nitride synthesis by using a nanocasting process of a mesoporous CMK-3 carbon is presented. Two borazinic precursors, the tri(methylamino)borazine (MAB) and the tri(chloro)borazine (TCB), have been converted to boron nitride (BN) inside the mesopores of a CMK-3 carbon mesoporous template by using thermal or chemical polycondensation processes. Ordered mesoporous boron nitride with a specific surface area around 800 m2/g, a mesoporous volume around 0.6 cm3/g, and a pore-size distribution located at 6 nm in diameter was synthesized by thermal condensation of a molecular MAB precursor. In addition, chemical condensation of TCB led to a disordered mesoporous boron nitride.

Mesoporous carbon nitride materials have been synthesized using SBA-15 by pore filling technique whereas mesoporous boron nitride and boron carbon nitride have been prepared by elemental substitution technique using mesoporous carbon as template. The obtained materials have been unambiguously characterized by sophisticated techniques such as XRD, HRTEM, EELS, XPS, FT-IR and N2 adsorption. The textural parameters of the materials are quite higher as compared to the respective nonporous nitrides. These materials could offer great potential for the applications, such as catalytic supports, gas storage, biomolecule adsorption and drug delivery.

A novel photocatalyst, AgCl loaded mesoporous graphitic carbon nitride (mpg-C3N4) in which silver chloride nanoparticles were introduced into the mesopores carbon nitride, was prepared by a dip-coating procedure. The as-prepared photocatalyst was characterized by X-ray diffraction, transmission electron microscopy, UV-visible spectrophotometry. The novel photocatalyst manifested a better photocatalytic activity than that of pure mpg-C3N4 for degradation of methyl orange.

A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this review
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this review.
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Research Doctorate - Doctor of Philosophy (PhD)
A high demand of energy in the field of potable electronics and electric vehicles has constantly stimulated the sustainable development of energy storage devices such as supercapacitors and electrochemical batteries toward higher energy density and power density. However, the performance of these clean energy devices depends mainly on the advanced materials that are used as electrodes for these devices. As these materials play a significant role in deciding the final efficiency and total cost of these devices, research focussed on the development of novel advanced electrode materials with unique electrochemical and textural properties including high conductivity and high specific surface area, tunable pore structures and chemical composition is needed. Among different electrode materials, nanostructured carbon based materials have been regarded as the most promising alternatives to replace the conventional graphite as the electrode material in electrochemical energy storage devices owing to their unique properties including controllable pore size on nanometer scales, high surface area and large pore volume. Especially, mesoporous carbon, carbon nanotube and graphene based materials have been extensively studied and reviewed. It is found out that the morphology or structure of these electrode materials highly influences on the enhanced electrochemical performances in energy storage devices. However, the achieved capacity is still remained low, and thus more intensive works are needed to make these devices commercially viable. In addition to the capacity, production cost of electrode materials should not be ignored for the large scale manufacturing in the industries. The cost of raw materials of electrodes must be low and synthesizing processes of the materials must be as simple and cheap as possible. Thus, research developments on the design of nanostructured carbon materials with controllable structures, simple fabrication processes, and high yield and enhanced electronic properties toward energy storage applications from cheap resources are needed. In this thesis, these challenges are being addressed by designing advanced nanoporous electrode materials with ordered porous structures, excellent textural parameters including tunable pore diameters and high specific surface areas and different chemical composition. This thesis begins with an overview of advancement and prospects for carbon nanomaterials for electrochemical energy storage technology including Li ion batteries, Na ion batteries and supercapacitors. The carbon nanomaterials include graphene, carbon nanotube, porous carbon, fullerene and their hybridized composites. The synthetic methods and properties of the nanomaterials are specifically explained and their electrochemical properties in the applications are investigated. Moreover, in order to advance the nano materials research, challenges and future perspectives are stressed at the end of the overview. Chapter 2 presents the design of highly ordered 3-dimensional mesoporous carbon for the supercapacitor application. The materials are synthesized via nanocasting approach using FDU-12 silica as a template. Pore size is varied with simply changing aging temperature of nanoporous silica templates. Highly sophisticated characterization techniques including powder X-ray diffraction, high resolution transmission electron microscopy (HR-TEM), high resolution scanning electron microscopy (HR-SEM), and N₂ adsorption‒ desorption techniques were employed to analyse the structure and textural properties of the synthesized mesoporous carbon materials. The characterization results prove that all the mesoporous carbons show 3-D mesostructure with highly ordered inter-connected mesopores. The prepared materials show excellent textural properties with tuneable pore diameters (5.7 to 9.4 nm) and a large specific surface area in the range from 451 to 1251 m² g^-1. The supercapacitive performance of the cubic structured mesoporous carbons is determined by cyclic voltammetry, electrochemical impedance and charge-discharge measurements. The materials show an excellent capacitive behaviour with a high specific capacitance of 315.3 F g^-1 at the current density of 1A g^-1, which is much higher than that of hexagonally ordered mesoporous carbon, activated carbon, and carbon nanotubes. The materials also show a superior cyclic stability and extremely low resistance. The high specific capacitance of these materials is attributed to the combination of excellent surface properties such as large specific surface area, large pore volume and uniform pore diameter, spherical morphology, and 3-D porous system with a cage type pores. Chapter 3 includes the design and development of highly ordered sulfur-doped mesoporous carbon nitrides (S-MCNs) for the sodium ion battery application. The materials are prepared through the hard template approach by employing a single precursor of dithiooxamide (DTO) as sources of carbon, nitrogen and sulfur. The interlayer space of the prepared materials is highly expanded upon S-doping on carbon nitride frameworks of S-MCNs. It is also confirmed that the chemical composition, crystallinity and textural properties of S-MCNs are simply tuned by varying the carbonization temperature from 500 to 700 °C. The crystallinity and textural properties of S-MCNs are optimized at carbonization temperature of 700 °C. In contrast to nonporous sulfur doped carbon nitrides (S-CNs) and nonporous graphitic carbon nitride (g-C₃N₄), the S-MCNs show much better Na⁺ intercalation property with a high discharge capacity of 304.2 mAh g^-1 in the 100^th cycle as well as an outstanding retention capability. Chapter 4 deals with the synthesis of highly ordered oxygen-doped mesoporous carbon nitrides (O-MCNs) with tailored pore size. These materials were successfully synthesized by using a single molecular precursor of carbohydrazide (CBZ) as a C, N, O containing precursor via a hard templating method using SBA-15 as a template. The sophisticated analysis such as near-edge X-ray absorption fine structure (NEXAFS), X-ray photoemission spectroscopy (XPS), UV-Vis spectroscopy and Fourier transform infrared spectroscopy (FT-IR) are used to find out the chemical bonding nature and existence of oxygen dopant in the materials. Highly ordered structure of O-MCNs is proved through Xray power diffraction (XRD) in low angle and transmission electron microscopy (TEM). The exceptional large surface area (~224.6 m² g^-1) and high pore volume (~0.58 cm³ g^-1) are proved by using N2 adsorption-desorption measurement. Moreover, the optimized O-MCN is used as an anode material for Li-ion battery and delivered 4 times higher reversible capacity than that of non-porous g-C₃N₄ with remarkable stability. Lastly, Chaper 5 addresses an overrole summary of each chapter and future perspectives of nano structured carbon based materials for the sustainable electrochemical applications such as Li ion batteries, Na ion batteries and supercapacitors.

碩士
國立中央大學
化學學系
107
This study consists of two main parts. In the first part, the Palladium nanoparticles (Pd NPs) with a particle size of 2-3nm are successfully confined within the 2D mesoporous silica SBA-15 and the 3D mesoporous silica KIT-6. Under the wet impregnation process, SBA-15 and KIT-6 were immersed in Pd2+ precursor and adsorbed into the pores, then. The mixture chemically reduced by reagent containing NaBH4 and NH3BH3 to obtain Pd(x)@SBA-15 and Pd(x)@KIT-6. It was found that the use of SBA-15 and KIT-6 support can highly enhance the dispersion and efficiency due to the high surface area and large pore volume. In addition, SBA-15 and KIT-6 with the pore size of 9.09 nm and 9.56 nm, respectively, may effectively confine the Pd NPs and subsequently avoid the aggregation. According to the X-ray diffraction pattern and TEM image, it can be confirmed that the particle size of Pd NPs is about 2-3 nm and highly dispersed without aggregation. The Pd(x)@SBA-15 and Pd(x)@KIT-6 exhibited superior catalytic activity and chemoselectivity for the catalytic transfer hydrogenation of styrene under mild conditions with formic acid and ammonium formate as a hydrogen donor. Among all the as-prepared catalysts, the Pd(30)@KIT-6 exhibited the highest turnover frequency (TOF) of 363 h-1. In addition, Pd(30)@KIT-6 exhibited an excellent high stability after five successive cycles without significant loss of its catalytic activity. In the second part of study, heteroatom doped carbon materials have received considerable attention in the field of catalysis. Herein, we report a catalyst made of palladium nanoparticles (Pd NPs) supported on mesoporous nitrogen-doped carbon (MUFC), Pd@MUFC. The use of the mixture of melamine-urea-formaldehyde as a precursor and the mesoporous silica SBA-15 as a hard template afforded a high-nitrogen-content mesoporous carbon material that showed high activity in stabilizing Pd NPs. The N-doped mesoporous carbon, MUFC, can provide a large surface area to adsorb the reductant and substrate, and enhance the accessibility of the active sites of the Pd NPs in the catalytic reaction process. When Pd@MUFC was applied as catalyst in the catalytic aerobic oxidation of benzyl alcohol, it achieved conversion rate and selectivity of 99.9% within 30 minutes. Among all the as-prepared catalysts, the Pd(30)@MUFC exhibited the highest turnover frequency of 750 h-1. The remarkable catalytic activity for the benzyl alcohol oxidation can be attributed to the ultra-small Pd NPs confined in the hexagonal N-doped carbonaceous MUFC.