Exploration Research On Synthesis And Coupling Properties Of Titanium Dioxide/Porous Carbon

Accompanied with the global industrialization, pollution has also increased with urban development. The environmental protection and sustainable development would be the prime concern for consideration. Photocatalysis, as a new subject merged with chemistry, physics, materials and environment, has been considered as a cost-effective method for cleaning organic pollutants,which would get widely application and social and economic benefit. TiO₂ is one of the most popular photocatalysts for the heterogeneous photocatalysis because of its various merits,such as low cost,high photocatalytic activity,chemical stability and non-toxicity, no selectivity,complete oxidation, and so on.Generally speaking, photocatalysis of the nanosized TiO₂ occurred on the liquid-solid surface or gas-solid surface. The widespread application of TiO₂ is restricted by two factors: coagulation and high filtration cost [4]. Therefore, through physical vapor deposition, chemical vapor deposition, and sol-gel method, TiO₂ was loaded onto activated carbon, sand, silica, alumina, and zeolite, which had uniform micropore structure and high specific surface area TiO₂ was loaded onto some porous substrates. On one hand, the porous substrates could disperse TiO₂ and enhance its photocatalytic rate; and on the other hand, the substrate could enhance the organic concentration around the supported TiO₂, and improve the photocatalysis efficiency.However, the active surface of the photocatalyst composites are easy to be covered based on the present methods or the traditional porous substrates. In the present work, we firstly prepared hierarchical porous carbon and high-surface-area activated carbon through physical activation and chemical-physical activation. Several methods were doped to load TiO₂ on the two kinds of activated carbons, and study the influence of the preparation parameters, the amount of the loaded TiO₂, and pore size of the photocatlyst composite on the photocatalysis. The conclusions were as following:(1) Zizania latifolia leaves could be prepared into hierarchical porous carbon physically activated with rarified air. The carbon contained replicated natural pores (micrometer size) and the newly created nanometer-sized pores by oxygen activation. The hierarchical pore structure makes the HPCs suitable as a catalyst support, in which the reagent and products diffuse easily through pore channels so that undesired pore blocking would be avoided. It is safe to say that the HPCs could enhance the photocatalytic performance of TiO₂ loaded on them.(2) An activated carbon with high–porosity was prepared from Zizania latifolia leaves by a one–step method combining chemical and physical activation. K2CO3 was employed as a chemical reagent, and air as a physical agent. During the activation, several key parameters were discussed, including the effects of activation temperature, K2CO3 impregnation ratio, amount of introduced air on the surface area and pore volumes evolution of the activated carbons derived from the Zizania latifolia leaves. The synergistic effect between the chemical agent and the physical agent was also investigated. Under optimal activation conditions, the as-synthesized activated carbon attained a maximum surface area up to 2481m2/g, with 1.21cm3/g pore volume, and it had a micro/meso porosity developed by the combining activation. The crystal sizes of the as-synthesized activated carbon along the a-axes and c-axes were about 5nm and 1-2nm, respectively. The average thickness of the crystallites is 3-4 layers with about 0.37nm interlayer spacing.(3) A new method, low-temperature impregnation, was developed to prepare hybrid photocatalysts: TiO₂ coated activated carbon (TiO₂/AC) and N-TiO₂ coated activated carbon (N-TiO₂/AC) . The concentration of TiO₂ and N-TiO₂ played an important role in deciding the specific surface area of the hybrid photocatalysts. When TiO₂ concentration in the TiO₂/AC and N-TiO₂ concentration in the N-TiO₂/AC are 7.7wt% and 8.3wt%, respectively, the specific surface area of TiO₂/AC was 1483m2/g, and the specific surface area of the N-TiO₂/AC TiO₂ was 1321m2/g.(4) Hierarchical porous carbons made from biomass provide an effective support for catalysts due to the dual pore structure. The hierarchical porous carbons were coated with TiO₂ particles and nitrogen doped TiO₂ particles by the hydrolytic precipitation of titanium tetraethoxide. N-TiO₂ and N-TiO₂ particles were deposited uniformly on walls of micrometer sized pores in the dual pore structure of micro and nanometer sizes which was replicated from the natural pore structure. They had ]anatase phase with the particle size of 50nm. X-ray diffraction, XPS and AES analyses indicated that nitrogen atoms were doped with carbon into anatase TiO₂ lattices. The final hybrid photocatalysts showed a high degradation rate of organic pollutantin water with UV and visible light irradiation.(5) Based on TiO₂/hierarchical porous carbon,Morph-genetic TiC can be prepared by combustion synthesis with Mg powders as ignition. The Morph-genetic TiC was heated in air at 400℃to prepare Morph-genetic carbon doped TiO₂. The combustion synthesis was proved to be a good method to prepare morph-genetic materials.(6) according to the photocatalytic dynamics, absorption dynamics of the different photocatalysts in the organic solution, it was found there is a synergism between the absorption capacity of the substrates and the photocatalysis efficiency of the TiO₂ materials. The experiments showed that the porous substrates could enhance the photocatalysis efficiency of the TiO₂ or N-TiO₂ by several times.