Fabrication And Application Of Three-Dimensional Macroporous Materials Based On Polystyrene Microsphere

Three-dimensional macroporous materials have received much attention in recent years. It possesses continuous pore system and has wide applications in the fields such as catalysts, clean energy, sensors, and biotechnology. In general, the fabrication of three-dimensional macroporous materials rely on the templates. For instance, three-dimensional ordered macroporous materials (3DOM) can be made by the utilization of colloidal crystal template. Meanwhile, the uniform pore size of the 3DOM materials can be adjusted by the template microspheres. And other non-template method, such as hydrothermal self-assembly, can produce three-dimensional macroporous materials with uneven distribution of pore size and a high porosity. However, in the current research, the formation and stability of the templates are subject to the environment, which will have impact on the pore structure. Meanwhile, the materials with single pore structure are limited to the certain application field. Therefore, it is in dire need of exploring the new fabrication method and develop the various macroporous matrix. Meanwhile, hierarchical three-dimensional porous materials can be designed to meet the demands of the high specific surface area and fast transportation channel in practice applications.We have concentrated on two aspects in this thesis. The first one is to develop various macroporous matrix. The second one is to design hierarchical three-dimensional porous materials to meet the demands in practice applications. This work consists of four parts of contents:the spherical inverse opals made by colloidal crystal balls templates applied in photodegradation of methyl orange; hierarchical three-dimensional porous materials fabricated by dual-template gravity deposition method applied as anode materials in lithium ion battery; the three-dimensional macroporous composite materials templated by Pickering emulsion droplets applied in adsorption of tetracycline; the three-dimensional macroporous composite materials applied as humidity sensors fabricated by simultaneously deposition with microsphere templates, and then coated with polyaniline (PANI) in situ. The main contents and results are as follows:1. Three-dimensional inverse opal SnO2/reduced graphene oxide (IO-SnO2/rGO) microspheres with a size of several tens microns are first prepared by a well-designed two-step calcination of polystyrene (PS) colloidal crystal template balls infiltrated with the sol precursor of SnO2 and graphene oxide (GO). The polystyrene (PS) colloidal crystal template balls are formed by the self-assembly of monodiserpersed PS microspheres confined in water droplets of an inverse emulsion, induced by the slow evaporation of water. Raman spectra, X-ray diffraction, and X-ray photoelectron spectroscopy proves the ordered macroporous of inverse opal composed of crystalline SnO2 and in situ reduced GO into rGO during the calcination. The pore size depends on the PS microspheres. The photoluminescence spectra indicate that the IO structure and the introduction of rGO make the charge carriers transfer fast and retard the hole/electron recombination in the IO-SnO2/rGO microspheres so that their photocatalytic performance on the UV photolysis of methyl orange are much enhanced. However, the photocatalytic performance also depends on the content of GO. The addition of 0.06 wt% of GO achieves the best photocatalytic effect. Excessive GO will result in a diminished catalytic activity.2. A solvent-evaporation induced codeposition of monodispersed polystyrene (PS) microspheres (241 nm) and γ-ray radiation induced GO into rGO at the presence of the surfactant, cetyltrimethylammonium bromide (CTAB), has been firstly conducted to prepare a self-stand PS/rGO composite template film, which can transform into a porous SnO2/rGO composite materials after being infiltrated with the precursor of SnO2 and further calcinated at 420℃. Scanning electron microscope (SEM) and nitrogen adsorption-desorption isotherms analyses indicate that the prepared SnO2/rGO composite materials have a hierarchical pore structure, i.e., mesopores (3.312 nm) and macropores (～200 nm) coexist. The half-cell using the hierarchical porous structured SnO2/rGO composite as the electrode exhibits an excellent cycle performance (850 mAh g-1 in 100 cycles at a current density of 0.3 C) and rate property of 436 mAh g-1 at a current density of 4.5 C. The results demonstrate that the design of hierarchical porous structure and the incorporation of rGO will contribute to enhanced electrochemical performance.3. Macroporous polystyrene microsphere/graphene oxide (PS/GO) composite monolith was first prepared using Pickering emulsion droplets as the soft template. The Pickering emulsion was stabilized by PS/GO composite particles in-situ formed in an acidic water phase. With the evaporation of water and the oil phase (octane), the Pickering emulsion droplets agglomerated and combined with each other, forming a three-dimensional macroporous PS/GO composite matrix with excellent mechanical strength. The size of the macrospores ranged from 4 to 20μm. The macroporous PS/GO composite monolith exhibited high adsorption capacity for tetracycline (TC) in an aqueous solution. The maximum adsorption capacity reached 197.9 mg g-1 at pH =6.The adsorption behaviour of TC fitted well with the Langmuir model and pseudo-second-order kinetic model.4. Flexible sulfonated polystyrene (SPS)/poly (vinyl alcohol) (PVA) composite particulate films with humidity sensitivity were successfully fabricated by simultaneously deposition of SPS microspheres with PVA, followed by the vacuum treatment (< 150 Pa) at 80℃ for 10 h. As a result, the hydrophilicity of the SPS/PVA film increases. Meanwhile, the contact angle difference between up-side and down-side increases from 12° to 20°. After the removal of SPS templates with toluene, the three-dimensional macroporous PVA films were obtained at room temperature. Subsequently, we fabricated PVA/PANI composite films by in-situ polymerization of aniline on the surface of PVA films. The films can be applied as humidity sensors and show great responsivity in low humidity environment.