Preparation Of Monolithic Hierarchical Porous Photocatalyst And Its Properties

Photocatalysis,as a widely studied green technology,has been applied in the production of clean energy and environmental protection.Titanium dioxide（TiO₂）and graphitic carbon nitride（g-C₃N₄）have attracted extensive attention by researchers because of their advantages,and have been applied in photocatalytic degradation of organic pollutants.However,powder photocatalyst is easy to aggregate,difficult to separate in solution and recover.In order to solve the problem affecting the practical application,several photocatalysts with macroscopic size and hierarchical pore structure were prepared and applied to the degradation of various simulated pollutants,and the relationship between their structures and photocatalytic performances was explored.The main research work of this paper is as follows:（1）Novel large-sized mesoporous nanofilm-constructed macroporous SiO₂（LMNCMS）with two sets of well-defined 3D continuous pass-through macropores（pore size of 0.5–1.0μm,wall thickness of 40–50 nm）was prepared through a dual-templating approach,and used as an advanced support for TiO₂nanocrystalline photocatalyst.The structural and optical properties of the as-prepared materials were investigated by various characterization techniques in order to explore the connections between catalysts’features and catalytic performance.The photocatalytic activities were evaluated by degradations of methylene blue（MB）and phenol under the simulated sunlight irradiation.To gain insight into the impact of preparation and operation conditions on photocatalytic degradation processes,experiments were conducted at wide ranges of TiO₂loading content,calcination temperature,solution p H,and photocatalyst dosage.The trapping experiments were performed to identify the main reactive species in the catalytic reactions.Nano-TiO₂/LMNCMS exhibited high photocatalytic activity and stability.Rapid matter transport,good accessibility of pollutants to TiO₂and high light harvesting could mainly account for the superior photocatalytic performance.（2）g-C₃N₄/LMNCMS photocatalyst was obtained by impregnation and high-temperature calcination using the LMNCMS as the support.The structure and properties of the prepared materials were studied by various characterization techniques to explore the relationship between catalysts’features and catalytic performance.Photocatalytic activity was evaluated by degradation of rhodamine B（Rh B）under visible light irradiation.In order to further explore the effects of preparation conditions and operating conditions on photocatalytic degradation process,experiments were carried out under various g-C₃N₄loading,solution p H value and photocatalyst dosage,and the main reactive species in catalytic reactions were explored by capturing experiments.Compared with pure g-C₃N₄,g-C₃N₄/LMNCMS exhibited higher photocatalytic activity and was easy to recover.The improved photocatalytic performance is mainly due to the unique hierarchical pore structure,which not only enables rapid transport of matter in the pore channel,but also improves the accessibility of g-C₃N₄.