Synthesis and application of mesoporous materials using an ultrasonic spray method

Abstract

Nanoporous materials with regular geometries have a high surface area, uniform pore size and high pore volume. Due to these properties, they are used for gas sensors, catalysis, separation processes and other various fields. In general, mesoporous materials can be synthesized with well-known hydrothermal synthesis processes. However, the EISA (Evaporation Induced Self Assembly) method has several advantages over the hydrothermal synthesis method, as follows: it does not require additional processing for the continuous and rapid production of mesoporous materials; the time required for the synthesis of mesoporous materials is only several seconds or less; the stoichiometry of its product is the same as that of the precursor in solution; the resulting particles are generally spherical, which is advantageous for subsequent powder processing; and this method is easy to scale up. In spite of these features, researches of mesoporous materials using EISA have been focused on a few synthesis and applications only. In this study, various mesoporous materials were synthesized using EISA process with the ultrasonic spray reactor and applied to various fields. Firstly, highly photo-active mesoporous $TiO_2$ particles were synthesized within 1 min from a chelated complex. The synthesized particles had worm-like pore walls in the anatase crystalline phase, and small crystallite size in the range 7.8-18.6 nm. The photocatalytic activity of the synthesized particles was evaluated by measuring the generation of hydrogen from water/MeOH. The mesoporous $TiO_2$ particles calcined at 823 K had a large surface area ($144 m^2/g$), high pore volume ($0.33 cm^3/g$), narrow pore size distribution, and an ultrafine crystallite size (7.8 nm). Moreover, they had strong absorption below 350 nm, which enhanced their photo-activity efficiency with UV light. These complex properties led to remarkable photocatalytic hydrogen generation from water/MeOH, with the quantum yield and apparent ph...