Synthesis of Hierarchical Porous Silica by Sol-Gel of Sodium Silicate and Nanoemulsion Templating: Effective Combination Conditions

Abstract

Hierarchical porous materials have attracted a considerable attention owing to the increased interest in their applications. Hierarchical Porous Silica (HPS) was synthesized by combining the sol-gel of sodium silicate (SS) and oil in water nanoemulsion (O/W-NE) templating. The oil droplets of NE acted as pore forming agent and the sol-gel built the silica framework. The O/W-NE was prepared by a low energy method, i. e., the phase inversion composition (PIC) method. The influence of pH of SS and NE on HPS was studied. The volume of ammonia, used to induce gelling, was studied as a factor influencing the HPS. The calcined samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), FTIR, N2 adsorption and small-angel X-ray scattering (SAXS). The results show that the microstructure is highly affected by pH and can be; macropores inserted in a dense matrix; a blend of a dense and a porous structure; or fully hierarchical porous silica. HPS has a specific surface area of 240 m2/g and a large pore volume (1.5 cm3/g) and a surface roughness of 2.95.