Synthesis of mesoporous tin dioxide assisted by resorcinol-formaldehyde gel

Abstract

Mesoporous tin dioxide was synthesized by sol-gel method using resorcinol-formaldehyde gel (RF gel) as a template. Using RF gel as a template is better than surfactant template due to low cost and easy to handle. The template was prepared by sol-gel polycondensation of the mixture between resorcinol and formaldehyde. Tin tetrachloride pentahydrate (SnCl4.5H2O) or tin precursor was not directly added into RF-gel due to rapid solidification. First, the preformed tin sol was formed by mixing tin precursor and formaldehyde. In order to prevent non-homogeneous of the mixed gel, diluting solvent such as ethanol was applied to fabricate this material. The results showed that when the template was used, the product has mesoporous structure and higher surface area than the product without assisting template. Process conditions were found to be the important factors that affect the morphology and properties of the product. For example, increasing the aging time of RF-gel resulted in enhanced surface area and smaller connected tin dioxide particles. Concentration of reactants, i.e., tin-to-formaldehyde molar ratio (Sn/F) and tin-to-resorcinol resorcinol molar ratio (Sn/R) significantly affect both the morphology and properties of the obtained product. Moreover, the effect of other parameters, namely, resorcinol-to-catalyst molar ratio (R/C), tin sol aging time, aging time for mixed gel, type of diluting solvent and drying process, were also studied. It was found that interaction between tin sol and RF gel is the important factor affecting mesoporous structure of tin dioxide.