Mass Production of Multishell Hollow SiO₂ Spheres With Adjustable Void Ratios and Pore Structures

SiO₂ multishell hollow spheres (MHSs) as supports have multiple porous layers and internal voids, which present notable advantages in regulating mass transport and chemical reactions. However, practical applications of SiO₂ MHSs are severely hindered because of their high costs and low production efficiency issues. Herein, it is overcome these obstacles by developing a precursor hydrolysis method and demonstrate a cost-effective production of void-ratio tunable SiO₂ MHSs on a large scale, which has a much lower cavitation temperature (25 °C) and one order of magnitude decrease in cost. In addition, the new method can also be applied to fabricate TiO₂ and SnO₂ hollow spheres (HSs). In particular, an NH₄Cl precipitation-pyrolysis strategy is developed to tune the pore diameters and pore distributions of SiO₂ MHSs with different void ratios. SiO₂ MHSs with varying void ratios and pore distributions have the broadest controlling release time ranges (30-430 h). The precursor hydrolysis method and NH₄Cl precipitation-pyrolysis strategy offer adequate stimulus to push forward SiO₂ MHSs from laboratory-scale to industry-scale applications.