Mass Production of Nanoscale Materials with Uniform Ultralarge Mesopores via Colloidal Solution Combustion Synthesis

Abstract

Mesoporous metal oxides are commonly synthesized via soft or hard templates. However, these multistep laborious methods normally result in low product yield. Furthermore, mesoporous hard templates (e.g., SBA-15, KIT-6, and CMK-3) are very expensive, and high capital costs are needed for the production. Facile and economical synthesis of mesoporous oxides with tailored porosity on a large scale still remains a challenging task for commercialization. Here we demonstrate a scalable, economic, energy and time efficient colloidal solution combustion synthesis (CSCS) method to produce crystalline mesoporous materials with tailored porosity using inexpensive colloidal silica [1,2]. CSCS utilizes the internal chemical energy of reactants which is released in the form of the heat, converting precursors into the products. For the proof of concept 0.5 kg of crystalline CeO2 with uniform 22 nm ultralarge mesopores, 130 m2/g surface area, 0.6 ml/g pore volume and high yield has been synthesized at low cost. Importantly, by eliminating the use of an organic solvent or surfactant, CSCS provides relatively green chemistry route to a scalable synthesis of nanomaterials. In addition to large-scale synthesis capability, CSCS method provides exceptional advantages compared to other well-established template-assisted methods. Specifically, the large surface area, uniform ultralarge mesoporosity, high crystallinity, and small crystal size of the oxide can be achieved at the same time, whereas prolonged high-temperature post-synthesis calcination for crystallization usually leads to the collapse of the mesoporous structure in other template-assisted methods. These can be achieved because the formation and crystallization of nuclei occur almost simultaneously through the heat generated from the exothermic reaction between the reactants in the CSCS. [1] A. A. Voskanyan, K.-Y. Chan, C.-Y. V. Li, Colloidal Solution Combustion Synthesis: Toward mass production of a crystalline uniform mesoporous CeO2 catalyst with tunable porosity. Chem. Mater. 2016, 28, 2768-2775. [2] A. A. Voskanyan, K.-Y. Chan, Scalable Synthesis of Three-Dimensional Meso-Macroporous NiO with Uniform Ultralarge Randomly Packed Mesopores and High Catalytic Activity for Soot Oxidation, ACS Appl. Nano Materials, 2018, 1, 556-563.