Scalable Synthesis of Three-Dimensional Meso/Macroporous NiO with Uniform Ultralarge Randomly Packed Mesopores and High Catalytic Activity for Soot Oxidation

Functional nanomaterials with uniform ultralarge mesoporosity possess great potential for advanced technological applications. However, their cost-effective synthesis at a large scale still remains a major challenge. In this work, a three-dimensional (3D) hierarchical meso/macroporous NiO catalyst with uniform ultralarge randomly packed 22 nm mesopores has been synthesized for the first time by a facile, economical, and highly scalable colloidal solution combustion synthesis (CSCS) and applied for catalytic soot oxidation. The structural parameters of the catalyst (specific surface area, pore volume, and pore size) can be readily tuned by the amount of colloids added, and NiO with a high surface area (221.6 m2/g), a large pore volume (0.39 mL/g), and a small crystal size (3–5 nm) has been produced. The addition of silica colloids confines the exothermic reaction in small nanovoids between closely arranged 22 nm hard-sphere colloids, leading to a combustion at the nanoscale level, which we denote as nanoco...