A general synthesis of mesoporous metal oxides with well-dispersed metal nanoparticlesvia a versatile sol–gel process

Abstract

The design and preparation of efficient, stable and economical metal nanoparticles supported on mesoporous metal oxides (MNPs/MMOs) has been a major direction in many applications especially in the catalysis area. The conventional synthesis methods for MNPs/MMOs are complex and lack high-degree control over different compositional/structural parameters. Herein, we reported a general synthesis of MNP/MMO composites via a one-step, versatile sol–gel process under strongly acidic conditions. The successful introduction of stable, PVP-capped MNPs into the AcHE sol–gel system (Ac, H, and E represent acetic acid, HCl, and EtOH, respectively) allows us to synthesize a large variety of MNPs/MMOs (M = Pt, Au, Pd, and MMOs = TiO₂, SiO₂, ZrO₂, Al₂O₃). In addition to the compositional variation, the preformed PVP-capped MNPs in the AcHE sol–gel system decouple the particle nucleation and inorganic–organic co-assembly processes, permitting a stabilization of the MNPs in the nano-scale range over a wide particle concentration. Meanwhile, structural regulation can also be achieved by variation of the block copolymer concentration. The high-degree control over different compositional/structural parameters of MNPs/MMOs provides a useful material candidate platform to further study their structure–property relationship for the design of a better catalyst for a specific reaction. The best Pt/Si–TiO₂ catalyst for n-hexane combustion obtained in this study serves as an example to show that the control of the adsorption and diffusion of reactants and products may be achieved by the optimization of composition and structure of the MNP/MMO catalysts, which may provide valuable insights for a detailed understanding of the structure- or composition-dependent chemical reactivity of the catalysts.