In situ controllable assembly of layered-double-hydroxide-based nickel nanocatalysts for carbon dioxide reforming of methane

Abstract

Producing loaded metal nano-cluster catalysts possessing at the same time enhanced reactivity and durability has become increasingly important, but still remains a tremendous challenge in nanoparticle hetero-catalysis. In our current study, Mg-functionalized Ni-based nanohybrids with both a large dispersion and small size of nickel particles as well as excellent anti-sintering imbedded in a hierarchical mesostructured γ-Al₂O₃ substrate were successfully developed using an easy and reproducible procedure. This procedure involved an in situ growth mechanism of Ni-containing layered double hydroxides (LDHs) that used alumina substrates as the sole Al³⁺ source. The developed nanohybrid shows both exceptional reactivity and durability for carbon dioxide reforming of methane. A combination of techniques, including XRD, N₂ adsorption and desorption, FT-IR, TGA, SEM, ICP-AES, XPS, H₂-TPR, CO₂-TPD, TEM, and in situ CH₄/CO₂-TPSR, was used to determine a strong structure–function relationship for the catalyst. The highly reducible and dispersed active surface Ni species greatly enhanced the activation of methane, while fine tuning the acidity/basicity of the surface supplied sufficient reactive centers for the adsorption/activation of CO₂. In addition, the reciprocally strengthened dual confinement effects imparted by both the mesoporous γ-Al₂O₃ matrix and the in situ-grown LDH precursors resulted in the extraordinary catalytic stability, without pronounced sintering and/or agglomeration of reactive phases in the demanding working conditions.