Distinct morphology-dependent behaviors for Au/γ-Al2O3 catalysts: enhanced thermal stabilization in CO oxidation reaction

Abstract

The durability of supported metal catalysts usually suffers from sintering, the metal nanoparticles aggregating into larger sizes and subsequent loss of reactive surface, resulting in catalysts deactivation when heated at elevated temperatures. Herein, we investigate the evolution of Au species on different morphologies of γ-Al₂O₃ and surprisingly found vastly different behavior for the dispersion of surface Au nanoparticles. A nanorod-shaped γ-Al₂O₃ is prepared by the hydrothermal method resulting in an extraordinary catalyst support that can stabilize Au nanoparticles at annealing temperatures up to 700 °C. In contrast, the Au-supported catalyst prepared using commercial γ-Al₂O₃ shows a greater degree of inactivation under the same conditions. Remarkably, the unique morphology of such nanorod-shaped γ-Al₂O₃ is beneficial in preventing Au nanoparticles from sintering. The γ-Al₂O₃ nanorods are more effective than the commercial γ-Al₂O₃ at anchoring the Au nanoparticles. The results of X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and H₂-TPR, reveal the interfacial interactions between Au nanoparticles and γ-Al₂O₃ nanorods, yielding a sinter-stability of the obtained Au/γ-Al₂O₃ nanorods catalyst. This synthetic strategy is simple and amenable to the large-scale manufacture of thermally stable γ-Al₂O₃ for industrial applications. Here, we investigate the morphology-dependent behavior of Au nanoparticles dispersed on different morphologies of γ-Al₂O₃. The result of X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and H₂-TPR, reveal the interfacial interactions between Au nanoparticles and gamma alumina nanorods. Au nanoparticles on γ-Al₂O₃ nanorods exhibit higher sinter-resistant performance than those on commercial γ-Al₂O₃.