Density Functional Theory Study of Small Au Nanoparticles Anchored on the Inner Surface of Mesoporous Co₃O₄for the Catalytic Reduction of 4-Nitrophenol

Noble-metal nanoparticles (NPs), due to their high surface energy, suffer from serious problems, such as ease of agglomeration at high temperatures, which unfortunately causes a significant decline in their original catalytic activity during the reaction and recycling processes. To solve these problems, in this work, a multiple-step synthetic method is proposed to construct an advanced core-shell structure by anchoring ultrasmall Au nanoparticles on the inner surface of mesoporous Co3O4 (m-Co3O4). The m-Co3O4, which has a high surface area, is fabricated by a hard-templating method, and the ultrasmall Au NPs (1.9 nm) are confined to the inner surface of the m-Co3O4. The target sample of Au-m-Co3O4 is found to achieve the highest catalytic efficiency in the probe reaction of the catalytic reduction of 4-nitrophenol to 4-aminophenol, and more importantly, thermal stability tests demonstrate that the Au-m-Co3O4 catalyst is more stable at higher temperatures. Furthermore, DFT calculations have verified that both activated hydrogen adsorption and 4-aminophenol desorption are significantly promoted on the surface of the Au-m-Co3O4 catalyst due to a strong synergetic effect between Au and the m-Co3O4. The construction of this advanced architecture for Au-based catalysts could provide a facile method for stabilizing ultrasmall noble-metal NPs and reasonably designing noble-metal catalysts with desirable activity and stability.