Atomic layer deposition (ALD) is an advanced thin film deposition technique. By using the technical features and advantages of ALD, a new type of highly efficient nanocatalyst can be designed and the surface interface structure of the catalyst can be precisely controlled. The research team led by Yan Yong, a researcher at the State Key Laboratory of Coal Conversion in the Institute of Coal Chemistry, the Chinese Academy of Sciences, used ALD technology to design and fabricate a multiple-constrained Ni-based hydrogenation catalyst. Compared with the unconstrained catalysts, the activity and stability of the multi-restricted Ni-based catalysts for the hydrogenation of cinnamaldehyde and nitrobenzene have been significantly improved. Related work was recently published at Angew. Chem. Int. Ed.
The interfacial structure of the metal-oxide support strongly influences the performance of the heterogeneous catalyst. Accurately designing and adjusting the interface structure is very important for the preparation of new and efficient catalysts. The research team used ALD technology to deposit NiO nanoparticles first on the template surface using carbon nano spirals or carbon nanotubes as templates, and then deposited Al2O3 nano-films. After calcination and reduction treatment, an alumina nanotube (ANT) package was obtained. Covered Ni catalysts (Ni-in-ANTs). This approach allows Ni particles to be confined not only in the alumina nanotubes but also in the pits on the inner walls of the alumina nanotubes, which is called multiple confinement. The NiO nanoparticle and Al2O3 nanofilms were deposited in different order. After calcination and reduction, Ni-out-ANTs were loaded on the outer wall of the nanotubes.
A large number of characterization results show that the two have the same Ni content, Ni nanoparticle size, alumina nanotube wall thickness, channel structure and Ni reduction. However, for the catalytic hydrogenation of cinnamaldehyde and nitrobenzene, the activity of Ni-based multiple-restricted catalysts is much higher than that of uncatalyzed catalysts. This is because the Ni particles in the limited-domain catalyst are confined to the pits in the inner wall of the alumina nanotubes, with more Ni-Al2O3 interfacial sites, and the metal-support interaction is stronger, which promotes Hydrogen overflow phenomenon, thereby enhancing the hydrogenation reaction activity of the catalyst. In addition, the alumina nanotubes can protect the Ni particles in the limited range, preventing them from falling off and releasing in the reaction, so that the multiple-restricted catalyst has better cycle stability than the unconstrained catalyst.
The method is universal and can be used to synthesize the limited catalysts of other systems for catalyzing different reactions. It provides an important scientific reference for the design of high-efficiency nanocatalysts in the future.
The study was funded by the National Natural Science Foundation of China (21173248, 21403272, 21227002, 21376256, 51362010), the Chinese Academy of Sciences 100-person plan, and the 100-person plan of Shanxi Province.
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