Oxide-supported metal materials are widely employed as heterogeneous catalysts. The support facilitates the dispersion of metal nanoparticles and enhances the catalytic performance through metal-support interactions. Atomic layer deposition (ALD) is a useful method to apply oxide coatings to metal surfaces for optimal interactions and thus improved catalysis.
Zhe Gao, Yong Quin, State Key Laboratory of Coal Conversion, Taiyuan, China, and colleagues have developed a strategy to increase metal-support interfaces by adding an ultrathin coating of alumina onto platinum nanoparticles which are confined in Al2O3 nanotubes .
The team’s ALD preparation utilized carbon nanocoils as sacrificial templates. These have a lower annealing temperature than nanotubes, allowing for easy removal. Trimethylaluminum (TMA) was used as a precursor for alumina, and [MeCpPtMe3] was used as a platinum source for the deposition process. For comparison, the researchers also prepared uncoated platinum nanoparticles confined in Al2O3 nanotubes (Pt-in-ANTs).
The Pt-in-ANTs and the ultrathin-Al2O3-coated samples (xAl-Pt-in-ANTs, x = number of coating cycles) were evaluated for their catalytic performance in the hydrogenation of 4-nitrophenol. The catalytic activity was significantly greater for the thinly coated 2Al-Pt-in-ANTs than for Pt-in-ANTs, thus proving the beneficial effect of maximizing the interfacial sites and the potential of this method for heterogeneous catalysis.
Qin and his team have also applied ALD to design a new tandem catalyst with multiple metal-oxide interfaces based on a tube-in-tube nanostructure . This catalyst has both Ni/Al2O3 and Pt/TiO2 interfaces. It exhibits very high catalytic efficiency in the tandem hydrogenation of nitrobenzene.
-  Ultrathin coating of confined Pt nanocatalysts by atomic layer deposition for enhanced catalytic performance in hydrogenation reactions,
Meihua Wang, Zhe Gao, Bin Zhang, Huimin Yang, Yan Qiao, Shuai Chen, Huibin Ge, Jiankang Zhang, Yong Qin,
Chem. Eur. J. 2016.
-  A Tandem Catalyst with Multiple Metal-Oxide Interfaces Produced by Atomic Layer Deposition,
Huibin Ge, Bin Zhang, Xiaomin Gu, Haojie Liang, Huimin Yang, Zhe Gao, Jianguo Wang, Yong Qin,
Angew. Chem. Int. Ed. 2016.