J Liu

Advanced Electron Microscopy of Metal–Support Interactions in Supported Metal Catalysts

Electron microscopy and its associated techniques have contributed significantly to the characterization of heterogeneous catalysts, especially supported metal catalysts, and can provide nano‐ or atomic‐scale information on the structure, morphology, composition, and electronic state of the area of interest. With the recent advancement in aberration corrections to achieve an image resolution below 0.1 nm and the rapid development of in situ techniques, advanced electron microscopy is poised to probe fundamental questions of heterogeneous catalysis and catalysts. Understanding the nature of metal–support interactions becomes critical if we want to achieve the goal of designing and fabricating nanoarchitectured catalysts with desired performances. To reliably probe the fundamental mechanisms of charge transfer, which is the core of catalysis, between individual nanoscale components and under a realistic gas environment and temperature is still a formidable challenge. This Review discusses the recent contribution of advanced electron microscopy to the study of metal–support interactions, as well as the challenges and opportunities of applying aberration‐corrected electron microscopy techniques to the investigation of atomic‐scale structures of complex heterogeneous catalysts.

Enhanced Catalytic Activity of Sub-nanometer Titania Clusters Confined inside Double-Wall Carbon Nanotubes

Sub-nanometer titania clusters have been homogeneously dispersed within double-wall carbon nantubes (DWNTs) with an inner diameter ranging from 1.0 to 1.5 nm. The confined titania exhibits a much higher activity than the titania particles attached on the outside walls of the DWNTs (the outside titania) in the epoxidation of propylene by H(2)O(2). XPS, XANES and Raman spectroscopy data suggest electron transfer from titanium to the inner surfaces of the DWNTs. In contrast, no electron transfer has been observed for the outside titania. We also found that the extent of this confinement-induced electron transfer is temperature dependent. The enhanced activity of the confined titania clusters is likely attributed to their small sizes and the interaction with the DWNT surface. The synthesis method that we developed here can be readily applied to incorporation of other metal/metal oxide nanoparticles into carbon nanotubes.

Chemically deposited Sb2S3 thin films for optical recording

Laser induced changes in the properties of Sb2S3 thin films prepared by chemical bath deposition are described in this paper. Sb2S3 thin films of thickness 550 nm were deposited from a solution containing SbCl3 and Na2S2O3 at 27 °C for 5 h. These thin films were irradiated by a 532 nm continuous wave laser beam under different conditions at ambient atmosphere. X-ray diffraction analysis showed amorphous to polycrystalline transformation due to laser exposure of these thin films. Morphology and composition of these films were described. Optical properties of these films before and after laser irradiation were analysed. The optical band gap of the material was decreased due to laser induced crystallization. The results obtained confirm that there is further scope for developing this material as an optical recording media.