Particle shape optimization by changing from an isotropic to an anisotropic nanostructure: preparation of highly active and stable supported Pt catalysts in microemulsions

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.We recently introduced a new method to synthesize an active and stable Pt catalyst, namely thermo-destabilization of microemulsions (see R. Y. Parapat, V. Parwoto, M. Schwarze, B. Zhang, D. S. Su and R. Schomäcker, J. Mater. Chem., 2012, 22 (23), 11605–11614). We are able to produce Pt nanocrystals with a small size (2.5 nm) of an isotropic structure i.e. truncated octahedral and deposit them well on support materials. Although we have obtained good results, the performance of the catalyst still needed to be improved and optimized. We followed the strategy to retain the small size but change the shape to an anisotropic structure of Pt nanocrystals which produces more active sites by means of a weaker reducing agent. We found that our catalysts are more active than those we reported before and even show the potential to be applied in a challenging reaction such as hydrogenation of levulinic acid.DFG, EXC 314, Unifying Concepts in Catalysi

A new method to synthesize very active and stable supported metal Pt catalysts: thermo-destabilization of microemulsions

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.A new technique to deposit nanoparticles synthesized in reverse micellar microemulsions onto support material without agglomeration is named thermal destabilization of microemulsion. The multifaceted Pt crystals, mostly truncated octahedra, were produced inside reverse micelles with an average size of 2.5 nm and a narrow size distribution. After deposition, the Pt crystals were found to be well dispersed on the support with an average size of 2.5 nm. After testing with hydrogenation of α-methyl styrene, the produced Pt-catalyst showed higher activity (6 times higher) and stability than commercial ones. The advantages of this synthesis route of nanoparticles include simple operation, and the ease of controlling the size and shape of nanoparticles without using capping agents.DFG, EXC 314, Unifying Concepts in Catalysi

Support effect in the preparation of supported metal catalysts via microemulsion

It is well known that the activities of supported metal catalysts are strongly dependent upon the size, shape and dispersion of the nanoparticles on the support material. There are several techniques which can be implemented in order to produce such catalysts, e.g. wet impregnation, however the deposition of nanoparticles (NPs) on the support material without agglomeration still proves a challenge. This is particularly significant when attempting to maintain the size and shape of the particles during the deposition process. We have introduced a new method to deposit metal NPs, namely thermo-destabilization of microemulsions (please see J. Mater. Chem., 2012, 22, 11605–11614 and Nanoscale, 2013, 5, 796–805), in which the NPs are formed prior the deposition process. This method is an ingenious approach to control the dispersion of NPs on the support material and depositing NPs evenly with a narrow size distribution. In this paper we expound the important role of the surface charges of NPs and the support material, as indicated by zeta potentials, on the metal dispersion, and how they affect the catalytic activity. We also investigate the influence of other parameters such as the pore size and the pre-calcination of the support on the catalytic activities of the resulting supported metal catalysts.DFG, EXC 314, Unifying Concepts in Catalysi