Room temperature ionic liquids for size control of noble metal nanoparticles on carbon supports

Unsupported noble metal nanoparticles and Pt nanoparticles supported on various carbon nanostructures were prepared in the absence and presence of various room temperature ionic liquids (RTILs) by a microwave process. UV–VIS spectroscopy analysis showed that RTILs accelerate the reduction rate of metal precursors and, depending on their anions, can act as a promoter, a capping material, and a reducing agent at the same time in the MW process to reduce metal precursors to metal particles. Transmission electron microscopy and X-ray diffraction analyses showed that Pt nanoparticles synthesized with the addition of RTILs are formed as discrete particles with sizes less than 2 nm and a very narrow size distribution, while most of the Pt nanoparticles without the addition of RTILs are highly agglomerated. It was also found that the size of Pt particles can be tailored by controlling the concentration of RTILs. Excellent, uniform dispersion of Pt nanoparticles on carbon supports can be achieved by the addition of RTILs. This approach enables size control of noble metal nanoparticles regardless of the nature of the supports and provides an easy way to investigate the effect of carbon supports on the catalytic activities of supported catalysts.