Monitoring Supported-Nanocluster Heterogeneous Catalyst Formation: Product and Kinetic Evidence for a 2-Step, Nucleation and Autocatalytic Growth Mechanism of Pt(0)n Formation from H2PtCl6 on Al2O3 or TiO2

A pressing problem in supported-metal-nanoparticle heterogeneous catalysis—despite the long history and considerable fundamental as well as industrial importance of such heterogeneous catalysts—is how to monitor such catalysts’ formation more routinely, rapidly, and in real time. Such information is needed to better control the size, shape, composition, and thus resultant catalytic activity, selectivity, and lifetime of these important catalysts. To this end, a study is reported of the formation of supported Pt(0)n nanoparticles by H2 reduction of H2PtCl6 on Al2O3 (or TiO2) to give 6 equivalents of HCl plus supported Pt(0)n/Al2O3 (or Pt(0)n/TiO2), all while in contact with a solution of EtOH and cyclohexene. The HCl and Pt(0)n products were confirmed, respectively, by the stoichiometry of HCl formation using pHapparent measurements, appropriate standards, and by TEM and EDX measurements. The hypothesis of this research is that the kinetics of formation of this supported heterogeneous catalyst could be suc...