It is frequently desired to synthesize supported metal catalysts that consist of very small clusters or single atoms. In this work, we combine strong electrostatic adsorption (SEA) of H2PtCl6 and engineered oxide supports to ultimately produce very small Pt clusters, including a large fraction of single Pt atoms. The supports are synthesized by depositing controlled amounts of SiO2 onto Al2O3 (SiO2@Al2O3) that has been previously grafted with bulky organic templates. After the templates are removed, the oxide supports are largely negatively charged, like SiO2, but have small patches of positively charged Al2O3, derived from the regions previously covered by the template. The overall point of zero charge of these materials decreases from pH 6.4 for 1 cycle of SiO2 deposition to a SiO2-like <2 for materials with more than 5 cycles of SiO2 deposition. SEA at pH 4 on templated SiO2@Al2O3 deposits from 1 wt. % to 0.05 wt. % Pt as the amount of SiO2 increases. Pt loadings drop to near zero in the absence of a template. The resulting Pt nanoparticles are generally <1 nm and have dispersion near 100% by CO chemisorption. Finally, CO DRIFTS shows that the CO nanoparticles become increasingly well defined and have a higher percentage of Pt single atoms as the amount of SiO2 increases on the SiO2@Al2O3 particles. Overall, this method of synthesizing patches of charge on a carrier particle appears to be a viable route to creating extremely highly dispersed supported metal catalysts.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry