Highly dispersed Pt nanoparticle catalyst prepared by atomic layer deposition

Abstract

Nanoparticulate platinum has been well dispersed onto large quantities of micron-sized mesoporous silica gel using atomic layer deposition in a fluidized bed reactor (i.e. ALD-FBR). Transmission electron microscopy (TEM) cross-sectional investigations showed that the Pt nanoparticles were homogeneously distributed throughout primary 30–75μm silica gel particles, including the inner surfaces comprising 5–7nm pores. The Pt catalyst loading level was tightly controlled by the number of coating cycles. An extremely low Pt loading with 3.1×10−6mg Pt/cm2 (0.10atom/nm2), 4.8×10−6mg Pt/cm2 (0.15atom/nm2) and 2.9×10−5mg Pt/cm2 (0.91atom/nm2) was prepared with 3, 5 and 10 coating cycles, respectively. The average Pt particle size is approximately 1.2nm for 3 cycles. For 5 and 10 coating cycles, the Pt particle size is measured to be 1.9nm and 2.3nm, respectively. The sample with a 3.1×10−6mg Pt/cm2 loading exhibits the highest metal dispersion of 90%. Thermal stability studies indicated an initial sintering of the Pt particles during the first 4h of heat treatment at 450°C in an air environment. After that, there was no noticeable change of the particle size during the following heat treatment process. Carbon monoxide oxidation demonstrated nearly 100% conversion of CO to CO2 over 20mg of 4.8×10−6mg Pt/cm2 loaded silica gel particles at 180°C for 100sccm flow rate of 1% CO in argon.