Highly dispersed Pt nanoparticle catalyst prepared by atomic layer deposition

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 30–75 μm silica gel particles, including the inner surfaces comprising 5–7 nm pores. The Pt catalyst loading level was tightly controlled by the number of coating cycles. An extremely low Pt loading with 3.1 × 10−6 mg Pt/cm2 (0.10 atom/nm2), 4.8 × 10−6 mg Pt/cm2 (0.15 atom/nm2) and 2.9 × 10−5 mg Pt/cm2 (0.91 atom/nm2) was prepared with 3, 5 and 10 coating cycles, respectively. The average Pt particle size is approximately 1.2 nm for 3 cycles. For 5 and 10 coating cycles, the Pt particle size is measured to be 1.9 nm and 2.3 nm, respectively. The sample with a 3.1 × 10−6 mg Pt/cm2 loading exhibits the highest metal dispersion of 90%. Thermal stability studies indicated an initial sintering of the Pt particles during the first 4 h 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 20 mg of 4.8 × 10−6 mg Pt/cm2 loaded silica gel particles at 180 °C for 100 sccm flow rate of 1% CO in argon.