Methane combustion activity of alumina supported Pt, Pd, and Rh catalysts modified by high-energy ion beam irradiation

100 keV O+ or N+ ion implantation was used to study the irradiation effect on the methane combustion activity of 1 mass%Pd, Pt, and Rh supported on gamma-Al2O3. The catalytic activity of both Pt/Al2O3 and Rh/Al2O3 was enhanced by the implantation, probably due to the improved dispersion of noble metals. On the other hand, the activity of Pd/Al(2)O3 decreased substantially with an increased dose amount of O+ or N+. The Pd 3d(5/2) XPS measurement demonstrated that the as-prepared catalyst contains PdO, which is reduced to Pd metal with increasing ion implantation. This irradiation-induced reaction process also resulted in not only a significant increase of the Pd particle size from 3 to 20 nm, but also a phase transformation of gamma- to alpha-Al2O3 after implanting O+ of 7.5 x 10(18) ion g(-1).