Oxygen and carbon monoxide interaction on novel clusters like ruthenium: a WAXS study

Ruthenium oxide-like (RuxOy) nanoparticles were prepared by the decomposition of carbonyl precursors in organic solvents under mild conditions. CO oxidation over the reduced particles was studied by combined in situ X-ray diffraction and gas-phase analysis. For a sample prepared in dichlorobenzene, in a flow of CO/O2 = 0.55, oxidation of CO started at ca. 70 °C with the simultaneous formation of amorphous surface oxide. On further heating, the CO2 production increased proportionally with the rate of formation of surface oxide. Below ca. 130 °C the catalyst can be reversibly reduced in CO to the disordered precursor state, average size ca. 2.8 nm. After catalytic performance for 3 h at 180 °C, reduction in CO of partially oxidized RuxOy is accompanied by a burst of CO2 partial pressure and induces particle growth to ∼5nm due to the exothermic heat of the reaction. These results are comparable to earlier results for ruthenium single-crystal surfaces studied under low pressure conditions.