Monolayer dispersion of RuO2 on SnO2 support: Elucidating the threshold effect on the intrinsic activity for toluene deep oxidation

RuO2/SnO2 catalysts with different contents of RuO2 supported on CVD-SnO2 were fabricated via a deposition-precipitation method for toluene deep oxidation. The monolayer dispersion threshold of RuO2 on SnO2 was determined quantitatively using an XRD extrapolation method, yielding a value of 0.94 mmol/100 m2 SnO2 surface, equivalent to a 3.5 wt% RuO2 loading. Raman, TEM, HRTEM, EDS mapping and XPS analyses have further confirmed RuO2 monolayer dispersion. RuO2 surface accumulation and crystallization take place when the loading exceeds the threshold, with less significant activity increase. H2-TPR, O2-TPD, NH3-TPD and tolueneTPD demonstrated that RuO2 interacts with the SnO2 surface to form possibly interfacial Ru-O-Sn bonds. This interaction enhances the redox performance, and generates a greater amount of surface oxygen vacancies and acidic sites on the catalysts. Consequently, the resulted catalysts exhibit improved catalytic performance, along with enhanced stability, water resistance, and sulfur resistance.