Study of surface mobility by isotopic exchange: recent developments and perspectives

Oxygen and hydrogen surface mobility can be involved in many catalytic processes. However, quantitative measurements of surface diffusion are relatively scarce. We present the recent developments of the isotopic methods which are based on the determination of the rates of exchange between (18)O2 or of D2 with O-16 and H species of oxides, via metal particles (mainly Rh) deposited on these oxides. O and H surface mobility on SiO2, Al2O3, ZrO2, MgO and CeO2 is reviewed. Great differences between these various oxides can be observed. H and O species are very mobile on ceria while they are not on silica. The impact of surface mobility in steam reforming, three-way catalysis (oxygen storage capacity) and in selective oxidations is also discussed.