Adsorption of Rh(CO)2(acac) On TiO2(110): A DFT and STM Study

In this combined STM and DFT study, we examined the adsorption of Rh(CO)₂(acac) (acac is acetylacetonate) on a TiO₂(110) single crystal surface. The goal of this study is to develop an understanding of the relationship between the preferred adsorption sites of the supported organometallic species and the nucleation behavior of the rhodium clusters produced from the decomposition of the precursor compound. The type of adsorption sites present will be altered by using different surface treatments that affect the oxygen vacancy concentration and the OH coverage. After exposing Rh(CO)₂(acac) to the surface at room temperature the formation of small particles is observed. After annealing the sample to 630°C the density and number of the particles is significantly reduced. The particles appear to be monodisperse, with their lateral diameter increased to a few nm. The findings can be rationalized in terms of deligation of the parent species and agglomeration of the denuded rhodium. After further treatment of the sample with CO and then H₂, nanocrystals undergo dynamic reversible shape changes in response to the gas exposures. The details of the adsorption and deligation process have been characterized with DFT calculations.