In-situ monitoring of transition metal complex adsorption on oxide surfaces during the first stages of supported metal catalyst preparation

• Proof of concept of QCM as tool to study TMC adsorption on oxide surfaces.
• Evidence for reversible adsorption of platinum complexes on silica and alumina surfaces.
• Surface coverage obtained by QCM consistent with powdered solids.

In the preparation of supported catalysts by deposition, in solution, of a transition metal complex (TMC) on an oxide support, the interactions occurring at the solid/liquid interface between the TMC and the oxide have a crucial impact on the properties of the final catalyst. However, these interactions remain difficult to investigate and monitor as most of the spectroscopic characterization techniques can only be used once the solvent has been removed, which eliminates an essential partner of the interaction. In this paper, we show that Quartz Crystal Microbalance with dissipation monitoring (QCM-D), a highly sensitive technique operating in situ at the solid/liquid interface, can be used to undo this technical lock. QCM-D was used to study two well-known systems: the adsorption of [Pt(NH3)4]2+ on silica at high pH and the adsorption of [PtCl6]2− on alumina at low pH, in order to demonstrate that QCM-D can be a very useful tool for the investigation of the interaction between a TMC and an oxide surface in solution.

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