In situ observation of metal precipitation on metal oxide using polymer brushes as a template by X-ray absorption spectroscopy

directly related to catalytic function and optical properties. In this study, we tried to deposit Pd on the TiO2 surface using a polymer brush on the substrate as a “template” without the adsorption of metal ions to the polymer. We also investigated the interaction of the substrate (TiO2), polymer (PMMA), and metal (Pd) by observing the reduction process using energy-dispersive X-ray absorption spectroscopy (DXAFS). The molecular weight and graft density of PMMA on the TiO2 were 22,600 and 0.26 /nm2, respectively. Pd deposition reaction was performed by mixing [PdCl4]2- aq. and PMMA modified TiO2 (PMMA-TiO2) or no treatment TiO2 (NT-TiO2) and photoreduction. Comparing the average grain size of Pd precipitated on the TiO2 surface, PMMA-TiO2 promoted grain growth of Pd more than NT-TiO2. Furthermore, the grain size distribution suggests that the polymer brush on TiO2 suppressed grain growth of Pd, indicating that the brush acted as a template. DXAFS measurements observed the Pd reduction behavior, and it was found that the reduction reaction proceeded with the presence of PMMA and TiO2 in the reaction system. The Pd chemical state at the beginning of the reduction reaction was changed by PMMA, forming a brush morphology, suggesting that the space created by the PMMA brush functions as a unique reaction field.