Abstract
Simultaneous time-resolved SAXS and XANES techniques were employed to follow in situ the formation of Pd nanoparticles from palladium acetate precursor in two porous polymeric supports: polystyrene (PS) and poly(4-vinyl-pyridine) (P4VP). In this study we have investigated the effect of the use of different reducing agents (H2 and CO) from the gas phase. These results, in conjunction with data obtained by diffuse reflectance IR (DRIFT) spectroscopy and TEM measurements, allowed us to unravel the different roles played by gaseous H2 and CO in the formation of the Pd nanoparticles for both PS and P4VP hosting scaffolds.
Highlights
In recent years, Pd nanoparticles (NPs) supported on porous polymers have become a promising class of catalysts because of their unique physical−chemical properties and attractive catalytic performances [1]
We have demonstrated that the nature of the polymeric matrix has a strong influence on the formation of the Pd NPs and affects their final properties, in terms of particle size, electronic properties, and type and fraction of accessible surface sites
For the Pd/PS systems the following conclusions have been obtained: (i) Reduction of palladium acetate starts at lower temperature and proceeds faster in the presence of CO than with H2. (ii) The Pd NPs are bigger when formed in CO and show peculiar morphologies, whereas those formed in H2 are smaller and spherical in shape (Figure 2b). (iii) Pd NPs formed in CO have unclean surfaces, probably as a consequence of residual by-products that are not desorbed at the reduction temperature, as evidenced by DRIFT [9]
Summary
Pd nanoparticles (NPs) supported on porous polymers have become a promising class of catalysts because of their unique physical−chemical properties and attractive catalytic performances [1]. FT-IR spectra were collected in reflectance mode (DRIFT) on a Nicolet 6700 instrument, equipped with a MCT detector. As the readout and erasing time of the 2D Mar detector was 180 s, each SAXS pattern was collected for 120 s resulting in a 1 to 1 correspondence between XANES spectra and SAXS patterns.
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