Redox catalytic property of still-growing and final palladium particles: Acomparative study

Authors
Citation
Nr. Jana et T. Pal, Redox catalytic property of still-growing and final palladium particles: Acomparative study, LANGMUIR, 15(10), 1999, pp. 3458-3463
Citations number
33
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
LANGMUIR
ISSN journal
07437463 → ACNP
Volume
15
Issue
10
Year of publication
1999
Pages
3458 - 3463
Database
ISI
SICI code
0743-7463(19990511)15:10<3458:RCPOSA>2.0.ZU;2-7
Abstract
The redox catalytic property of still-growing and final particles of pallad ium has been investigated using methylene blue (MB) and fluorescein (F) as redox probes. Reductions of MB by N2H4 and of F by NaBH4 were observed to b e catalyzed by both the still-growing and the final Pd particles. In most c ases the catalytic rate increases exponentially with the increase in cataly st precursor ion concentration, that is, [Pd-II] and [N2H4/NaBH4]. However, with the increase in [dye], the rate decreases in most cases, and this eff ect is more prominent for still-growing particles than final particles. The study shows that particle size has a significant role in influencing the c atalytic property of the metal. Still-growing particles are smaller in size and render more catalytic activity provided they are sufficiently stable a nd their surface is not poisoned by the chemisorption of reactants or any o ther foreign ions/molecules. Palladized charcoal has been observed to be a much weaker catalyst than the two studied here because of its larger partic le size and carbon-covered surface. An ion-exchange mechanism is proposed t o explain the catalytic rate. The dye and the reducing agent are in equilib rium between the catalyst surface and bulk water. Thus, the rate of dye red uction depends on the surface concentration of dye and reducing agent.