Premium
On the Nature of Selective Palladium‐Based Nanoparticles on Nitrogen‐Doped Carbon Nanotubes for the Direct Synthesis of H 2 O 2
Author(s) -
Abate S.,
Freni M.,
Arrigo R.,
Schuster M. E.,
Perathoner S.,
Centi G.
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201200914
Subject(s) - selectivity , catalysis , hydrogenolysis , chemisorption , carbon nanotube , palladium , nanoparticle , chemistry , metal , inorganic chemistry , materials science , chemical engineering , nanotechnology , organic chemistry , engineering
Catalysts based on Pd and Pd–Au nanoparticles supported on N‐doped carbon nanotubes (N‐CNTs) are studied in the direct synthesis of H 2 O 2 . The initial selectivity in H 2 O 2 formation is rather high (>95 %); however, there is a fast initial decrease during the first hour of time on stream. This was due to the initial presence of an organic capping agent (polyvinyl alcohol, which is used in the catalyst synthesis to obtain a high dispersion of metal particles). The removal of this capping agent during the reaction leads to a high mobility of metal nanoparticles. The high initial selectivity, when the capping agent is present, is due to small Pd terraces fully covered with chemisorbed O 2 and limited H 2 chemisorbed sites that consecutively hydrogenate the formed H 2 O 2 . The alloying of Pd with Au decreases the intrinsic reaction rate (per mg of Pd) and increases the selectivity in H 2 O 2 formation, whereas Au alone is inactive. Au also has a minor effect on the consecutive conversion of H 2 O 2 in both the decomposition and hydrogenolysis (in the presence of H 2 only) reactions. These results suggest that Au does not block the unselective sites of H 2 O 2 conversion but mainly creates isolated small terraces of Pd that can limit H 2 chemisorption sites, which thus leads to higher selectivity to H 2 O 2 under given reaction conditions.