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Supported Vanadium Oxide Clusters in Partial Oxidation Processes: Catalytic Consequences of Size and Electronic Structure
Author(s) -
Yun Dongmin,
Song Yang,
Herrera José E.
Publication year - 2017
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.201700503
Subject(s) - nanoclusters , catalysis , vanadium oxide , trimer , vanadium , dimer , raman spectroscopy , chemistry , inorganic chemistry , oxide , titanium , monomer , density functional theory , cluster (spacecraft) , photochemistry , polymer , computational chemistry , organic chemistry , computer science , programming language , physics , optics
Abstract The catalytic activity for ethanol partial oxidation of vanadium oxide (VO x ) anchored on titanium oxide was correlated to their electronic structure. In situ Raman spectroscopy and temperature‐programmed desorption (TPD) experiments indicate that the presence of catalytically active VO x moieties is very sensitive to vanadia loading: highly dispersed VO x predominantly exists at low VO x contents whereas larger vanadia clusters coexist at higher VO x loadings. In situ UV/Vis spectroscopy revealed that a significant fraction of these larger clusters remain reduced during catalysis, and thus do not fully participate in catalytic turnovers. The electronic structures of model VO x nanoclusters of different sizes (monomer, dimer, trimer, and one‐dimensional polymers) were investigated by using periodic density functional theoretical calculations. Results indicate that their electronic structures are significantly affected by their size. Our analysis also revealed that the formation of reduced VO x species (V 4+ ) during catalysis is concomitant to the reduction of adjacent Ti cations (Ti 3+ ). Theoretically calculated optical absorption spectra matched the experimental spectroscopic results obtained under in situ reaction conditions. Furthermore, the determination of defect formation enthalpies reported previously as the main descriptor for catalytic activity of vanadia nanoclusters, predicted that isolated monomeric VO x clusters predominantly take part in catalytic turnovers.