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Abstract:
Co 3 O 4 spinel has been widely investigated as a promising catalyst for the oxidation of volatile organic compounds (VOCs). However, the roles of tetrahedrally coordinated Co 2+ sites (Co 2+ T d ) and octahedrally coordinated Co 3+ sites (Co 3+ O h ) still remain elusive, because their oxidation states are strongly influenced by the local geometric and electronic structures of the cobalt ion. In this work, we separately studied the geometrical-site-dependent catalytic activity of Co 2+ and Co 3+ in VOC oxidation on the basis of a metal ion substitution strategy, by substituting Co 2+ and Co 3+ with inactive or low-active Zn 2+ (d 0 ), Al 3+ (d 0 ), and Fe 3+ (d 5 ), respectively. Raman spectroscopy, X-ray absorption fine structure (XAFS), and in situ DRIFTS spectra were thoroughly applied to elucidate the active sites of a Co-based spinel catalyst. The results demonstrate that octahedrally coordinated Co 2+ sites (Co 2+ Oh ) are more easily oxidized to Co 3+ species in comparison to Co 2+ Td , and Co 3+ are responsible for the oxidative breakage of the benzene rings to generate the carboxylate intermediate species. CoO with Co 2+ Oh and ZnCo 2 O 4 with Co 3+ Oh species have demonstrated good catalytic activity and high TOF Co values at low temperature. Benzene conversions for CoO and ZnCo 2 O 4 are greater than 50% at 196 and 212 °C, respectively. However, CoAl 2 O 4 with Co 2+ T d sites shows poor catalytic activity and a low TOF Co value. In addition, ZnCo 2 O 4 exhibits good durability at 500 °C and strong H 2 O resistance ability. © 2017 American Chemical Society.
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ACS Catalysis
ISSN: 2155-5435
Year: 2017
Issue: 3
Volume: 7
Page: 1626-1636
1 1 . 3 8 4
JCR@2017
1 1 . 7 0 0
JCR@2023
ESI HC Threshold:226
JCR Journal Grade:1
CAS Journal Grade:2
Cited Count:
WoS CC Cited Count: 0
SCOPUS Cited Count: 310
ESI Highly Cited Papers on the List: 0 Unfold All
WanFang Cited Count:
Chinese Cited Count:
30 Days PV: 1
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