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Multiple‐Oxidation‐State Tungsten‐Oxide Clusters on a Carbon Surface as an Intersection between Molecular and Bulk Oxides
Author(s) -
Wakizaka Masanori,
Chun WangJae,
Imaoka Takane,
Yamamoto Kimihisa
Publication year - 2021
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.202001104
Subject(s) - chemistry , oxidation state , tungsten , oxide , x ray photoelectron spectroscopy , carbon fibers , redox , dendrimer , hydrogen , crystallography , inorganic chemistry , photochemistry , metal , polymer chemistry , chemical engineering , organic chemistry , materials science , composite number , composite material , engineering
Bulk tungsten oxides exhibit a wide range of oxidation states, whereas the oxidation states available in molecular oxides such as polyoxometalates (POMs) is limited. In this paper, tungsten oxide clusters with diameters of 1.2±0.4 ( W 60 O x /C ), 1.1±0.4 ( W 28 O x /C ), and 0.9±0.3 nm ( W 12 O x /C ) were produced in a size‐selective manner on graphitic carbon by using a phenyl‐azomethine‐type dendrimer as a template and applying hydrogen reduction after fixing the dendrimers on a support. X‐ray photoelectron spectroscopy revealed that the W atoms in the clusters exhibited multiple oxidation states, i. e., W δ + , W 4+ , W 5+ , and W 6+ . Moreover, X‐ray absorption fine structure measurements indicated the W−W bond length of 2.84–2.85±0.01 Å in these clusters. Auto‐oxidation with adventitious oxygen after hydrogen reduction is proposed as a reasonable mechanism for the formation of these clusters on the carbon surface.