The development of efficient and stable catalyst systems using low-cost, abundant,
and nontoxic materials is the primary demand for photocatalytic water oxidation. Distinguishing
the true active species in a heterogeneous catalytic system is important for construction
of efficient catalytic systems. Herein, hydrothermally synthesized Ti3+ self-doped
TiO2, labeled as Ti3+/TiO2, was first used as a light absorber in a powder visible
light-driven photocatalytic water oxidation reaction. When an iron-containing polyoxometalate
Na-27[Fe-11(H2O)(14)(OH)(2)(W3O10)(2)(alpha-SbW9O33)(6)] (Fe11) was used as a cocatalyst,
an amorphous layer of active species was wrapped outside the initial Ti3+/TiO2 nanorod
and the in situ formed composite was labeled as F/Ti3+/TiO2. When the composite F/Ti3+/TiO2
was tested as a photocatalytic water oxidation catalyst, dramatically improved oxygen
evolution performance was achieved. The composite F/Ti3+/TiO2 showed an oxygen evolution
rate of 410 mu mol/g/h, which was about 11-fold higher than that of prism Ti3+/TiO2.
After 24 h of illumination, an O-2 yield of 36.4% was achieved. The contrast experiments,
high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy
characterization demonstrated that FeOx is the true cocatalyst that enhanced the oxygen
evolution activity of TiO2. A recycling experiment proved that the composite F/Ti3+/TiO2
has favorable stability in the oxygen production process.
