Influence
of Defects on the Photocatalytic Activity of ZnO
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Abstract
The influence of defects on the photoactivity
of ZnO has been revealed. The defects can be formed via ball-milling
treatment, and part of the defects can be repaired via annealing treatment.
The photocatalytic activity of the ZnO sharply decreased as the ball-milling
speed and milling time increased. After the annealing treatment, the
photocatalytic activity recovered partly but could not return to the
activity of the pristine ZnO. The bulk defects such as oxygen vacancies
(V<sub>O</sub>), zinc vacancies (V<sub>Zn</sub>) and a lot of nonradiative
defects were formed after the milling treatment. The annealing treatment
can only repair part of the bulk defects and nonradiative defects.
Thus, only part of the photoactivity was recovered. The species trapping
experiments showed that the introduction of the bulk defects did not
change the photocatalytic mechanism. The main oxidative species for
the pristine ZnO, the milled ZnO, and the annealed ZnO are photogenerated
holes and hydroxyl radicals