1 research outputs found
Photocatalysis with Pt–Au–ZnO and Au–ZnO Hybrids: Effect of Charge Accumulation and Discharge Properties of Metal Nanoparticles
Metal–semiconductor
hybrid nanomaterials are becoming increasingly
popular for photocatalytic degradation of organic pollutants. Herein,
a seed-assisted photodeposition approach is put forward for the site-specific
growth of Pt on Au–ZnO particles (Pt–Au–ZnO).
A similar approach was also utilized to enlarge the Au nanoparticles
at epitaxial Au–ZnO particles (Au@Au–ZnO). An epitaxial
connection at the Au–ZnO interface was found to be critical
for the site-specific deposition of Pt or Au. Light on–off
photocatalysis tests, utilizing a thiazine dye (toluidine blue) as
a model organic compound, were conducted and confirmed the superior
photodegradation properties of Pt–Au–ZnO hybrids compared
to Au–ZnO. In contrast, Au–ZnO type hybrids were more
effective toward photoreduction of toluidine blue to leuco-toluidine
blue. It was deemed that photoexcited electrons of Au–ZnO (Au,
∼5 nm) possessed high reducing power owing to electron accumulation
and negative shift in Fermi level/redox potential; however, exciton
recombination due to possible Fermi-level equilibration slowed down
the complete degradation of toluidine blue. In the case of Au@Au–ZnO
(Au, ∼15 nm), the photodegradation efficiency was enhanced
and the photoreduction rate reduced compared to Au–ZnO. Pt–Au–ZnO
hybrids showed better photodegradation and mineralization properties
compared to both Au–ZnO and Au@Au–ZnO owing to a fast
electron discharge (i.e. better electron-hole seperation). However,
photoexcited electrons lacked the reducing power for the photoreduction
of toluidine blue. The ultimate photodegradation efficiencies of Pt–Au–ZnO,
Au@Au–ZnO, and Au–ZnO were 84, 66, and 39%, respectively.
In the interest of effective metal–semiconductor type photocatalysts,
the present study points out the importance of choosing the right
metal, depending on whether a photoreduction and/or photodegradation
process is desired