Yongchun Lu

Surface charge transfer properties of high-performance Ag-decorated ZnO photocatalysts

Silver-decorated ZnO (Ag/ZnO) chain-like nanoparticle aggregates were prepared by a facile nonaqueous sol–gel method. The influence of Ag decoration on the surface photo-induced charge transfer behaviour of ZnO was investigated by means of surface photovoltage spectroscopy, electric field-induced surface photovoltage spectroscopy and transient photovoltage techniques. The photovoltage spectra revealed that an electronic interaction between Ag and ZnO formed. Ag acted as electron acceptors and effectively inhibited the charge recombination in ZnO with UV light illumination, while under the illumination of visible light a redshift was observed due to the appearance of a plasmon-induced band resulting from the formation of Ag nanoparticle clusters. These were responsible for the significant enhancement in the photocatalytic activity of the Ag/ZnO sample. The results also suggested that the high-performance visible light photocatalytic activity could be manipulated by external biases.

Effect of photogenerated charge transfer on the photocatalysis in high-performance hybrid Pt-Co:ZnO nanostructure photocatalyst.

Hybrid Pt-Co:ZnO nanostructure photocatalysts were prepared via a facile two-step synthetic strategy. SPS and TPV investigations demonstrate the existence of the synergetic effect between Pt and Co dopants. Such synergetic effect could make use of visible photons as well as facilitates the separation of photogenerated charges to prevent recombination, effectively prolongating the charges lifetime to participate photocatalytic reaction. The synergetic effect exist in Pt-Co:ZnO inducing as high as 7.7-fold in photovoltaic response and 10-fold in the photo-activity for hybrids compared to Co:ZnO.

Surface photovoltage phase spectra for analysing the photogenerated charge transfer and photocatalytic activity of ZnFe2O4–TiO2 nanotube arrays

The transfer properties of the photogenerated charge carriers in TiO2 nanotube arrays (TNAs) and ZnFe2O4 modified TiO2 nanotube arrays (ZFO-TNAs) were investigated by surface photovoltage phase spectra. The modification of ZnFe2O4 on TNAs will lead to a new process of photogeneration of charge carriers. When irradiated with UV or visible light, before ZnFe2O4 modification photogenerated holes can transfer to the surface of TNAs; while after ZnFe2O4 modification, a process of photogenerated electrons transferring to the surface occurred. The different detected photogenerated charge transfer processes agree well with the photocatalytic reduction of Cr(VI) and the degradation of methyl orange experiments, which confirmed that the photogenerated holes transferring to the surface of the TNAs or ZFO-TNAs were beneficial for the reactions of photocatalytic reduction and electrons transferring to the surface were beneficial for photocatalytic degradation.