Properties Of The Noble Metal Modified ZnO Composites

One of the main problems of the semiconductor photooxidation is how to enhance the photocatalytic activity, the quantum yield and the photocatalytic reaction rate of the semiconductor. Originally, one efficient way was to deposit the noble metals such as Ag, Au, Pt, and Pd on the surface of the semiconductor, which could separate the electrons and holes. In this paper, the noble metal (Au, Ag, Pt, Pd) modified ZnO were prepared through a facile one-pot hydro- and alcohol- thermal method. The photocatalytic performance for the degradation of rhodamine B was evaluated. At the same time, the relationship between the electron structure and surface structrue of the samples was also evaluated with their optical properties. Our study may give some ideas on the research of the semiconductor photocatalyst and the semiconductor device. The following are the results of the research:1. Ag/ZnO composites were prepared by a simple hydrothermal approach. The addition of AgNO3 to the reaction system reduces the concentration of vacancies and surface hydroxyl of ZnO. The photocatalytic activity of Ag/ZnO was tested with the photocatalytic degradation of rhodamine B and the results indicated that the influence of the structure of ZnO on the photocatalytic activity could be neglected comparing with that of deposition of Ag on the surface of ZnO.2. Pd/ZnO samples with various palladium contents were prepared through the hydrothermal method. The results demonstrate that partial Pd loads on the surface and that the rest is doped in the lattice of ZnO. It is found that the modification of palladium not only modulates the electronic structure of ZnO but also affects the amount of surface hydroxyl. The former determines the optical properties of Pd/ZnO, leading to the shift of absorption and PL peaks, while the latter influences the photocatalytic activity of the samples. The modification of palladium at the optimal value (4.07 at.% Pd/ZnO) not only promotes the separation of photogenerated electron-hole pairs but also increases the amount of the surface hydroxyl resulting in the promotion of photodegradation efficiency.3. M(Au, Ag, Pt)/ZnO samples with various metal contents were prepared through the alcohol thermal method. The photocatalytic activity of M(Au, Ag, Pt)/ZnO was tested with the photocatalytic degradation of rhodamine B. The results demonstrate that the noble metal could enhance the photocatalytic performance, and they all have an optimal value (0.00014 wt.% Au/ZnO,2.59 wt.% Ag/ZnO and 0.46 wt.% Pt/ZnO). At the same time, when the ZnO was modified with different optimal value of different noble metals, their degradation rates are different. The photocatalytic performance of 0.46 wt.% Pt/ZnO is the best.