Aiming at reducing the recombination of photo-induced carriers in semiconductor photocatalytic process, we prepared TiO2 thin film with its surface modified by a connected Cu micro-grid via a microsphere lithography strategy, which showed higher photocatalytic activity than the pure TiO2 film. The improvement of photocatalytic activity of Cu micro-grid to the TiO2 film is due to the charge carrier separation and electron transfer by the conducting metal grid. The photocatalytic activity was improved as metal loading increased, which obtained the best performance at a certain loading amount, and then decreased at higher loading amount. This phenomenon was attributed to the metal’s bulk effect which could be explained by the relationship between the energetic positions and the metal cluster size.
ZHU HaiLing1, ZHANG JunYing1, WANG TianMin1, WANG LiuGang1, LAN Xiang1 & HUANG BaiBiao2 1 School of Science, Beihang University, Beijing 100191, China
The N-doping effects on the electronic properties of Cu2O crystals are investigated using density functional theory.The calculated results show that N-doped Cu2O with or without oxygen vacancy exhibits different modifications of electronic band structure.In N anion-doped Cu2O,some N 2p states overlap and mix with the O2p valence band,leading to a slight narrowing of band gap compared with the undoped Cu2O.However,it is found that the coexistence of both N impurity and oxygen vacancy contributes to band gap widening which may account for the experimentally observed optical band gap widening by N doping.
A layer of zinc oxide(ZnO)micro-grid was deposited on the surface of ZnO film using the DC reactive magnetron sputtering method and the micro-sphere lithography technique on glass substrates.Samples of this layer were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),atomic force microscopy(AFM),and ultraviolet-visible light spectroscopy.X-ray diffraction showed the high crystallinity of ZnO film and the regular arrangement of the micro-grid.The microgrid ZnO has a lower specular reflection and a higher diffuse reflection,allowing incident light to reflect two or three times to enhance the usage of light.Photocatalytic degradation experiments on methylene blue using both ZnO micro-grid and ordinary film showed that the ZnO micro-grid has better photocatalytic properties than ordinary film.The ZnO micro-grid enhanced the photocatalytic efficiency of ZnO film by 28%with a degradation time of 300 min.
Chunzhi LIWenwen WANGJunying ZHANGHailing ZHUWeiwei ZHANGTianmin WANG
The adsorptions of CO and O2 molecules individually on the stoichiometric Cu-terminated Cu2O(111) surface are investigated by first-principles calculations on the basis of the density functional theory.The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of -1.69 eV,whereas the O2 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cu1 site,and has an adsorption energy of -1.97 eV.From the analysis of density of states,it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate.The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption,and overlaps substantially with bands of the adsorbed CO molecule.There is a broadening of the 2π orbital of the O2 molecule because of its overlapping with the Cu 3d orbital,indicating that strong 3d-2π interactions are involved in the chemisorption of the O2 molecule on the surface.
