Preparation And Photocatalytic Properties Of Cu-plated Hollow Glass Microspheres

As a kind of inorganic non-metallic materials with particle size of ten to several hundred micrometers, hollow glass microspheres(HGMs) have a lot of advantages, such as good chemical stability, large surface area, lightweight and inexpensive price. In this paper, copper nanoparticles were designed to be plated on the surface of HGMs by electroless plating technique and their p hotocatatlytic activities for hydrogen production and photodegradation have been investigated.Since the low chemical activity of the surface of hollow glass microspheres, before plating, the pretreatment including sodium hydroxide and ammonia solution of silver for HGMs are required to form active catalytic centers on its surface and to trigger the electroless plating reaction. The reaction solution was composed of copper sulfate pentahydrate(20.0g/L), potassium sodium tartrate(14.0 g/L) and edetate disodium(25.0g/L). During the plating process, formaldehyde(25.0 ml/L) was added into the bath as a reducing agent. Therefore, the preparation of Cu-plated hollow glass microspheres was accomplished. By changing the mass of copper sulfate pentahydrate(0g / L, 0.2g / L, 2g / L, 10 g / L, 20 g / L and 30 g / L),we could obtain different copper content of hollow glass microspheres(HGM0, HGM0. 2, HGM2, HGM10, HGM20 and HGM30). The composition and microstructure of the products were characterized by X-ray diffraction, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and the results show that the surface of the HGMs were plated of nano-scale copper. Their UV-visible spectrum, photoluminescence spectrum and the photoelectric response spectrum were analyzed. At last, their photocatalytic properties(including photocatalytic hydrogen production and photocatalytic degradation) were studied.In the research of photocatalytic hydrogen production, by changing sacrificial agent, we select the best sacrificial agent: lactic acid. Furthermore, the photocatalytic hydrogen production efficiency of different copper content of HGMs was determinate under these conditions. The results indicate that when the bath of copper sulfate pentahydrate content was 2g/L, the maximum amount of hydrogen(HGM2) reached 3845μmol/g?h with good stability. Further analysis showed that the reason is that the particle size of the plated copper is small and distributed evenly on the surface of the HGMsThe photocatalytic hydrogen production of the same quality including HGM2, nano-copper(50nm) and cuprous oxide were compared under the same conditions and found the highest hydrogen yield was HGM2. The existence of HGMs can effectively prevent the reunion of Cu nanoparticles and increase the contact area, improving the efficiency of photocatalytic hydrogen production. Finally, the photocatalytic hydrogen production of HGMs without sacrificing agent were researched and the results show that the maximum amount of hydrogen(HGM2) was 55μmol/g?h. The presence of the sacrificial agent may consume the hole generated in the process of photocatalytic reaction substantial so that the hydrogen production increased.In the study of photocatalytic degradation of methyl orange, we select the optimal concentration of methyl orange solution. In this condition, HGM2 still exhibit the best degradation rate which reached to 95.75%. The HGM2 was reused after washing, separated and recovered after the reaction for three times, the degradation rate was 95.12%, 84.23%, 79.57%.Finally, the mechanism of copper glass beads photocatalytic hydrogen production was discussed. Specifically, under the UV- vis, the surface plasmon resonance of the plated copper nanoparticles generated photo-generated electrons and holes, and then the proton in the solution accepted electrons to hydrogen.