Preparation And Structure Control Of Metal And Metal Oxide Catalytic Materials Based On Amorphous Alloys

Nowadays,photocatalytic and sonocatalytic techniques have been the most popular approach used for the dye degradation.Not only are they green and energy-saving,but also efficient and practical.Active radicals produced in these processes can effectively degrade organic dyes owing to their strong oxidizing.In order to obtain high efficient photocatalytic and sonocatalytic materials,various kinds of synthetic methods have been developed,e.g.,hydrothermal,co-precipitation,sol-gel,microwave,electrospinning,et al.Unfortunately,these methods not only involve the use of sophisticated equipments,but also contain rigorous experimental conditions and complex procedures.In view of this,the preparation methods of catalytic materials based on amorphous alloys were proposed in this paper?dealloying and self-propagating combustion?,and metal oxide photocatalytic materials and nanoporous copper sonocatalytic materials were fabricated by using the precursors of Cu-based amorphous ribbons.By controlling the microstructures,the catalytic activities of the synthesized products were improved,which can be investigated by decomposing the dyes of rhodamine B?RhB?and methyl orange?MO?.The details and corresponding experimental results are showed as follows:Nano-TiO₂ photocatalytic materials were prepared by dealloying Cu-Ti amorphous ribbons in the corrosion system of nitric acid?HNO₃?.The microstructure and catalytic activity of the corrosion products of Cu₇₀Ti₃₀ amorphous ribbons can be tuned by the addition of surface active agent in the corrosion process,the active element substitution in amorphous alloys and heat treatment for corrosion products.The results showed that the addition of surface active agent?K₂SO₄?extended the preparation period of nano-TiO₂,thus achieving the goals of crystal structure control of TiO₂.However,the photocatalytic activity of nano-TiO₂ was not improved by this method.By contrast,the active element?Y?substitution not only shortened the preparation period of nano-TiO₂,but also refined its microstructure and improved the photocatalytic activity.Besides the preparation of nano-TiO₂,SnO₂-TiO₂ solid solution and composites were fabricated by dealloying Cu₆₀Ti₃₀Sn₁₀0 amorphous ribbons in nitric acid solution.The rutile TiO₂/Sn_0.42Ti_0.58O₂ exhibited enhanced photodegradation activity towards RhB compared to rutile TiO₂ and Sn_0.42Ti_0.58O₂.The p-CuO/n-CeO₂ heterojunction photocatalyst was synthesized through a self-propagating combustion technique based on Cu-Ce amorphous ribbons.The results showed that the sample was composed of well-dispersed blocky-shaped particles of size approximately 20 nm-2?m.Owing to the formation of p-n heterojunction and the synergistic effect of the semiconductors,the CuO/CeO₂exhibited significantly enhanced photocatalytic degradation activity compared with pure CuO and CeO₂.The reaction rate constant of CuO/CeO₂ is 0.18 min^-1,which is much higher than those of CuO(0.12 min^-1)and CeO₂(0.10 min^-1).Nanoporous copper?NPC?was fabricated by dealloying Cu-Ce/Cu-Y amorphous ribbons in the corrosion system of sulphuric acid?H₂SO₄?.The results showed that the ligament sizes of NPC can be tuned by changing alloy composition,acid concentration,reaction temperature and immersion time.Among them,the ligament sizes of NPC prepared by dealloying Cu-Ce amorphous ribbons are from 107 nm to 438 nm,while those of NPC synthesized by dealloying Cu-Y amorphous ribbons are between 137 nm and 327 nm.In view of the facts that the growth of the ligaments is caused by the surface diffusion of Cu atoms in solid-liquid interface,the relationships between dealloying conditions?reaction temperature and leaching time?and ligament size of NPC can be described by the surface diffusion controlled isothermal grain growth model,which provides experimental foundation and theoretical basis for the optimization of the morphology of NPC.Because of the unique 3D nanoporous structure,NPC has been successfully applied in the sono-catalytic degradation of MO.Among them,NPC with higher dispersion and smaller ligament size exhibited more excellent sono-catalytic performance owing to larger specific surface area and higher total pore volume,which provides more nucleus and diffusion paths for cavitation bubbles and hydroxyl radicals,respectively.Besides the synthesis of NPC,fcc Cu-Ag nanoporous material was prepared by dealloying Cu₇₀Y₂₈Ag₂ amorphous ribbons.The ligament size of nanoporous fcc Cu-Ag is several orders of magnitude smaller than that of NPC fabricated by dealloying Cu₇₂Y₂₈,thus suggesting that the ligaments of the nanoporous material have been significantly refined by the substitution of Ag atoms for Cu.