The Preparation, Modification And Photocatalytic Performance Of Niobates And Tantalates

Environmental pollution and energy crisis were the matters in the 21 st century. In the past decades, the semiconductor catalytic properties were found to be candidate for these problems. Many efforts have been devoted to the research of semiconductor catalytic performance, while a lot of semiconductors and modified methods for the enhanced catalytic performance have been reported. The new semiconductors of niobates and tantalates have attracted much attention, because their unique electronic structure, energy band structure and stability, resulting the excellent catalytic activity on degradation of organic dyes and splitting of water. But their photocatalytic efficiency was need to further improve.In this paper, we revolved around work of “The Preparation, Modification and Photocatalytic Performance of Niobates and Tantalates”. The relevant results and the primary coverages are as following:1. The Fabrication and Photocatalytic Performance of Ag Decorated K2Nb2O6(KNO) Nanocomposites.The preparation of KNO octahedrons via one-pot solvothermal method was reported. The KNO octahedrons were prepared in the medium of water-ethanol at 230℃for hours, where the raw materials were Nb2O5, KOH, urea. The effect of water-ethanol ratio for the phase of product was investigated. And the influence for the phase and product with adding urea was also studied. It was displayed that the urea would decompose to CO2 and NH3. And these released gas had two roles: one hand, the residual content of KOH was controlled by released CO2; on the other hand, NH3 absorbed on the surface of the reactants, facilitating the formation of KNO octahedrons. What’s more, the formation mechanism of KNO was proposed based on the XRD and SEM of products at the different duration.The Ag-KNO nanocomposites were prepared by the photoreduction of Ag NO3 to Ag particles, which were deposited on the surface of KNO. The SEM、TEM、XPS characterization demonstrated that the Ag was successfully deposited on the surface of KNO. And DRS showed that light absorption of the Ag-KNO were stronger the pure KNO and the absorption band of nanocomposites were red shift. What’s more, the Ag-KNO nanocomposites showed higher photocatalytic efficiency on the degradation of Rh B under UV-vis light irradiation than pure KNO. Because that the Ag nanoparticles improved the light absorption of KNO and the separation efficiency of photoelectron-holes. Nanocomposite sample by loading 6% Ag showed the highest photocatalytic activity, which is two times than pure KNO. And the possible photocatalytic mechanism of Ag-KNO on the degradaiton of Rh B was proposed.2. The Preparation and Photocatalytic Activity of S Doped K2Ta2O6(KTO)The S-doped KTO were synthesized via one-step hydrothermal. The as-obtained samples were characterized by XRD, SEM and XPS. The results showed that the as-prepared samples were assigned to cubic lattice and the diffiraction peaks was shift caused by the introduced S, which was S2-(XPS results). And the doped samples were still octaheral. The doped S anion cuased the red shift for KTO, indicating the decrease of band gap. The as-prepared samples showed the higher photocatalytic activity than bare KTO, during the photocatalytic degradation MO under UV-vis light irradiation, while S#3 sample exhibited the highest photocatalytic efficiency. Because doped S decreased the band gap of KTO, facilitating the formation of elecron-holes. What’s more, the effect of solution p H value for the activity and reliable recycling photocatalytic degradation of MO were investigated.3. The Preparation of Ag@AgCl Decorated K2Ta2O6(KTO) and Their Photocatalytic Property Under Natural Light Irradiation.The Ag@AgCl nanoparticles were deposited on the surface of KTO via precipitationphotoreduction method. The obtained Ag@AgCl-KTO nanocomposites were characterized by XRD, SEM, TEM, XPS. The results indicated that the Ag@AgCl nanoparticles with the size of ~20nm were successfully deposited on the KTO surface. While Ag@AgCl-KTO showed higher absorption intensity in visible light region than pure KTO from DRS characterization. The degradation experiment displayed that Ag@AgCl-KTO composites exhibited the higher degradation efficiency of Rh B than pure KTO under natural light irradiation, indicating that the Ag@AgCl improved the photocatalytic performance of KTO, which was ascribed to the increase amount and separation efficiency of electron-holes by Ag@AgCl. And the possible mechanism of enhanced photocatalytic activity for Ag@AgCl-KTO was also proposed.