Preparation And Properties Of Heterojunction Photocatalyst For Polyoxoniobate/graphite Phase Carbon Material

Polyoxometalate(Referred to as POM)are oxygen-containing ions of transition metals with d0 electron configuration,which are well structured and nanometer sized metal-oxygen clusters.Due to their unique molecular structure,composition,oxidation reducibility and band structure tunability,POM have attracted extensive attention from researchers.Polyoxoniobate is an important branch of photocatalysis in POM materials.In terms of the design of polyoxoniobate catalyst,the functionalization strategy is realized by combining with graphite phase carbon material,which improves the specific surface area of the material,exposes a large number of active sites,effectively inhibits electron-hole composite,and improves the photocatalytic activity.In this paper,Lindqvist polyoxoniobate[Nb6O19]8-was combined with g-C3N4 and RGO for the first time,and the noble metal-free photocatalyst was prepared through micromorphological regulation,and the performance test of photodegradation tetracycline and photodegraded aquatic production H2 was carried out,the specific content is as follows:1.Using a simple hydrothermal method,a novel "honeycomb" ultrathin nanometer sheet photocatalyst was prepared from[Nb6O19]8-and graphite carbon nitride(g-C3N4)as raw materials.Under UV-visible light irradiation,the degradation rate of Nb-CN-0.4 to tetracycline solution reached 81.34%within 30 min.The degradation mechanism of polyoxoniobate/carbon nitride heterojunction photocatalyst was confirmed by a series of characterization,capture experiments and stability tests.2.Using[Nb6O19]8-and graphite oxide(GO)as precursors,GO was reduced to RGO in the process of solvothermal reaction by simple solvothermal method,while[Nb6O19]8-was grown in situ on the surface of RGO to form two-dimensional nanosheets.Nb-RGO-0.5 can reach 68.12%for 30 mg/L tetracycline solution within 60 min driven by visible light.The degradation mechanism of polyoxoniobate/graphene heterojunction photocatalyst and the intermediate products of photocatalytic oxidation were discussed based on the analysis of experimental and characterization results.3.At present,most of the POM photocatalysts used for hydrogen production are single crystal compounds with low yield and the need to use precious metals as co-catalysts.The polyoxoniobate composite photocatalyst prepared in this paper shows excellent hydrogen production performance without noble metal assisted catalysis.The hydrogen production rate of Nb-RGO-0.625 reached 49.35 ?mol/g/h,and that of Nb-CN-0.4 reached 359.89 ?mol/g/h,which was better than the photocatalytic activity of polyoxoniobate reported in most literatures.The reason is that the composite photocatalyst formed a compact interface,which is helpful for electron hole separation and photocatalytic activity improvement.The heterojunction photocatalyst was successfully prepared by the combination of polyoxoniobate and graphite phase carbon.It is hoped that this work will provide ideas for the design of heterojunction photocatalyst of other POM and two-dimensional materials.