Microstructural Control,Photocatalytic Performance And Mechanism Of Oxyasalt/Organic Semiconductor Catalysts

According to the increased energy shortage and climate change,it is an urgent to develop new alternative and environmentally friendly energies.Photocatalytic hydrogen production provides a clean and sustainable way for transferring solar energy.Therefore,the development of new photocatalytic materials with high activity and stability for hydrogen production has been one of the research focuses in recent years.In this paper,potassium niobate(K₄Nb₆O₁₇),cadmium molybdate（CdMoO₄）and graphite-phase carbon nitride（g-C₃N₄）were taken as the research objects,and their microstructures,photocatalytic hydrogen production and mechanisms were investigated in detail.The main research contents are as follows:1.A novel and highly active photocatalytic materials,self-doped potassium niobate composite microflowers stimulated by noble-metal-free copper nanoparticles(Cu/K₄Nb₆O₁₇),was achieved.Composition and structure of the composite microflowers were characterized by X-ray diffraction（XRD）,high resolution transmission electron microscope（HRTEM）,and X-ray photoelectron spectroscopy（XPS）.The results showed that Cu nanoparticles were evenly and closely loaded onto the flower slices of the composite microflowers.As testified by XPS,electrochemical impedance spectrum and fluorescence spectrum,the presence of Cu in K₄Nb₆O₁₇ microflowers quickened the self-doping of Nb⁴⁺,enhanced light absorption and the unsaturated defects as active sites,and improved separation efficiency of electron/hole pairs,which led to excellent photocatalytic activity for hydrogen evolution over the composite microflowers.Subsequently,the optimal hydrogen generation rate for the composite microflowers was about 9 times higher than that of pure K₄Nb₆O₁₇ microflowers under same conditions.Moreover,the composite photocatalyst was stable and easy to be recycled.The results demonstrated that the construction of the special heterojunction by facile interfacial modification is a promising strategy to efficiently enhance photocatalytic performance of semiconductor photocatalysts.2.A novel self-adjusting structure of pompoms-like cadmium molybdate composite（Cu-CdMoO₄）stimulated by copper ions was achieved by one-step hydrothermal synthesis.It was found that the composition and morphology of the CdMoO₄ were affected greatly by the introduced Cu.The photocatalytic activity experiment indicated that the photocatalytic property of CdMoO₄ samples was strongly dependent on their morphologies and microstructures,and the pompoms-like Cu-CdMoO₄ composite exhibited a higher photocatalytic activity in the photocatalytic hydrogen evolution than pure CdMoO₄,which indicated the vital role of the Cu in the composite.The optimal hydrogen generation amount for the pompoms-like Cu-CdMoO₄ composite was about 77.4 times higher than that of pure CdMoO₄ under the same conditions.The significantly improved photocatalytic activity is associated with wider light response,and more active sites and effective separation of photogenerated charges over the Cu-CdMoO₄ composite.Due to simple one-step synthesis,uniform composition and phase,and the convenience of morphology and size controlling,the present work could afford some guidance for the rationally controllable synthesis of other photocatalytic materials.3.A novel graphite-phase carbon nitride/porphyrin nanocomposite（g-C₃N₄-Cu-TCPP）was fabricated by noncovalent interaction using Cu as interfacial linker,TCPP as visible light absorption antenna and g-C₃N₄ as carrier,which effectively enhanced the spectral absorption of organic semiconductors.The composition,structure and morphology of the composites were characterized by transmission electron microscopy（TEM）,XPS,XRD and infrared spectroscopy.The results showed that Cu nanoparticles were introduced in the interface of g-C₃N₄ and TCPPs can facilely regulate the morphology and structure of g-C₃N₄-TCPP composites.More importantly,with the introduction of Cu,the interaction between TCPP and g-C₃N₄ was strengthened,thus electron transfer between g-C₃N₄ and TCPP was effectively promoted.Subsequently,the activity of photocatalytic hydrogen production has been greatly improved.This study provides a theoretical and experimental basis for the facile construction of nanocomposite catalysts with high photocatalytic hydrogen production and mechanism of interfacial photo-producedelectron transfer.