Preparation And Photocatalytic Fixation Nitrogen Activities Of Zinc Oxide And Potassium Niobate Based Photocatalysts

Ammonia?NH₃?is a�catalyst�for the development of modern military and agricultural industries.Meanwhile,it is considered as an ideal hydrogen storage fuel.Many scientists have invested a lot of effort in converting N₂ to ammonia.At present,the Haber-Bosch method is used in the industry to synthesize ammonia,which requires high temperature and high pressure,consumes a lot of energy,and produces a large amount of greenhouse gas CO₂,which should be partial responsible for the two crises of energy shortage and greenhouse effect.Scientists devote their efforts in exploring renewable energy and materials,and have developed a variety of renewable energy including solar energy.Compared with fossil fuel system,solar energy has no pollution and high efficient.Photocatalytic N₂ fixation uses the abundant solar energy as the energy sources,conversing from nitrogen to ammonia by using photocatalysts.The process is greenly,friendly,cheaply,and efficently which is the ideal process to fix nitrogen.This paper synthesized ZnO and KNbO₃ as the based materials,although these two materials have traditional adventages of wide band gap photocatalysts such as non-toxic,simple synthesis and high stability.However they can only be excited by ultraviolet light,and low energy utilization rate.We promoted the photocatalytic activity with other improved methods.We have synthesized three photocatalysts,MoS₂/C-ZnO,Ag/KNbO₃ and NiO/KNbO₃,and foced their application on photocatalytic nitrogen fixation.?1?Ternary MoS₂/C-ZnO composite was prepared via a combination of hydrothermal and photodeposition method.Zinc chloride andglucose were synthesed the C-Zn O.MoS₂/C-ZnO photocatalysts was prepared via one-step photodeposition method.Under simulated sunlight irradiation,the optimal1%MoS₂/C-ZnO-300 composite presents the fastest NH₃ generation rate of245.7?mol�g^-1�h^-1,which is 9.7 times higher than that of ZnO.The loaded carbon layer can provide good adsorption of reactants and improve the charge separation efficiency.MoS₂ shows good capability in chemisorptions and activation of N?N,which improves the acitvity of photocatalytic fixation nitrogen.?2?Ag/KNbO₃ nano composite for efficiently photocatalytic conversion of N₂ to NH₃.KNbO₃ was prepared in 4M KOH concentration solution at 260 ^oC,while Ag nanopartilces?NPs?were loaded on KNbO₃ by a photodeposition procedure.The synthesized nano composite presented excellent performance in photocatalytic N₂ fixation.Under simulated sunlight,the NH₃ generation rate reaches 385.0?mol�g^-1�h^-1,which is 4 times higher than that of pure KNbO_3.The Ag NPs'decoration further increased the surface separation of charge carriers via trapping the electrons from KNbO₃,which improves the acitvity of photocatalytic fixation nitrogen.?3?This paper synthesized NiO loaded KNbO₃ nanocomposite via photodeposition method and applied it in photocatalytic N₂fixation for the first time.The optimal NiO/KNbO₃ sample showed an NH₃-generation rate of 470.6?mol�g^-1�h^-1,which reaches 4.8 times that of pristine KNbO₃.The introduced NiO fabricated a p-n heterojunction structure with KNbO₃ and hence achieved the enhanced efficiency in separating electrons and holes via a type-II mechanism.The prepared composite was characterized by multi techniques including X-ray diffraction?XRD?,Raman,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,UV-vis diffuse reflectance spectroscopy?DRS?,N₂ adsorption,transient photocurrent response?PC?an electrochemical impedance spectroscopy?EIS?.The suggested mechanisms have been confirmed by those analyses methods.