Synthesis Of New Niobate Potassium Based Materials And Photocatalytic Water Splitting Performance

The development of clean and renewable chemical fuels is widely regarded as the most promising way to reduce environmental pollution and energy-related problems.As a kind of sustainable and clean fuel,H₂ energy has been paid more attention because of its advantages of no pollution,high combustion value and renewable et.al.Photocatalytic water splitting is one of the most promising methods for the preparation of H₂.However,there are some problems in the practical application of this technology,especially the catalytic performance of photocatalysts.Therefore,various highly efficient water splitting catalysts have been developed.Potassium niobate is considered as a promising photocatalyst for H₂ production due to the adjustable band gap,long life and non-toxicity.However,the gap width of the potassium niobate is greater than 3.3 eV,which means it can only react in ultraviolet light,and the electron-hole pairs will recombine quickly.All these factors limit the photocatalytic activity of potassium niobate.In this theses,potassium niobate was modified by constructing heterojunction,element doping and surface modification to improve the photocatalytic activity.The research contents of this paper are as follows:?1?CoO/KNbO₃ p-n heterojunction photocatalysts were prepared by hydrothermal method and calcining method,and the morphology,structure and performance were analyzed by a series of characterization and test.UV-Vis diffuse reflectance spectra shows that when CoO is loaded,the light range response of CoO/KNbO₃ p-n heterojunction photocatalyst extends to the visible region,which indicates that CoO on the surface of KNbO₃ has the effect of broadening photocatalyst light absorption.The results of EIS and Mott-Schottky show that CoO/KNbO₃ p-n heterojunction has less interface resistance and higher carrier migration rate and separation efficiency than pure KNbO₃.Under the deposition of2wt%Pt as catalyst and full spectrum irradiation,and 0.1 mol?L^-1 L-Ascorbic acid solution was used as sacrifice agent,and the H₂ production of 2.0 mM-CoO/KNbO₃reached 577.44?mol?g^-1 within the test of 4 hours,which was 2.5 times of that of pure KNbO₃.Other experimental conditions remain the same,except that the illuminated light is changed to visible light??>420nm?,the H₂ production of pure KNbO₃ was almost zero,while the hydrogen production of 2.0 mM-CoO/KNbO₃reached 307.13?mol·g^-1·h^-1.?2?K_0.027Nb_0.93O₃ was prepared by hydrothermal method,and the Co₃O₄/K_0.027Nb_0.93O₃ composite catalyst material was obtained by calcining different amounts of ZIF-67/K_0.027Nb_0.93O₃ at high temperature.According to the Uv-vis diffuse reflection spectra,CO₃O₄ on the K_0.027Nb_0.93O₃ surface has the effect of broadening the photocatalyst's photoabsorption range.The EIS and mott-schottky results show that the electron migration rate increases and the charge transfer resistance decreases at the Co₃O₄/K_0.027Nb_0.93O₃ interface.In the photocatalytic system,0.1mol·L^-1 L-Ascorbic acid solution was used as the sacrificial agent,and2wt%Pt was deposited as the co-catalyst.The hydrogen production rate of Co₃O₄/K_0.027Nb_0.93O₃ modified by 0.3 mL ZIF-67 reached 717.84 mol·g^-1·h^-1,while that of pure K_0.027Nb_0.93O₃ was 213.52 mol·g^-1·h^-1.The catalytic performance of the modified catalyst was improved by 3.36 times.?3?Carbon doped potassium niobate has enhanced full spectral drive photocatalytic activity for hydrogen production from decomposed water C-KNO was prepared by simple hydrothermal method and the morphology,structure and optical properties of C-KNO were studied by means of scanning electron microscope?SEM?,transmission electron microscope?TEM?,X-ray photoelectron spectroscopy?XPS?and Uv-vis and so on.Under the simulated sunlight irradiation,0.1 mol·L^-1 L-ascorbic acid solution was used as the sacrificial agent,and 2wt%Pt was deposited to form a photocatalytic splitting water system.The hydrogen evolution rate of C-KNO reached34.22 mol·g^-1·h^-1,while that of unadulterated KNO was 18.24 mol·g^-1·h^-1.The rate of hydrogen evolution increased by about 1.9 times after doping.The results show that carbon doping can reduce the intrinsic band gap of potassium niobate,expand its light absorption range,improve the efficiency of solar energy,promote the transport of carriers,and improve its catalytic performance of H₂ production from water splitting.