Construction Of Visible Light Responsive Nanomaterials Based On G-C₃N₅ And Their Photocatalytic Properties

With the rapid growth of population and social economy,energy shortage and environmental pollution have become a major problem hindering economic development.Among them,the consumption of energy such as oil,coal and natural gas is increasing year by year,and the large-scale burning of fossil energy will emit the greenhouse gas CO₂,which will lead to the global greenhouse effect,and the development of new renewable energy has become a major strategy.In addition,dye compounds are often used in industries such as textiles,dyes,food,leather and paper making.These dye compounds are carcinogenic to human body,irritating to skin,and damaging to eyes.It will pollute the ecological environment and enter bioaccumulation through the ecological cycle,posing a threat to human health.Faced with the problems of global environmental pollution and energy crisis,people are committed to developing high-efficiency photocatalysts,using photocatalytic processes to convert solar energy.Solar energy is a green,environmentally friendly and sustainable energy source,and it is a promising technology to use solar energy to hydrogen evolution and purify water through photocatalysis.Carbon nitride（g-C₃N₅）has been studied and applied in the field of photocatalysis because of its suitable band gap,stable structure and rich basic nitrogen.In this paper,three visible light nanomaterial catalysts were constructed based on g-C₃N₅.Scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,high-resolution transmission electron microscopy（HRTEM）,N₂ physical adsorption-desorption,X-ray powder diffraction（XRD）.The morphology and structure of the materials were characterized by characterization methods such as,Fourier transform infrared spectroscopy（FT-IR）and X-ray photoelectron spectroscopy（XPS）.Photoluminescence spectroscopy（PL）and time-resolved photoluminescence spectroscopy（TRPL）were used to study the optical properties of the prepared catalysts,to explore the structure-activity relationship between the structure and optical properties of the catalysts.The prepared photocatalyst was used for photocatalytic degradation of Rhodamine B（RhB）,methylene blue（MB）,methyl orange（MO）and hydrogen evolution,and to explore the possible photocatalytic mechanism of the prepared catalysts.This paper has carried out the following work:1.A photocatalyst with large specific surface area was constructed based on g-C₃N₅.In this work,3-amino-1,2,4-triazole（3-AT）was used as g-C₃N₅ precursor and peanut oil was used as carbon（C）precursor.The experimental conditions of pyrolysis temperature and carbon activation temperature were optimized first,and then a series of different g-C₃N₅/C catalysts were prepared by optimizing different C content.It is found that the prepared g-C₃N₅/C catalyst has a pyrolysis temperature of 600℃,a carbon activation temperature of 550℃,and when the content of 3-AT and peanut oil is 6:1.0,the specific surface area of g-C₃N₅/C-1.0 is 60 m2/g.Using g-C₃N₅/C-1.0 for photocatalytic water splitting to produce hydrogen,chloroplatinic acid（H₂PtCl₆）as cocatalyst,triethanolamine（TEOA）as oxidation sacrificial agent,under visible light irradiation,the hydrogen evolution rate is 303.3 μmol/（g·h）It was used for photocatalytic degradation of organic pollutants,with Rhodamine B（RhB）as the target pollutant,and the degradation rate of RhB reached 96% after 150 min of visible light irradiation,and showed good stability in the cycle experiment.2.g-C₃N₅ and CeO₂ were used to construct a Ⅱ-type heterojunction composite.Using 3-AT as g-C₃N₅ precursor and Ce（NO₃）₃·6H₂O as CeO₂ precursor,a series of different CeO₂/g-C₃N₅ catalysts were prepared by optimizing the content of CeO₂ and the calcination temperature.The results show that the photocatalytic performance of the prepared CeO₂/g-C₃N₅ was the best when the mass fraction of CeO₂ was 10% and the calcination temperature was 400℃.When 10 wt% CeO₂/g-C₃N₅-400 was used to degrade different dye compounds,such as rhodamine B（RhB）,methylene blue（MB）and methyl orange（MO）,the degradation rates of RhB and MB were 71% and 99%,respectively,after visible light irradiation for 150 min.Moreover,the degradation rates of RhB showed good stability in the cycle experiment.3.The noble metal Ag was added to construct a highly efficient Z-scheme heterojunction Ag-CeO₂/g-C₃N₅ composite.In this work,3-AT was used as g-C₃N₅ precursor,Ce（NO₃）₃·6H₂O was used as CeO₂ precursor,and silver nitrate（Ag NO3）was used as Ag precursor.Spherical,rod-shaped,sheet-shaped and cubic Ag-CeO₂ were first prepared,and then recombined with g-C₃N₅,and then the Ag and Ag-CeO₂ contents were optimized to obtain a series of different Ag-CeO₂/g-C₃N₅ catalysts.It is found that when the morphology is spherical,the molar ratio of Ag to CeO₂ is 6:1.50,and the mass fraction of Ag-CeO₂ is 50 wt%,it exhibits the best photocatalytic performance.When 50 wt% Ag（1.50）-CeO₂/g-C₃N₅ was used to degrade different dye compounds,such as RhB,MB and MO respectively,the degradation rates were 96%,100% and 87%,after visible light irradiation for 150 min.Moreover,the degradation rates of RhB showed good stability in the cycle experiment.