Modification And Enhanced Photocatalytic Performance Of Visible-light-responsive Nitride Carbon Photocatalytic Material

The environmental pollution and energy exhaustion are the two important aspects that restrict the sustainable development of human beings.Photodegradation of organic pollutants and photocatalytic hydrogen production based on photocatalysts are considered to be the effective ways for environmental pollution treatment and renewable energy production,which has become a research hotspot in recent years.Graphite-carbon nitride?g-C₃N₄?,which is considered a novel type of visible light responsive photocatalyst,exhibits advantages including excellent chemical stability,thermal stability,nontoxicity and rich raw materials.However,the bulk g-C₃N₄ has small surface area,low visible light utilization rate and easy recombination of photogenerated carriers,resulting in lower photocatalytic activity.Herein,three strategies are proposed in this thesis to modify the physicochemical properties of g-C₃N₄for the enhancement of photocatalytic activity of g-C₃N₄ photocatalysts.The main research achivements have been made as follows.1.Microwave irradiation treatment was performed to increase the hydroxyl content of g-C₃N₄ materials.The effect of microwave irradiation on the structure,morphology,chemical composition and photoelectric properties of g-C₃N₄ was obtained by microwave irradiation treatment of g-C₃N₄ dispersed uniformly in ethanol,and RhB solution was used to simulate organic pollutants to investigate the photodegradation performance of g-C₃N₄ samples.The results show that microwave irradiation can improve the hydroxyl content on the surface of the material,thus trapping more photoreceptic holes to form hydroxyl radicals,and effectively limiting the recombination of photogenic carriers.At the same time,microwave irradiation results in the increase of-OH group on the hydrophilic surface,and also enhances the hydrophilicity of the g-C₃N₄ materials,making it easier to adsorb more organic molecules,thus improving the photocatalytic activity.2.The carbon vacancy caused by magnesium reduction g-C₃N₄ increased the spectrum of visible light response.The carbon vacancy caused by magnesium reduction g-C₃N₄ increased the spectrum of visible light response.The structure,morphology,chemical composition,photoelectric properties and photocatalytic hydrogen production of initial g-C₃N₄ and carbon-vacancy containing g-C₃N₄ materials were studied.The experimental results show that the formation of carbon vacancy can enhance the absorption of visible light and improve the photocatalytic activity of g-C₃N₄ materials effectively.3.The construction of g-C₃N₄-Si heterojunction improved the separation efficiency of photogenerated carriers.Si nanosheets was obtained by acid etching CaSi₂ method,and then combined with g-C₃N₄ to construct the g-C₃N₄-Si heterostructure.By comparing the structure features,chemical composition and optoelectronic properties of g-C₃N₄ and g-C₃N₄-Si,it was found that the heterojunction formed between the interface of g-C₃N₄ and Si nanosheets can improve the separation efficiency of photogenerated electron-hole and thus enhance the photocatalytic activity.