Preparation Of G-C₃N₄ With Co?S,O?_x As Cocatalyst And Its Application On Photocatalytic Hydrogen Evolution

The increasingly serious energy shortage and environmental problems are becoming a serious threat to the long-term development of human society,so it is urgent to develop a kind of green and sustainable energy.Abundant solar energy resources,efficient use of solar energy resources is considered to be an effective way to solve the fossil energy crisis.Photocatalytic water decomposition technology uses semiconductor materials to directly convert solar energy into hydrogen energy,photocatalytic hydrogen evolution via water splitting has attracted a lot of attention because its combustion products do not pollute the environment and emit more heat.In 1972,Fujishima and Honda found that water can be decomposed into hydrogen on TiO₂ photoelectrode,which means that people can directly use photocatalytic material to decompose water for clean energy.However,the application of traditional photocatalytic materials represented by TiO₂ is limited because they can only absorb ultraviolet light.Therefore,the development of photocatalytic materials with high visible light response is of great significance to promote the practical application of photocatalytic materials.In recent years,in has reported a variety of H₂ production material under UV and visible light irradiation,the graphite carbon nitride?g-C₃N₄?has attracted much attention because of its unique two-dimensional graphene structure,non-toxic,the friction coefficient is small,light,heat conduction performance is good,high temperature resistance,oxidation resistance,corrosion resistance,and in visible light to produce H₂ has higher activity and stability.However,its disadvantages are small specific surface area,high recombination rate of photogenerated electrons and holes,and low quantum efficiency.Therefore,it is the focus of current research to improve the separation of photogenerated electron-hole pairs and the photodecomposition water efficiency in the visible and near-infrared regions of this material.Therefore,in this work,g-C₃N₄ is taken as the research object to explore the best experimental conditions and methods to improve the performance of g-C₃N₄ materials.The mainresearch contents are as follows:Part ?:taking thiourea as the original material,we obtained g-C₃N₄?donated by CN?by means of high-temperature polymerization.Then,CoS₂ was deposited on g-C₃N₄ by means of photochemical deposition to obtain CoS₂/CN photocatalyst with low cost and high visible light catalytic activity.In this process,CoS₂ is formed by photochemical method,which can load CoS₂ on the effective site of CN electron focusing.A series of m-CoS₂/CN?m represents the amount of cobalt acetate?photocatalysts was obtained by changing the amount of cobalt salt and thiourea.The results showed that CoS₂/CN exhibited excellent catalytic activity under visible light,and the activity was the highest when the amount of cobalt acetate was 5mg and the amount of thiourea was 15.2mg.On the one hand,compared with pure CN,CoS₂ is introduced as co-catalytic and evenly distributed on the photoelectron exit site of CN,which is conducive to electron enrichment and inhibiting photogenic electron-hole recombination.On the other hand,due to the size effect of particles,the appropriate particle size has high photocatalytic efficiency.Too large or too small size will reduce the photocatalytic efficienc.Part ?:the melamine as carbon-nitrogen source,cobalt acetate for cobalt source.The cobalt supramolecular polymer was obtained in methanol solvent,and then by high temperature calcination method to obtain CoO_x-CN nanotube structures.Then the nanotube photocatalyst of Co-CNTs was obtained by in-situ reduction method.Finally,the Co-CNTs nanotubes were treated with hydrochloric acid.In this experiment,Co as cocatalyst can effectively promote charge separation.At the same time,the tubular structure is conducive to the directional transmission of electrons,so as to improve the catalytic activity of CN.