| With the continuous progress of science and technology and the rapidly development of industry,the problems of energy shortage and environmental pollution have become increasingly serious.Photocatalysis technology has broad application prospects in solving energy shortage and environmental pollution due to the use of inexhaustible solar energy,economic security,and environmental friendliness.g-C3N4 photocatalyst has become a research focus in the field of photocatalysis because of its advantages such as facile preparation,cheap raw materials,high physical and chemical stability,and narrow band gap.However,the bulk g-C3N4 has the disadvantages of high photo-generated electron,hole recombination rate and low quantum efficiency,which limits its photocatalytic performances.Based on this,this dissertation aims to improve the photocatalytic performance of the catalyst by modifying g-C3N4.The specific research work are as follows:1.Preparation of high specific surface area graphitic carbon nitride nanosheets and study on photocatalytic degradation of pollutants.Using melamine and ammonium chloride as precursors,the effect of the mass ratio of ammonium chloride and melamine on the photocatalytic activity of the product was investigated.The results showed that when the mass ratio of ammonium chloride to melamine is 4:1,the prepared g-C3N4 photocatalyst has the largest specific surface area and the best photocatalytic activity.When exposed to light for 14 min,the degradation rate of RhB by g-C3N4-4 reached 99%,which was 6.97 times higher than that of g-C3N4.When exposed to light for 30 min,the degradation rate of MO by g-C3N4-4 photocatalyst reached 95.1%,which was 9.1 times over that of g-C3N4.When exposed to light for 24 min,the degradation rate of TT by g-C3N4-4photocatalyst reached 98.2%,which was 3.24 times more than that of g-C3N4.The improved performance of photocatalytic degradation of organic dyes by modified g-C3N4-4 can be attributed to the significant increase in the specific surface area of g-C3N4-4 with the addition of ammonium chloride,which provides more active sites for degradation of organic dyes.2.Preparation of Ag/g-C3N4 composite photocatalytic material and study of hydrogen production performance.The Ag/g-C3N4 composite photocatalytic material was synthesized through thermal polymerization and silver mirror reaction.A series of Ag/g-C3N4 composite photocatalysts were synthesized by adjusting the ratio of silver nitrate and g-C3N4.Through photocatalytic water splitting,it was determined that when the percentage content of silver was 5%,the photocatalytic activity of the composite photocatalyst to decompose water to produce hydrogen was the best.Its hydrogen production rate reached 568.9mmol×g-1×h-1,which is 39 times more than that of the bulk g-C3N4.The improved performance of Ag/g-C3N4 complex photocatalytic hydrogen production can be attributed to the incorporation of Ag particles into g-C3N4,which can improve the visible light absorption rate of g-C3N4 through surface plasmon effect（SPR）,and the Schottky barrier formed between g-C3N4 and Ag particles can suppresses the recombination of photo-generated carriers.3.Preparation of Ag/Ni（OH）2/g-C3N4 composite photocatalytic material and study on its hydrogen production performance.Ag/Ni（OH）2/g-C3N4 composite photocatalytic material was synthesized by thermal polymerization,hydrothermal reaction and silver mirror reaction.Photocatalytic splitting of water confirms that when the mass ratio of Ag and Ni（OH）2was 5%,the three-way composite photocatalyst has the best photocatalytic performance,and its hydrogen production rate reached 1663.2mmol×g-1×h-1,which was 114.7 times higher than that of the bulk g-C3N4.The improved photocatalytic hydrogen evolution performance of Ag/Ni（OH）2/g-C3N4 can be attributed to the key role that Ag plays in promoting the transfer of charge from g-C3N4 to p-type Ni（OH）2cocatalyst,thereby improving the catalyst Photocatalytic activity. |
