Preparation Of Modified G-C₃N₄ Photocatalyst And Research On Its Hydrogen Production Performance

Semiconductor photocatalysts can catalyze the decomposition of water to produce hydrogen under visible light,and can convert low-energy-density solar energy into high-energy-density hydrogen energy.This is considered to be an effective way to solve the energy crisis.Therefore,the core problem of photocatalysis technology is the development of an efficient,stable and low-cost photocatalyst.Graphite carbon nitride（g-C₃N₄）has a wide range of applications in the field of photocatalysis due to its visible light response,excellent stability,abundant active sites and low preparation cost.However,ordinary g-C₃N₄ has the disadvantages of severe photo-generated carrier recombination,small absorption range of the visible light spectrum and low photocatalytic activity,which limits the application of g-C₃N₄.The photocatalytic activity can be improved to a certain extent by means of doping and semiconductor recombination.This thesis is devoted to the use of cheap and easily available modified materials and a simpler method to modify g-C₃N₄ to improve the charge separation and transport efficiency of the g-C₃N₄ photocatalyst,inhibit the recombination of photogenerated carriers,and expand in the light response range.Preparing a g-C₃N₄-based photocatalytic material with high-efficiency hydrogen production performance,and the main research contents are as follows:1.The g-C₃N₄ precursor was prepared by using acetylacetone as the modifier,and then directly calcined in a muffle furnace to obtain acetylacetone-modified g-C₃N₄.The study found that after using acetylacetone to modify the precursor,the light absorption performance of the obtained g-C₃N₄ was enhanced,and the band gap value of the catalyst was reduced.This reduces the recombination efficiency of photo-generated carriers and improves the performance of the catalyst.The photocatalytic performance of the catalyst was evaluated by the photocatalytic hydrogen production experiment.The results showed that the photocatalytic hydrogen production efficiency of the optimal sample could reach 199.84μmol g^-1h^-1,which was 1.85 times that of unmodified g-C₃N₄.2.The g-C₃N₄ was prepared by directly calcining melamine,then Fe was doped into g-C₃N₄,and the second calcination was carried out.The specific surface area of the obtained g-C₃N₄ has been greatly increased,reaching a maximum of 117.37 m² g^-1,which is about 3.4times that of unmodified g-C₃N₄(34.45 m² g^-1).The situation of serious stacking has been improved,and the energy band structure has been changed.The separation efficiency of photogenerated electrons and holes in g-C₃N₄ is increased.The photocatalytic hydrogen production rate of the catalyst under visible light is as high as 385.44μmol g^-1h^-1,which is about 3.2 times that of unmodified g-C₃N₄.The photocatalytic hydrogen production mechanism of the catalyst is proposed.