| The planar structure of the two-dimensional(2D)polymer g-C3N4 semiconductor photocatalyst consists of triazine units,and the bonding between layers is a weak van der Waals force,so this type of structure is easier to peel off than graphene.g-C3N4 has the following advantages.First,it has a narrow band gap(Eg=2.73eV at room temperature),so it has a good response to visible light.The second is that on the g-C3N4 plane,more superoxide radical active sites can be generated under light excitation,and they participate in redox reactions and show higher photodegradation and hydrogen production capab:ilities.Third,the preparation process is simple,and there are many materials to choose from for preparing the precursor,such as melamine,urea,thiourea,etc.,which are all low-cost materials and have no special requirements for preparation.However,the catalytic performance of a single g-C3N4 as a semiconductor photocatalyst is restricted by many factors,such as high electron-hole recombination rate,low specific surface area,low crystallinity,and slow charge transport speed.Combining g-C3N4 with other efficient and compatible catalysts to form a composite structure is conducive to further enhancing the visible light absorption rate and increasing the specific surface area.At the same time,increasing the specific surface area will increase the number of active sites on the catalyst surface and improve the stability of the composite.The characteristics of reducing the electron-hole recombination rate and increasing the service life can greatly improve the photocatalytic performance of g-C3N4,and provide a new way to build a new catalyst composite.The main research contents and results are as follows:1.Based on a simple hydrothermal synthesis and ultrasonic chemical loading,a sandwich structure including g-C3N4 and MoS2 nanolayers were constructed with acetylene black(AB)as a bridge.Loading 1%AB on 2D g-C3N4/(x%)Mo S2 can not only accelerate charge transfer,but also reduce the electron-hole recombination rate,thereby improving the photocatalytic efficiency per unit time.Studies have shown that the degradation rate of ternary g-C3N4/AB/3.1%MoS2 catalytic materials for methyl blue within 130 minutes can reach 94.29%,which is significantly higher than pure g-C3N4(80%)or MoS2(51.74%).The ternary heterogeneous catalyst achieves the complementary characteristics between materials,broadens the photocatalytic performance,accelerates the degradation rate of pollutants,and provides a feasible solution for environmental friendliness.2.Using g-C3N4 as the substrate combining with sulfide MoS2/SnS2 to form a two-dimensional sheet-stacked ternary composite by hydrothermal method,the three-layer sheet-shaped composite fully increases the surface area and surface active sites.Structural characterization shows that the three catalytic materials can be effectively compounded together.Thanks to the matched energy level structure and complementary advantages of the three materials,the composites show superior photocatalytic performance in the degradation of organics.In the ternary compound g-C3N4/SnS2/MoS2,when SnS2/MoS2 accounts for 20%,the photocatalytic performance is far better than that of a single C3N4,SnS2,MoS2 and any of their binary structures.It shows that only 60min of visible light irradiation can achieve 100%degradation of organic pollutants.The above research shows that g-C3N4 as a star photocatalytic material has shortcomings such as high electron-hole recombination rate,small specific surface area,and low visible light absorption.Combining it with non-metallic simple substance and metal sulfide forms an effective low-dimensional heterostructure,which increases the specific surface area and accelerates photo-generated electron-hole separation through morphological control,which greatly improves the photocatalytic performance index of the system.It has very important application value in the fields of semiconductor sensors,optoelectronic devices and energy storage components in the future. |
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