Study On A New Preparation Method Of G-C₃N₄-based Composites And Their Photocatalytic Properties

g-C3N4-based composites have improved photo-electrical properties and many methods have been developed for the preparation of g-C3N4-based composites,such as mixing calcination method,hydrothermal method,microwave-assisted method and deposited calcination method.However,these methods suffered from some shortcomings,including the uneven distribution of the reinforcement material and the matrix,the non-close structure of the heterojunction,weaker interaction.In order to obtain a g-C3N4-based composite with a stable homogeneous,heterostructures which are with close and high performance composite materials,it is of great significance to develop a new method of synthesizing g-C3N4-based composites.In this paper,a novel preparation method was developed,in which a single source precursor containing melamine and metal acid ion was firstly prepared,and then calcined to achieve a g-C3N4-metal oxide composite.The details are as follows:(1)g-C3N4/MoOx was successfully prepared by calcining the single-source precursor melamine molybdate.The precursor of the[C3(NH2)2NH3]8Mo8O28 precursor was successfully prepared and the g-C3N4/MoOx composite was synthesized by calcining the precursor.Experimental results show that,Mo enters the layer of g-C3N4 in the form of MoOx.The morphology of the sample is loose and porous.Compared with the pure g-C3N4,the samples prepared by our method have excellent photocatalytic performance for the degradation of MO,and have a certain cycle stability and acid resistance.The electrons are more likely to be excited under visible light.Sample has excellent electron-hole separation/transfer ability.The experimental results show the feasibility and superiority of the new method.(2)([C3(NH2)2NH3]22W12O47)precursor was prepared by the combination of anions and cations,g-C3N4/WO3 was successfully obtained by calcining the single source precursor.The experimental results show that WO3 is embedded in the g-C3N4 layered structure in fine granular form,and they are closly contacted.The sample is loose and porous and has excellent visible light response ability.The BET measurements prove that W-CN-5 has higher specific surface area than that of pure g-C3N4.Compared with pure phase g-C3N4,the photocatalytic activity of MO was improved.The photodegradation efficiency of MO in W-CN-5 catalyst sample was employed to 93%within 120 min.Thus,single-source precursor-could be a effective method for the preparation of g-C3N4 based heterostructures.(3)g-C3N4/ZnAl2O4 was prepared by sedimentationcalcination.ZnAl2O4 deposited on the surface of g-C3N4 and formed a heterojunction,which improves the electron-hole separation and transferability of g-C3N4.It is effectively involved in the catalytic degradation of MO process.In summary,a new strategy for the preparation of g-C3N4-based heterostructures has been developed and it was successfully applied to achieve g-C3N4/MoOx and g-C3Na4/WO3.These products possess closely heterogeneous structure,uniform distribution and excellent photocatalytic performance by calcining single-source precursor.This study open a new way for the preparation of heterostructures with desirable properties.