Preparation And Photocatalytic Properties Of G-C₃N₄ Nanocomposites

In response to the global energy crisis and environmental pollution,visible-light-induced semiconductor photocatalysts have become sustainable development technologies to solve these two most important challenges.Therefore,the development of efficient visible photocatalyst has become a hot topic.Since g-C₃N₄is first reported in photocatalytic decomposition of water for hydrogen production,this material has attracted great attention and has been widely studied in photocatalytic applications.For the purpose of further improving the photocatalytic activity of g-C₃N₄,researchers have developed many methods and greatly enhanced their photocatalytic activity,such as ion doping,heterojunction construction and cocatalyst can effectively improve the photocatalytic performance of the catalyst.In this paper,firstly,the two-dimensional porous nanosheets g-C₃N₄（PCN）is prepared by using NH₄Cl as a gas template and the effect of gas template on its photocatalytic performance is investigated.Secondly,the ZCS/PCN heterojunction is constructed by in-situ solvothermal with Zn_0.2Cd_0.8S solid solution（ZCS）and Ni₂P is further anchored to construct Ni₂P/ZCS/PCN ternary composite,using to enhance the photocatalytic performance of PCN.Then we performed a variety of analytical characterization and photocatalytic decomposition of water activity tests on the synthesized photocatalysts.Combined with all the analysis results,we discuss the mechanism of photocatalytic decomposition of water under visible light irradiation.The main research contents are as follows:1.Using urea as the precursor and gas template NH₄Cl assisted calcination to synthesize 2D nanoporous sheet PCN material.Through XRD characterization analysis,it can be seen that the peak position of the prepared catalyst is basically unchanged compared with characteristic diffraction peak of the pristine PCN and the changed intensity indicates a certain decrease in crystallinity.The hydrogen production activity of PCN is higher than that of CN,which is 538.41μmol h^-1·g^-1.The results of nitrogen adsorption and desorption show that the mesoporous structure with pore size of about 4nm accords with PCN slit stacking and its specific surface area is 111.709 m²·g^-1.Moreover,the results of DRS analysis exhibit that the red shift of PCN,which represents broadened visible light absorption range and the decreasing band gap.2.PCN and ZCS are combined to construct heterojunction by one-pot in situ solvothermal method.ZCS/PCN samples with different loading ratios are prepared by changing the mass percentage of the ZCS.Through the photocatalytic hydrogen production test under visible light,it can be seen that the 12 wt%ZCS/PCN photocatalyst exhibites best visible photocatalytic hydrogen production activity of1188.59μmol h^-1·g^-1.SEM characterization showes that many irregular nanoparticles are deposited on the PCN nanosheet layer compared to the pristine PCN,indicating that the ZCS successfully loaded on the PCN;the TEM characterization results showes that the morphology of the PCN is not changed by the obtained ZCS/PCN after solvothermal treatment.After combining with ZCS,the light absorption edge of the sample is further red shift and the results of PL and EIS test show that the recombination efficiency of photogenerated electron-hole pairs is effectively reduced.These results conclude that the tight heterojunction interface formed by ZCS/PCN composite improves the photocatalytic performance of the catalyst.Ni₂P/ZCS/PCN photocatalytic materials are synthesized by physical ultrasonic assisted solvothermal method.A series of Ni₂P/ZCS/PCN composites with different proportions are prepared by changing the mass percentage of the Ni₂P.When the composite is loaded with 10 wt%of Ni₂P,we found that the optimum photocatalytic activity is about 1638.26μmol h^-1·g^-1.SEM and TEM analysis show that Ni₂P is successfully deposited on the surface of PCN.The loading of Ni₂P can broaden the absorption of visible light,greatly improve the separation efficiency of photo generated carriers and the photocatalytic activity of water decomposition for hydrogen production.