Preparation And Photocatalytic Properties Of G-C₃N₄-ZnO Based Composites

A series of highly efficient visible photocatalytic composites based on graphite like carbon nitride-zinc oxide（g-C₃N₄-ZnO）composite with graphene（GO）and molybdic sulfide（MoS₂）were prepared by hydrothermal method,including binary composites g-C₃N₄-ZnO（CZ）,ternary composites GO-20%g-C₃N₄-ZnO（GCZ）and MoS₂-20%g-C₃N₄-ZnO（MCZ）.The samples were characterized by scanning electron microscope（SEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,photoluminescence（PL）spectra,UV-visible spectrophoto-meter（UV-Vis DRS）and transient photocurrent response.The effects of g-C₃N₄ introduced alone and synergistic action with MoS₂ or GO on the crystal structure,morphology,composition and photocatalytic activity of ZnO were studied.The main experimental results are as follows:Ⅰ A high efficient binary composite catalytic material g-C₃N₄-ZnO（g-C₃N₄:0²0wt%）was prepared.XRD and SEM analysis show that CZ（g-C₃N₄:0²0wt%）maintained the hexagonal wurtzite structure of ZnO,and g-C₃N₄ was graphite-like phase.The microscopic morphology showed the irregular aggregation of nanoparticles and the intergranular pores.XPS analysis further confirmed that Zn was+2 valence.UV-vis DRS absorption spectrum analysis showed that with the increase of g-C₃N₄ mass ratio,the absorption edge of CZ gradually shifted red,indicating that g-C₃N₄ and ZnO could be well coupled together.After230 min of visible light irradiation,the degradation rates of 4%CZ,8%CZ,16%CZ and 20%CZ degraded methylene blue（MB）solution were 65.4%,71.9%,80.9%and 87.8%respectively.As the percentage of g-C₃N₄ increased,the photocatalytic efficiency of visible light gradually increased.Ⅱ The efficient ternary composite catalytic material GO-20%g-C₃N₄-ZnO（GO:2wt%²0wt%）was prepared.XRD and SEM analysis show that GCZ（GO:2wt%²0wt%）maintained the hexagonal wurtzite structure of ZnO,and g-C₃N₄ was graphite-like phase.XPS analysis further confirmed that Zn was+2 valence,the high-resolution maps of N 1s and C 1s showed the coexistence mode of nitrogen and carbon in different chemical states,indicating the successful synthesis of GO-20%g-C₃N₄-ZnO.After 230 min of visible light irradiation,the degradation rates of 2%GCZ,10%GCZ,15%GCZ and 20%GCZ degraded methylene blue solution were 75.8%,92.5%,100%and 93.4%of the initial concentration.The visible light catalytic efficiency of 10-20%GCZ composites was significantly better than that of 20%CZ.When GO takes up 15%of the mass,it shows the best visible light catalytic efficiency.PL spectrum and transient photocurrent test analysis showed that GO,as an effective carrier,was coupled with g-C₃N₄-ZnO similar heterogeneous structure and had obvious electron transfer phenomenon,which inhibited the combination of photogenerated electron-hole pairs in g-C₃N₄-ZnO and improved its visible light catalytic performance.Ⅲ The composite catalytic material MoS₂-20%g-C₃N₄-ZnO（MoS₂:0.2wt%²wt%）was prepared.With the increase of MoS₂ mass proportion,PL spectral intensity decreases gradually.The absorption edge of 0.2-0.8%MCZ is redshifted.After 230 min of visible light irradiation,the degradation rates of 0.2%MCZ,0.8%MCZ,1.6%MCZ and 2%MCZ degraded methylene blue solution were 89.3%,74.0%,78.2%and 69.0%respectively.