| The demand for clean energy in society has spawned the rise of new energy technology research.The conversion of solar energy into stable chemical energy is considered to be one of the important methods to solve the problems of energy transformation and environmental degradation.In the way of solar energy utilization,the unique properties of metal oxides have been paid more and more attention by environmental protection in the field of photocatalysis.Among them,Co3O4 shows very high photocatalytic activity in the field of photocatalytic degradation of pollutants and new energy sources.In order to further improve the photocatalytic activity of Co3O4 materials,a great deal of research has been done at home and abroad on ion doping and noble metal loading of Co3O4 materials.In this paper,the preparation of Co3O4/g-C3N4/Pt composites was studied,and the photocatalytic properties of the composites were studied by photolysis of water to oxygen.The details are as follows:?1?using Co?NO3?2·6H2O and degreased cotton as raw materials,orthogonal design was used to optimize the preparation process of Co3O4 particles.The different concentration?1mol/L,2 mol/L,3 mol/L?Co?NO3?2·6H2O and degreased cotton as raw materials were calcined at different temperature?500C,600C,700C?for different time?2h,3h?by carbon-assisted method.Co3O4 particles were obtained for 4h.The results of X-ray diffraction?XRD?and Fourier transform infrared spectroscopy?FT-IR?showed that the high purity Co3O4.was successfully prepared by carbon-assisted method.At the same time,the band gap and elemental composition of Co3O4 particles were characterized by UV-vis diffuse reflectance spectroscopy?UV-Vis?and X-ray photoelectron spectroscopy?XPS?.The oxygen production of water by photocatalysis decomposition with xenon lamp simulated solar light was used as the experimental index.The orthogonal test data were analyzed by variance method and extreme difference method.The results showed that the concentration and calcination time of,Co?NO3?2·6H2O had the greatest effect on the oxygen production of Co3O4,and the optimum technological conditions for the preparation of Co3O4 were:Co?NO3?2·6H2O 2mol/L,calcination temperature 600C and calcination time 4 h.The photocatalytic activity of the Co3O4 sample prepared under this reaction condition was the best,and the oxygen production reached 164.4530446?mol.at 9h.?2?on the basis of carbon-assisted experiment based on orthogonal method,using urea as raw material,calcining at 550C for 3h,using urea as raw material and calcining at 550C for 3h,the g-C3N4 material was successfully prepared,which was combined with ultrasonic stripping method.After ultrasonic peeling of Co3O4 and g-C3N4in ethanol for 1h,Co3O4/g-C3N4 composite nano-materials were successfully prepared by mixing and stirring until ethanol evaporated completely and calcined at 300C for 2h.The effects of the mass fraction of g-C3N4 on the morphology,structure and photocatalytic properties of Co3O4/g-C3N4 composite particles were studied.The structure and morphology of the samples were characterized by Fourier transform infrared spectroscopy?FT-IR?,X-ray diffraction?XRD?,scanning electron microscopy and X-ray energy dispersive spectroscopy?SEM-EDS?.At the same time,X-ray photoelectron spectroscopy?XPS?,)photoluminescence spectrum?PL?,The band gap,electron hole separation efficiency and specific surface area of Co3O4/g-C3N4 composites were characterized by UV-vis diffuse reflectance spectroscopy?UV-Vis?and specific surface area?BET?.The photocatalytic performance test results showed that with the increase of the mass fraction of g-C3N4,the photocatalytic oxygen production of Co3O4/g-C3N4 increased first and then decreased.When the mass fraction of g-C3N4 was 2%,the photocatalysis oxygen production of g-C3N4 increased first and then decreased,when the mass fraction of g-C3N4 was 2%.Co3O4/g-C3N4 composite exhibited higher oxygen production,and its oxygen production solution reached 197.9450327?mol.in 9h.The main reason is that g-C3N4 is added to Co3O4 to form pn junction,which leads to its high photocatalytic activity.?3?using chloroplatinic acid as raw material,Co3O4/g-C3N4/Pt composites were prepared by photoreduction method under 30 W UV lamp.The effects of different mass fraction of Pt on the photocatalytic properties of nano-Co3O4/g-C3N4/Pt composites were also studied.The samples were characterized by X-ray photoelectron spectroscopy?XPS?,photoluminescence spectroscopy?PL?and ultraviolet-visible diffuse reflectance spectroscopy?UV-Vis?.The results of photocatalytic performance test show that the oxygen production of Co3O4/g-C3N4/Pt composites is different with the increase of mass fraction of Pt.When the mass fraction of Pt is 0.25%,the oxygen production of Co3O4/g-C3N4/Pt composites is different.The oxygen production of Co3O4/g-C3N4/Pt composites reached 214.26055?mol.in 9 h.The main reason is that the introduction of precious metal Pt makes it produce Schottky barrier between semiconductor materials.On the basis of pn junction the carrier is further separated and the photocatalytic performance of the material is improved. |
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