| With the rapid development of industrial civilization,more and more inevitable environmental problems plague normal social production activities.For example,the emission of greenhouse gases such as CO2 and nitrogen oxides.The precious fresh water resources caused by industrial sewage,agricultural sewage,and domestic wastewater are seriously wasted.Different from traditional environmental pollution control methods,photocatalytic degradation technology as a new green catalytic technology using renewable light energy has gradually attracted the attention of many scientific researchers.This technology will be of great significance to green life and sustainable development.Graphite carbon nitride(g-C3N4),as a new type of semiconductor photocatalyst,has become one of the hot research areas due to its advantages of simple preparation,low toxicity,low cost and excellent stability.However,it also has the disadvantages such as low light utilization efficiency,small specific surface area and high recombination rate of photogenerated electrons and holes,which limit its further development in the field of photocatalysis.This article aims to develop a highly efficient g-C3N4-based photocatalytic system using various approaches such as molecular design and morphology control.The specific work is as follows:(1)The key to developing efficient Z-scheme photocatalysts is to improve the electron transport ability of the interface through structural design via the preparation method.For the first time,a Z-scheme α-Fe2O3/g-C3N4 photocatalyst with Fe-O-C bonds was prepared by high-temperature calcination using the hydrogen bond between Fe(OH)3 colloid and dicyandiamide.Through the tests of XRD,FTIR,HRTEM,XPS,XAFS and EXAFS,the structure and composition of the composite photocatalyst and the existence of Fe-O-C bonds were confirmed.Studies have found that Fe-O-C bonds can act as special electron transport channels to accelerate charge transfer and effectively promote the separation of photogenerated carriers.The Z-scheme structure ensures that the composite photocatalyst achieves the best redox activity.The results of the photocatalytic degradation experiment show that the photocatalytic activity of the Z-scheme α-Fe2O3/g-C3N4 photocatalyst with Fe-O-C bonds has been improved.(2)The g-C3N4/Cu(OH)2 composite photocatalyst with coordinated covalent bond was synthesized by chemical deposition method.With only 60 min of light,the g-C3N4/Cu(OH)2-0.1 catalyzed the degradation of 80.6%MB solution,and its photocatalytic activity was almost 15.8 times that of the original g-C3N4.The research results show that the Cu2+ in Cu(OH)2 can be bonded to the electron-rich N atom in g-C3N4 through the coordinated covalent bond.The stronger interaction promotes the change of the local electric field in g-C3N4/Cu(OH)2 composite photocatalyst,thereby obtaining a higher valence band potential.This will provide photogenerated holes with stronger oxidizing ability for the catalytic degradation reaction.In addition,the Cu(OH)2 can act as an electron trap to promote the effective separation of photogenerated carriers.(3)The carbon-doped porous g-C3N4 photocatalyst was prepared by calcining the composite material of non-ionic surfactants(PVA,PVP and F127)and dicyandiamide.The study found that the different changes of the non-ionic surfactant/dicyandiamide composite with special micro-morphology caused the formation of porous structure in the subsequent products,which would significantly increase the specific surface area and active sites of the composite photocatalyst.In addition,the nonionic surfactant are carbonized at high temperature to form carbon doping in the g-C3N4 structure network.It can act as a conductive medium to increase the transfer rate of photo-generated charges and inhibit the recombination of photo-generated carriers.Due to the above advantages,the carbon-doped porous g-C3N4 photocatalyst has high-efficiency adsorption performance and catalytic performance.Figure[56]Table[7]References[137]... |
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