Synthesis And Photocatalyatic Properties Of Graphitic Carbon Nitride,Zinc Oxide Nanostructures

Semiconductor photocatalytic technology based on nanotechnology not only could convert solar energy to chemical energy,but also could degrade many organics completely.Therefore,it has long time been considered as a plausible solution to solar energy conversion and environmental pollution control.Graphitic carbon nitride?g-C₃N₄?with bandgap of around 2.7 eV has attracted increasing attention because of its right position of valence band and conduction band,response to visible light and excellent physical and chemical stability.But highly stacked structure,small specific surface area and easy recombination of photoinduced carriers are its inherited weaknesses of the imperfect condensation process,leading to its unsatisfactory photocatalyst performance.In this regard,to develop and design efficient photocatalyst and extend its response to visible light has been the mainstream of the modification of carbon nitride.Due to its vast kinds of morphologies,versatile synthesis and extraordinary electron mobility,the traditional inorganic semiconductor ZnO has caught researchers' attention at the very beginning,and has vast application especially in photocatalyst and dye sensitized solar cells.Hoever,it has some detrimental defects,such as poor solar energy utilization especially in visible wavelength and low quantum efficiency.These seriously impose restrictions to application of photocataysis.In this represent research,great efforts have been paid to the modifying the bone structure,adjustment of the electronic structure of carbon nitride.Moreover,we also have a lot work on design and control the morphology and defect of ZnO.With the delicate characterization of Nyquist Plot,XPS,EPR and other techniques,the mechanism involved in the process has been explored.The main achievement is as follows:?1?With the co-condensation of additive with high content of nitrogen and precursor of carbon nitride,nitrogen self-doped carbon nitride has been successfully synthesized.The effects of substitution on visible light absorption,electronic structure and water splitting have extensively explored.It turns out that the self-doping carbon nitride has modified light absorption,retarded recombination of photoinduced carriers,and,finally,improved hydrogen evolution rates?HER?.It has lifted up to 1.8 times than that of pristine carbon nitride.?2?Instead of the conventional way to sensitize the sample with dyes,commercial dyes have been sensitized with the precursor of carbon nitride.After that follows condensation.The color of resultants has direct relationship with the amount and the type of dyes,and its light response has been extended to IR,corresponding bandgap decreasing from 2.65 eV to 1.65 eV.The probable mechanism has been also proposed.HER of dyed carbon nitride has lifted up to 1.66 times better than that of pristine carbon nitride.?3?The amount of added capping agent,in this case,HMTA,in hydrothermal reaction directly determines the morphology of ZnO evolving from microrods to nanosheets.Compared with microrods,nanosheets have larger specific surface area?21.96 m2/g?,response to visible light,suppressed carrier recombination and more loaded amount of dyes.Last but not the least,the IV test shows that the photoanodes based on different morphology has different performance.?4?The ZnO nanorod stemmed from solid phase method---by directly calcination of zinc acetate has better performance,and it can decompose RhB in17.5 min.T The quenching method based on this method could design and control the type and concentration of surface defect by controlling the cooling rate.he corresponding constant rate is 0.274 min-1.