| Water pollution is one of the major problems that have troubled people in recent years.The traditional treatment method was restricted to applicate widely for the slow treatment rate and secondary pollution.Semiconductor photocatalysis technology has attracted the interest of research scholars due to its advantages of low cost,fast degradation rate and no secondary pollution.As a new type of narrow-bandgap photocatalyst,Cu2O has a lot of advantages,such as the wide absorption range for sunlight,abundant reserves,and low cost,so it is favored by scientists.However,due to its higher photogenerated electron-hole are compounded easily,its actual photocatalytic efficiency is far from the theoretical value.Research have shown that this situation can be improved by forming a heterojunction with a wide band gap material,because of its special internal electric field structure,it can improve the transfer and conduction of carriers,which is very helpful for catalytic performance of the semiconductor.In this paper,the Cu2O heterojunction was prepared by electrochemical deposition method.The crystal phase and composition were analyzed by XRD and XPS.The morphology was analyzed by SEM.The UV-Vis DRS was used to characterize the optical properties.Combined with transient photocurrent,mott-schottky curve,and linear cyclic voltammetry,the electrochemical performance of the heterojunction was analyzed.The factors that affect the performance of the heterojunction were discussed.It was applied to the degradation of methine blue and norfloxacin,and the effects of the main active species on the photocatalytic performance during the degradation of heterojunction catalysts were analyzed.The specific research content and results are as follows:(1)Preparation of Cu2O thin film and study on its photoelectric properties.By discussing the influence of deposition potential and electrolyte pH on the performance of the film,the best preparation conditions were obtained.At the optimum deposition potential of-0.45V,the(111)crystal plane diffraction peak intensity of Cu2O is the highest,the band gap is the narrowest,the transient photocurrent value of Cu2O is the largest,the corresponding charge transfer resistance value is the smallest,and the degradation rate of blue is 72.23%.(2)Study on preparation and performance of p-Cu2O/n-ZnO heterojunction.The pCu2O/n-ZnO heterojunction thin film was prepared by a two-step electrochemical deposition method.By discussing the effect of deposition conditions on the performance of n-ZnO,the best preparation conditions of n-ZnO were obtained:Ea=-1.0V,n((CH2)6N4:Zn2+)=1:0.5,the deposition temperature is 70℃.The prepared n-ZnO thin film exhibits the(002)preferred orientation,the band gap is 3.350 eV,the regular hexagons are uniformly arranged,and the particle size is about 1 μm.When the deposition potential is-0.5V,the peak intensity of the(111)crystal plane of the p-Cu2O/n-ZnO heterojunction is the highest,the band gap is increased by 0.18eV compared to Cu2O,and the transient photocurrent value is the highest,compared to pure Cu2O increased by 2 times,and the charge transfer resistance was the smallest.The n-type and p-type regions showed high donor and acceptor concentrations,good rectification behavior,and a degradation rate of methine blue of 91.00%,which was an increase of 18.77%compared to the Cu2O film.(3)Preparation and performance study of p-Cu2O/n-SnO2 heterojunction.The p-Cu2O/nSnO2 heterojunction was prepared by a combination of Sol-gel and electrochemical deposition,and the effect of annealing temperature on the performance of n-SnO2 was discussed.When the annealing temperature is 500℃,n-SnO2 has a higher carrier concentration and better photoelectric performance.The effect of electrolyte concentration on the photoelectric properties of p-Cu2O/n-SnO2 heterojunction was studied.The results showed that when the Cu2+concentration was 60 mM,the prepared sample had the strongest(111)crystal plane diffraction peak and enhanced UV-Vis absorption intensity.Compared with Cu2O,the band gap is increased by 0.14eV,and the larger forbidden band width is conducive to the improvement of photogenerated electronic and cavity separation efficiency.The Mott-Schottky curve shows an inverted"V" shape,and the flat band potential decreases,indicating that it has an enhanced ability to reduce electrons.The carrier concentration reaches 28.5 × 1022cm-3,which is an order of magnitude higher than that of Cu2O.The degradation rate of MB reached 92.80%.(4)Preparation and photoelectric properties of Cu2O/g-C3N4Composite thin film.The combination of electrochemical deposition and thermal polymerization was used to synthesize Cu20/g-C3N4 thin films.The results show that band gap of Cu2O/g-C3N4 has increased compared to Cu2O,which is more conducive to carrier separation.The SEM shows that pure Cu2O is spherical particles with a diameter of about 500nm,and Cu2O/g-C3N4 film is interlaced triangular pyramid.And as the amount of g-C3N4 continues to increase,a certain amount of shedding occurs on the surface of the composite film,particles agglomerate,and the particle size becomes larger.Photocurrent test shows that the addition of g-C3N4 is conducive to the improvement of the photocurrent of the thin film,which may be the formation of Cu2O/g-C3N4 heterojunction,However,with the content of g-C3N4 increasing,the photocurrent of the g-C3N4/Cu2O film is reduced and the charge transfer resistance is increased,which is caused by the corrosion of composite film.The Mott-Schottky(M-S)curve shows that the composite film is "inverted Vshaped",which indicates the formation of Cu2O/g-C3N4 heterojunction structure.The gC3N4/Cu2O film show high carrier concentration in the n-type and p-type region.Combined with fluorescence(PL)analysis,we come to the conclusion that the 3wt%-Cu2O/g-C3N4 heterojunction behave better carrier separation efficiency.During the degradation of MB by Cu2O/g-C3N4 composite film,·OH is the main active species,the degradation rate of MB is 91.43%,and the degradation rate of norfloxacin is 72.80%. |
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