Preparation And Photocatalytic Property Of Cu₂O-Based Materials

In the 21st century,green development is our common wish.However,it has become a concern for everyone because of the increasingly serious environmental problems.Semiconductor catalytic technology is one of the most promising large-scale green technologies for degradating organic contanminant in waste water.As a new and functional material widely used,Cu₂O possesses low toxicity,low cost,high plasticity,environmental friendliness,high catalytic efficiency under visible light.Therefore,it has good application value in the field of photocatalysis.However,the photo electron-hole pair of Cu₂O photocatalyst is prone to recombination during the catalytic process,which would result in low catalytic activity.Simultaneously,photocatalyst would not produce catalytic activity in dark,which limits its catalytic activity and application range.Therefore,our work has been dedicated to synthesis high active,stable and memory-effect photocatalysts.On the one hand,the morphology of Cu₂O catalyst was controlled in order to improve its photocatalytic performance.Furthermore,a kind of Cu₂O-based composite photocatalyst was prepared to enchance Cu₂O photoctalytic property.On the other hand,a kind of Cu₂O-based composite photocatalyst with photocatalytic"memory effect"was developed to improve its photocatalytic activity and application range.Based on the characterization of the spectroscopy,the mechanism of the improvement of photocatalytic activity was explored.The main contents of this paper are as follows:?1?In order to obtain Cu₂O nanoparticles with great photocatalytic activity,a simple chemical reduction method was adopted to control the growth of Cu₂O so as to adjust its particles size via effective controlling the sodium hydroxide concentration and experimental reaction temperature.The phase and morphology of Cu₂O nanoparticles were characterized by X-ray powder diffraction?XRD?,field scanning electron microscopy?FESEM?and transmission electron microscopy?TEM?.The visible light photocatalytic activity of Cu₂O nanoparticles was studied through degradating methyl orange?MO?solution.The results show that the prepared Cu₂O particles are of 25 nm cubic structure,when the reaction temperature is 40?,the concentration of sodium hydroxide is0.125 mol·L^-1.And after visible light irradiation for 30 min,the degradation rate of 10 mg Cu₂O to MO solution?50 mL 20 mg/L?could reach up 84.2%,and the degradation rate reached 95.6%with the illumination time extension to 2 h,indicating that the prepared Cu₂O possesses excellent photocatalytic activity.Meanwhile,the several recycle tests of the Cu₂O show that the degradation efficiency could still reach more than 75%after used 4 times,which confirms that the photocatalytic stability of obtained Cu₂O is great.?2?Microspheres-like Cu-Cu₂O composites were successfully fabricated through a facial one-step solvothermal method.The phase and morphology of Cu-Cu₂O composites were characterized by X-ray diffraction?XRD?,field scanning electron microscopy?FE-SEM?and high-resolution transmission electron microscopy?TEM?.The photodegradation experimental of methyl orange?MO?displayes that the as-obtain Cu-Cu₂O composites possess excellent photocatalytic activity.After 120 min visible light irradiation,the photodegradation rates of MO on pure Cu₂O and Cu-Cu₂O were up to 11.8%and90.6%,respectively.Moreover,the photodegradation rate of MO on Cu-Cu₂O was 19.5 times than that on pure Cu₂O.The great photocatalytic activity of Cu-Cu₂O composites might be ascribed to appropriate amount of Cu,which could promote the transfer of photo-generated electrons and restrain the recombination of electron-hole.?3?Cu-Cu₂O/SnO₂ composites with different SnO₂ contents were prepared by adding different amount SnO₂ solloidal solution to Cu-Cu₂O suspension via secondary solvothermal method.The products were characterized by XRD,SEM,TEM,inductively coupled plasma mass spectroscopy?ICP-MS?,UV-Vis DRS and X-ray photoelectron spectroscope?XPS?.The photocatalytic performance and"memory effect"of different Cu-Cu₂O/SnO₂ composites were investigated through MO solution degradation experiments.The results show that when the weight percentage of SnO₂ in the composite is 13.2%,Cu-Cu₂O/SnO₂ possesses the best photocatalytic performance and its degradation rate of MO?50 mL 20mg/L?is 93.7%under visible light for 120 min.And after used 4 times,the degradation rate of MO solution is still up to 79.0%,indicating that the obtained Cu-Cu₂O/SnO₂ composite possesses excellent photocatalytic activity and stability performance.At the same time,the removal rate of MO solution is increased by 17.2%in dark for 3 h after 5 h illumination,which could be contributed to the photocatalysis“memory effect”of Cu-Cu₂O/SnO₂.The reason may be that Sn⁴⁺captures excited electron from the Cu₂O and become Sn²⁺,and Sn²⁺could release the trapped electron in dark which would react and produce reactive groups and lead to the photocatalytic activity in dark.