Study On The Control Of Cuprous Oxide Composition And Its Photocatalytic Degradation Performance

Cu2O is a P-type direct band gap semiconductor with a forbidden band width of 2.2 eV and a wide range of light absorption,which is widely used in the photocatalytic direction.However,Cu2O is unstable in water and easily reacts with photogenerated electrons to cause photocorrosion.Rapid separation and transfer of photogenerated electrons are the keys to improving the photocatalytic efficiency and stability of Cu2O.By combining Cu2O with other semiconductors or metals to form a heterojunction or a Schottky junction,the transfer efficiency of photogenerated electrons and holes can be effectively improved under illumination conditions.The electric field between the heterojunction and the Schottky junction can effectively separate the electron and hole pairs,while there is also an interfacial composite effect.In this paper,by controlling the growth process of Cu2O nanowires,Cu4O3 and Cu particles appear in Cu2O nanowires,which constitute Cu2O/Cu4O3 heterojunction and Cu2O/Cu Schottky junction,improving the stability and photocatalytic degradation efficiency of Cu2O nanowires.Cu(Ac)2 was used as the Cu source by hydrothermal method.O-anisidine was used as the reducing agent,and HAc as the additive.The reaction temperature was 110 ?,130 ?,150 ?,170 ?,190 ?,and the reaction time was 12 hours.A Cu2O nanowire with a dendritic structure on the surface was prepared.The SEM characterization results show that the structure difference between Cu2O nanowires prepared at different reaction temperatures is small,and the diameters of nanowires are 60-100 nm.However,the XRD characterization results show that the relative content of Cu4O3 and Cu in Cu2O nanowires are different at different reaction temperatures.The preparation temperature is increased from 110 ? to 190?,and the amount of Cu4O3 reduced from 35.3%to 4.2%.When the preparation temperature was at 170 ?,Cu particles appearing,and the Cu content reached 7.1%until 190 ?.The TEM,XPS and FT-IR characterization results show that the surface of the nanowires are covered with a layer of o-anisidine.Thermal annealing in air atmosphere revealed that the decomposition temperature of o-anisidine reached at 430 ?,while Cu2O and Cu4O3 were oxidized to CuO at 430 ?.The UV-Vis characterization results show that the Cu2O nanowires with different Cu4O3 and Cu content have a light absorption threshold about 480 nm,and the differences are small.The optical band gap value approaches to 2.5 eV.The BET characterization results show that the Cu2O nanowires prepared at 150 ? have large specific surface area of 20.80 m2/g.In this study,quantitative control of Cu4O3 and Cu content in Cu2O nanowires is achieved by controlling preparation temperature.The photoelectrochemical performance of Cu2O nanowire samples with different Cu4O3 and Cu content were tested.For the characterization of photocatalytic degradation performance,methyl orange was used as degradation substrate.The characterization of photocatalytic degradation was carried under dark and light conditions,respectively.Under dark condition,Cu2O nanowires had excellent performance.After 30 min of reaction,the concentration of methyl orange decreased by 40%-60%.The electrochemical test results under illumination condition are consistent with those of photocatalytic degradation.The photocatalytic efficiency of 150 ?-Cu2O nanowires is the highest.With the preparation temperature decreasing from 150 ? to 110 ?,the photocatalytic degradation efficiency of Cu2O nanowires is gradually reduced.As the preparation temperature increases from 150 ?to 190 ?,the photocatalytic degradation efficiency of Cu2O nanowires decreases gradually.The Cu2O/Cu4O3 heterojunction and Cu2O/Cu Schottky junction in the Cu2O nanowires possess interfacial composite effect under dark condition.So the more interfaces,the stronger the interfacial composite effect appears.In the electrochemical impedance test,under dark condition,the interfacial composite effect of Cu2O nanowires prepared at 150 0C is minimal.Under the illumination condition,the photogenerated carriers are effectively separated under the electric field of Cu2O/Cu4O3 heterojunction and Cu2O/Cu Schottky interface.When the interface is located on the semiconductor surface,the separated photogenerated carriers are transferred to the semiconductor surface to participate in the light catalytic reaction.But when the interface is located in the semiconductor body,the separated photogenerated carriers can not be transferred to the contact surface of solution to join in the photocatalytic reaction,and will recombine in Cu4O3 or Cu.At this moment,the interfacial composite effect is dominant,so the photocatalytic degradation efficiency declines.Therefore,the photocatalytic efficiency of Cu2O nanowires prepared at 150 ?.is the highest.With the increase of Cu4O3 content,the interface of heterojunction is excessively distributed in the body of Cu2O,and the interface recombination becomes dominant,inducing the photocatalytic efficiency decreasing gradually With the increase of Cu content,the Schottky interface is excessively distributed in the body of Cu2O,and the interface recombination dominates.The photocatalytic efficiency of Cu2O nanowires decreases gradually.In this paper,quantitative control of Cu4O3 and Cu in Cu2O nanowires is achieved by controlling the temperature of hydrothermal reaction.Thus,Cu2O/Cu4O3 heterojunction and Cu2O/Cu Schottky junction are formed in Cu2O,which improves the photocatalytic degradation efficiency.However,when the heterojunction interface is located in the body of Cu2O,the interfacial composite effect dominates and the catalytic performance decreases.Therefore,in the design of the heterojunction,it is necessary to controllably construct the heterojunction onto the surface of the semiconductor,or connect the contact interface in the body to the surface to form a bulk heterojunction,realizing effective separation of photogenerated carriers and improving light Catalytic degradation efficiency.