Fabracation And Photocatalytic Properties Of ZnO@Cu₂O Heterojunction Composites

Cu2O is one of the P-type direct semiconductor with a bandgap of 2.0-2.2 eV.So it can widely absorb the visible light.It is widely applied in the field of solar cell or photocatalysis.But in the process of photocatalysis,the recombination of photon-generated carrier is easy to occur at the interface of Cu2O particles,which leads to the low utilization of photogenerated carriers and directly affects its degradation efficiency.In order to reduce the carrier recombination,forming heterojunction with other semiconductors is generally used.Generally,the built-in electric field formed by heterojunction could effectively separate electrons and holes to reduce the carrier recombination.Moreover,the bandgap of semiconductor determines the range of light absorption,so the introduction of heterojunction can broaden the visible light absorption range of Cu2O.ZnO is an n-type direct semiconductor,and its band gap is about 3.3 eV,which could form p/n-type heterojunction with Cu2O.As forming heterojunction,photogenerated electrons are transferred to the conduction band of ZnO,and holes are transferred to the valence band of Cu2O,which could effectively reduce the carrier recombination.In this paper,the fabrication of ZnO@Cu2O heterojunction composites and their photocatalytic properties were studied.ZnO@Cu2O composites were fabricated by two-step method:firstly,Cu2O particles were synthesized by glucose reduction method.Then,for fabrication of ZnO@Cu2O heterojunction composites,Cu2O is used as the nucleus and ZnO is grown on the Cu2O surface under the water bath.In the preparation of Cu2O particles,the effects of glucose concentration,NaOH concentration and time on the growth of Cu2O were studied.After oppotimice The Cu2O with the best efficiency to degradate the Methyl orange is filtrated,which is used as the nuclear.Then,ZnO was prepared by controlling the concentration of zinc acetate(Zn(CH3COO)2)to obtain ZnO.after optimising the growth condition of ZnO,the ZnO@Cu2O heterojunction composites were obtained by two-step method.The photocatalytic degradation of methyl orange for ZnO@Cu2O were compared with that of pure ZnO and pure Cu2O.Here,ZnO@Cu2O heterojunction composites were successfully synthesised.ZnO particles were supported on the surface of Cu2O indicated by SEM,and the molar ratio of ZnO to Cu2O was about 3:4 by XRF analysis.In the photocatalytic degradation of methyl orange,the degradation rate was as high as 55%which was 46%higher than that of pure Cu2O and 10%higher than that of pure ZnO under the same conditions.The Cu2O prepared in the experiment is mainly brick red octahedral cuprite structure and khaki-like spherical cuprite structure.The size distribution of Cu2O is in the range of 1-4 ?m The results of the degradation efficiency showed that octahedral structure was slightly higher than that of the spherical one.The size of the ZnO particles is around 1 ?m,and the ZnO particles size was increasing with the increase mount of the Zn(AC)2 concentration.