Preparation Of Zinc Oxide And Zinc Sulfide Nanomaterials And Their Photocatalytic Properties

Zinc oxide（ZnO）and zinc sulfide（ZnS）,as two common semiconductors,have widely used in the field of optoelectronics and microelectronics due to their unique physicochemical properties.However,owing to their wide band gap,ZnO and ZnS can only be excited by UV light,which greatly limits their photocatalytic applications in visible light.Morphology modulation and heterojunction structure are two effective modification strategies for semiconductor catalysts,which have been widely used to improve the photocatalytic properties of semiconductor catalysts.In this work,the modification of ZnO and ZnS were carried out through morphology modulation and heterojunction structure,and the main research contents and results are as follows:（1）ZnO cones,rods and disks with mainly exposed{10（?）1、{10（?）0and{0001 crystal planes,respectively,have been successfully prepared.The density of Zn-O broken bond on different crystal planes were obtained in the following order:D_{（10（?）1）}<D_{（10（?）0）}<D_（0001）.The dominant exposure of{0001 crystal planes could not only endow ZnO disks with a narrower band gap（3.17 e V）,but also provide more active sites to trap photogenerated electrons or holes,and then reduce the complexation of photogenerated carriers.As a result,ZnO disks exhibited better photocatalytic performance,and the degradation efficiency for 10 mg/L methylene blue（MB）could reach 86%in 7 h under LED lamp（5W,400-760 nm）.（2）ZnS nanotubes,short nanotubes and nanosheets were synthesized by substitution reaction using ZnO as templates.The obtained ZnS nanomaterials existed in the forms of ZnO pseudomorph with cubic sphalerite structure and were composed of numerous nanocrystal ZnS.The XRD analysis results showed that the exposure ratio of{100 crystal planes on ZnS nanosheets was higher than that of nanotubes or short nanotubes.The broken bonds density of Zn-S bonds on different crystal planes were obtained in the following order:D_（111）<D_（110）<D_（100）.The higher exposure ratio of{100 crystalline planes could not also endow ZnS nanosheets with a narrower band gap（3.41 e V）,but also provide more active sites to trap photogenerated electrons or holes,and then reduce the complexation of photogenerated carriers.As a result,the ZnS nanosheets exhibited better photocatalytic performance,and the degradation efficiency for 10 mg/L MB could reach 95%within 4 h under UV lamp（30 W）.（3）ZnO/ZnS core-shell heterojunction structure with different ZnS shell thickness were synthesized by controlling the sulfide reaction conditions using ZnO disks as the precursor and sodium sulfide as the sulfur source.When the content of ZnS shell was 55.5%,the synthesized core-shell heterojunction material with a band gap of 3.13 e V exhibited better photocatalytic performance,and the degradation efficiency for 10mg/L methylene blue reached 95%within 5 h under LED lamp.After calcination,the photocatalytic property of ZnO/ZnS heterojunction material was further improved.The ZnO/ZnS core-shell heterojunction material calcinated at 550°C with band gap energy of 2.90 e V showed better catalytic performance,and the degradation efficiency for 10 mg/L MB could reach 95%within 4 h under LED lamp.