Zinc Oxide Powders: Microscopic Morphology Control And Photocatalytic Properties

Zinc oxide（ZnO）has advantages of non-toxic,cheap,easy to prepare,and high catalytic activity.ZnO can be used in many fields-especially in the field of photocatalysis.In terms of photocatalysis,some inherent characteristics of ZnO,such as wide band gap,poor visible light response,high photo-generated charge recombination rate,and poor photo-corrosion resistance,often lead to poor photocatalytic effects.Therefore,the optimization of photocatalytic performance of ZnO has always been a research hotspot.There are many methods to control the photocatalytic performance of ZnO,among which the effects of microscopic morphology control and ion doping are particularly obvious.In this paper,systematic exploration towards ZnO has been carried out,maninly from the two aspects of morphology control and ion doping.The research focuses on the construction of ZnO one-dimensional micro-nano structures on substrates and their photocatalytic properties for photoelectrochemical water splitting.The morphology control mechanism of ZnO liquid phase chemical growth and the optimization mechanism of ion doping performance were discussed.The specific work is as follows:（1）The influence of In³⁺on the morphology of ZnO and the photocatalytic properties of ZnO.The ZnO samples with In³⁺as the morphology control agent were grown on the fluorine-doped tin oxide substrates coated with the seed layer by hydrothermal method.The influence of some factors on the morphology and structure of ZnO was explored.These factors include reaction conditions（reaction time,reaction temperature,heat treatment temperature）,concentrations of reactants(Zn（NO₃）₂,hexamethylenetetramine,polyethyleneimine concentration,In³⁺concentration)and other conditions（seed layer）.The growth mechanism was also discussed in depth.It was foumd that when the reaction temperature is 100°C,the Zn²⁺concentration is 0.1 M,and the molar ratio of Zn²⁺to polyethyleneimine is 1:0.1,the prepared ZnO has the best photocatalytic performance,and its photoelectrochemical water splitting revealed a photocurrent density of 0.7 m A/cm²（1.23 V vs.RHE）.（2）The pristine ZnO and Y doped ZnO nanorod arrays were successfully synthesized by the hydrothermal method on the fluorine-doped tin oxide substrates coated with the seed layer.The effects of Y doping amount,reaction time,reaction temperature and heat treatment temperature on the morphology and structure of ZnO structures and their performance of photoelectrochemical water splitting were systematically studied.It was found that Y doping can effectively improve the photocatalytic performance of the ZnO.The research results show that when the Y amount in the reactant solution is 6%,the reaction time is 5 h,the reaction temperature is 95°C,and the heat treatment temperature is 400°C,the photocurrent density of the material reaches the maximum value,which is 0.85 m A/cm²（1.23 V vs.RHE）,about 2.8times that of the pristine ZnO.The incident photon to curent conversion efficiency（IPCE）of73%is achieved at 370 nm,which is 1.9 times that of the original ZnO.（3）By adding F in the precursor solution,fluorine-doped ZnO nanorod array was grown on fluorine-doped tin oxide substrates by a hydrothermal method.The effect of the amount of F in the precursor solution,hydrothermal reaction time,hydrothermal reaction temperature,and heat treatment temperature on the photocatalytic performance of ZnO materials was explored.The reaction conditions were optimized,and related tests of photocatalysis were carried out.The reason why F doping improves the photocatalytic performance of ZnO materials was proposed.It shows that when the F doping amount in the reactant solution is 6%,the reaction time is 3 h,the reaction temperature is 95°C,and the heat treatment temperature is 450°C,the photocatalytic performance of the material is the best,and the photocurrent density is 0.79m A/cm²（1.23 V vs.RHE）,which is about 2.6 times that of pure ZnO.The incident photon to curent conversion efficiency（IPCE）tests show that the F-doped ZnO has an IPCE of 75%at330 nm,which is more than twice that of the original ZnO.