Preparation And Photocatalytic Performance Of ZrO₂ Nanoparticles

Photocatalysis is a renewable technology based on semiconductor photocatalysts with redox capability under light irradiation and widely used in energy production,environmental protection and water purification.Currently,ZrO ₂ is an ideal photocatalyst material due to its weak acid and base sites and redox stability.However,the photocatalytic performance of ZrO₂ is affected by its surface morphology,grain size,specific surface area,and its wider bandgap（?5 e V）reduces its sunlight utilization efficiency.In response to the above problems,this paper prepared pristine ZrO₂ nanoparticles by liquid phase method,and prepared Fe-doped ZrO₂ photocatalyst with visible-light absorption ability by metal-doping method,which revealed the mechanism of improving photocatalytic performance of ZrO₂ by nanocrystallization and Fe modification.Nano-ZrO₂ photocatalysts were prepared by liquid-phase method（sol-gel method,direct precipitation method and hydrothermal method）.ZrO₂ prepared by sol-gel method and direct precipitation method was a biphase structure of tetragonal phase and monocline phase,and the prepared ZrO₂ was a single monoclinic phase structure by hydrothermal method.The study showed that the ZrO₂ prepared by the liquid phase method had the same light-absorption edge（240 nm）.The ZrO₂ prepared by the hydrothermal method had good photocatalytic performance,and the efficiency of photocatalytic degradation of Rh B reached 98%in 90 minutes under simulated sunlight irradiation,which was attributed to it s smaller grain size,larger specific surface area and better carrier separation efficiency.A series of Fe-doped ZrO₂ photocatalysts were prepared by the sol-gel method.After annealing at 550℃for 3 h,the crystallinity was high.When the Fe doping amount was between 0.2-5 at%,the prepared Fe-doped ZrO₂ had a biphase structure of tetragonal phase and monocline phase,when the doping amount was 10 at%,the prepared Fe-doped ZrO₂ had a single tetragonal phase structure.The results show that the Fe doping was beneficial to stabilize the high-temperature tetragonal phase of ZrO₂.Fe doping increased the light-absorption edge of ZrO₂ from the ultraviolet region to the visible region,and the maximum light-absorption edge was 475 nm.Fe doping reduced the bandgap of ZrO₂ with maintaining the highly negative value of the conduction band（CB）potential,which was about-0.5 e V（vs NHE）.This is due to the3d electrons of the doped Fe had an excellent contribution to the narrow bandgap of ZrO₂.0.5 at%Fe-ZrO₂ had the optimum photocatalytic performance.The efficiency of photocatalytic degradation of Rh B reached 96%in 150 minutes under visible light irradiation,which was attributed to its smaller grain size and larger specific surface area,better carrier separation efficiency and lower carrier recombination rate.The mechanism of photocatalytic degradation of Rh B for Fe-doped ZrO₂ was preliminarily explored through radical species trapping experiments.Among them,superoxide radical(·O^2-)played an important role in the process of photocatalytic degradation of Rh B,and holes（h⁺）in the valence band can also play an important role in directly oxidizing Rh B.In this paper,the nano-ZrO₂ photocatalyst is prepared by liquid phase method to improve its photocatalytic performance under simulated sunlight irradiation.At the same time,the Fe-doping method is used to improve the solar light utilization efficiency of ZrO₂ and enhance its light-absorption edge to the visible light region.It is successfully to obtaine ZrO₂ photocatalyst with high visible light photocatalytic degradation of Rh B.The studies in this paper also reveal the photocatalytic mechanism of Fe-doped ZrO₂,which lays a theoretical foundation for the application of ZrO ₂photocatalyst in the fields of photocatalytic degradation of pollutants in water resources,environmental purification,sterilization and anti-virus.