Preparation And Photocatalytic Performance Of Black Zirconia

As one of the important semiconductor materials,ZrO₂is widely used in the environment and energy fields.However,its wide band gap,low sunlight utilization rate and low quantum efficiency limits the further application.Reducing the band ap and increasing the utilization rate of sunlight are two effective methods.Black ZrO₂has attracted much attention due to its excellent visible light absorption performance.In this paper,ZrOCl₂·8H₂O was used as the zirconium source,and H₃BO₃and NH₄F were used as the mineralizers.ZrO₂with different reaction time and ratios of the mineralizers were prepared.The structure and properties of the samples were studied,and the relevant mechanism was analyzed.ZrO₂ was prepared by hydrothermal method,and the crystallization of 12h samples was the best,but the effect of hydrothermal reaction time on photocatalytic performance was not significant.The micro-morphology of this nanomaterial is mostly spindle-shaped,with a small number of short columns.The roughness of the ZrO₂surface increases as the reaction time increases.This is not conducive to crystal growth,and therefore affects the photocatalytic performance of the sample.The mechanism of the effect of time on the morphological growth of ZrO₂is analyzed from the growth state of the grains at different times.Grain size of ZrO₂also increases with time in the initial stage,and then the grain size increases slow with time from 12h to 72 h.On the basis of controlling the hydrothermal reaction time,the effect of the proportion of mineralizer on the microstructure and photocatalytic performance of ZrO₂was studied.With the different mineralizer concentration,the nano-morphology of the nano-material exhibited spindle-like,short column-like,round cake-like,and broken round cake-like shapes.Through the photocatalysis,it is concluded that c³⁺_?B?:c^-_?F?=1:1 has the best photocatalysis performance,and the effect of the ratio of mineralizers on the photocatalytic performance was analyzed.The surface F^-and interstitial F^-jointly promote photocatalytic efficiency.Black ZrO₂ was prepared by aluminothermic reaction under argon atmosphere.Its microstructure and photocatalytic performan were studied.After the reduction,the oxygen vacancies in the grains and the surface roughness of the grains increases sharply.The surface roughness is proportional to the amount of aluminum powder.In the meanwhile,the band gap of black ZrO₂decreases,and the peak position of the PL spectrum changes.Through the analysing of the photocatalysis effect of black ZrO₂,it is found that the photocatalysis efficiency of m_?AL?:m_?ZrO2?=1:5 is the best,and the photocatalysis mechanism of black ZrO₂is analyzed:methylene blue adsorbs on the surface of ZrO₂,the light causes the increase of the number of photons on the surface of ZrO₂,and the energy of the system.The separated electrons and holes are trapped by defects and are not easy to compound.With the increase of illumination,more electrons and holes are trapped,and then interact with free hydroxyl?·OH?and superoxide?·O₂?to degrade the dye.