Research On Photothermal Enhanced Black TiO₂ Photocatalytic Biomimetic Composites

With the shortage of energy and the deterioration of environment,photocatalysis plays an increasingly important role.The energy of ultraviolet light in sunlight is only 5%,and the energy of visible light and near-infrared light reaches 95%.While the traditional photocatalyst can only use ultraviolet light,resulting in its low utilization rate of solar energy.There are many methods to improve the photocatalytic performance of semiconductors,such as semiconductor modification for band gap width reduction,and external fields enhancement of catalytic performance.But none of these methods can make use of solar energy in the near-infrared region.On the one hand,photothermal enhancement of photocatalysis can utilize the long wavelength of sunlight to produce photothermal effect.On the other hand,carriers generated by semiconductor photoexcitation provide photocatalytic activity.The photothermal effect can affect the photocatalytic performance by temperature rise and enhance the photocatalytic performance.The existing research idea of photothermally enhanced photocatalysis is to combine semiconductors with other materials with photothermal effects to provide photothermally enhanced effects,including precious metals and graphene.However,because photothermal and photocatalytic activities are generated by different materials,it is easy to separate the active sites of the two,which will easily lead to the decrease of the overall activity and fail to achieve the effect of synergistic enhancement.Moreover,there ara few researches on photothermal enhanced photocatalysis at home and abroad.Therefore,how to integrate photothermal and photocatalysis on the same material has become the current research direction.In recent years,black TiO₂ has received extensive research and attention.Black TiO₂ retains the main structure of TiO₂,and its color changes from white to gray or even black.Black TiO₂ can not only extend light absorption to visible or near-infrared,improve solar energy utilization,but also improve photocatalytic activity,which can be applied in various fields.Therefore,black TiO₂ can be studied as a photothermally enhanced photocatalytic material.However,the preparation of traditional black TiO₂needs to be completed under high pressure conditions of hydrogen,and the process is relatively complex and dangerous.Moreover,photocatalytic cycling is poor because photogenerated electrons and hole pairs are easily oxidized in the air,resulting in low carrier lifetime and poor photocatalytic cycling.In response to these problems,this study has a unique approach to integrating light absorption and photocatalytic active sites on a single material.Using TiH₂ as raw material,black TiO₂ material with photothermal enhanced photocatalytic properties was obtained by oxidation treatment and subsequent calcination process.At the same time,by controlling the calcining temperature,the light absorption and photocatalytic activity of black TiO₂ were adjusted to enhance the photocatalytic performance in coordination with the overall photothermal enhanced photocatalysis.As the recovery of powder catalyst is difficult and may cause secondary pollution,some carrier materials are needed to expand its application range.Inspired by the microstructure of lotus leaf surface and its strong hydrophobicity and self-cleanliness,black TiO₂ thin film/glass fiber cloth composites were prepared based on glass fiber cloth in this study.The composites successfully imitate the rough structure of lotus leaf surface,and has strong hydrophobicity and anti-reflection properties,and achieves the effect of photothermal enhancement of photocatalytic properties.In summary,the main contents of this study are as follows:?1?Secondary precursors containing polyvalent titanium ions were obtained by pretreatment with bivalent titanium ion hydride as the initial precursor.Taking this as the main composites'agent,the influences of sintering atmosphere,hot sintering temperature and thermal reaction time on the photothermal enhanced photocatalytic performance were studied to optimize the black TiO₂ formula combination with the best.The synthesized TiO₂?B?has strong light absorption capacity in the wavelength range of 250 nm to 2000 nm.The TiO₂?B?calcined at T°C has the best photocatalytic ability to degrade organic pollutants,and the degradation efficiency at 2 h is 1.6 times that of P25.This temperature is the best calcination temperature for photothermal photocatalytic performance.?2?Inspired by the lotus leaf configuration with surface superhydrophobicity and anti-reflective properties of disordered mastoid arrays,black TiO₂ thin film/glass fiber cloth composites material with microstructure of bionic lotus leaf surface was prepared by combining black TiO₂ with glass fiber cloth with optimized photothermally enhanced photocatalytic properties by facile sol-gel method.By studying the surface morphology,composition structure and light absorption performance of the composites,the bionic structure and the influence mechanism of composition defects on light absorption and photocatalysis were confirmed.?3?After determining the composition and structure of the composites,this chapter focuses on testing the various properties of the material,including its hydrophobic properties,photothermal properties,low light absorption angle dependence,and photocatalytic properties and cycle stability.Through these tests,the photothermal properties and photocatalytic properties of the materials were investigated,and the effects of photothermal on the photocatalytic properties were verified.Finally,the photothermal enhanced photocatalytic properties were also confirmed.The photothermal test confirmed that the synthetic biomimetic composites had better photothermal heating effect,and the photocatalytic degradation efficiency of the composite was 2.5 times that of P25,which had excellent photothermal enhanced photocatalytic performance.