Study On The Preparation And Photocatalytic Performance Of Micro-/nano-structured TiO₂

As a green and sustainable technology,semiconductor-based heterogeneous photocatalysis has received much attention in the last few decades because it has potential to solve both energy and environmental problems.To obtain efficient photocatalysts,various hierarchical semiconductors have been designed and fabricated at the micro/nanometer scale in recent years.TiO₂ is most often investigated due to its biological compatibility,strong oxidizing power,low cost,and long-term stability.It was demonstrated that various hierarchical nanostructures or macro/mesopores in TiO₂ photocatalysts could increase their photodegradation efficiency due to the positive synergistic effect of adsorption,light absorption and charge separation.In this work,we attempted to synthesize micro-/nano-structured TiO₂ by facile solvothermal method,due to its low cost and potential advantage for large-scale production.In the solvothermal reaction system,a series of micro-/nano-structured TiO₂ materials were designed and synthesized through the regulation of the reaction conditions,and the main influencing factors of the preparation of the micro-/nano-structured TiO₂ were investigated.Whereafter,the surface modification of the prepared micro-/nano-structured TiO₂ was studied,and the effect of acetic acid chelation were discussed.The corresponding investigations were mainly focused on the following aspects:1.Micro-/nano-structured carbon-doped mesoporous TiO₂ photocatalysts with different morphologies have been prepared by a facile solvothermal combined with calcining method.The performance of the catalysts was characterized by a variety of characterization methods,such as SEM,TEM,XRD,N₂ adsorption/desorption,XPS,ATR-FTIR,UV-Vis DRS,PL,etc.Using phenol as a model pollutant,the photocatalytic degradation activities of the catalysts were evaluated.The results indicated that micro-/nano-structured TiO₂ was doped by carbonate-like species,and the morphology of the sample can be controlled by controlling the solvothermal time.With the prolonged solvothermal time,the crystallinity of TiO₂ increased,the degree of agglomeration of micro-/nano-structures also increased,and the specific surface area and pore size decreased.Morphological changes can change the energy band structure of the catalyst,leading to the positive shift of the valence band edge,enhancing the oxidative properties of photogenerated holes,reducing the recombination rate of photogenerated carriers,and thus enhancing the photocatalytic degradation activity.2.Based on spherical flower-like micro-/nano-structured TiO₂,surface modification was carried out with acetic acid.Characterization of the sample was performed by a variety of characterization methods.The photocatalytic activity was also evaluated by phenol degradation.The results showed that the obtained samples can possess pure anatase phases,and the crystal phases and morphologies did not change after the modification and degradation.The surface carbon component of the sample was mainly carbonate-like species,which was bonded to TiO₂ in the form of carboxyl chelation and did not change significantly after three rounds of degradation,indicating that the surface modification component was more strongly bound.After the surface modification,the band gap of the sample was significantly reduced,and the absorption in the visible light region was significantly improved.At the same time,the valence band maximum moved towards the positive direction,which enhanced the oxidative properties of the photogenerated holes.The photocatalyst carrier recombination rate of the modified sample was significantly reduced.The results of photocatalytic degradation revealed that the carbon-modified micro-/nano-structured TiO₂ photocatalyst possess high degradation activity and excellent stability.