Modified Preparation And Photocatalytic Applications Of Titanium Dioxide Nanowire Microspheres

With the rapid development of modern industrial civilization and the continuous progress of human society,environmental pollution and energy problems have become the major problems that human society needs to solve in the 21st century.Photocatalysis technology can utilize abundant solar energy for energy production and environmental treatment,and has attracted much attention because of its advantages such as being green,economic,mild reaction conditions,and high efficiency.However,the high cost of semiconductor materials,low solar energy utilization and easy compounding of photogenerated electron-hole pairs have hindered the large-scale application of this technology.Therefore,it is of great significance to design cost-effective photocatalysts to further their practical application.Currently,titanium dioxide（TiO₂）is considered as the most typical photocatalytic material,which is widely studied in the application fields of photocatalytic CO₂ reduction and antibacterial because of its excellent stability,low cost and non-toxicity.However,TiO₂ has a wide band gap and can only absorb ultraviolet light,and the solar energy utilization and photocatalytic efficiency are low,so there are still some limitations in practical applications.Thus,it is of great importance to develop green,economical and efficient TiO₂ photocatalytic materials for CO₂ reduction and antibacterial packaging.In this paper,TiO₂ nanowire microspheres were used as the substrate,and different TiO₂ photocatalytic materials were modified by surface design and energy band modulation to achieve a significant improvement of TiO₂ photocatalytic efficiency.Then,the mechanism of photocatalytic CO₂ hydrogenation and antibacterial reaction was explored,as well as the practical application performance of TiO₂ materials assembled into macroscopic components,which provides guidance for the practical application of TiO₂ materials in environment and energy.The main content includes the following two areas:（1）The TiO₂ nanowire microspheres were prepared by alkali hydrothermal method,and then Cu Pt alloy and TiO_2-x（OH）_y disordered layer were constructed on the surface by the"double catalytic site"strategy,and the TiO₂ was modified by SFLP and Cu Pt alloy.The structure,composition,morphology,optical properties and photocatalytic CO₂ hydrogenation mechanism of the photocatalytic materials were also investigated by XRD,SEM,TEM,EPR,XPS,BET and DRIFTS.The characterization results show that TiO_2-x（OH）_y disordered layers and Cu Pt alloys are successfully constructed on the TiO₂ surface,while metal nanoparticles affect the energy band structure of TiO₂,and the band gap is significantly narrowed after the loading alloy.The photocatalytic CO₂ hydrogenation performance experiments showed that Cu Pt/TiO_2-x（OH）_y/TiO₂ was significantly more active in the RWGS reaction compared with TiO_2-x（OH）_y/TiO₂,Cu Pt/TiO₂ and pristine TiO₂,with CO yields up to 20 mmol?g?¹?h?¹,with CO selectivity above 99%.This can be attributed to the fact that the amorphous TiO_2-x（OH）_y can form an effective SFLP to increase the activation of CO₂,while the Cu Pt alloy facilitates the dissociation of H₂ to promote the formation of protonated/hydrogenated hydrogen.In addition,the cycling experiments showed that the Cu Pt/TiO_2-x（OH）_y/TiO₂ catalyst also has good stability.This study provides guidance for further exploration of TiO₂ modification strategies as a feasible way to address the greenhouse effect and energy shortage.（2）The g-C₃N₄-modified TiO₂ composite photocatalyst was prepared by a one-step calcination method using TiO₂ nanowire microspheres as the substrate,and the TiO₂ was modified by using heterojunctions.The composite photocatalyst was further introduced into the chitosan（CS）and polyvinyl alcohol（PVA）blends,and the g-C₃N₄-TiO₂/CS/PVA photocatalytic composite film was prepared by the phase transition method.The structure,composition and morphology of the materials were also characterized by XRD,SEM,TEM and XPS analysis techniques.The results showed that the g-C₃N₄/TiO₂ nanoparticles were successfully prepared and regularly distributed in the CS/PVA film.The physical properties of g-C₃N₄-TiO₂/CS/PVA photocatalytic composite films were also analyzed by tensile test,water contact angle（WCA）and water vapor permeability（WVP）.The results illustrated that the incorporation of g-C₃N₄/TiO₂ nanoparticles reduced the hydrophilicity and water vapor permeability of the films.The g-C₃N₄-TiO₂/CS/PVA composite film was found to have better antibacterial freshness preservation performance through photocatalytic antibacterial preservation experiments.At the preservation time of 96 h,the strawberries preserved by g-C₃N₄-TiO₂/CS/PVA composite film also remained in a better condition without bacterial infestation compared with PE film,CS/PVA film,g-C₃N₄/CS/PVA film and TiO₂/CS/PVA film.This was attributed to the successful formation of Z-type heterojunction of g-C₃N₄/TiO₂,which effectively improved the separation efficiency of photogenerated electrons and holes with excellent photocatalytic activity.In addition,the g-C₃N₄-TiO₂/CS/PVA composite film possesses recyclability and the antimicrobial preservation properties remain largely unchanged.This study provides a new approach in food preservation and packaging,saves resources and generates no secondary pollution,and promotes the development of photocatalytic technology in the agricultural field.