Preparation And Application Of TiO₂,SiO₂@Ni/TiO₂ Microspheres

TiO₂ is one of the most widely concerned materials in the field of photochemistry due to its high stability,low cost,non-toxicity and good light collection characteristics.Scattering is an important physical phenomenon in the interaction between light and matter.When the scattering wavelength is located in the visible light,the scattering color will be generated.TiO₂?anatase,².5?can lead to more effective scattering because of the high refractive index.Mie scattering theory,as an important scattering theory,can describe the scattering characteristics of spherical particle.In addition,the light scattering efficiency largely depends on the size of scattered particles,so the preparation of monodisperse TiO₂ spheres with appropriate particle size is crucial for Mie scattering structure color.In this paper,monodisperse TiO₂ with large particle size?>400 nm?was synthesized by room temperature method.Oleic acid?OA?and polyvinylpyrrolidone?PVP?were used as ligands to reduce the hydrolysis rate of titanium source?n-butyl titanate?,and steric effect was used to prevent the aggregation of nanoparticles.Amorphous TiO₂ microspheres with average particle sizes of 480 nm,650 nm and 930 nm were prepared by adjusting the amount of deionized water.TiO₂microspheres were sprayed on the glass slides,and the strong scattering of TiO₂ spheres was utilized to achieve color rendering.TiO₂ microspheres were calcined at 500?because of the low refractive index,so that the crystal form of TiO₂ microspheres changes into anatase.The scattering effect is enhanced with the increase of refractive index,and the scattering color is red-shifted,which is consistent with the corresponding color of the transmission spectrum measured.In the field of photochemistry,TiO₂ is limited by high electron-hole recombination rate,wide band gap and low adsorption capacity in photocatalytic application.Doping noble metal nanoparticles can inhibit the recombination of photo-generated carriers,but greatly increase the cost.The photonic band gap?PBG?structure of photonic crystal?PC?prohibits the propagation of light at specific wavelengths.Meanwhile,the metal Ni has low cost and high CO₂ adsorption affinity,which can be used for photocatalytic CO₂ reduction instead of noble metals.In this paper,SiO₂@Ni/TiO₂ PC were prepared to improve the catalytic activity of photocatalytic CO₂ reduction by using the PC to inhibit photo-generated electron of organic dyes and Ni with the high adsorption affinity of CO₂.Monodisperse SiO₂@NiSiO₃ microspheres were prepared with SiO₂microspheres as templates under hydrothermal conditions.They were assembled into PC by consecutive dip-coating method,then TiO₂ precursors were filled in the void of SiO₂@NiSiO₃ PC.Finally,SiO₂@Ni/TiO₂ PC were prepared under high temperature reduction atmosphere.The photocatalytic reaction system was composed of SiO₂@Ni/TiO₂ PC as photocatalyst,triethanolamine as sacrificial agent and tripyridine ruthenium as photosensitizer to reduce CO₂ to CO.It has been proved that when the PBG of SiO₂@Ni/TiO₂ PC matches with electron-hole combination energy of the photosensitizer,the excited electron-hole combination of the photosensitizer can be effectively inhibited.Meanwhile,increasing the specific surface area can strengthen the adsorption of CO₂ and improve the photocatalytic reduction performance,which provides a new solution for the field of photocatalytic CO₂ reduction.