Synthesis Of Titanium Based Photocatalyst And Its Photocatalytic Activity

Light absorption,carrier separation and interfacial reaction are three key scientific problems in the field of photocatalytic process.In this paper,doping metal ions,loading precious metals,crystal surface engineering and composed with other materials were used to prepare high efficient,inexpensive and stable wide spectral response titanium-based photocatalyst.These studies may provide some basic data and theoretical support for the large-scale application of titanium-based semiconductor.(1)Anatase TiO2 nanocrystals with regular polyhedron morphology and co-exposed{001} and {101} facets are prepared,and then ultrafine Ag nanoparticles(SAg NPs)with different sizes are loaded on those TiO2 facets(denoted as SAg-TiO2)through a novel in situ photoreduction approach.By adjusting the illumination time,light wavelength and temperature,SAg NPs with a small size(1-6 nm)are highly dispersed on both {001} and {101} facets of TiO2.SAg-TiO2 with ultrafine SAg NPs on both{001} and {101} facets of TiO2 results in more substantial visible-light-responsive photoactivity and stability than PAg-TiO2 with larger Ag NPs on {101} facets of TiO2.Moreover,the RhB photodegradation reaction rate constant of SAg-TiO2 with Ag particle size of 1 nm is 10 and 21.3 times higher than that of PAg-TiO2 and the pristine TiO2,respectively.This work can provide guiding information for the other M@semiconductor(M = Au,Pt,Cu,Pd)nanostructured materials with tunable photocatalytic activity.(2)Three anatase TiO2 with different {001} and {101} facets exposing percentage are prepared,then Ag and MnOx co-loaded on those TiO2 facets through a classical photo-deposition method(denoted as Ag-TiO2-MnOx(N%),where N%means the percentage of exposed {001} facets.The interfacial effects of as-prepared samples were analyzed by X-ray photoelectron spectroscopy(XPS),which demonstrated that different connection mode were formed between cocatalyst-TiO2(N%)interfaces.No chemical bond in cocatalyst-TiO2(20%)interfaces;a strong chemical bond(Ti-O-Mn)at Ag-TiO2-MnOx(40%)interface and a Ti-O-H bond was formed at cocatalyst-TiO2(60%)interfaces.PL and VB spectrum revealed the chemical bond at Ag-TiO2-MnOx interface greatly accelerate the holes mobility rate and the photo-induced carrier separation efficiency which result in higher photo-reduction CO2 activity.This work provide an experimental and theoretical support for understanding the interfacial effects of crystal surface engineering and co-catalyst.(3)A large number of TiO2NPs are in-situ grown into the cages of MOFs via a mild conditions.The CO and CH4 production rate are reached at 9200 and 1900 μmolg-1h-1,respectively,which is about a thousand times of pure TiO2.Mechanism studies show MOFs play dual roles in this composite photocatalyst:firstly,increased contact interface between semiconductor and MOF,and then enhance the carrier separation efficiency.TiO2-in-MOF composite materials may provide an example to construction of new photocatalyst for reduction of CO2.(4)A ternary photocatalyst(Na2TixCu1-xO3-CuO-Ag)with specific surface nanostructure has been prepared by an one-pot calcination process while using anatase TiO2 as raw material.The unique architecture exhibits a highest NH3 production rate of 300 μmolg-1 h-1 under near-intrared(NIR)light irradiation,and also shown excellent NH3 production activity of 1.3 mmolg-1h-1 under full solar spectrum of Xe-lamp.It is the first time to utilize NIR light to the nitrogen fixation reaction.DRS spectra revealed that doped-Na2TiO3 can absorb the light wavelengths below 1200 nm.The CuO phase can not only absorb the light from visible to NIR regions,but also form a Type II heterogeneous junction with doped-Na2TiO3,then to enhance separation efficiency of photo-induced carriers.XPS spectra demonstrated Ag conenenct with CuO phase.The path of photo-generated carrier were investgated by cryogenic EPR and XPS,which shown photo-generated electrons firstly transfer to Cu2+,and then migrate to superficial Ag to converted N2 to ammonia.This study opens a new idea for how to design a synthetic wide spectrum catalyst for high efficiency nitrogen fixation.