Synthesis Of Carbon Modified Ti³⁺ Doped Porous Structure TiO₂ With Enhanced Photocatalysis

Titanium dioxides have played an important role in photocatalysis because of its low cost,non-toxic and high thermostability.However,the quick recombination of electron-hole pairs and the low visible light response limits its extensive application.Carbon is one of the modification materials for TiO₂ due to its well adsorbability to organic pollutant,stable chemical property and non-toxic.Meanwhile,doping could reduce the energy gap of TiO₂,trap the electrons to stop the recombination of electron-hole pairs and enhance the electronic conductivity,resulting in enhanced photocatalysis of TiO₂.In this paper,we synthesize the mesoporous and hierarchical porous titania,getting the carbon-modified Ti³⁺self-doped hierarchical porous and mesoporous titanium dioxides though tune the calcination atmosphere.The phase structure,microstructure,BET surface area and photocatalysis performance were characterized.The main conclusions were summmarized as follows:The mesoporous TiO₂ was synthesized by the one step method,getting anatase TiO₂ after heating treatment at 400°C in air atmosphere.To get the carbon-modified Ti³⁺self-doped mesoporous titanium dioxides,we heat treatment the samples at400°C in argon atmosphere.The contents of carbon and Ti³⁺of the catalysts were tuned through a facile heat treatment in air.When the carbon content is 19%and Ti³⁺content is 24%,exhibiting a best degradation ratio of crystal violet up to 91.8%than the pure mesoporous TiO₂?34.7%?after 120 min light illumination.The improved photocatalysis properties can be ascribes to carbon and Ti³⁺synergistic effect.The photocatalysis properties improved obvious due to the existence of mesoporous structure.However,the pore size is small and narrow limiting its contact with the organic pollutant.So using PSA microspheres as the macroporous templates to synthesize the hierarchical porous titanium dioxides based on the mesoporous synthesis process.The as-synthesized samples were heat treated at400°C under argon atmosphere to obtain carbon modified Ti³⁺self-doped hierarchical porous titanium dioxides.And then heat treated at 385°C for various time with air flow to tune the content of carbon and Ti³⁺.The results same with the mesoporous titanium show that the crystallite size increases when the air calcination time prolongs and the carbon combined with TiO₂ via the interfacial C-O-Ti bonds.Photodegradation results show that when the carbon content is 18%and Ti³⁺content is 31%,exhibiting high photocatalysis performance to crystal violet than pure TiO₂sample.The degradation ratio is up to 96.5%after 120 min,higher than the pure hierarchical porous TiO₂?49.6%?.Because the macro-mesoporous structure,the hierarchical porous TiO₂ has bigger surface area.These texture structure making the TiO₂ has stronger adsorbability to organic pollutant,faster transmission speeding and more active site,so the hierarchical porous TiO₂ has better catalytic efficiency than the mesoporous TiO₂.Above all,the carbon could broaden the adsorption range of TiO₂ and the doping of Ti³⁺can introduce inpurity energy level to the energy gap of TiO₂,stoping the recombination of electron-hole pairs and enhance the electronic conductivity.The synergistic effect of carbon and Ti³⁺cause the enhanced photocatalysis of TiO₂.