Preparation Of TiO₂-based Photocatalyst And Study Of Its Photocatalytic Water Splitting For Hydrogen Production

Nowadays,with the rapid depletion of natural resources such as coal,petroleum and natural gas,exploring long-term sustainable renewable energy has become one of the primary tasks for human survival and development.As an environmental friendly energy source,hydrogen has many advantages,such as high calorific value,easy to transport and regeneration.Therefore,converting solar energy to hydrogen is one of the best ways to develop new energy sources.Photocatalytic water splitting for hydrogen production can directly use solar energy to produce hydrogen from water,without consuming other energy sources,and it doesn't pollute the environment.Photocatalytic water splitting for hydrogen production has been extensively studied and became the most promising technology of hydrogen production.It is well known that TiO₂ is one of the most promising photocatalysts due to its excellent performance of photoelectrochemical properties,low cost,corrosion resistance and strong redox ability.However,due to low absorption of sunlight,high recombination of photogenerated carriers and low quantum efficiency,the development of TiO₂ in the photocatalytic hydrogen production field is severely restricted.In order to solve the above issues of TiO₂ catalysts,this paper focuses on how to control the surface and interface structures,promoting the efficient separation and transmission of photo-generated carriers,enhancing the absorbance of sunlight,achieving the unity of the high efficiency and stability.The main work is as follows:TiO₂ nanorods were prepared by an hydrothermal process.Using TiO₂ nanorods as precursor and hydroquinone as carbon source,TiO₂/C nanorods without a Ti-C chemical bond and TiO₂-C nanorods with a Ti-C chemical bond connection were constructed by a vacuum infiltration and a solid sintering process.The microstructure,composition,the separation efficiency of electron and hole,band structure and hydrogen production performance of the obtained materials were studied.Compared with TiO₂/C nanorods without a Ti-C bonded interface,the separation efficiency of photogenerated electrons and holes in TiO₂-C nanorods with a Ti-C chemical bond interface improves significantly.More active electrons can be generated on the surface of TiO₂-C nanorods,the H₂ evolution rate of TiO₂-C catalysts is around 7294?mol h^-1 g^-1 at 420 nm,which is significantly higher than those of TiO₂/C(605?mol h^-1g^-1).Meanwhile,the TiO₂-C nanorods also retain high photocatalytic activity after ten cycles of 40 h reaction,which proves the catalytic stability of this material.This composite material with a chemical bond connection can promotes the effective separation of electrons and holes.A lot of stable Ti³⁺doping in the TiO₂/C/Pt is achieved by a simple chemical reduction method.The absorbance ability and electron transport behavior of the sample were characterizedbyUV-visabsorptionspectroscopy,photocurrentmeasurements,photoluminescence measurements,Mott-Schottky measurements.It is demonstrated that a lot of stable Ti³⁺doped TiO₂/C/Pt material shows high photocatalytic activity under visible light irradiation,the carrier density is up to 13.9×10¹⁸cm^-3.The rate of photocatalytic water splitting for H₂ generation is 8117?mol h^-1 g^-1,which is sixteen times as high as that of TiO₂/C nanorods(507?mol h^-1 g^-1).Therefore,under visible light irradiation,photocatalytic water splitting for hydrogen production of the abtained sample greatly improves and maintains good stability.This method opens up a new window for constructing a large number of stable Ti³⁺doped TiO₂ photocatalysts.TiO₂ nanosheets with F selectively doped and etched{001}facets were prepared by a simple hydrothermal method.The transport behavior of photogenerated carriers in the sample were characterized by photocurrent measurements,photoluminescence measurements,Mott-Schottky measurements.The results show that F selectively doped and etched{001}facets of anatase TiO₂ can use its own characteristics,photogenerated electrons and holes can transport to different crystal planes.By reducing the transport distance of photogenerated holes and introducing of Ti³⁺and oxygen vacancy defects in the{001}crystal plane,the separation and transfer efficiency of carriers is effectively improved.Under visible light irradiation,the photocurrent density is up to 0.71 mA cm^-2,which is much higher than that of of TiO₂ precursor nanosheets(0.11 mA cm^-2).Therefore,the photocatalytic activity of TiO₂ is greatly improved.The maximum hydrogen production rate of the abtained nanosheets can reach 18270?mol h^-1 g^-1.The 2D g-C₃N₄/{001}TiO₂ composite photocatalysts with a Ti-C chemical bond connected interface were constructed by a solvothermal method and a solid sintering method.And 2D g-C₃N₄ nanosheets in g-C₃N₄/{001}TiO₂ composite photocatalysts are ultrathin.The large area of the strong contact interface can effectively reduce the energy loss in the transfer process of photogenerated electron and hole,reduce the recombination rate of photogenerated carriers and accelerate the mobility of photogenerated carriers.Consequently,the hydrogen production performance of the photocatalyst is greatly enhanced.Under visible light irradiation,the carrier density is up to 24.06×10¹⁸cm^-3,which is outstanding higher than that of TiO₂ nanosheets precursor(3.92×10¹⁸ cm^-3).The TCN nanosheets show high hydrogen production rate of 11367?mol h^-1 g^-1 and stable photocatalytic activity by optimized the content of g-C₃N₄ in the catalyst.After a 40 h reaction cycle,the hydrogen production rate of the obtained sample didn't change.