| Hydrogen is one of the most potential substitutes for fossil fuels with high energy density and high calorific value.In the preparation of hydrogen,photocatalytic water splitting technology is an ideal way of hydrogen production,which can convert solar energy into hydrogen energy.Ti O2 Photocatalyst is corrosion-resistant,nontoxic and cheap.However,the wide band gap,low specific surface area and rapid recombination of electron and hole limit its photocatalytic efficiency.Modification through morphology control and semiconductor compounding is effective approach to improve the photocatalytic efficiency of Ti O2.As a Ti-based metal-organic frameworks（MOFs）,MIL-125 can be used as a precursor to synthesize Ti O2,which has the advantages of controllable morphology and size,stable porous structure and not easy to agglomerate.In addition,the MIL-125 composites after further rational design and modification can be oriented to synthesize Ti O2-based photocatalysts.In view of this,Ti O2 based photocatalyst for the photocatalytic hydrogen evolution was designed and synthesized by a simple and efficient controllable MOFs precursor method.The main conclusions are as follows:（1）Prepared g-C3N4/MIL-125 by solvothermal method and H2WO4/MIL-125 by gradient heating method,and calcined the two in air to prepare mesoporous g-C3N4/Ti O2 and WO3/Ti O2 composite photocatalyst.The structure-activity relationship and photocatalytic mechanism of g-C3N4/Ti O2 and WO3/Ti O2 photocatalysts were studied by XRD,SEM,N2-BET,XPS,UV-vis absorption and electrochemical testing.The results show that Ti O2 derived from MIL-125 inherits the structural characteristics of the parent MOF,has rich mesoporous structure and large specific surface area,which can provide electron transport channels and active sites for photocatalytic reactions.With the increase of g-C3N4 and WO3 content,the band gap of g-C3N4/Ti O2 and WO3/Ti O2were gradually narrowed,the light response range were gradually widened.Furthermore,these two composite materials formed a type II heterojunction at the interface which can promote the separation of photo-generated electrons and holes and extend the life of the charge.（2）The hydrogen evolution performance of g-C3N4/Ti O2 and WO3/Ti O2 composite materials were tested under the irradiation of a simulated solar light source,with the triethanolamine aqueous solution as reaction system.The results show that the hydrogen evolution performance of the two was significantly better than that of single-component semiconductors,and the content of g-C3N4 and WO3 in the composite material has an optimal value.When the g-C3N4 content of g-C3N4/Ti O2was 4.12%and the WO3content of WO3/Ti O2 was 2%,the average hydrogen evolution rates of the two composite materials were the highest,which transcended that of as-prepared mesoporous Ti O2 by a factor of 4.41 and 2.48,respectively. |
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