Preparation And Photocatalytic Performance Of Titanium Dioxide Composite For Hydrogen Production

The problems of energy and environment are becoming more and more prominent,people’s survival and development of the most important task is to find sustainable development of renewable energy.Photocatalytic decomposition of water to produce hydrogen has attracted wide attention because of its clean and environmentally friendly use of solar energy.On this basis,various photocatalysts were designed and synthesized.Among them,titanium dioxide is widely used because of its non-toxicity,low cost and chemical stability.In this paper,a porous hybrid material（NDI/CS-Ti O₂）was designed and prepared using titanium dioxide as the carrier.The material combined with CS-Ti O₂ and organic semiconductor NDI showed high efficiency and lasting photocatalytic activity in the visible light field.At the same time,benzodithiophene-titanium dioxide hybrid material was prepared by sol-gel method.The material also showed photocatalytic performance in the visible light field,which expanded the research of hybrid polymer and titanium dioxide in the field of photocatalytic decomposition of water to hydrogen production.Specific research contents are as follows:（1）Organic-inorganic hybrid materials 1,4,5,8-naphthalenediimide/chitosan-Ti O₂（NDI/CS-Ti O₂）was fabricated via a facile solvothermal process by covalently grafting 1,4,5,8-naphthalenetetracarboxylic dianhydride onto nitrogen doped mesoporous Ti O₂,using chitosan as nitrogen source and porogen.Uv-vis diffuse reflectance spectroscopy（DRS）,Fourier-transform infrared spectroscopy（FT-IR）and X-ray photoelectron spectroscopy（XPS）characterization results illustrated that nitrogen doped mesoporous Ti O₂ nanopowder was successfully prepared and covalently grafted with 1,4,5,8-naphthalenediimide via primary amino groups and the formed organic-inorganic composites not only have porous surface morphology,but also have excellent visible light absorption ability with range even extended to 800 nm.Under visible-light irradiation,the optimized Pt@NDI/CS-Ti O₂system exhibits high hydrogen production activity(618.3 mmol g^-1 h^-1 based on Pt mass),which is over 26 times of CS-Ti O₂ and over 3 times of NDI/Ti O₂.The apparent quantum yields were determined to be 1.9%at 405 nm and 1.6%at 450 nm for Pt@NDI/CS-Ti O₂.This work offers inspiration for the design and synthesis of new organic-inorganic hybrid systems for efficient photocatalysis facilely and low-costly.（2）Titanium dioxide（Ti O₂）has been limited in the field of photocatalysis due to its wide band gap（3.2 e V）and limited absorption in the ultraviolet range.Therefore,organic components have been introduced to hybrid with Ti O₂ for enhanced photocatalytic efficiency under visible light.Here,we report that benzo[1,2-b:4,5-b’]dithiophene polythiophene was an ideal organic material for the preparation of a hybrid material with Ti O₂.The energy band gap of the hybrid material decreased to 2.9 e V and the resulting photocatalytic hydrogen production performance reached 745.0μmol·g^-1·h^-1 under visible light irradiation.Meanwhile,the material still maintained the stability of hydrogen production performance after 40hours of photocatalytic cycle.The analysis of the transient current response and electrochemical impedance revealed that the main reasons for the enhanced water splitting of the hybrid materials were the faster separation of electron hole pairs and the lower recombination of photocarrier ions.Our findings suggest that polythiophene is a promising organic material for exploring hybrid materials that have enhanced photocatalytic hydrogen production.