Synthesis And Modification Of Ti-based Photocatalyst Materials And Study On The Photocatalytic Performance For Water Splitting Into Hydrogen

Energy sources are materials or movements providing energy for human.They are the foundation for human activity and development of human society.Compared with traditional fossil fuels,such as coal and oil,bring destruction on the environment; Hydrogen is an alternative energy source with high efficiency and pollution free. Hydrogen can be produced from clean and renewable energy sources,and thus its life cycle is clean and renewable.The photocatalytic water-splitting into hydrogen using semiconductor is a potentially clean and renewable method which is of both theoretical and practical significance.Searching for highly reactive and functional photocatalyst is the key.TiO₂ as a traditional photocatalyst and another photocatalyst with perovskite-layered structure have drawn more and more attention.The paper reports synthesis and modification of Sr₃Ti₂O₇ and TiO₂ semiconductor.The detailed contents are as follows:(1) Sr₃Ti₂O₇ photocatalyst with perovskite-layered structure was synthesized by polymerized complex method(PCM).Cu ion as an effective dopant was loaded onto Sr₃Ti₂O₇ catalyst,ωCu/Sr₃Ti₂O₇ catalyst was applied in the mixture of water and methanol,methanol was used as a sacrificial agent under ultra-violet irradiation,and the catalyst was characterized by XPS,XRD,and UV-Vis DRS.The results showed that Cu ion existed in several kinds of valence and the photocatalytic activity of Cu/ Sr₃Ti₂O₇ was superior to that of pure Sr₃Ti₂O₇.Cu⁺ and adsorption oxygen can accelerate the interfacial electron transfer.When the amount of Cu ion was 1.5%(w), the best catalytic effect was obtained and the stable average hydrogen evolution rate was about 550-600μmol·h^-1.TheωCu/Sr₃Ti₂O₇ after reduction attained the highest hydrogen evolution rate that was close to 1140.8μmol·h^-1.The value was seven times of NiO/Sr₃Ti₂O₇ reported before.The paper reported that synthesis method of Sr₃Ti₂O₇ with perovskite-layered structure loaded with transition metal ion(Cu,Ag ion) with several valences.The optimal loading of Cu ion could enhance the photocatalytic activity greatly and that was explained by the mechanism that of loading Cu ion like such several valences can help semiconductor transferring charge and reaction.The content of Cu⁺ and adsorption oxygen in photocatalyst tested by XPS characterization could testify the explanation.In addition,loading of the same main group Ag ion has been investigated. At the optimal loading of Cu ion,hydrogen production rate was enhanced as much as 35.5 times higher than loading of Ag ion.(2) Mesoporous TiO₂ nanocrystals with anatase phase and high specific surface area was synthesized by sol-gel process using nonionic surfactant EO₂₀PO₇₀EO₂₀ as a structure-directing agent,C₁₆H₃₆Ti as Ti precursor,La₂O₃ as catalyst support and ethanol as an extraction agent.Then removed template in moderate condition that was washing by reagent.The results indicated that the amount of doped La₂O₃ greatly effected on the formation of TiO₂ with anatase phase,and the optimal content of doped La₂O₃ was 0.1%(mole fraction).The characterizations of XRD,BET,IR and HRTEM showed that an ordered mesostructure of TiO₂ with narrow pore size distribution and large surface area(～367.7 m²Â·g^-1) was obtained under the synthesis conditions.In the paper,Mesoporous TiO₂ doped with rare earth was synthesized.The intensity of TiO₂ inorganic framework and the stability of the mesoporous structure were stronger than non-La₂O₃ doped.When the template was washed by boiling ethanol,anatase phase was formed.It indicated that doping La₂O₃ could accelerate the formation of anatase phase.Study on rare earth how to affect structure,crystal and photocatalytic activity.Both of two experiments have indicated the optimal loading of Cu or doping of La₂O₃ clearly.