Preparation Of Porphyrin-sensitized PSf/TiO₂ Organic-inorganic Film And Its Photocatalytic Hydrogen Production Performanc

The massive consumption of traditional fossil fuels leads to serious problem of environmental pollution.Hydrogen is regarded as an efficient and green energy in the 21^st century with the advantages of high combustion heat and no by-products.The preparation of hydrogen from splitting water by solar energy has attracted much attention because of its green and environmental friendly.It means that the development of efficient photocatalysts with great solar response is the key to carry out this new technology.Porphyrin sensitized TiO₂ has excellent performance of splitting water to hydrogen,but porphyrin molecules tend to aggregate on the surface of TiO₂,resulting in intermolecular energy quenching.What’s more,it is cumbersome to separate the photocatalytic nanoparticles from reaction system for recycling purposes.These limit the practical application of porphyrin sensitized TiO₂.In order to solve the above problems,porphyrin sensitized organic-inorganic photocatalytic membranes（MMMs）were constructed in this paper with polysulfone（PSF）as the carrier and linker of porphyrin and TiO₂,and the performance of MMMs in splitting water to hydrogen induced by UV-visible light was investigated.Firstly,5,10,15,20-meso-tetra（p-hydroxyphenyl）porphyrin grafted on surface of polysulfone/TiO₂ MMMs（THPP-sg-PSf/TiO₂MMMs,abbreviated as P_y-M_x,y is the grafting time of THPP and x is the mass fraction of the added TiO₂）were prepared by NIPS and in-situ grafting method.It was characterized by FT-IR,XRD,SEM and XPS.Then,the influence of TiO₂ doping amount,THPP grafting amount and sacrificial agent on the performance of UV-Vis induced hydrogen evolution were explored.The hydrogen production performance of P₁₂-M₃ under 12 h UV-vis light irradiation is 9.74mmol/m²,which is 1.73 times higher than that of M₃.The apparent quantum yield（AQY）atλ=420 nm P₁₂-M₃ is 6.4%.Finally,the electron transfer rate constant(k _ET),the excited state oxidation potential of the dye(E_OX（dye*）),electron spin resonance（ESR）and the density functional theory（DFT）of the dye were tested,and it is verified that P_y-M_x can quickly produce photogenerated electrons to participate in splitting water to hydrogen.Inspired by photosynthesis,metal ions complexed in the central of porphyrins can further enhance their photosensitization abitity.Metal（Ⅱ）-5,10,15,20-meso-tetra（p-hydroxyphenyl）porphyrin grafted on surface of polysulfone/TiO₂ MMMs（MTHPP-sg-PSf/TiO₂MMMs,abbreviated as MP_y-M_x,M=Cu,Zn,Ni）were constructed by NIPS and in-situ grafting method.Similarly,it was characterized by FT-IR,XRD,SEM and XPS.The performance of UV-Vis induced splitting water to hydrogen catalyzed by MP_y-M_xshows an increasing order of Ni P₁₂-M₃<P₁₂-M₃<Zn P₁₂-M₃<Cu P₁₂-M₃,and the hydrogen production by Cu P12-M3 was up to 70.63 mmol/m²,which is 7.25 times higher than that of control membrane without metal ion(P₁₂-M₃).The AQY atλ=420 nm and solar-to-hydrogen（STH）efficiency of Cu P₁₂-M₃ were 31.7%and 8.26%respectively,which are better than most reported photocatalysts.Finally,the k _ET,E_OX（dye*）,ESR and DFT were further tested.It proved that different metal ions complexed in porphyrin center can change the transfer rate of photogenerated electrons and lead to the difference in the performance of splitting water to hydrogen.It also provides an effective strategy for improving dye-sensitized semiconductors performance of photo induced splitting water to hydrogen.