Organic Dye Sensitized Reduced Graphene Oxide:Formation And Application For Photocatalytic Water Splitting

Hydrogen,one of the primary candidates as a future energy carrier,has recently attracted increasing attention due to the growing environmental concerns and the increasing energy demands.One of the best ways to produce H₂ from renewable sources is water splitting under solar irradiation in the presence of photocatalysts.To achieve this goal,many semiconductors,organic/inorganic composites and carbon-based photocatalysts have been intensively investigated.Recently,graphene has been attracted much attention because of its superior applications in the fields of electronics,optics and catalysis.Due to its high specific surface area,and high electron mobility up to10000 cm² V^-1 s^-1,graphene is a very prospective electron transporter to enhance photoinduced charge transfer for improving catalytic activity.In this paper,we firstly report the synthesis,characterization and photocatalysis of siliconphthalocyanine?SiPc?andtri?isothiocyanato??2,2';6'2”,-terpyridyl-4,4';4”-tricarboxylicacid?ruthenium?II??N749?covalently functionalized reduced graphene oxide.These nanohybrid were used as photocatalysts for photocatalytic hydrogen evolution from water.Then,in order to achieve the ideal process of photocatalytic water splitting,we designedaphotoelectricchemicalcell.TheMn₃O₄and meso-Tetratolylporphyrin-Mn?III?-chloride?PMA?sensitized TiO₂ photonic crystal?Mn₃O₄/PMA/TPC?electrode was used as photoanode,and the MnPP sensitized reduced graphene oxide?RGO/PMA?electrode was used as photocathode.The photoanode and photocathode were characterized by SEM,TEM,UV-vis spectra,and linear sweep.We studied the H₂ and O₂ evolution ability of the photoelectric-chemical cell.The main points were summarized as follows:?1?We designed and synthesized silicon phthalocyanine?SiPc?covalently functionalized N-doped ultra-small reduced graphene oxide?N-usRGO?through 1,3dipolar cycloaddition of azomethine ylides.SiPc covalently functionalized N-usRGO?N-usRGO/SiPc?exhibits much improved photocatalytic activity compared to N-usRGO,which is attributed to nice absorption to the visible light of SiPc moiety and its covalent bonding to the usRGO sheet as well as the effective restraint of the recombination of the photoexcited electrons and holes.To improve H₂ production,Pt nanoparticles?NPs?were loaded on N-us RGO/SiPc sheets as cocatalyst by photodeposition.The platinized N-usRGO/SiPc?N-usRGO/SiPc/Pt?exhibited satisfactory photocatalytic activity under both UV-vis and visible light??>400 nm?irradiation.Moreover,with the increasing of amount of the doped N in usRGO,N-usRGO/SiPc/Pt showed the enhanced photocatalytic activity.These results reveal that N-usRGO/SiPc/Pt nanocomposite with the full advantages of SiPc,N-usRGO and Pt NPs can act as a novel candidate to produce hydrogen from water under solar light irradiation.?2?In order to extend the range of light absorption of graphene to near infrared region,we report design,synthesis and photocatalysis of a novel N749 covalently functionalized reduced graphene oxide?RGO/N749?nanocomposite.Here,N749grafted on the RGO acts as a sensitizer to harvest incident light,and the RGO acts as an excellent electron mediator to adjust electron transfer.The RGO/N749 nanocomposite exhibits much improved photocatalytic activity compared to rGO.Moreover,platinized RGO/N749?RGO/N749/Pt?shows satisfactory photocatalytic activity under both UV-vis and visible light??>400 nm?irradiation.These results reveal that RGO/N749/Pt nanocomposite with the full advantages of N749,RGO and Pt NPs can act as a novel candidate to produce hydrogen from water under solar light irradiation.?3?In order to achieve the ideal process of photocatalytic water splitting,we designedaphotoelectric-chemicalcell.TheMn₃O₄and meso-Tetratolylporphine-Mn?III?-chloride sensitized TiO₂ photonic crystal?Mn₃O₄/PMA/TPC?electrode was used as photoanode,and the Pt was used as counter electrode.The two electrodes were assembled in a photoelectric-chemical cell,and used for photocatalytic water splitting.The photoanode was characterized by SEM,TEM,UV-vis spectra,and linear sweep.We also studied the H₂ and O₂ evolution ability of the photoelectric-chemical cell.?4?We prepared PMA sensitized reduced graphene oxide?RGO/PMA?by?-?stacking.We designed a photoelectric-chemical cell which was consisited of RGO/PMA covered FTO electrode acting as photocathode and Mn₃O₄/PMA/TPC electrode acting as photoanode.The two electrodes were assembled in a photoelectric-chemical cell,and used for photocatalytic water splitting.The photocathode was characterized by AFM,UV-vis spectra,Raman spectra and linear sweep.We also studied the H₂ and O₂evolution ability of the photoelectric-chemical cell.