Preparation Of Novel Carbon-Based Composite Material And Its Photocatalytic Hydrogen Pruduction

Graphene-based carbon materials and carbon-coated nickel （Ni@C） were chosen asinitial materials, and composited with the well-known photocatalyst: TiO₂and CdS. Thus, weprepared a series of graphite oxide （GTO）-TiO₂, graphene oxide （GO）-CdS, reduced grapheneoxide （RGO）-CdS, Ni@C/TiO₂and Ni@C/CdS nanocomposites, and studied theirphotocatalytic H2production. Moreover, we proposed the possible mechanism ofphotocataytic H2production over these composite materials under visible light irradiation.The main contents and conclusion were as follows:（1）. Graphite Oxide （GTO） was prepared by a modified Hummer’s method firstly. Then,a series of GTO-TiO₂nanocomposite was successfully fabricated through a facilehydrothermal process. TiO₂nanocomposites are attached to ptharet isculerfsa cwe iothf GaTvOer aagned/opr airntitcelrec alsaitzeed inotfo～2th0e innmte rlainy ert hoefGTO. The obtained products showed highly visible-light-driven photocatalytic activity in thepresence of triethanolamine （TEOA）.2wt%GTO-TiO₂showed the maximum H2evolutionrate of6.8μmol h^-1under visible light （≥420nm） irradiation and photocatalytic H2evolutionefficiency was significantly enhanced after loading1wt%Pt, reaching380μmol h^-1, whichwas about91.7times higher than that of GTO. Furthermore, the composite showed anexcellent stability during a long time photoreaction test.2wt%GTO-TiO₂also showed awide photoresponse under monochromatic light wavelength ranged from350to550nm. TheAQY under420nm monochromatic light irradiation was ca.8.2%. The GTO could serve as aphotosensitizer in the present GTO-TiO₂system and expand the spectral responsive range ofTiO₂to visible light. Moreover, the photogenerated electron could transfer from GTO to TiO₂in this system. Therefore, we believed that GTO-TiO₂composite was a widely spectralresponsive, efficient and stable photocatalyst. It showed a potential application prospect inphotocatalytic H2production under visible light irradiation.（2）. Graphene-based carbon materials （GT, GO and RGO） were used raw materials, aseries of RGO-CdS and GO-CdS were prepared by dimethylsulfoxide （DMSO） solvothermalprocess and precipitation process, respectively. The aggregation was suppressed afterimplanting carbon materials. It was found that all carbon-based CdS composites, includingGraphite-CdS, GO-CdS, and RGO-CdS, showed enhancement of photoactivity compared to CdS.10wt%RGO-CdS showed the maximum H2evolution rate of420μmol h^-1in thepresence of sacrificial reagents （Na2S+Na2SO3） under visible light irradiation. Besides,5wt%GO-CdS prepared by a precipitation process showed the maximum H2evolution rate of314μmol h^-1in this condition.5wt%GO-CdS and10wt%RGO-CdS without Pt-loading bothshowed an excellent photoactivity with AQY of ca.4.8%and10.4%at420nmmonochromatic light irradiation, respectively. The implanted graphene-based carbonmaterials could enhance the photoactivity and photostability of CdS, and played twoimportant roles such as suppressing the photogenerated carrier recombination as anelectron-transfer channel and acceptor, and support of CdS in aqueous solution.（3）. Carbon-coated Ni （Ni@C）/TiO₂（anatase phase） composite was prepared through ahydrothermal process. The resultant Ni@C/TiO₂composite was composed of nanorods withan average diameter of ca.10nm and length in the range of40-100nm. Controllableexperiment demonstrated that Ni@C structure was the key point to the highly photocatalyticacvitity over Ni@C/TiO₂, although Ni@C showed limited photoactivites. A H2generationrate of up to300μmol h^-1over150mg5wt%Ni@C/TiO₂without Pt-loading in the presenceof10vol%TEOA was achieved under visible light≥（420nm） irradiation. In addition, theAQY under420and520nm monochromatic light irradiation was ca.12%and7%,respectively. Ni@C/TiO₂could be regarded as a new class, highly efficient and visible lightresponsive photocatalytic material, ahthough further investigations on its systematiccharacterization and photocatalytic mechanism are under progress.（4）. Ni@C/CdS composite was prepared by a DMSO solvothermal process. Thecomposite was composed of Ni@C nanoparticles with an average diameter of ca.50nm andCdS with an average diameter of ca.5-10nm. All the Ni@C/CdS with different Ni@Ccontents showed enhancement of photocatalyic H2production efficiency as compared topristine CdS.5wt%Ni@C/CdS showed a maximum H2evolution rate of610μmol h^-1undervisible light （≥420nm） irradiation, and the AQY under420nm even reached ca.20.5%, muchhigher than that of GTO-TiO₂、RGO-CdS and Ni@C/TiO₂system. An effective combinationbetween Ni@C and CdS was achieved by the solvothermal process and the Schottky barrierbetween each other was formed which was similar to Pt/CdS system.