Preparation Of Organic Sensitizer Covalently Functionalized Graphene Nanohybrid And Their Photocatalitic Properties For Hydrogen Production

Hydrogen is a renewable, environmentally friendly and carbon-free alternative energy resources in the face of increasing global energy supply and environmental concerns which restrict the human sustainable development. Photocatalytic water splitting to produce hydrogen has been considered as an ideal strategy for converting solar energy into chemical energy since because water and sunlight are renewable sources. In this article, we report the synthesis, characterization and photocatalysis of manganese phthalocyanine(MnPc), bis(2,2′-bipyridine-4,4′-dicarboxylate) ruthenium(II)(N3) covalently functionalized graphene and N3 sensitized BiOCl. And then platinum nanoparticles as cocatalyst loaded on sensitizer covalently functionalized graphene via photodeposition. These nanohybrid were used as photocatalysts for photocatalytic hydrogen evolution from water. The main points were summarized as follows:(1) Manganese phthalocyanine(MnPc) covalently functionalized graphene nanohybrid(MnPcG) has been successfully synthesized by 1, 3-dipolar cycloaddition, and used as a photocatalyst after modified with platinum nanoparticles via photodeposition. The nanocomposite was characterized by SEM, TEM, UV-vis spectra, FTIR, XPS, and Raman spectra. These characterization results confirmed the grafting of MnPc moiety onto the graphene sheets. The intermolecular electron transfer was facilitated and the photoexcited charges recombination was suppressed as confirmed by the fluorescence quenching and enhanced photocurrent density in MnPcG nanohybrid. In comparison to graphene, the MnPcG nanohybrid shows a substantial improvement in the photocatalytic hydrogen evolution. The yields of hydrogen production of MnPcG/Pt reached to 8.59 and 1.45 μmol mg-1 under 10 h UV-vis and visible light(λ>400 nm) irradiation, respectively. Metallophthalocyanines covalently functionalized graphene is a novel photocatalyst for solar energy conversion to produce hydrogen from water.(2) A novel nanohybrid composed of cis-dithiocyanato bis(2,2′-bipyridine-4,4′-dicarboxylate) ruthenium(II)(N3) covalently functionalized reduced graphene oxide(N3-RGO) has been synthesized. The nanocomposite is characterized by TEM, FTIR, Raman spectroscopy, XPS, fluorescence, and UV-vis spectroscopy. The results demonstrate the N3 dye molecules have been covalently grafted on the graphene sheets. The efficient fluorescence quenching and the enhanced photocurrent response confirm that the photoinduced electron transfers from the N3 moiety to the graphene sheet and charge recombination has been suppressed. Platinum nanoparticles as cocatalyst loaded on N3-RGO nanosheets shows remarkable improvement in the photocatalytic hydrogen evolution. The amount of hydrogen evolved from N3-RGO/Pt reached to 11.25 and 1.78 ?mol mg-1 under 7 h of UV-vis and visible light irradiation, respectively. The work provides a new instance to design more efficient graphene-based nanocomposite photocatalysts for solar energy conversion.(3) BiOCl owns a broad band gap of about 3.2 eV, which limits its photocatalytic applications under solar light irradiation. We prepared BiOCl by a facile hydrothermal method and then fabricated BiOCl-N3 nanocompisites through ultrasonic-assisted method. The as-prepared samples were characterized by XRD and TEM. The amount of hydrogen evolved from BiOCl and BiOCl-N3 reached to 51.1 and 85.5 ?mol g-1 under 6 h of UV-vis light irradiation, respectively. In this work N3 plays a role of an antenna, which could harvest the irradiation light and transfer the photoinduced electron to BiOCl.