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ABSTRACT:In this paper, graphene oxide (GO) sheets covalently functionalized with (5,10,15,20-tetraphenyl) porphinato manganese(III) (MnTPP) has been successfully synthesized and tested as a photocatalyst for hydrogen evolution from water under UV-vis light irradiation. The obtained sample was systematically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis, Fourier transform infrared (FTIR), and Raman spectroscopy. The results show that the MnTPP moiety has been successfully grafted on the graphene oxide surface to form MnTPP modified GO (GO-MnTPP). The fluorescence quenching and photocurrent enhancement of GOMnTPP confirm that the rapid electrons transfer from photoexcited the MnTPP moiety to the GO sheets. The platinized GO-MnTPP exhibits enhanced photocatalytic activity for water reduction to produce hydrogen. Moreover, with the assistance of polyvinyl pyrrolidone (PVP), the photocatalytic activity is further improved because of aggregation prevention of the GO-MnTPP nanocomposite. This study provides a facile method to build porphyrin-graphene-based photocatalysts for solar energy conversion.

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We report the synthesis and photoelectrochemical characterization of a novel composite consisting of Mn 3 O 4 nanoparticles, porphine manganese(III) (PMA), and TiO 2 photonic crystal (TPC). The prepared composite (Mn 3 O 4 /PMA/TPC) was used for fabricating the photoanode of a photoelectrochemical tandem cell. The obtained Mn 3 O 4 /PMA/TPC composite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV−vis diffuse reflectance spectroscopy (DRS). The results demonstrated that PMA and Mn 3 O 4 nanoparticles had been loaded in the hole of TPC successfully. The photoelectrochemical characterization of the Mn 3 O 4 /PMA/TPC electrode revealed an enhanced light harvesting and effective electron−hole separation. The photoelectrochemical tandem cell, of which Mn 3 O 4 /PMA/TPC electrode acted as a photoanode and a Pt plate as counter electrode, was used to evaluate the feasibility for water splitting to produce H 2 and O 2 under a 300 W solar simulator irradiation. The gases evolved from the system when the applied voltage was 1.0 V (vs RHE). The evolution amount of hydrogen and oxygen can reach to 12.2 μmol and 4.4 μmol, respectively, under 4 h simulated solar-light irradiation. The possible mechanism of the surface modification effects was proposed. The results suggest that Mn 3 O 4 nanoparticles and PMA modified TPC can act as efficient catalyst for fabricating photoanode in a photoelectrochemical tandem cell.

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A robust and efficient photocatalyst based on ruthenium dye N3 covalently immobilized on reduced graphene oxide was used for photocatalytic hydrogen evolution.