TiO2 Photonic Crystal Sensitized with Mn3O4 Nanoparticles and Porphine Manganese(III) as Efficient Photoanode for Photoelectrochemical Water Splitting

We report the synthesis and photoelectrochemical characterization of a novel composite consisting of Mn3O4 nanoparticles, porphine manganese(III) (PMA), and TiO2 photonic crystal (TPC). The prepared composite (Mn3O4/PMA/TPC) was used for fabricating the photoanode of a photoelectrochemical tandem cell. The obtained Mn3O4/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 Mn3O4 nanoparticles had been loaded in the hole of TPC successfully. The photoelectrochemical characterization of the Mn3O4/PMA/TPC electrode revealed an enhanced light harvesting and effective electron hole separation. The photoelectrochemical tandem cell, of which Mn3O4/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 mu mol and 4.4 mu mol, respectively, under 4 h simulated solar-light irradiation. The possible mechanism of the surface modification effects was proposed. The results suggest that Mn3O4 nanoparticles and PMA modified TPC can act as efficient catalyst for fabricating photoanode in a. photoelectrochemical tandem cell.