Photochemical hydrogen evolution using Pt/titania nanosheet catalysts prepared by chemical-reduction and photo-deposition methods

Photocatalysts where platinum nanoparticles are loaded on titania nanosheets (TNS) were synthesized by the chemical reduction with sodium borohydride (CR-Pt/TNS) and the photo-deposition (PD-Pt/TNS). In the case of UV light irradiation to Pt/TNS, H-2 production activity of PD-Pt/TNS was about 3 times higher than that of CR-Pt/TNS. Visible light (455 nm) induced H-2 photoproduction using Pt/TNS and Zn(II)5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (Zn(II)TMPyP4+) adsorbed on TNS was carried out in the presence of an electron donor (ascorbic acid). In the case of visible light irradiation to Pt/TNS-Zn(II)TMPyP4+, H-2 production activity of PD-Pt/TNS-Zn(II)TMPyP4+ was about 20 times higher than that of CR-Pt/TNS- Zn(II)TMPyP4+. Because TNS has an anisotropy in the direction of carrier migration, the excited electrons tend to move to the edge of nanosheet. It is known that metal nanoparticles tend to be loaded at the edge of nanosheet for PD-Pt/TNS. Therefore, the difference in hydrogen evolution activity between CR- and PD-Pt/TNS is expected to be due to the selective loading of Pt at the edge of nanosheet and the efficient electron transfer to Pt at the edge for PD-Pt/TNS.