Abstract
A template- and surfactant-free process, thermally assisted photoreduction, is developed to prepare vertically grown ultra-long Pt nanowires (NWs) (about 30-40 nm in diameter, 5-6 μm in length, and up to 80 NWs/100 μm2 in the wire density) on TiO2 coated substrates, including Si wafers and carbon fibers, with the assistance of the photocatalytic ability and semiconductor characteristics of TiO2. A remarkable aspect ratio of up to 200 can be achieved. TEM analytical results suggest that the Pt NWs are single-crystalline with a preferred 〈111〉 growth direction. The precursor adopted and the heat treatment conditions are crucial for the yield of NWs. The photoelectrons supplied by TiO2 gives rise to the formation of nano-sized Pt nuclei from salt melt or solution. The subsequent growth of NWs is supported by the thermal electrons which also generated from TiO2 during the post thermal treatment. The interactions between the ions and the electrons in the Pt/TiO2 junction are discussed in this study.
Highlights
Platinum has become a crucial material due to its outstanding catalystic characters in fuel-cell technology, hydrogenation reaction, three-way automobile catalytic conversion and gas sensing [1,2,3,4]
Xia et al [5,6,7] have demonstrated the synthesis of single crystalline Pt NWs on polymeric, ceramic or metallic substrate by a polyol process, combined with a trace addition of an iron species (Fe2+ or Fe3+) and poly(vinylpyrrolidone) (PVP) as the surfactant
For Na2Pt(OH)6 (Figure 3b), all the Pt salt was transformed into Pt NWs in large quantities, with an average diameter of 34 nm and remarkable length of about 6 μm, grew vertically on the TiO2 coated Si substrate
Summary
Platinum has become a crucial material due to its outstanding catalystic characters in fuel-cell technology, hydrogenation reaction, three-way automobile catalytic conversion and gas sensing [1,2,3,4]. A recently developed process, thermally assisted photoreduction (TAP), has been applied to prepare metallic NWs via the photoreduction of metallic ions on the surface of thin-film TiO2 under certain irradiating and heating conditions [16,17]. It has so far not been possible to produce Pt NWs with the commonly used precursor, H2PtCl6, which was ascribed to the high charge number of Pt ions. In addition to Si wafers, carbon cloths are chosen as the substrate for investigation, since nanostructured Pt-TiO2 on carbon fibers or nanotubes
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