Gold Nanotubes with a Nanoporous Wall: Their Ultrathin Platinum Coating and Superior Electrocatalytic Activity toward Methanol Oxidation

Abstract

This paper describes a new strategy for synthesizing hollow nanotubes (pore d > 100 nm) with nanoporous walls (pore d < 10 nm) as well as how the nanoporous hollow nanotubes exhibit better intrinsic electrocatalytic activity toward methanol oxidation compared with an analogous nanotube system with smooth walls. Compared with vertical arrays of a nanorod system, the nanotube system is better in terms of increasing the effective surface area because the inner and outer surfaces are both in contact with the reaction medium. Au nanotubes with smooth wall and nanoporous walls were synthesized using AAO and conducting polymer nanorod templates. The surface of Au nanotube walls could be electrochemically coated with ultrathin Pt layers without changing the nanoporous structure. The resulting nanotubes showed different “intrinsic” electrocatalytic activities toward methanol oxidations depending on the wall structure (smooth or nanoporous). We compared its catalytic activity with the commercially available carbon-supported Pt nanoparticles and found that the catalytic activity of nanoporous nanotubes is the best among the investigated samples. The reason for this superior catalytic activity was attributed to the higher CO-poisoning tolerance and shorter effective length for electronic transportation.