Nano-Pt Modified Aligned Carbon Nanotube Arrays Are Efficient, Robust, High Surface Area Electrocatalysts

Heterogeneous, precious metal catalysts in electrochemical devices like methanol or H2/O2 fuel cells are typically relatively inefficient per metal atom present. In most metallic Pt catalysts, for example, the majority of atoms lie within the bulk of the metal and are therefore unable to participate in the catalysis. A large scale uptake of current fuel cell technology would, consequently, require an annual production of Pt greater than the total mined to date.1 Pt replacement technologies or catalytic structures with greater atom ef- ficiency are needed.1 A possible solution to this problem is to thinly coat precious metal catalysts onto electrically conducting supports having high surface areas. Carbon nanotubes offer important opportunities in this respect. For example, metal nanoparticles supported on carbon nanotubes exhibit substantial enhancements in catalytic activities,2 maximum power densities,3,4 and excellent selectivity in commercially important processes, such as the electrooxidation of methanol.5 Of particular interest are perpendicularly aligned carbon nanotubes (ACNTs).6 ACNTs have special advantages over their randomly aligned counterparts. These include larger and better-defined surface areas, as well as a capacity for controlled surface modification using various transduction materials.7,8But how could an array of aligned, multiwall carbon nanotubes be turned into an electrocatalyst? Moreover, would such an array survive the often dramatic physical stresses created by mass transport during catalysis?9 In this work we describe a free-standing, conductive ACNT array that, when coated with Pt nanoparticles, acts as an efficient and astonishingly robust electrocatalyst.