|Schematic image depicting the growth of PtNWs on Sn@CNT nanocable support. Source: Sun et al. Click to enlarge.
Researchers from the University of Western Ontario and General Motors R&D have developed a 3D coaxial nanocable electrode consisting of platinum on a tin nanowire and a carbon nanotube support using a new simple synthesis procedure.
The novel PtNWSn@CNT electrode exhibits enhanced electrochemical performance in the oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells (PEMFCs), methanol oxidation (MOR) for direct methanol fuel cells (DMFCs), and CO tolerance compared with commercial ETEK Pt/C catalyst made of Pt nanoparticles.
A paper on the work was published earlier this year in Chemistry—a European Journal.
Platinum is currently the primary electrocatalyst in use in polymer electrolyte membrane (PEM) fuel cells, where it catalyzes oxygen reduction reaction (ORR) at the cathode and fuel (including hydrogen and methanol) oxidation reaction at the anode.
Other work has determined that the catalytic reactivity of platinum nanostructures is highly dependant on their morphology; accordingly considerable efforts have gone into the synthesis of Pt nanostructures with well-controlled shapes and sizes.
...most of these studies focused on spherical nanoparticles or nanoparticles with an undetermined shape. Very recently, one dimensional (1D) Pt structures, such as nanowires, have drawn much attention owing to their unique anisotropic structure and surface properties, as well as excellent electrocatalytic activities...Despite the progress made in the past, the production of Pt catalyst with great catalytic performance and utilization efficiency is still costly and far from being trivial.
In this study, through a facile surfactant-free aqueous solution method, we synthesized ultrathin single-crystal Pt nanowires, at room temperature, on a Sn@CNT nanocable support directly grown on carbon paper fuel cell backing to form a novel 3D fuel-cell electrode (PtNWSn@CNT). Such a Sn@CNT 3D nanocable support holds many advantages, including enhancing effect of tin, higher gas permeability, improved metal-support interactions, and enhanced mass transport. This approach allows us to combine the advantages of both a PtNW catalyst and a Sn@CNT 3D nanocable support for fuel cell applications.
—Sun et al.
Compared to a commercial catalyst made of Pt nanoparticles on carbon black, the PtNWSn@CNT composite shows:
- For ORR, 1.2 times higher mass activity and 2.4-fold better specific activity.
- For MOR, 1.35 times higher mass activity and 2.8-fold better specific activity.
The researchers conclude that this electrode structure has the potential to possess high Pt utilization, high activity, and high durability for fuel cell applications. Further optimization of the dimensional control, the preparation and evaluation of membrane electrode assemblies based on PtNWSn@CNT catalysts are underway.
This simple and unique approach can be extended to grow Pt nanowires on other 1D nanostructures, such as CNT, SnO2, WO3, TiO2 etc., for wider applications.
—Sun et al.
Shuhui Sun, Gaixia Zhang, Dongsheng Geng, Yougui Chen, Mohammad Norouzi Banis, Ruying Li, Mei Cai, Xueliang Sun (2010) Direct Growth of Single-Crystal Pt Nanowires on Sn@CNT Nanocable: 3D Electrodes for Highly Active Electrocatalysts. Chem. Eur. J. 3/2010) (p 732) doi: 10.1002/chem.200902320