|An illustration of the new IBN nanocomposite material which is composed of gold-copper alloy atoms in the core and platinum atoms at the outer layer. Source: IBN. Click to enlarge.|
Researchers at the Institute of Bioengineering and Nanotechnology (IBN) in Singapore report the synthesis of core–shell AuCu@Pt nanoparticles exhibiting superior electrocatalytic activity and excellent stability towards the oxygen reduction reaction (ORR) in fuel cells. A paper on their work appears in the RSC journal Energy and Environmental Science.
A general challenge in fuel cell development involves improving the durability and electrocatalytic activity of platinum-based electrocatalysts, while reducing the loading of the expensive metal. Professor Jackie Y. Ying and colleagues discovered that by replacing the central part of the catalyst with gold and copper alloy and leaving just the outer layer in platinum, the new hybrid material can provide 5 times higher activity and much greater stability than the commercial platinum catalyst. With further optimization, it would be possible to further increase the material’s catalytic properties, they said.
IBN’s new nanocomposite material can produce at least 0.571 amps of electric current per milligram of platinum, compared to 0.109 amps per milligram of platinum for commercial platinum catalysts. This is also the first time that a catalyst has been shown to enhance both the stability and activity for the fuel cell reaction with a significantly reduced platinum content.
In the IBN catalyst, the gold (Au) component in the gold-copper (AuC) alloy core is crucial toward stabilizing the platinum (Pt) shell during ORR. The team attributed the extraordinary electrocatalytic activity of the AuCu@Pt nanoparticles for ORR to the compressive strain effect exerted by the AuCu alloy core on the Pt shell, which is induced by the slightly smaller lattice spacing of the AuCu core. In contrast, a pure Au core with a larger lattice spacing than Pt would induce a tensile strain effect on the Pt shell, decreasing the electrocatalytic activity of Pt for ORR.
Replacing the core of the nanoparticle with the less expensive gold-copper alloy also cuts down the usage of platinum.
Professor Ying said, “A key research focus at IBN is to develop green energy technologies that can lead to greater efficiency and environmental sustainability. More active and less costly than conventional platinum catalysts, our new nanocomposite system has enabled us to significantly advance fuel cell development and make the technology more practical for industrial applications.”
This study illustrates that tuning the surface strain in Pt-based nanomaterials can be an effective way to manipulate the specific electrocatalytic activity. Moreover, the replacement of precious Pt core with the less expensive AuCu alloy can significantly reduce Pt loading and the associated catalyst cost, while achieving a superior electrocatalytic activity.—Yang et al.
J. Yang, X. Chen, X. Yang and J. Y. Ying (2012) Stabilization and Compressive Strain Effect of AuCu Core on Pt Shell for Oxygen Reduction Reaction Energy and Environmental Science, doi: 10.1039/C2EE22172A