High-performance polypyrrole functionalized PtPd electrocatalysts based on PtPd/PPy/PtPd three-layered nanotube arrays for the electrooxidation of small organic molecules

Abstract

Here, we report novel high-performance polypyrrole (PPy) functionalized PtPd electrocatalysts based on PtPd/PPy/PtPd three-layered nanotube arrays (TNTAs) for the electrooxidation of small organic molecules, such as methanol, ethanol and formic acid, which are superior fuels for direct alcohol fuel cells (DAFCs) or direct formic acid fuel cells (DFAFCs). The unique hollow structures, array structures and sandwich-like structures of PtPd/PPy/PtPd TNTAs will provide fast transport and short diffusion paths for electroactive species as well as a large exposed surface area for efficient interaction with electroactive species. In particular, the unique sandwich-like structure of PtPd/PPy/PtPd TNTAs results in electron delocalization among the Pt 4f orbitals, Pd 3d orbitals and PPy π-conjugated ligands, and in electron transfer from the PPy to Pt and Pd atoms, leading to higher contents of metallic Pt and Pd and synergistic effects for electrocatalytic reactions. Because of the above merits, the designed PtPd/PPy/PtPd TNTAs exhibit significantly improved catalytic activity and durability for the electrooxidation of small organic molecules compared with those of PtPd TNTAs and commercial Pt/C and Pd/C catalysts. High-Performance Polypyrrole Functionalized PtPd Electrocatalysts. Direct alcohol fuel cells are preferable to conventional hydrogen-powered devices because small, liquid organic molecules such as methanol and ethanol are easier to store and transport than hydrogen gas. Gao-Ren Li and co-workers from Sun Yat-sen University in China have devised a new type of oxidation catalyst for substrates based on hollow nanotubes containing sandwiched metal-polymer complexes. As these systems normally use expensive precious metals their activity and durability are of the utmost importance. The researchers deposited a three-layered material — a platnium-palladium composite (PtPd), a conductive polymer, and another PtPd coating — onto a zinc oxide nanorod template using electrochemical methods. They then dissolved the template to produce durable nanotube assemblies with exposed metal surfaces and short diffusion paths that can oxidize methanol, ethanol, and formic acid much more efficiently than conventional catalysts. This performance enhancement is ascribed to their unique structure and favorable metal–polymer electronic interactions leading to higher uptake of the catalytic metals.