Controllable self-assembly of Pd nanowire networks as highly active electrocatalysts for direct formic acid fuel cells

Highly dispersed and uniform palladium nanowire networks (NWNs) are synthesized by a controllable, templateless and polyelectrolyte-mediated self-assembly process. In this method, anisotropic Pd2+-polysodium-p-styrenesulfonate (PSS) networks are assembled between Pd2+ ions and SO3-attached to the pendent aromatic ring of PSS in solution by an electrostatic attraction. Reduction of Pd(II) cations to metallic Pd(0) leads to the formation of Pd nanostructures from cubic nanoparticles to highly dispersed NWNs. The Pd nanostructure formation depends on the rate of nucleation and crystallization of Pd(0) which in turn is controlled by the solution pH and reducing agent. The results demonstrate that highly dispersed and uniform Pd NWNs have a very high aspect ratio and are highly active and stable for the formic acid electrooxidation in acid media, demonstrating the promising potential of Pd NWNs as effective electrocatalysts for direct formic acid fuel cells.