Reactive Nanoparticle Composed Bilayers: An Alternate Route Toward the Production of Pt/Al Nanofoils.

Gas-phase electrodeposition is presented as a nanoparticle-based route toward the fabrication of Pt/Al bimetallic stacks (self-propagating reactive system). This approach enables localized self-assembly of spark discharge-synthesized sub-10-nm Pt and Al nanoparticles on patterned substrates. Precise control over Pt film morphology (porosity) through modulation of spark power and carrier gas flow rate is demonstrated. Porous Pt layers lead to diffused Pt/Al interfaces, which become sharper for densely packed Pt layers. On ignition, the self-sustained high-temperature alloy formation reaction wavefronts are recorded. The bimetallic interface strongly influences the Pt/Al reaction kinetics, with three orders of magnitude faster reaction speeds for sharper interfaces. Porous morphologies and hence diffused interfaces are hindered by excessive air gaps and premixed regions, intermediate porosities achieved speeds of 0.012 m s-1, and dense morphologies have sharp interfaces with minimal air pockets reaching speeds up to 6 m s-1. Selected area (electron) diffraction (SAED) and X-Ray diffraction (XRD) studies reveal Al2Pt and Al3Pt2 as the dominant alloy phases amongst other intermediate PtAl phases. Furthermore, XRD demonstrates temperature-dependent facet growth of Pt-Al alloys. These results prove the critical influence of film morphology on reaction kinetics and emphasize the potential of tuneable Pt/Al bimetallic systems for future energy-related applications.