(400g) Extended Thin Film Electrocatalyst Structures Via Pt Atomic Layer Deposition

Platinum-nickel nanowires are a promising advanced catalyst material for the oxygen reduction reaction (ORR) in fuel cell applications. When synthesized by galvanic displacement of nickel nanowires (NiNWs), these extended surface electrocatalysts have demonstrated activity and durability superior to benchmark carbon-supported Pt catalysts. However, challenges in scale-up and reproducibility of this fabrication process have prompted investigation into atomic layer deposition (ALD) of Pt as a facile, scalable synthesis alternative for the production of Pt-NiNWs. Atomic layer deposition of Pt nanoparticles on NiNW substrate was performed in a packed bed reactor, using trimethyl(methylcyclopentadienyl)platinum(IV) (MeCpPtMe₃) as a metal source, and either H₂ or O₂ for ligand removal. Gases exiting the ALD reactor were monitored via an in-line mass spectrometer, which provided information on reaction mechanisms. Deposition of Pt was confirmed through inductively coupled plasma mass spectroscopy for a range of ALD cycles; oxidative ALD chemistry was found to yield greater Pt content at high cycle numbers. Transmission electron microscopy and elemental mapping techniques were also used to analyze the morphology and structure of ALD-modified NiNWs. The effects of post-processing treatments, such as H₂ annealing and acid leaching, were also studied. Electrochemical performance of ALD-synthesized catalysts in both half-cell and full-cell analyses was found to be comparable to that obtained with galvanic displacement catalysts, thereby demonstrating the efficacy of ALD as a fabrication method for extended thin film electrocatalyst structures.