Oxygen Reduction Reaction Activity of Nanocolumnar Pt Thin Film Electrocatalyst Deposited on Carbon Support By High Pressure Sputtering

Abstract

Proton-exchange membrane fuel cell (PEMFC) is one of the most important sources of clean energy especially for automotive applications, which currently utilizes platinum nanoparticles dispersed on carbon (Pt/C) as a catalyst. However, the catalyst activity and durability need to be improved and the cost of the fuel cell need to be reduced for successful commercialization. Extensive research has been done to improve the catalyst activity and durability, reduce the amount of platinum used and reduce its manufacturing cost. Continuous thin film layer approach is a promising candidate for non-conventional catalysts to address these challenges. For this purpose, nanocolumnar Pt thin film (Pt-TF) layers supported on carbon was fabricated by high pressure sputtering (HIPS) and investigated as oxygen reduction reaction (ORR) electrocatalysts for PEMFCs. HIPS is a simple physical vapor deposition method that is scalable and easily applicable to industrial sputter deposition systems, in which atoms come to the substrate surface with oblique angles and form columnar structures. Different Pt-TF/C weight ratios ranging from 5% to 20% and Pt:Ni (1:3) TF/C were studied. Weight loading was controlled by changing the sputter deposition time. X-ray diffraction analysis revealed the existence of Pt and formation of the Pt:Ni alloy on carbon support. Electrochemical characterization of the carbon-supported Pt-TF samples was conducted by cyclic voltammetry and rotating disk electrode measurements in an aqueous perchloric acid electrolyte. The electrochemically active surface area, mass activity and specific activity of the Pt-TF/C samples were found to be increasing as the Pt-TF/C ratio was increased.