Core-Shell Electrocatalysts with Nanocolumnar Pt Thin Film Shell on Carbon Support Core for Polymer Electrolyte Membrane Fuel Cells

Abstract

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is one of the most promising energy conversion technologies with zero carbon emission, and has received significant attention especially for automotive applications. State-of-the-art PEMFCs use platinum or platinum-alloy nanoparticles distributed on carbon as the electrocatalyst. However, there are still significant challenges for PEMFCs before widespread commercialization including short lifetime and high initial cost mainly originating from the catalyst related issues. Recent research efforts have focused on approaches that would improve catalyst lifetime, reduce its manufacturing cost, and reduce the amount of platinum used without losing activity. In this work, we present a new core-shell electrocatalyst design that can potentially address the challenges of conventional PEMFC catalysts. The design involves a shell of nanocolumnar Pt thin film coated on carbon support core (Pt-TF/C). Pt-TF layers were deposited on carbon powder by high-pressure sputtering (HIPS) and their oxygen reduction reaction (ORR) activity relevant to PEMFCs was investigated. HIPS is a simple physical vapor deposition technique that is scalable and easily applicable to industrial sputter deposition systems, in which atoms come to the substrate surface at different angles to form columnar structures. Pt-TF/C powder samples with various types of carbon were produced and studied to investigate their ORR performance. Electrochemical characterization of the samples was performed by cyclic voltammetry and rotating disk electrode measurements. The Pt-TF-to-carbon mass ratios were measured by quartz crystal microbalance and thermogravimetric analysis. X-ray diffraction analysis showed the presence of Pt on the carbon support. Our preliminary results on specific activity, mass activity, and electrochemically active surface area indicate a promising electrocatalyst durability.