Stacked and Core–Shell Pt:Ni/WC Nanorod Array Electrocatalyst for Enhanced Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells

Abstract

In this study, we developed a stacked core−shell nanorod array electrocatalyst design to improve oxygen reduction reaction (ORR) kinetics and catalyst stability for polymer electrolyte fuel cell (PEMFC) applications. For this purpose, we fabricated two-layer stacked nanorod arrays with each layer consisting of a tungsten carbide (WC) core and a platinum−nickel (Pt−Ni) alloy shell. WC nanorods were grown by a glancing angle deposition (GLAD) method. Then, WC nanorods were coated with a Pt−Ni shell conformally by a highpressure sputtering (HIPS) method. This process was repeated twice to form the second layer of the stack. We investigated three different Pt:Ni ratios including 3:7, 1:1, and 3:1. Cyclic voltammetry (CV) and rotating disk electrode (RDE) methods were used for electrochemical characterization of the Pt:Ni/WC electrodes in a 0.1 M HClO 4 electrolyte solution. Morphological and crystallographic analyses were performed using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Pt mass loading values were measured using a quartz crystal microbalance. Electrochemically active surface area (ECSA) values change in the order of 3:7 > 1:1 > 3:1 in the Pt:Ni ratio. Specific activity (SA) and mass activity (MA) were higher for the 3:7 composition after accelerated stability tests were comparable to those of other compositions.

Nanocolumnar Pt:Ni Alloy Thin Films by High Pressure Sputtering for Oxygen Reduction Reaction

“…Pt:Ni atomic ratios of 3:1, 1:1, and 1:3 were chosen based on the literature data 7,23,44,45 and our previous work. 28,32,46 In order to mimic catalyst-coated gas diffusion layers (gas diffusion electrode, GDE) in PEMFCs, Pt:Ni-TFs were deposited on MPL-like surface composed of carbon particles, which better relates the catalyst performance of extended catalyst layers obtained by benchtop tests directly to MEA results. 42…”