Nanoporous $Pt_xNi_{1-x}$ thin films fabricated by dealloying for a low-temperature solid oxide fuel cell cathode

Abstract

Thin-film based, low-temperature solid oxide fuel cells (LT-SOFCs) have been considered as an alternative power source for portable electronic devices because they can tap the high energy densities of hydrocarbon fuels and are readily recharged. Pt has been widely used as a cathode material given its high electronic conductivity and excellent oxygen reduction reaction (ORR) activity. Pt electrode has a highly porous and continuously connected Pt structure, serving as a gas permeable and electronic conducting layer, as well as an electrocatalyst. The common strategy for fabricating such a porous Pt structure is based on sacrificial template technique, Ostwald ripening, reactive sputtering. However, these methods have disadvantage such as difficult and time consuming to manufacture or require post-annealing. Here, we address this issue through the application of a selective dissolution method, known as dealloying. This simple and cost-effective method enables fabricate a nanoporous sponge-like structure without pre-annealing process. Nanoporous Pt-Ni thin films deposited onto an YSZ electrolyte were obtained by co-sputtering of Pt and Ni targets, followed by the subsequent electrochemical etching of Ni species. The obtained films are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray Fluorescence Spectrometer (XRF) and energy dispersive spectroscopy (EDS). AC impedance spectroscopy (ACIS) of symmetric cells (cathode

electrolyte

cathode) demonstrates the critical role of nano-pores in achieving satisfactory LT-SOFCs cathode activity and stability.