Enhancing Oxygen Reduction Reactions in Solid Oxide Fuel Cells with Ultrathin Nanofilm Electrode–Electrolyte Interfacial Layers

Abstract

Low- and intermediate-temperature solid oxide fuel cells (SOFCs) and solid oxide membrane reactors are gaining considerable attention for applications in energy conversion, chemical synthesis, and electrolysis. The sluggish oxygen reduction reaction (ORR) causes significant voltage losses for the air electrodes (cathode) in these systems, particularly at lower temperatures (400–600 °C). Surface engineering of electrolytes with nanograined, thin-film interfaces introduced between the cathode and electrolyte is a promising method of reducing the voltage losses associated with ORR on the cathode. In this work, we deposited a nanocrystalline ceria ultrathin film (nanofilm) interface layer on yttria-stabilized zirconia (YSZ) and samaria-doped ceria (SDC) electrolytes using a simple and scalable solution-based deposition process. The effect of the interfacial layers on cathode polarization resistance was studied using impedance spectroscopy and surface imaging techniques. At low temperature (400 °C), the nanofilm interface layer reduced cell polarization resistance substantially for both YSZ and SDC electrolytes. The reduction in the polarization resistance is primarily attributed to the increased interfacial surface area between the platinum electrode and the electrolyte, as confirmed by almost an order of magnitude increase in the interfacial capacitance with nanofilm interface and three-dimensional reconstruction of the surface structures using Confocal Microscopy and Atomic Force Microscopy. The testing of anode-supported thin electrolyte SOFCs at 600 °C clearly demonstrated the benefits of nanofilm interfacial layer in improving the power output of a cell.