Achieving Fast Oxygen Reduction on Oxide Electrodes by Creating 3D Multiscale Micro-Nano Structures for Low-Temperature Solid Oxide Fuel Cells

Gene Yang; Sang-Hoon Nam; Gina Han; Nicholas X Fang; Dongkyu Lee

doi:10.1021/acsami.3c07115

Achieving Fast Oxygen Reduction on Oxide Electrodes by Creating 3D Multiscale Micro-Nano Structures for Low-Temperature Solid Oxide Fuel Cells

ACS Appl Mater Interfaces. 2023 Nov 1;15(43):50427-50436. doi: 10.1021/acsami.3c07115. Epub 2023 Oct 19.

Authors

Gene Yang¹, Sang-Hoon Nam², Gina Han², Nicholas X Fang^{2

3}, Dongkyu Lee¹

Affiliations

¹ Department of Mechanical Engineering, University of South Carolina, Columbia, South Carolina 29208, United States.
² Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
³ Department of Mechanical Engineering, University of Hong Kong, 999077, Hong Kong.

Abstract

Fast oxygen reduction reaction (ORR) at the cathode is a key requirement for the realization of low-temperature solid oxide fuel cells (SOFCs). While the design of three-dimensional (3D) structures has emerged as a new and promising approach to improving the electrochemical performance of SOFC cathodes, achieving versatile structures and structural stability is still challenging. In this study, we demonstrate a novel architectural design for a superior cathode with fast ORR activity. By employing a completely new fabrication process comprising a 3D printing technique and pulsed laser deposition (PLD), we design 3D La_0.8Sr_0.2CoO_3-δ (LSC) micro-nano structures with the desired shape. 3D-printed yttria-stabilized ZrO₂ (YSZ) microstructures significantly increase the ratio of surface area to volume while maintaining suitable ionic conductivity comparable to that of single-crystalline YSZ substrates. Scanning electron microscopy and energy dispersive X-ray microanalysis reveal the formation of crack- or void-free YSZ microstructures and the uniform deposition of LSC films by PLD on the YSZ microstructures. The 3D LSC micro-nano structures show significantly enhanced oxygen surface exchange coefficients (k_chem) extracted from electrical conductivity relaxation (ECR) measurements by up to 3 orders of magnitude relative to the bulk LSC. Furthermore, electrochemical impedance spectroscopy measurements verify the k_chem values from ECR and no directional difference in the measured ORR activity depending on the shape of 3D microstructures. The dramatic enhancement of the ORR activity of LSC is attributed to the increased film surface areas resulting from the 3D YSZ microstructures.

Keywords: 3D printing; additive manufacturing; electrolytes; oxygen reduction reaction; pulsed laser deposition; solid oxide fuel cells; stereolithography; thin film electrodes.