High Performance Anode Material for Solid Oxide Fuel Cells: Ni Exsolution on a-Site Deficient La0.4Sr0.4Sc0.9Ni0.1O3

Abstract

Highly efficient and environment-friendly devices for energy transformation are in urgent demand for the sustainable production of power. Solid oxide fuel cells (SOFCs) are among the most efficient systems that can convert chemical energy directly into electricity. Currently, Ni/yttria-stabilized ZrO2 (YSZ) is the state-of-the-art SOFC anode material (or the cathode material of solid oxide electrolysis cells), due to its relatively high mechanical strength, high performance, and low cost. However, the Ni/YSZ anode still has several limitations including Ni agglomeration at high temperature, sulfur poison, and carbon coking. While perovskite-type materials have been used as SOFC anodes to overcome many of these challenges, their catalytic activity is typically poor. Recently, exsolution of catalytic nanoparticles on the surface of perovskites has drawn great research interest because of the potential enhancement in electrochemical activity. Irvine and collaborators have shown that A-site deficient perovskites allow easier and more controllable exsolution, and several materials capable of growing nanoparticles in-situ have been developed. However, the catalytic activity delivered by A-site deficient perovskites with exsolved nanoparticles is still not comparable to that of state-of-the-art SOFC anode materials. There are still many opportunities for materials development and improvement, since most of the recent studies have focused on La0.5Sr0.5TiO3 or NbTiO4 related materials. Perovskites based on other non-easily-reducible metals may be used to deliver even better activity. In this work, we report a novel Sc-based A-site deficient perovskite La0.4Sr0.4Sc0.9Ni0.1O3-δ (LSSN), synthesized as an anode material for solid oxide fuel cells. LSSN is reduced in hydrogen at 900 oC for 15 hours to form a highly active and stable anode. Spherical Ni nanoparticles (~100 nm in diameter) with well-defined boundaries are exsolved on the surface after reduction. the reduced LSSN (rLSSN) show high electrochemical catalytic activity, with the area specific resistances as low as 0.055 Ω cm2 at 800 °C in humid H2. Our work introduces a new anode material with potential to enhance electrochemical catalytic activity and suggests a new series of A-site deficient perovskites for SOFC anodes.