Thermodynamic NiO exsolution for durable and efficient cobalt-free cathodes in proton-conducting solid oxide fuel cells
Bofeng Wan, Tao Liu, Yinlin Chang, Min Fu, Zetian Tao, Hong Zhou
Abstract
Developing high-performance cathodes is critical to advancing proton-conducting solid oxide fuel cells (PCFCs). However, their practical application remains constrained by sluggish oxygen reduction reaction (ORR) kinetics and the instability of nanoscale catalytic features under oxidizing environments. Here, a cobalt-free nanocomposite cathode is rationally engineered using a Mo-induced ion-topological strategy, based on the perovskite oxide BaCe<sub>0.26</sub>Ni<sub>0.1</sub>Fe<sub>0.64</sub>O<sub>3-δ</sub> (BCNF10). Through the introduction of B-site Mo, the spontaneous exsolution of highly dispersed NiO nanoparticles, significantly enhances surface oxygen exchange kinetics and leads to the formation of stable and well-defined heterointerfaces. The single cell with the optimized composite cathode Ba<sub>0.95</sub>Ce<sub>0.25</sub>Ni<sub>0.1</sub>Mo<sub>0.05</sub>Fe<sub>0.6</sub>O<sub>3-δ</sub> (BCNMF10) achieves an outstanding maximum power density (MPD) of 2002 mW·cm<sup>-2</sup> at 700 °C, accompanied by excellent long-term operational durability and humidity tolerance. First-principles calculations further elucidate the underlying mechanism, revealing a thermodynamically favorable, defect-mediated pathway for NiO formation and underscore the crucial role of dopant-defect interactions in tailoring surface reactivity. This work provides a robust and scalable framework for the development of durable, high-efficiency cathodes for next-generation PCFCs.