An Active and Stable Cobalt‐Free Ruddlesden–Popper Nd<sub>0.8</sub>Sr<sub>1.2</sub>Ni<sub>1‐x</sub>Fe<sub>x</sub>O<sub>4±δ</sub> Air Electrode for Reversible Proton‐Conducting Solid Oxide Cells
Ting Chen, Guangjun Zhang, Kui Liu, Chenxiao Wang, Guozhu Zheng, Zuzhi Huang, Ning Sun, Lang Xu, Juan Zhou, Yucun Zhou, Shaorong Wang
Abstract
Abstract Reversible proton‐conducting solid oxide cells (R‐PSOCs) are considered to be one of the most promising devices for efficient power generation and hydrogen production. However, the requirement of high catalytic activity for fast oxygen reduction/evolution reaction (ORR/OER) and durability under high steam concentration of air electrode materials remains the major challenge for the practical application of R‐PSOCs. Here, a series of cobalt‐free Ruddlesden–Popper perovskite of Nd 0.8 Sr 1.2 Ni 1‐x Fe x O 4±δ are reported with mixed conductivity for enhanced ORR/OER kinetics. The R‐PSOCs with an optimal Nd 0.8 Sr 1.2 Ni 0.7 Fe 0.3 O 4±δ air electrode show a high peak power density of 1.28 W cm −2 in the fuel cell mode and a promising current density of 3.24 A cm −2 at 1.3 V in the electrolysis cell mode at 700 °C. In addition, the R‐PSOCs show favorable stability under the fuel cell, electrolysis, and reversible modes for hundreds of hours. This work demonstrates that the Ruddlesden–Popper materials can be utilized as suitable air electrodes for R‐PSOCs.