Highly Efficient A- and B‑Site-Doped Ruddlesden–Popper Perovskite Oxide Nd_2–xSr_xNi_0.9Cu_0.1O_4+δ as a Cathode for PCFCs

At medium and low operating temperatures, the slow reaction kinetics of the cathode is a significant limiting factor hindering proton ceramic fuel cell (PCFC) development. This work reports a Nd_2–xSr_xNi_0.9Cu_0.1O_4+δ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) Ruddlesden–Popper cathode through a combination strategy of A-site Sr²⁺ and B-site Cu²⁺ codoping. Appropriate Sr²⁺ doping has achieved the synergistic optimization of conductivity and electrocatalytic activity by modulating the amount of surface oxygen defects and the valence state of B-site Ni²⁺. Nd_1.4Sr_0.6Ni_0.9Cu_0.1O_4+δ (NSNC6) exhibits a remarkably improved conductivity (exceeding 100 S cm^–1 from 450 to 750 °C) and an enhanced electrocatalytic activity. The PCFC with the NSNC6-BZCNY triple-conducting cathode exhibits sufficient long-term stability and a maximum power density of 445 mW cm^–2 at 650 °C, which is approximately 50% higher than that of the PCFC with the NSNC6 cathode, highlighting its potential as a cathode material for PCFCs.