Chlorine turned the cobalt-free oxygen electrode of SrTa_0.1Fe_0.9O_3–δ perovskite oxide towards protonic ceramic fuel cells

Protonic ceramic fuel cells (PCFCs) have been deemed as the advanced technology for highly efficient energy conversion, while the practical application of this technology is limited by the oxygen electrode's sluggish reaction kinetics for the oxygen reduction reaction (ORR). Herein, we propose facile anion engineering to develop an innovative oxide with a nominal composition of SrTa_0.1Fe_0.9O_2.95–δCl_0.05 (denoted as STFCl0.05). The ORR activity, hydration, and operation stability of STFCl0.05 are enhanced owing to doping chlorine. STFCl0.05 possesses low area-specific resistance (ASR) values in 3 vol % H₂O-air (e.g., 0.12 Ω cm² at 650 °C), which are lower than those of SrTa_0.1Fe_0.9O_3–δ (STF). Furthermore, the resultant STFCl0.05 based-PCFCs at 650 °C can achieve a superior peak power density (PPD) value of 804 mW cm⁻² under a wet H₂ atmosphere. More attractively, the symmetrical cell operates stably for 180 h, and the single cell operates for 200 h. This anion engineering may be rewarding for in-depth design for developing high-performance PCFCs oxygen electrodes in the future.