Performance and distribution of relaxation times analysis of Ruddlesden-Popper oxide Sr3Fe1.3Co0.2Mo0.5O7-δ as a potential cathode for protonic solid oxide fuel cells

• Published in: Electrochimica acta 2020-08, Vol.352, p.136444, Article 136444
• Main Authors: Zhao, Yiqian, Zhang, Kun, Wei, Zhaoling, Li, Zhongbiao, Wang, Yao, Zhu, Zhiwen, Liu, Tong
• Format: Article
• Language: English
• Subjects: Cathode; Cathodes; Cathodic polarization; Charge transfer; Charge transport; Distribution of relaxation times; Electrochemical analysis; Electrochemical impedance spectra; Electrode materials; Electrode polarization; Maximum power density; Protonic solid oxide fuel cells; Ruddlesden-popper oxide; Solid oxide fuel cells
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2020.136444

In this work, Ruddlesden-Popper oxide Sr3Fe1.3Co0.2Mo0.5O7-δ-BaZr0.1Ce0.7Y0.2O3-δ (SCFMO-BZCY) composite cathode has been developed as a novel proton conducting cathode for protonic solid oxide fuel cells (P–SOFCs) application, and been systematically evaluated by charactering the electrochemical performance of the symmetrical cells and single cells. The symmetrical cell with SCFMO-BZCY cathode shows a low electrode polarization resistance (Rp) of 0.96 Ωcm2 at 700 °C in air. It is also found that Rp for SCFMO-BZCY cathode continually goes down in the initial 40 h, and then keeps almost stable in the following durability testing. The maximum power density of 390 mWcm−2 and low Rp value of 0.23 Ωcm2 are obtained at 700 °C for the anode-supported single cell with a configuration or Ni-BZCY/BZCY/SCFMO-BZCY by fueled with 3%H2O humidified H2. In addition, distribution of relaxation times analysis results indicate that the sub-step corresponding to high-frequency peak, strongly related to the charge transfer and ionic transport in the cathode, is the predominant rate-limiting step, which can be effectively accelerated by increasing the electrical conductivities of the cathode materials. The experimental results demonstrate that SCFMO is a promising cathode candidate for P–SOFCs because of its good electrochemical performance and robust stability, and the findings in this work can guide the development of other cathode materials.