BaZr0.1Fe0.9-xNixO3-δ cubic perovskite oxides for protonic ceramic fuel cell cathodes

Abstract

The pure cubic perovskite structure of BaZr 0.1 Fe 0.9-x Ni x O 3-δ could be maintained when the Ni-doping concentration is ranged from 15 to 20%. The characteristics of BaZr 0.1 Fe 0.9-x Ni x O 3-δ (x = 0.15, 0.2, BZFN) cubic perovskite oxides are investigated systematically to develop a low-cost and cobalt-free cathode for protonic ceramic fuel cells (PCFCs). There is a good chemical compatibility between BZFN and BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BZCY) materials. The BaZr 0.1 Fe 0.75 Ni 0.15 O 3-δ (BZFN15) material exhibits more rich oxygen vacancies, higher electrical conductivity and surface exchange coefficients, and better oxygen adsorption ability than BaZr 0.1 Fe 0.7 Ni 0.2 O 3-δ (BZFN20). The symmetrical cell with BZFN15-BZCY composite cathode shows lower polarization resistance than that with BZFN20-BZCY composite cathode, e. g. 0.36 vs 0.41 Ω cm 2 at 700 °C. The distribution of relaxation times (DRT) analysis of the cathode process reveals that the main rate-limiting step is oxygen adsorption and dissociation. The anode-supported single cell with the BZFN15-BZCY cathode displays high power density of 583 mW cm −2 and low polarization resistance of 0.087 Ω cm 2 at 700 °C, demonstrating the potential of the BZFN15 oxide as PCFC cathode. • BaZr 0.1 Fe 0.9-x Ni x O 3-δ oxides shows pure cubic phase in the range of x = 0.15–0.20. • Electrode reaction processes were analysed by DRT technique. • The peak power density of the single cell reaches 583 mW cm −2 at 700 °C.