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. 2013:3:2426.
doi: 10.1038/srep02426.

Highly efficient and robust cathode materials for low-temperature solid oxide fuel cells: PrBa0.5Sr0.5Co(2-x)Fe(x)O(5+δ)

Sihyuk Choi  1 , Seonyoung Yoo, Jiyoun Kim, Seonhye Park, Areum Jun, Sivaprakash Sengodan, Junyoung Kim, Jeeyoung Shin, Hu Young Jeong, YongMan Choi, Guntae Kim, Meilin Liu
Affiliations

Highly efficient and robust cathode materials for low-temperature solid oxide fuel cells: PrBa0.5Sr0.5Co(2-x)Fe(x)O(5+δ)

Sihyuk Choi et al. Sci Rep. 2013.

Abstract

Solid oxide fuel cells (SOFC) are the cleanest, most efficient, and cost-effective option for direct conversion to electricity of a wide variety of fuels. While significant progress has been made in anode materials with enhanced tolerance to coking and contaminant poisoning, cathodic polarization still contributes considerably to energy loss, more so at lower operating temperatures. Here we report a synergistic effect of co-doping in a cation-ordered double-perovskite material, PrBa0.5Sr0.5Co(2-x)Fe(x)O(5+δ), which has created pore channels that dramatically enhance oxygen ion diffusion and surface oxygen exchange while maintaining excellent compatibility and stability under operating conditions. Test cells based on these cathode materials demonstrate peak power densities ~2.2 W cm(-2) at 600°C, representing an important step toward commercially viable SOFC technologies.

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Figures

Figure 1
Figure 1
Transmission electron microscopy (TEM) analysis (a) A bright-field (BF) TEM image and an electron diffraction (ED) pattern obtained from an as-synthesized PrBa0.5Sr0.5Co2-xFexO5+δ sample. (b) A high-resolution TEM image of a grain in (a). (c) A BF-TEM image and an ED pattern of the sample annealed at 700°C for 600 hours. (d) A high-resolution TEM image of a grain after annealing.
Figure 2
Figure 2
Electrical and chemical properties of PrBa0.5Sr0.5Co2−xFexO5+δ (a) Electrical conductivities of PrBa0.5Sr0.5Co2−xFexO5+δ (x = 0, 0.5, and 1.0) measured at 700°C in different p(O2). (b) Oxygen non-stoichiometry of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ and Ba0.5Sr0.5Co0.8Fe0.2O3−δ as a function of p(O2) at 700°C.
Figure 3
Figure 3
Electrochemical properties of PrBa0.5Sr0.5Co2−xFexO5+δ in fuel cells (a) Arrhenius plot of reciprocal ASR for PrBa0.5Sr0.5Co2−xFexO5+δ-GDC (x = 0, 0.5, and 1.0) cathode. The inset shows the ASR of PBSCF05-GDC cathode measured at 600°C in air under open-circuit conditions. (b) I–V curves and the corresponding power densities of test cells with PBSCF05-GDC cathode using humidified H2 (3% H2O) as the fuel and ambient air as the oxidant to the cathode at 500 ~ 650°C. (c) Peak power densities of cells with LnBa0.5Sr0.5Co1.5Fe0.5O5+δ-GDC (Ln = Pr and Nd) cathode. (d) Short term stability measurement for a test cell, Ni-GDC | GDC | PBSCF05-GDC, at a constant cell voltage of 0.6 V at 550°C.
Figure 4
Figure 4
DFT calculations for elucidating the most probable elementary pathway for the ORR on the PBSCFO (a) Schematic illustration of PBSCFO with a pore channel labeled with a round box on the (010) plane. To illustrate the pore channel through the PrO plane and the CoO plane (perpendicular to the PrO plane), only the PrO and the CoO layers were shown. (b) A proposed mechanism for the surface ORR and the bulk diffusion via the pore channels in PrBa0.5Sr0.5Co2−xFexO5+δ (010). VE is an oxygen vacancy in the GDC electrolyte.
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