Correlation between fast oxygen kinetics and enhanced performance in Fe doped layered perovskite cathodes for solid oxide fuel cells

Abstract

Many researchers have recently focused on layered perovskite oxides as cathode materials for solid oxide fuel cells because of their much higher chemical diffusion and surface exchange coefficients relative to those of ABO 3 -type perovskite oxides. Herein, we study the catalytic effect of Fe doping in SmBa 0.5 Sr 0.5 Co 2 O 5+δ for the oxygen reduction reaction (ORR) and investigate the optimal Fe substitution through an analysis of the structural characteristics, electrical properties, redox properties, oxygen kinetics, and electrochemical performance of SmBa 0.5 Sr 0.5 Co 2-x Fe x O 5+δ (x = 0, 0.25, 0.5, 0.75, and 1.0). The optimal Fe substitution, SmBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ , enhanced the performance and redox stability remarkably and also exhibited satisfactory electrical properties and electrochemical performance due to its fast oxygen bulk diffusion and high surface kinetics under typical fuel cell operating conditions. The results suggest that SmBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ is a promising cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Figure 2. (a) High-angle annular dark field (HAADF) STEM image and corresponding selectivearea electron diffraction (SAED) pattern obtained from an as-synthesized SmBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ sample. (b) A high-resolution HAADF STEM image of the grain marked with a white rectangle in (a). The crystal structure of ordered SmBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ is represented in the right inset.Figure 3. Scanning electron microscopy images of SmBa 0.5 Sr 0.5 Co 2-x Fe x O 5+δ (x = 0, 0.25, 0.5, 0.75, and 1.0)-GDC cathodes: (a) a cross section consisting of the dense GDC electrolyte with the porous SmBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ -GDC composite cathode and NiO-GDC anode; (b)-(f) microstructure of SmBa 0.5 Sr 0.5 Co 2-x Fe x O 5+δ (x = 0, 0.25, 0.5, 0.75, and 1.0)-GDC cathodes fabricated using screen printing followed by sintering at 950 o C for 4 hours.Figure 7. (a) Depth profile of normalized isotope oxygen fraction in SmBa 0.5 Sr 0.5 Co 2-x Fe x O 5+δ (x = 0, 0.5, and 1.0) exchanged at 590 o C for 2400 sec, obtained by linescan measurement. The symbols and solid line show the measured results and fitted results, respectively. (b) D* and k fitted values for various values of Fe content obtained from the depth profile of the normalized isotope oxygen fraction.

Perovskite as a Cathode Material: A Review of its Role in Solid‐Oxide Fuel Cell Technology

“…Jun et al . focused on the catalytic effect of Fe doping in SmBa 0.5 Sr 0.5 Co 2− x Fe x O 5+ δ (x=0, 0.5, and 1.0) on the ORR.…”

Achieving High Efficiency and Eliminating Degradation in Solid Oxide Electrochemical Cells Using High Oxygen‐Capacity Perovskite

“…Accordingly,itisofgreat significance to develop fuel and air electrode materials that can provide more active and stable performance.I nr ecent years,m any researchers have focused on layered perovskites as electrode materials for SOFCs owing to their fast oxygen kinetics and stability. [17,18] A site-layered perovskite PrBaMn 2 O 5+d (PBM) exhibited high and durable performance and excellent redox stability. [6] Also, alayered PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+d (PBSCF50) perovskite was reported to provide excellent electrochemical performance and stability.…”

Structural, Electrical, and Electrochemical Characteristics of LnBa0.5Sr0.5Co1.5Fe0.5O5+δ (Ln=Pr, Sm, Gd) as Cathode Materials in Intermediate‐Temperature Solid Oxide Fuel Cells

“…However, Co‐rich layered perovskites generally show poor long‐term cell stability, which likely originates from the lack of thermal and chemical compatibility with other components. Hence, various ion substitution effects have been studied in an effort to enhance their stability and performance . Notably, among the investigated cathodes, Sr and Fe codoped double perovskite oxides show an outstanding electrical conductivity, electrochemical performance, and long‐term stability …”

“…[23,24] However, Co-rich layered perovskites generally show poor long-term cell stability,w hich likely originatesf rom the lack of thermal and chemical compatibilityw ith other components.H ence,v arious ion substitution effects have been studied in an effort to enhance their stability and performance. [25][26][27] Notably,a mong the investigated cathodes,S r and Fe codoped double perovskite oxidess how an outstanding electrical conductivity,e lectrochemical performance,a nd long-term stability. [4] As the As ite of al ayered perovskite oxide is occupied by aL ni on with ad ifferent ionic radius,t he characteristics that determine the performanceo ft he cell, for example,t he lattice parameters of unit cells,t he crystal structures,a nd the concentration of mobile oxygen species of layered perovskite oxides,c an be changed.…”