Evaluation of the CO₂ Poisoning Effect on a Highly Active Cathode SrSc_0.175Nb_0.025Co_0.8O_3-δ in the Oxygen Reduction Reaction

Abstract

A solid oxide fuel cell (SOFC) is a highly efficient device for converting chemical energy to electrical energy. In addition to the efforts to reduce the operating temperature of SOFCs to below 600 °C, research studies of the basic mechanism of CO2 poisoning on cathode materials are envisioned to improve the operation of dual-chamber SOFCs using ambient air. In this work, we comparatively studied the CO2 poisoning effect on two highly active perovskites SrSc(0.175)Nb(0.025)Co(0.8)O(3-δ) (SSNC) and Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-δ) (BSCF), using complementary characterization techniques, e.g., powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), CO2-temperature-programmed desorption (CO2-TPD), and electrochemical impedance spectroscopy (EIS). The SSNC cathode shows better tolerance to CO2 as compared with BSCF, which is attributed to the absence of Ba, higher average metal-oxygen bond energy (ABE) of SSNC, and the higher acidity of Nb(5+) cations, whereas the oxygen vacancy concentration plays a less important role.

Highly Oxygen Non‐Stoichiometric BaSc0.25Co0.75O3‐δ as a High‐Performance Cathode for Intermediate‐Temperature Solid Oxide Fuel Cells

“…Heating beyond 400 °C then led to continuous weight losses from the release of the lattice oxygens, as a result of the thermal reductions of Co 4+/3+ to Co 3+/2+ and Fe 4+ to Fe 3+ . The thermal evolution profile of oxygen non‐stoichiometry can be obtained by combining the room temperature oxygen non‐stoichiometry and the oxygen non‐stoichiometry at different temperatures according to Equation : …”

ChemInform Abstract: Recent Development on Perovskite‐type Cathode Materials Based on SrCoO3‐δ. Parent Oxide for Intermediate‐Temperature Solid Oxide Fuel Cells

“…Similarly, improved redox stability of SrSc 0.175 Nb 0.025 Co 0.8 O 3 À δ relative to BSCF when exposed to CO 2 was claimed to be partly related to the absence of Ba and relatively higher acidity of Nb than Fe. [144] Moreover, incorporation of Ta into Sr(Co,Fe)O 3 À δ oxygen permeable membrane increases the material acidity and therefore also significantly improves its performance stability in CO 2 -containing atmosphere. [145] Additionally, the AE phase segregation to the cathode surface is another issue related to the formation of carbonates on cathode surface and a heterogeneous phase near the surface.…”

High‐Performance Solid Oxide Fuel Cell with an Electrochemically Surface‐Tailored Oxygen Electrode

“…[7,10,[13][14][15] Te chnicala pproaches for improving the performance of the cathode at intermediate temperaturesa re generally divided into two categories:( i) development of highly active, alternative materials to LSM-YSZa nd (ii)surface andm icrostructural modification of the LSM-YSZ electrode. [8,9,[16][17][18][19][20][21][22][23] Practical application of the aforementioned approaches might be hindered by the following drawbacks. First, highly active materials such as Co/Fe-containing perovskite oxidesa re known to be less stable than LSM.…”