Synergistic electron doping and ion conductive phase incorporating of SrCoO3-δ as desirable cathode materials for intermediate-temperature solid oxide fuel cells

Abstract

Mixed conducting perovskite-structured oxides are desirable catalysts toward the oxygen reduction reaction (ORR) process. Pure cubic perovskite-structured SrCoO3–δ is a promising class of mixed conductors with high ORR activity. However, it suffers from structural instability and thermal incompatibility at elevated temperatures, thereby impeding its practical application in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this work, A-site electron doping in SrCoO3–δ was conducted to chemically compensate for the loss of lattice oxygen, thus improving the structural stability of SrCoO3–δ. Among the as-prepared Y-doped Sr1−xYxCoO3−δ (x = 0.05–0.20) samples, 10 mol% Y-doping of Sr0·9Y0·1CoO3–δ (SYC10) experimentally exhibits desirable electrical conductivity and lowest area specific resistance (ASR) while maintaining structural stability at elevated temperatures. The results are confirmed by first-principles calculations that involve density of states and oxygen vacancy formation energy. In addition, Gd0.1Ce0·9O1.95 incorporation further improves the thermal compatibility and cell performance, where the measured thermal expansion coefficients between 30 °C and 1000 °C decrease from 23.3 × 10−6 K−1 for SYC10 to 19.0 × 10−6 K−1 for SYC10–40GDC, and the corresponding ASRs with La0·9Sr0.1Ga0.8Mg0·2O3–δ electrolyte decrease from 0.080 Ω cm2 to 0.044 Ω cm2 at 700 °C. Results suggest that SYC10–40GDC is a desirable cathode material for IT-SOFCs.