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The commercialization of the Co-free solid oxide fuel cell (SOFC) cathode was hindered due to its insufficient oxygen reduction reaction (ORR) activity. In this paper, the ORR activity of the cathode material is effectively increased by doping a small amount of low-valence Ln3+ (Nd3+, Sm3+) ions at the B-site of Fe-based perovskite Bi 0.5 Sr 0.5 FeO 3-δ (BSF). Nd3+ increases the free volume (V free) per unit cell of perovskite due to its larger ionic radius, thus increasing the oxygen vacancy concentration of Bi 0.5 Sr 0.5 Fe 0.95 Nd 0.05 O 3-δ (BSFN). Compared with BSF, BSFN has greatly improved the surface oxygen exchange and volume diffusion rate through the electronic conductivity relaxation (ECR) method. At 700 °C, the area-specific resistance (ASR) of BSFN reached 0.062 Ω cm2, which was 65% lower than that of BSF (0.177 Ω cm2), and the peak power density (PDD) of BSFN-based single cell reached 1.10 W cm−2, which was 1.7 times higher than that of BSF-based single cell (0.64 W cm−2). Through DRT analysis, it is concluded that BSFN can accelerate the adsorption/dissociation process of oxygen due to its higher oxygen vacancy concentration compared with BSF, so that ORR is not limited to the three-phase interface but extends to the entire cathode surface. In addition, in the 80 h long-term stability test at 600 °C, the BSFN-based single cell has better long-term stability because the thermal expansion coefficient of BSFN (14.1 × 10−6 K−1) is lower than that of BSF (14.4 × 10−6 K−1). In general, BSFN is expected to become a Co-free base high-performance intermediate temperature SOFC cathode. [ABSTRACT FROM AUTHOR]

As a potential cathode material for solid oxide fuel cells, the commercial application of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) has to face the challenges in insufficient oxygen reduction reaction (ORR) activity, segregation of Sr element, and CO 2 poisoning. Therefore, the effect of A-site non-stoichiometry on the electrochemical performance of (LS) 1-x CFs (x = −0.05, 0, 0.05, 0.10, 0.15) from the aspect of microstructure/elemental surface chemical environment evolution is investigated in this paper. The results show that (LS) 0.90 CF has the best ORR activity and the highest electrochemical performance. The excellent electrochemical performance is attributed to the (LS) 0.90 CF/Co 2 FeO 4 /CoFe 2 O 4 -type heterostructure, formed by in-situ segregation induced by A-site defects, which improves the surface oxygen diffusion coefficient and chemical bulk diffusion coefficient of the cathode. At the same time, the A-site defect can effectively inhibit the segregation of Sr element in (LS) 0.90 CF, thereby improving the tolerance of CO 2. At 800 °C, the area-specific resistance (ASR) of (LS) 0.90 CF (0.023 Ω cm2) is 66.7% lower than that of LSCF (0.069 Ω cm2), and the peak power density (1.57 Wcm−2) is 1.8 times higher than that of LSCF (0.87 Wcm−2). Therefore, perovskite A-site defect-induced B-site segregation to form heterostructures provides an effective strategy for the preparation of high-performance cathode materials. [ABSTRACT FROM AUTHOR]

The development of cathode materials with high oxygen reduction reaction (ORR) activity and stability in intermediate temperature (IT) environments is a key factor in the commercialization of solid oxide fuel cells (SOFC). In this paper, the ORR activity of the cathode is improved by doping high-valent Sc3+ ions at the B-site of the Sr 0.5 La 0.5 Co 0.8 Cu 0.2-x Sc x O 3–δ (x = 0, 0.02, 0.04), in which Sr 0.5 La 0.5 Co 0.8 Cu 0.18 Sc 0.02 O 3–δ (SLCCS2) shows the best electrochemical performance, and the area-specific resistance of SLCCS2 at 700 °C is only 0.047 Ω cm2, much lower than the 0.087 Ω cm2 of Sr 0.5 La 0.5 Co 0.8 Cu 0.2 O 3–δ (SLCC), and the peak power density of SLCCS2 reached 1.098 W cm−2, which is 1.84 times that of SLCC (0.598 W cm−2). In addition, SLCCS2 effectively reduces the thermal expansion coefficient, improves thermal matching with traditional electrolytes, and overcomes the problem of insufficient long-term SOFC stability caused by the high thermal expansion coefficient of Co-based perovskite to a certain extent. SLCCS2 also exhibits excellent CO 2 tolerance. Considering comprehensively, SLCCS2 is expected to become an IT-SOFC cathode material with development potential. • Sc doping improves the ORR activity of Sr 0.5 La 0.5 Co 0.8 Cu 0.2 O 3–δ. • Sc doping reduces thermal expansion coefficient of Co-based perovskites. • Sr 0.5 La 0.5 Co 0.8 Cu 0.18 Sc 0.02 O 3–δ has excellent CO 2 tolerance. [ABSTRACT FROM AUTHOR]

As a Ruddlesden-Popper (RP) phase solid oxide fuel cell (SOFC) cathode material, Pr 2 NiO 4+δ (PNO) is a critical challenge for SOFC commercialization due to the lack of oxygen vacancies and insufficient redox reaction (ORR) activity. In this paper, various concentrations of La 0.6 Sr 0.4 CoO 3-δ (LSC) nanoparticles are coated on the surface of PNO by an impregnation method, and the ORR kinetics of PNO is found to be improved by constructing a composite cathode with heterointerfaces. The formation of the heterointerface effectively enhances the transfer of interstitial oxygen in the PNO and the oxygen vacancies in LSC, which can promote the conduction of O2− in the cathode and thus improves the ORR activity of the material. When the impregnation concentration of LSC reached C LSC = 0.2 mol L−1, the ORR activity can reach the highest level. At 700 °C, the area-specific resistance of PNO-LSC reaches 0.024 Ω cm2, which is 83.4% lower than that of PNO (0.145 Ω cm2). And the peak power density of PNO-LSC reaches 0.618 W cm−2, which is 1.89 times larger than that of PNO (0.327 W cm−2). Therefore, the construction of composite cathodes with heterointerfaces via impregnation provides an alternative strategy for enhancing the ORR activity of the cathode materials in SOFC. [Display omitted] • Pr 2 NiO 4+δ -La 0.6 Sr 0.4 COO 3-δ cathode is prepared by impregnation method. • The heterointerface promotes the ORR activity of the cathode. • Pr 2 NiO 4+δ -La 0.6 Sr 0.4 COO 3-δ has excellent ORR activity. [ABSTRACT FROM AUTHOR]