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• A negative expansion component SZM is used to balance the thermal expansion. • SNC/SZM heterogeneous interface is constructed by self-assembly. • Heterogeneous interface improves SNC-20SZM ORR kinetics. • The combined SZM increases the TPB length and the O2– transport pathways. • SNC-20SZM exhibits an impressive Rp value of 0.012 Ω cm2 at 700 °C. The discrepancy in thermal expansion coefficients (TECs) between the cobalt-based cathode and the electrolyte presents a notable obstacle in attaining optimal performance levels for solid oxide fuel cells (SOFCs). Here we propose to introduce negative thermal expansion (NTE) component Sm 0.85 Zn 0.15 MnO 3 (SZM) to SrNb 0.1 Co 0.9 O 3−δ (SNC) cathode to prepare SNC-xSZM (x = 0, 10, 20 and 30 %) composite cathode materials. The impact of incorporating negative thermal expansion material on the composition and properties of the matrix materials were examined by X-ray diffraction, thermal dilatometer, high-resolution transmission electron microscopy, and electrochemical workstation. The results show that SNC-xSZM can achieve more ideal thermal matching with Ce 0.8 Gd 0.2 O 1.9 (GDC), and the thermal expansion coefficient decreases observably from 25.47 × 10−6 K−1 for x = 0 to 13.74 × 10−6 K−1 for x = 30 %. The optimal comprehensive electrochemical performance is obtained for SNC-20SZM, which possesses the minimum polarization resistance (Rp) of 0.012 Ω cm2 at 700 °C. The SNC-20SZM-based cell shows a maximum peak power density (PPD) of 1.22 W cm−2 while exhibiting stable operation for a continuous duration of 120 h at a constant current of 0.8 A cm−2, with performance remaining optimal. Moreover, SNC-20SZM demonstrates exceptional durability and stability over prolonged durations even in high CO 2 atmospheres. An innovative approach for enhancing the development of intermediate-temperature solid oxide fuel cells (IT-SOFCs) involves incorporating SZM in the SNC cathode, thereby augmenting electrochemical performance and narrowing the gap in the thermal expansion coefficient among SOFC modules. [ABSTRACT FROM AUTHOR]

• Ni-doped Fe-based perovskite enhances ORR activity. • Ni doping reduces the energy barrier of surface oxygen diffusion and bulk diffusion. • LSCFN15 is expected to be an electrode with dual functions of ORR and OER.. • The ORR rate-limiting steps of Ni-doped electrodes were analyzed through DRT. This paper systematically studies Ni doping at Fe sites in La 0.6 Sr 0.4 Co 0.3 Fe 0.7 O 3-δ (LSCF) as an intermediate temperature solid oxide fuel cell (IT-SOFC) electrode. The electrocatalytic activity of Ni-doped electrodes in oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) modes was analyzed, rather than individual cathode or anode. The results indicate that Ni doping increases the internal vacancies, ORR activity, and charge transfer ability of La 0.6 Sr 0.4 Co 0.3 Fe 0.6 Ni 0.15 O 3-δ (LSCFN15). In addition, compared to LSCF, LSCFN15 also reduces the energy barriers for surface oxygen exchange and bulk diffusion, thereby increasing the overall ORR kinetic rate. Combined with the distribution of relaxation time (DRT) analysis, it was confirmed that Ni-doped LSCFN15 increased the adsorption and dissociation rates of oxygen. At 750 ℃, the area-specific resistance (ASR) of LSCFN15 reached 0.045 Ω cm2, which is only 58.4 % of LSCF (0.077 Ω cm2). As a SOFC cathode, the peak power density (PPD) reached 1175 mW cm−2, 1.31 times that of LSCF (898 mW cm−2). As a SOFC anode, the current exchange density of LSCFN15 in OER mode reaches 164 mA cm−2, which is higher than the 125 mA cm−2 of LSCF, indicating that LSCFN15 also has the potential to serve as an anode for SOFC. In addition, Ni doping reduces the thermal expansion coefficient of the electrode and improves its thermal compatibility with traditional electrolytes. As an electrode, LSCFN15 exhibits excellent long-term stability in both SOFC and SOEC modes. Overall, Ni-doped Fe-based perovskite can improve the ORR and OER activities while enhancing the stability of cell operation and is expected to obtain multifunctional SOFC electrode materials. [ABSTRACT FROM AUTHOR]