Introduction Mixing hydrogen into natural gas pipelines is one of the critical technologies for achieving large-scale and long-distance hydrogen transmission, which can be directly used for power generation or combined cooling, heating, and power supply through solid oxide fuel cells (SOFC), without the hydrogen separation and purification, enabling efficient energy conversion and utilization. Ni-YSZ metal-ceramic composite anodes are widely used in SOFC single cells, which have a superior performance under hydrogen and reformed hydrogen-rich fuel systems. However, carbon deposition susceptibly occurs under carbon-hydrogen fuels, and metal-nickel agglomeration migrates under high fuel utilization operating modes. Sr(Ti1-xFex)O3-δ (STF) is one of the potential alternative anodes with superior structural stability and mixed ionic-electronic conductivity, as well as great resistance to redox cycling, fuel impurities and hydrocarbon fuels. It was indicated that the introduction of transition metal (i.e., Co, Ni, Ru, etc.) doping into the B-site of STF perovskite oxides, which in-situ exsolved metal nanoparticles from substrate in reducing atmosphere, exhibiting a superior anodic catalytic activity. In this paper, A-deficient Sr0.95Ti0.4-xFe0.6CoxO3-δ (x=0.03, 0.05, 0.07) was prepared as a SOFC anode. In addition, the material structure evolution, porous anode conductivity, electrochemical performance and stability of single-cell under methane fuels with different hydrogen doping ratios were also investigated. Methods Sr0.95Ti0.4-xFe0.6CoxO3-δ (x=0.03, 0.05, 0.07) powder was prepared via a high-temperature solid-state reaction with SrCO3, TiO2, Fe2O3 and Co(NO3)2·6H2O. The precursors were mixed and ball-milled in ethanol for 48 h, dried and calcined at 1100 ℃ for 10 h. Subsequently, the perovskite electrode powders were obtained (i.e., denoted as STFC-3, STFC-5, STFC-7), Respectively. The electrode slurry with the powder and a binder in a mass ratio of 1.0:1.5 was prepared by a three-roll mill. The La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte pellets with a thickness of 300 μm and a diameter of 15.5 mm were prepared via tape casting and high-temperature sintering. La0.4Ce0.6O2-δ (LDC) was screen-printed on the LSGM electrolyte and calcined at 1 350 ℃ for 4 h, to prevent the potential reaction between STFC and LSGM. Afterwords, the STFC, La0.6Sr0.4Co0.2Fe0.8O3-δ-Gd0.1Ce0.9O1.95 (LSCF-GDC) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) electrode were screen-printed as anode and cathode, respectively, and then were co-fired at 1 075 ℃ for 3 h. The effective area of the cathode was 0.5 cm2. Finally, 1 mm×1 mm silver grids were printed on the cathode and anode of the single cell, as a current-collector, calcined at 600 ℃ for 1 h. The structural evolution of the materials obtained before and after reducing in humidified hydrogen (~4% H2O, in volume) at 800 ℃ for 3 h was characterized by a model Bruker D2 Advance X-ray diffracometer (XRD) and a model Escalab 250X-ray photoelectron spectrometer (XPS). The microscopic morphology of the electrode powder after reduction was characterized by a model JSM-IT500HR scanning electron microscope (SEM). The conductivity of the screen-printed STFC porous electrodes was tested in air and humidified hydrogen (~4% H2O, in volume) atmospheres through the van der Pauw method. The stability and electrochemical performance (i.e., the discharge curves and electrochemical AC impedance spectra (EIS, 0.1 Hz~1.0 MHz, 50 mV)of single cells under different hydrogen blended methane fuels were investigated by a model P4000A electrochemical workstation (Princeton). Results and discussion The peak power density (Pmax) and limiting current density (jmax) of the single cell at 800 ℃ enhance with the increase of the volume ratio of H2. Taking STFC-3 cell as an example, the Pmax of the single cell is 0.506, 0.467, 0.414, 0.338 W/cm2 at different hydrogen ratios of 80%, 60%, 40%, and 20% (in volume), respectively. According to the EIS spectra and DRT results, the polarization resistances (Rp) of the STFC anode single cell gradually increase with the increase of CH4 ratio, which mainly corresponds to the change of middle frequency P4 (~10 Hz) and low frequency P5 (1~10-1 Hz) responses, possibly due to the complexity of catalytic oxidation and slow reaction kinetics of CH4. The STFC-3 single cell is operated at 0.14 A/cm2 with humidified 10 H2-40 CH4 (~4% H2O, in volume). The STFC-3 cell can stably operate for 140 h without an obvious voltage decay, showing a superior long-term stability. The SEM images indicate that the interface contacts between the electrolyte, the barrier layer and the STFC anode is dense, without having anode structure changes. Moreover, little carbon deposition appears on the surface of the anode, indicating a decent coking-resistance property of STFC anode in hydrogen blended natural gas. It has significant guidance in response to the demand for high-performance and stability of SOFC with hydrogen and compressed natural gas. Conclusions The Co-Fe alloy nano particles were exsolved on the surface of STFC perovskite oxide after humidified hydrogen reduction, and the exsolution enhanced with increasing Co doping content. At 800 ℃, the conductivity of STFC-3 porous electrode under hydrogen atmosphere reached 3 S/cm, with a single cell maximum output power density of 0.457 W/cm2 in methane fuel doping with 20% (in volume) hydrogen. The continuous operation at 0.14 A/cm2 for ~140 h indicated good durability and coking resistant property.