Abstract: Interface engineering is an effective strategy to develop fuel electrode materials with excellent catalytic activity of CO₂ for solid oxide electrolysis cell. In this study, La_0.3Sr_0.6Ti_1-xNi_xO_3-δ/Ce_0.9Gd_0.1O_2-δ (LSTN_x/GDC) composite fibers were directly prepared by electrospinning technology, and the fiber-based fuel electrodes were constructed, which were composed of LSTN_x electronic channel skeleton, GDC ion channel embedding and in-situ Ni exsolution nanoparticles. The effect of B-site Ni-doping on the morphology, structure and CO₂ catalytic activity of fiber-based fuel electrode was studied. The results of Scanning Electron Microscope testing show that the LSTN_x/GDC composite fibers with uniform diameter (100-150 nm) and no obvious particle agglomeration or fracture gap are successfully prepared when the Ni-doping is x=0.15 and 0.20. More in-situ B-site nickel nanoparticles (20-30 nm) could be exsolved from the prepared fuel electrode under the reducing atmosphere. The relaxation time distribution analysis confirms that in-situ exsolution of B-site nickel metal nanoparticles can not only provide more active sites, but also form rich heterointerfaces with composite fiber and impregnate to accelerate the interfacial charge transfer, and then significantly enhance the adsorption and catalytic ability of CO₂. The electrolytic current density of the single cell with the doping of x=0.20 at 850 ℃, CO₂ : H₂=5 : 5 (in volume) under 1.5 V increases to 0.799 A·cm^-², and the polarization impedance decreases to 0.171 Ω·cm², and presents excellent stability without significant current fluctuation for 70 h at 1.3 V, 850 ℃ under CO₂ : H₂=5 : 5 (in volume).

Key words: solid oxide electrolysis cell, fuel electrode, composite fiber, in-situ Ni exsolution, distribution of relaxation time