Abstract
A novel anode for solid oxide fuel cells (SOFCs), consisting of a Ruddlesden-Popper compound, La0.6Sr1.4Fe0.4Cr0.6O3.8, with in situ exsolved α-Fe nanoparticles (RP-LSF + Fe), is prepared from the phase conversion of the La0.3Sr0.7Fe0.7Cr0.3O3-δ (LSFCr-3) perovskite under humid H2 at 800 °C. On the surface of the RP-LSF + Fe anode, Fe cations are presented to be a mixture of Fe2+ and Fe3+, of which the average valence is lower than that in the bulk (Fe3+). The coverage of atomic hydrogen on the RP-LSF + Fe anode is over 0.8 in the pH2 range of 0.017–0.27 atm, implying a significant effect of these small amount (∼8 mol% on the surface) of exsolved Fe nanoparticles (∼200–300 nm) on promoting the dissociative absorption of H2. The charge transfer resistance is found to be closely related to the concentration of surface oxygen vacancies of the oxide matrix. The addition of catalytic amount of Ni (1–3 wt.%) greatly improves the fuel flexibility of the RP-LSF + Fe anode. Furthermore, it contributes to acceleration the phase conversion of the LSFCr-3 perovskite and reduced time for in situ preparation of the RP-LSF + Fe anode. The RP-LSF + Fe anode with 2.7 wt.% Ni exhibits a stable cell performance under 2.7%H2O+1:1-(H2:CO) and 2.7%H2O + CH4 for ∼30 h. It costs shortest time (30 h) to reach a stable cell voltage of 0.76 V at a galvanostatic current density of 0.25 A/cm2 under humid H2, which is clearly an active and stable anode material for SOFCs.
Published Version
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