Enhanced surface exchange activity and electrode performance of (La2−2xSr2x)(Ni1−xMnx)O4+δ cathode for intermediate temperature solid oxide fuel cells

• Mn-doped La2NiO4+δ R-P phase cathode is investigated for the first time.
• k for LSNM is 1.57 × 10−6 cm/s at 700 °C, the highest among known R-P phase cathodes.
• Rp of LSNM is 0.42 Ωcm2 at 700 °C, the best among La2MO4+δ cathodes (M = transition metal).

Surface exchange kinetics of Ruddlesden-Popper (R-P) phase lanthanum nickelates upon Mn doping as an intermediate temperature solid oxide fuel cells (IT-SOFCs) cathode is investigated for the first time in this communication. To promote the exchange rate in oxygen reduction reaction (ORR) on nickelates, Mn is partially substituted for Ni. The oxygen exchange resistance is accurately measured by electrochemical impedance spectroscopy (EIS) with dense thin layer cathode. It is found that Mn substantially promotes the surface kinetics; a surface exchange coefficient (k) of 1.57 × 10−6 cm/s is obtained at 700 °C for La1.8Sr0.2Ni0.9Mn0.1O4+δ (Sr20Mn10), ∼80% higher than that of the undoped La2NiO4+δ (LNO). To our best knowledge, such coefficient is the highest values among the currently available R-P phase IT-SOFC cathodes. The corresponding polarization resistances (Rp) are evaluated on porous electrodes. Rp for LNO is 0.74 Ωcm2 at 750 °C, but decreases significantly to 0.42 Ωcm2 for Sr20Mn10 which is remarkably improved compared to the reported values in the literature for La2MO4+δ materials (M = transition metal). Those promising results demonstrate that Mn-doped LNO is a new excellent cathode material for IT-SOFC.