Low-valence Cu+-tailoring La0.5Sr1.5MnO4 as a novel single-phase cathode for proton-conducting solid oxide fuel cells

Development of highly-active electrodes is essential yet challenging for the designs of proton-conducting solid oxide fuel cells (H-SOFCs). Herein, the Ln2MnO4+δ manganite-based La0.5Sr1.5MnO4+δ (LSMO) is firstly modified with the low-valence Cu, resulting in the structure squeezing or stretching in different directions, and the addition of effective Mn3+-O-Mn4+ and Cu2+-O-Cu+ transition paths for electron-hopping, thus improving the electrocatalysis. The higher proton/oxygen diffusion rate in the resultant La0.5Sr1.5Mn0.8Cu0.2O4+δ (LSMC) sample, evidenced by the electrical conductivity relaxation results, contribute to the increased catalytic activity for faster oxygen reduction reaction. Next, based on a H-SOFC, the single-phase Cu-tailored LSMC cathode demonstrate significantly higher cell performance than Cu-free LSMO cathode, achieving a preferable power output of 1274 and 597 mW cm−2 at 700 and 600°C. The performance is also better than other Ln2NiO4-based cathodes employed to H-SOFCs in the literature. Though the single-phase Ln2MnO4+δ-based material is attempted as cathode for H-SOFCs, no compromise between the good fuel cell performance and operation stability is observed. The combination of high performance and good durability suggests that LSMC is a preferential alternative cathode material for H-SOFCs. This work provides a new idea to design highly-active electrode materials via regulating the distortions in different crystal orientations, which is also beneficial to the related electrocatalytic fields.