Compositional and Morphology Optimization to Boost the Bifunctionality of Perovskite Oxygen Electrocatalysts

Oxygen electrocatalysts are crucial for the development of renewable and sustainable energy conversion/storage (ECS) systems, but a shortage of efficient and low-cost oxygen electrocatalysts is impeding their widespread applications. In this work, to investigate the bifunctionality of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), Ni-substituted LaMnO3 perovskite oxides (LaNixMn1–xO3, x = 0.1, 0.3, 0.5, 0.7, and 0.9) and pristine LaNiO3 and LaMnO3 were synthesized using a sol–gel process. After the compositional optimization and electrochemical characterizations, we identified that LaNi0.3Mn0.7O3 (SG LNM-3) within the compositions exhibited balanced intrinsic activity for bifunctional ORR and OER. To further improve the apparent activity of the optimized SG LNM-3, electrospinning was used to prepare one-dimensional nanostructured LaNi0.3Mn0.7O3 (ES LNM-3). ES LNM-3 had a higher specific surface area and continuous electron-transfer pathways, resulting in much improved bifunctional activity in comparison to SG LNM-3. In addition to the morphological effect, we ascribed the high electrochemical performance of ES LNM-3 to the high-spin Mn3+ and low-spin Ni3+ with electron configurations of t2g3eg1 and t2g6eg1 (a well-recognized design descriptor), as well as the high degree of Jahn–Teller distortion. After assembling ES LNM-3 within Zn–air batteries, promising electrochemical performances such as high power density and rate capability were obtained. Our findings will advance the development of high-performance and inexpensive oxygen electrocatalysts and associated ECS devices.