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 t(2g)(3)e(g)(1) and t(2g)(6)e(g)(1) (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.

Automated summary

In this study, Ni-substituted LaMnO3 perovskite oxides were synthesized and their bifunctionality in the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) was investigated. The optimized LaNi0.3Mn0.7O3 material exhibited balanced intrinsic activity for ORR and OER, and electrospinning was used to further improve its apparent activity. The resulting one-dimensional nanostructured LaNi0.3Mn0.7O3 showed much improved bifunctional activity due to its higher specific surface area and continuous electron-transfer pathways. These findings are important for the development of high-performance and inexpensive oxygen electrocatalysts.