Rechargeable metal-air batteries with its high energy storage capacity and environment-friendly materials provide one of the most promising solutions as safer energy storage devices [1]. However, the air cathodes of rechargeable metal-air batteries have the issue of irreversibility of the oxygen evolution and reduction reactions [2]. Noble metals have good bifunctional catalytic ability but are not economical sustainable. Among the non-noble catalysts of interest, perovskites with the chemical formula of ABO₃have been studied extensively and have recently received increasing attention, due to their higher electrochemical performance and lifetime in the alkaline electrolyte [3,4].

The LaNiO₃ perovskite has attracted enormous interest as a substitute of carbon in bifunctional electrodes due to its metal-like conductivity and decent electrochemical activity [5,6]. Although, LaNiO₃ is a good oxygen evolution reaction (OER) catalyst with lower oxygen reduction reaction (ORR) capability, a study by Yuasa et al. showed that electrodes prepared using a composite of LaNiO₃/LaMnO₃ had remarkable bifunctional electrochemical performance due to the good ORR ability of LaMnO₃ [5]. Moreover, a LaNi_0.9Mn_0.1O₃ (LaNiO₃ with 10% Mn doping) electrode from the same study displayed excellent bifunctional ORR/OER activity showing the potential for doping using other element in LaNiO₃. A detailed mechanistic study of different elemental doping and their effect on actual electrode performance in real life conditions has not been previously studied.

In this study, a mechanistic study of the catalytic ability of different doping element on LaNiO₃ such as LaNi_0.9Mn_0.1O₃, LaNi_0.9Co_0.1O_3, and LaNi_0.9Fe_0.1O₃will be studied using RDE and RRDE. In addition, air electrodes prepared with these catalysts material will be evaluated for electrochemical performance and stability under real-life experimental conditions.

The XRD of the LaNiO₃ perovskite doped with 10 wt.% Mn/Co which were synthesized using the glycine nitrate method are shown in Fig. 1a while, a typical microstructure of these catalyst are shown in Fig.1b. The polarization curves for the electrodes prepared using carbon-free LaNi_0.9Mn_0.1O₃catalyst powder as well as the carbon (Vulcan XC 72R) support are shown in Fig. 2. The electrodes prepared with the perovskites showed exceptional anodic (OER) capabilities compared to carbon electrode. However, the carbon-based electrode had slightly better ORR capabilities. A mechanistic study using RDE/RRDE will provide a better understanding of the intrinsic catalytic ability of the perovskite catalysts and their synergic effect with the carbon support.

References

 [1] M. Jacoby, Chem. Eng. News Arch. 88, 29 (2010)

[2] L. Jörissen, J. Power Sources 155, 23 (2006)

[3] J. McBreen, J. Electrochem. Soc., 119, 1620 (1972)

[4] G. Che, B.B. Lakshmi, E.R. Fisher, C.R. Martin, Nature, 393, 346 (1998)

[5] M. Yuasa, M. Nishida, T. Kida, N. Yamazoe, and K. Shimanoe, J. Electrochem. Soc., 158, A605 (2011)

[6] G. Karlsson, Electrochimica Acta, 30, 1555 (1985)