Ni-Doped La0.6Sr0.4CoO3 Perovskite as an Efficient Electrocatalyst for Oxygen Reduction and Evolution Reactions in Alkaline Media

Abstract

The Co-based perovskite La0.6Sr0.4CoO3 has received significant attention as a potential electrocatalyst for its oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) due to its abundance, facile synthesis, and high oxygen kinetics. However, research on the catalytic performance of Ni-doped La0.6Sr0.4Co1−xNixO3 as a bifunctional cathode catalyst for Zn-air batteries (ZABs) is still scarce. In this work, lanthanum strontium cobalt-based perovskite catalysts with various Ni contents (La0.6Sr0.4Co1−xNixO3, x = 0, 0.2, 0.5, and 0.8) were synthesized using a simple combustion method. The effects of Ni doping on the morphology, structure, surface oxygen-related species, and valence states of the transition metals of the perovskite were characterized. The electrochemical behaviors of the perovskite catalysts in both ORR and OER were also assessed. The characterization results revealed that proper Ni doping can decrease particle size, increase surface oxygen vacancies, and create mixed valence states of the transition metal and, thus, lead to improvement of the electrocatalytic activity of perovskite catalysts. Among the different perovskite compositions, La0.6Sr0.4Co0.8Ni0.2O3 exhibited the best ORR/OER activity, with a higher limiting current density, smaller Tafel slope, higher half-wave potential, lower overpotential, and lower potential difference than the other compositions. When La0.6Sr0.4Co0.8Ni0.2O3 was applied as the cathodic catalyst in a primary ZAB, it delivered a peak power density of 81 mW cm−2. Additionally, in rechargeable ZABs, the La0.6Sr0.4Co0.8Ni0.2O3 catalyst exhibited a lower voltage gap (0.94 V) and higher stability during charge–discharge cycling than the commonly used catalyst Pt/C. These results indicate that Ni-doped La0.6Sr0.4Co0.8Ni0.2O3 is a promising bifunctional electrocatalyst for ZAB.