Surface Engineering of Perovskites for Rechargeable Zinc–Air Battery Application

The ABO_3−δ-type perovskite oxides are highly desirable electrocatalysts with interesting surface structures that could be modified to bring out their excellent catalytic performance. The La_0.6Sr_0.4CoO_3−δ (LSC) perovskite is one among the classes which is easy to fabricate, cost-effective, and scalable. Defect engineering by sintering and interface engineering by in situ surface modification are employed to positively transform the LSC perovskite electrode, that is, by sintering at a high temperature, phase-pure LSC is obtained with induced changes such as improved conductivity, crystal defects, and oxygen vacancies. By chemically modifying the surface of this LSC using highly catalytically active NiFe layered double hydroxide (LDH), excellent bifunctionality is achieved. For the latter, an optimized molar ratio of NiFe LDH (25%) is integrated onto the phase-pure LSC surface by a simple wet-chemical process. The phase purity and bifunctionality of the prepared composite are verified by various physical characterizations and redox processes. The surface-modified LSC/LDH (75/25) cathode demonstrates superior oxygen reduction and evolution reaction performances that are better than those of the native LSC with a low overall overpotential of 0.71 V at 5 mA cm^–2 in alkaline media. The same cathode when applied in a zinc–air battery exhibits a stable cycle performance with a reduced charge–discharge potential gap of 0.73 V at 5 mA cm^–2 for 100 cycles in alkaline media. Additionally, LSC/LDH (75/25) also ensures long-term performance with remarkable stability.