A sol-gel derived LaCoO3 perovskite as an electrocatalyst for Al-air batteries

Abstract

In this work, we report the performance of the LaCoO₃ perovskite oxide as a cathode catalyst for an Al-air battery. LaCoO₃ was prepared using the sol-gel method and its suitability as a catalyst has been studied. XRD studies of the perovskite revealed a monoclinic symmetry with no secondary phase being observed. An aggregated morphology with a porous structure was observed from SEM analysis. TEM studies showed that the aggregated LaCoO₃ particles exhibited an average diameter of 49.94 nm. The surface area obtained using the BET method is found to be 9.088 m² g^-1. The electrochemical activity of LaCoO₃ towards the oxygen reduction reaction (ORR) was higher than that of the bare glassy carbon electrode (GCE). From the kinetic studies, the number of electrons transferred was found to be 4.08, indicating that the reaction occurs through a 4e^- pathway. The mass activity and specific activity were found to be 3.05 mA mg^-1 and 0.33 mA cm^-2 at 1.2 V (vs. the reversible hydrogen electrode (RHE)), respectively. The stability of LaCoO₃ was studied using chronoamperometry and impedance analyses, which revealed less charge transfer resistance before and after the stability test. Subsequently, an Al-air battery was fabricated using LaCoO₃ as the cathode and Al as the anode. Polyvinyl alcohol (PVA) based KOH gel was used as an electrolyte. The cell exhibited an open circuit voltage (OCV) of 1.35 V with a discharging capacity of 1770 mA h g^-1. In addition, the power density was calculated to be 10.04 mW cm^-2 at 0.6 V vs. RHE. Our studies suggest that LaCoO₃ can be a promising candidate as a cathode for high-performance Al-air batteries.