Metal(Pt, Pd)-Perovskite Oxide(Ba0.5Sr0.5Co0.8Fe0.2O3-δ) Hybrid Material As a Bifunctional Electrocatalyst for Lithium-Air Battery

Abstract

The rapid depletion of fossil fuel resources and growing concerns over climate change have made the development of next-generation batteries a top priority. Among these, Li-O2 batteries have attracted significant interest due to their potential for much higher gravimetric energy storage density compared to other chemical batteries. However, efficient and cost-effective catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical for the efficient functioning of these batteries.In recent years, complex perovskite oxides, such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), have been identified as promising candidates for bifunctional catalysts due to their defective structures and excellent oxygen mobility. However, while BSCF exhibits high OER activity, its ORR performance is poor. To address this issue, researchers have turned to metal-oxide composite catalysts, where nanosized metals are deposited on the surface of perovskite oxides, to increase activity and stability towards ORR due to the synergistic effect between metal and oxide support.In this study, we report the development of bifunctional electrocatalysts with highly electrocatalytic activity for ORR and OER. We used a simple wet-chemical processing technique to deposit metal catalysts with superior ORR activity on perovskite oxide-based catalysts with high OER activity. The direct deposition method is an effective way to create a good distribution of metal catalysts, intimate contact between metal catalysts and BSCF perovskite oxide, which may contribute to the creation of a synergistic effect between them. Our results showed that the metal catalysts deposited on perovskite oxides of Pd@BSCF and Pt@BSCF exhibited better ORR activity than others and higher OER activity than the perovskite oxides alone, resulting in much-enhanced bifunctionality through a synergistic effect between the metal catalysts and perovskite oxides.We further investigated the enhanced bifunctional electrocatalytic activity of the metal catalysts deposited perovskite oxides for Li-O2 batteries. The assembled Li-O2 batteries with Pd@BSCF cathode demonstrated lower discharge/charge overpotential (0.8 V at the cutoff capacity of 500 mAh gcat -1) and improved cycling stability (over 70 cycles), indicating the effectiveness of our approach in enhancing the bifunctional activities of ORR and OER for application in electrochemical energy storage and conversion systems. The encouraging results obtained from this study might have been attributed to two mechanisms, namely, the synergistic effect of electronic transfer and RDS/spillover. Our study suggests that the deposition of metal catalysts on the surface of perovskite oxides (Pd@BSCF and Pt@BSCF) is an effective approach to enhance bifunctional activities of ORR and OER, making it a promising strategy for the development of next-generation batteries. Figure 1