Regulating the Interfacial Electron Density of La_0.8Sr_0.2Mn_0.5Co_0.5O₃/RuO_x for Efficient and Low-Cost Bifunctional Oxygen Electrocatalysts and Rechargeable Zn-Air Batteries

Abstract

La 0.8 Sr 0.2 Mn 0.5 Co 0.5 O 3 (LSMC) perovskite anchored with RuO x (LSMC-Ru) is fabricated as a new bifunctional electrocatalyst, with low dosage (2.43 wt %) and high utilization of noble metal Ru. The LSMC-Ru exhibits outstanding bifunctional activity with a low potential gap of 0.72 V between the oxygen evolution reaction (OER) potential at 10 mA cm −2 and the oxygen reduction reaction (ORR) half-wave potential. The strong electronic interaction between RuO x and LSMC is confirmed by both experiments and theoretical calculations. Consequently, the electron-rich Mn centers promote ORR, while the electrondeficient Ru centers facilitate OER. A Zn-air battery using the LSMC-Ru air electrode delivers a peak power density of 159 mW cm −2 and a low charge−discharge potential gap of 0.58 V at 2 mA cm −2 . The high round-trip energy efficiency of 60.6% is retained after 300 cycles. This strategy of anchoring a low dosage noble metal catalyst to perovskite can be extended to other systems of noble metal-non-noble metal composite electrocatalysts to achieve both competitive performance and low cost.

Promoting Bifunctional Oxygen Catalyst Activity of Double-Perovskite-Type Cubic Nanocrystallites for Aqueous and Quasi-Solid-State Rechargeable Zinc-Air Batteries

“…In addition, such integration in perovskite oxides can be easily achieved by facile one-step preparation in an ambient atmosphere, which is promising for practical production. In previous research, different single perovskite oxides (e.g., LaNiO 3 [18], La 1−x Sr x Co 1−y Mn y O 3−δ [19,20], LaMn 1−y Co y O 3−δ [21], Sr x Co 1−y Fe y O 3−δ [22,23], Sr(Co 0.8 Fe 0.2 ) 0.95 P 0.05 O 3−δ [24]) and double perovskite oxides (e.g., Sr 2 TiMnO 6 [25], Pr 0.5 Ba 0.5 Mn 1.8−x Nb x Co 0.2 O 6−δ [26], (PrBa 0.5 Sr 0.5 ) 0.95 Co 1.5 Fe 0.5 O 5+δ [27,28]) were developed and they showed promising capability for facilitating oxygen redox as catalysts for air cathodes in Zn-air batteries [29][30][31][32][33][34][35][36][37][38].…”

Innovating Rechargeable Zn-Air Batteries for Low Charging Voltage and High Energy Efficiency

“…The cost-effective commercialized MnO 2 catalyst for oxygen reduction reaction (ORR) of primary ZABs is not suitable for catalyzing oxygen evolution reaction (OER) in the charging process. − Noble-metal catalysts (e.g., Pt/C, IrO 2 , and RuO 2 ) deliver remarkable catalytic activity, but they are too expensive. Although novel bifunctional ORR/OER catalysts have been extensively developed these years, they undergo complicated synthesis steps with low yields, which is far from the requirement of commercialization. − In addition, due to OER’s high thermodynamic equilibrium voltage and intrinsically sluggish kinetics, most ZABs cannot charge below 2 V, which further leads to a low energy efficiency of less than 60%. − Moreover, cathode materials may readily degrade under higher charging voltages, resulting in shortened battery life. − Recently, researchers have proposed to use reaction modifiers like urea, ethanol, and other readily oxidized molecules to substitute the sluggish OER. − These reaction modifiers generally show a lower oxidation potential and favorable oxidation thermodynamics. However, the optimal oxidation environment of these molecules may not be suitable for the operation of ZABs.…”