Optimizing the Surface Characteristics of La_0.6Sr_0.4CoO_3−δ Perovskite Oxide by Rapid Flash Sintering Technology for Easy Fabrication and Fast Reaction Kinetics in Alkaline Medium

Abstract

Perovskites are a challenging new class of highly efficient bifunctional catalysts that hold huge significance in advanced batteries and water electrolysis. The surface chemistry and surface electronic structures of the La0.6Sr0.4CoO3−δ (LSC) perovskite is greatly modified upon postsynthesis sintering. Herein, a new strategy has been demonstrated by intense pulsed light technology to accomplish the sintering process in milliseconds, and is comparatively explored with conventionally sintered LSC. The optimized sintering conditions rejuvenated a new class of a highly active bifunctional LSC electrocatalyst. The electrochemical activity and surface characteristics are orders of magnitude superior to those of the thermally sintered LSC. The best performing LSC catalyst known as LSC 30 exhibits outstanding bifunctionality with a low overpotential (∼0.89 V). Furthermore, LSC 30 shows a positively shifted onset potential of 0.92 V and a high limiting current of −6.1 mA cm–2 at 20 mV s–1, during the oxygen reduction reaction in alkaline medium. When tested as the air cathode of a zinc–air battery, LSC 30 delivered a steady performance for 200 cycles. This study highlights the role of the new concept in the agile synthesis of perovskite oxides for oxygen catalysis and possible application as the air cathode in metal air batteries.

Surface Engineering of Perovskites for Rechargeable Zinc–Air Battery Application

“…The vertical shift in the N 2 adsorption of LSC/LDH (75/25) is indicative of its high surface area of 64.11 m 2 g –1 compared to that of LSC at 0.73 m 2 g –1 . In detail, the as-prepared LSC exhibited a BET surface area of 6.9 m 2 g –1 , which reduced to 0.73 m 2 g –1 after sintering at high temperature due to the enrichment of Sr on the surface . Addition of NiFe on the LSC surface contributes to additional micro/mesopores resulting in the increase in the overall surface area.…”

“…The perovskite LSC was synthesized by the Pechini method. , All the chemicals were purchased from Sigma-Aldrich and used without further purification. La­(NO 3 ) 3 ·6H 2 O (99.9%), Sr­(NO 3 ) 2 (99%), and Co­(NO 3 ) 2 ·6H 2 O (97.7%) precursor materials in a stoichiometric ratio of (0.6:0.4:1) were dissolved in 30 mL of DI water and 1 M mixed solution was prepared.…”

“…24 The resultant LSC/LDH In detail, the as-prepared LSC exhibited a BET surface area of 6.9 m 2 g −1 , which reduced to 0.73 m 2 g −1 after sintering at high temperature due to the enrichment of Sr on the surface. 52 Addition of NiFe on the LSC surface contributes to additional micro/mesopores resulting in the increase in the overall surface area. LSC/LDH (25/75) has the highest surface area of 107.44 m 2 g −1 , indicating the fact that NiFe majorly contributes to the increase in the surface area.…”

“…Following them, Mefford et al and Grimaud et al demonstrated the exploitation of O 2 from the LSC lattice oxygen for the enhancement of oxygen electrocatalysis. Similarly, in our previous study, a new class of highly electroactive LSC was rejuvenated by sintering, where the surface chemistry of LSC was significantly improved . Particularly, an optimized sintering method such as intense pulse light (IPL) sintering was used in the study, which delivered exceptional ORR kinetics for electrocatalysis.…”

“…Similarly, in our previous study, a new class of highly electroactive LSC was rejuvenated by sintering, where the surface chemistry of LSC was significantly improved. 34 Particularly, an optimized sintering method such as intense pulse light (IPL) sintering was used in the study, which delivered exceptional ORR kinetics for electrocatalysis. The defects and as-generated oxygen vacancies in the crystal structures of the material by sintering have escalated the charge transfer kinetics, resulting in the enhancement of ORR performance.…”