Fascinating Bifunctional Electrocatalytic Activity via a Mesoporous Structured FeMnO₃@ZrO₂ Matrix as an Efficient Cathode for Li–O₂ Batteries

Abstract

Nonaqueous Li−O 2 batteries have remarkable potential for use in future-generation sustainable green energy storage systems. Perovskites of the type ABO 3 provide bifunctional electrocatalytic activity superior to that of dual mixed-metal oxides due to the presence of crystallographic defects and oxygen vacancies, arising from the multivalency of the A and B cations. In this study, we used a facile hydrothermal method with an ammonia solution to modify coralline-like ZrO 2 with Fe 0.5 Mn 0.5 O 3 (FeMnO 3 ) and graphene nanosheets (GNSs). The porous structure of the resulting ZrO 2 @FeMnO 3 /GNS system featured a high surface area and large volume, thereby exposing a great number of active sites. X-ray photoelectron spectroscopy revealed that the surface of the as-synthesized FeMnO 3 @ZrO 2 /GNS cathode material was rich with oxygen vacancies (i.e., a huge quantity of defects). This coralline-like bifunctional electrocatalyst possessed effective redox capability between Li 2 O 2 and O 2 as a result of its excellent catalytic activity in the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). We examined the charge/ discharge behavior of corresponding electrodes (EL-cell type for Li−O 2 battery) in the voltage range of 2.0−4.5 V (vs Li/Li + ). The synergistic effects of the high catalytic ability and coralline-like microstructure of our ZrO 2 @FeMnO 3 /GNS catalyst for Li−O 2 batteries resulted in its superior rate capability and excellent long-term cyclability, sustaining 100 cycles at 100 mA g −1 with a limited capacity of 1000 mAh g −1 . The cell overpotential was ∼0.14 V when adding LiI as a redox mediator, resulting in a more practical Li− O 2 battery with the ZrO 2 @FeMnO 3 /GNS catalyst. Therefore, ZrO 2 @FeMnO 3 /GNS catalysts having distinctive coralline-like structures can display outstanding bifunctional catalytic activity and electrical conductivity, suggesting great potential for enhanced Li−O 2 battery applications.

Oxygen defect regulation, catalytic mechanism, and modification of HfO2 as a novel catalyst for lithium–oxygen batteries

“…Fluorite-structured ZrO 2 , CeO 2 , and Pr 6 O 11 exhibit good catalytic performance in Li–O 2 batteries, especially when riched in oxygen defects. 9–28 The large center space of the fluorite crystal cell benefits the adsorption and transport of oxygen. Because Hf and Zr are IVB group elements with similar atomic radii, fluorite or fluorite-like structured HfO 2 , existing in the crystal forms of tetragonal, cubic, and monoclinic, 29,30 might have comparable or better catalytic performance.…”