The use of spray-dried Mn3O4/C composites as electrocatalysts for Li-O2 batteries

Abstract

The electrocatalytic activities of Mn3O4/C composites are studied in lithium-oxygen (Li-O2) batteries as cathode catalysts. The Mn3O4/C composites are fabricated using ultrasonic spray pyrolysis (USP) with organic surfactants as the carbon sources. The physical and electrochemical performance of the composites is characterized by X-ray diffraction, scanning electronmicroscopy, particle size analysis, Brunauer-Emmett-Teller (BET) measurements, elemental analysis, galvanostatic charge-discharge methods and rotating ring-disk electrode (RRDE)measurements. The electrochemical tests demonstrate that the Mn3O4/C composite that is prepared using Trition X-114 (TX114) surfactant has higher activity as a bi-functional catalyst and delivers better oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performance in Li-O2 batteries because there is a larger surface area and particles are homogeneous with a meso/macro porous structure. The rate constant (kf) for the production of superoxide radical (O2●-) and the propylene carbonate (PC)-electrolyte decomposition rate constant (k) for M3O4/C and Super P electrodes are measured using RRDE experiments and analysis in the 0.1Mtetrabutylammonium hexafluorophosphate (TBAPF6)/PC electrolyte. The results show that TX114 has higher electrocatalytic activity for the first step of ORR to generate O2●- and produces a faster PC-electrolyte decomposition rate.