Oxygen Reduction and Evolution Reaction (ORR and OER) Bifunctional Electrocatalyst Operating in a Wide pH Range for Cathodic Application in Li–Air Batteries

Developing inexpensive, noble metal-free, efficient, stable, and bifunctional electrocatalysts has attracted significant research interest in electrocatalysis and air battery-based energy storage devices. The fluorinated copper–manganese oxide (FCMO) is synthesized in an aqueous medium through a simple way using a hot plate and a fume hood. The FCMO catalyst is relatively inexpensive compared to Pt-, Ru-, and Ir-based catalysts, less hazardous than a Co-based catalyst, and at the same time, comparable with an Fe–Ni-based catalyst that has stable performance only in a basic medium. The FCMO is used in combination with carbon black as FCMO–carbon black by dispersing FCMO over carbon black to improve the electron transport efficiency. The FCMO catalyst and FCMO–carbon black show oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in both acidic and basic media with an impressive property of larger pH window stability with bifunctional performance. The ORR was found to be a two-electron process on both catalytic systems in both acidic and alkaline media. The FCMO–carbon black showed ORR (0.43 V) and OER (1.51 V) versus RHE in 0.5 M H2SO4. The onset potential of FCMO–carbon black was found to be an impressive 0.94 V versus RHE for the ORR and a relatively competitive OER of 1.54 V versus RHE in 0.1 M KOH. The FCMO–carbon black catalyst was also deposited on a conducting carbon cloth and used as an air cathode in a hybrid Li–air cell with 1.0 M LiOH as the electrolyte. The cell showed a stable cycling performance at room temperature for more than 80 h under a cycling current density of 0.08 mA cm–2.