Ionic liquid modified graphenenanosheets anchoring manganese oxide nanoparticles as efficient electrocatalysts for Zn–air batteries

Abstract

Ionic liquid (IL) modified reduced graphene oxide (rGO–IL) nanosheets anchoring manganese oxide (Mn₃O₄) are synthesized via a facile solution-based growth mechanism and applied to a Zn–air battery as an effective electrocatalyst for the oxygen reduction reaction (ORR). In this study, the IL moiety in these composites increases not only the conductivity of the system, but also the electrocatalytic activity compared to pristine rGO, together with the synergic effect of facilitating the ORR with the intrinsic catalytic activity of Mn₃O₄. Based on the Koutecky–Levich plot, we suggest that the ORR pathway of these composites is tunable with the relative amount of Mn₃O₄ nanoparticles supported onto the graphene sheets; for example, the ORR mechanism of the system with a lower Mn₃O₄ (19.2%) nanoparticle content is similar to a Pt/C electrode, i.e., a one-step, quasi-4-electron transfer, unlike that with a higher Mn₃O₄ (52.5%) content, which undergoes a classical two-step, 2-electron pathway. We also demonstrate the potential of these hybrid rGO–IL/Mn₃O₄ nanoparticles as efficient catalysts for the ORR in the Zn–air battery with a maximum peak power density of 120 mW cm⁻²; a higher performance than that from commercial cathode catalysts.