Boosting oxygen catalytic kinetics of carbon nanotubes by oxygen-induced electron density modulation for advanced Zn-Air batteries

Abstract

Carbon materials hold great promise as oxygen catalysts in rechargeable Zn-air batteries (ZABs) but suffer from the sluggish catalytic kinetics due to unfavorable intermediate specie adsorption/desorption properties. Herein, we demonstrate an effective oxygen-induced surface electron density modulation strategy to significantly boost the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of carbon nanotubes. Experimental and theoretical studies conjointly reveal that the incorporation of electron-drawing oxygen atoms in the conjugated carbon nanotube plane imparts a relatively high positive charge density on adjacent carbon atoms, making them energetically favorable for OOH∗ adsorption in OER and OH∗ desorption in ORR. Such oxygen-modulated carbon nanotubes display excellent bifunctional catalytic activity toward both ORR and OER. The as-fabricated aqueous and flexible all-solid-state ZABs display superb peak power densities of 130.5 ​mW ​cm−2 and 103.5 ​mW ​cm−2 with good durability, outstripping most of recently reported ZABs. This surface electron density modulation method may open up valuable insights for designing other robust carbon electrocatalysts for ZABs and beyond.