Anthocephalus cadamba shaped FeNi encapsulated carbon nanostructures for metal–air batteries as a resilient bifunctional oxygen electrocatalyst

Abstract

Anthocephalus cadamba shaped carbon nanostructures comprising FeNi encapsulated in radially grown nitrogen-doped carbon nanotubes (NCNTs) are produced by controlled pyrolysis which exhibit advanced electrochemical oxygen evolution reaction (OER) performance with a low overpotential of ∼290 mV at 10 mA cm⁻², small Tafel slope (37 mV dec⁻¹) and endurance in an accelerated stability test. In addition to better surface electron transfer kinetics, the radial growth of NCNTs offers plenty of electrochemically active sites (high roughness factor ∼340) in tiny spaces, better accessibility to reactant species and appropriate gas outlets to prevent bubble accumulation during OER. Besides OER, the preferential 4e⁻ pathways for the oxygen reduction reaction (ORR) and excellent overall oxygen electrochemistry ΔE (E_j(OER)=10 − E_1/2(ORR) = 0.71 V) suggest excellent bifunctionality and advocate the practical importance of Anthocephalus cadamba shaped carbon nanostructures as a possible unitary oxygen electrocatalyst for metal–air battery systems.