High-performance FeOx@CoOx/NC electrocatalysts for the oxygen reduction reaction in alkaline media

Abstract

Herein, cobalt oxide encapsulated nitrogen-doped tubular carbon (CoO_x/NC) is derived via one-step carbonization of ZIF-12. Iron oxide nanoparticles are then generated over the CoO_x/NC support by decomposition of the iron phenanthroline complex to obtain FeO_x@CoO_x/NCs. The synthesized electrocatalysts are tested for the oxygen reduction reaction (ORR). The optimized electrocatalyst FeO_x@CoO_x/NC2 exhibits superior activity to 20 wt% Pt/C in 0.1 M KOH with the E_1/2 = 0.89 V_RHE, E_onset=1.03 V_RHE and j = 6.32 mA cm⁻² values. The enhanced activity is attributed to the cumulative effect of FeO_x, CoO_x and presence of four types of nitrogen atoms. For comparison, FeO_x@MWCNTs demonstrates lower activity than the synthesized catalysts (E_1/2 = 0.76 V_RHE and E_onset = 0.94 V_RHE) which proves the synergistic role of CoO_x towards the ORR. The oxygen reduction reaction ability of the synthesized catalyst (FeO_x@CoO_x/NC2) is also investigated in the presence of 0.5 M methanol. The catalyst exhibits enhanced tolerance to methanol addition. The accelerated durability test (ADT) performed in 0.1 M KOH over 10 000 cycles shows a decay of only 17 mV.