A Unique Nanocomposite with Feco Nanoalloy Anchored on S, N Co-Doped Carbonaceous Matrix for High Bifunctional Oxygen Reduction Reaction/Oxygen Evolution Reaction Electrocatalytic Property in Zn-Air Battery

Abstract

A unique nanocomposite of FeCo-NSCC (means FeCo nanoalloy anchored on N, S co-doped carbonaceous composite) is obtained by one-pot pyrolysis using mixed natural wool fibers, dicyandiamide and the corresponding metal salts. The FeCo-NSCC has a higher degree of graphitization and a high specific surface area of 359 m2 g-1. The FeCo-NSCC exhibits a promising bifunctional oxygen reduction reaction/oxygen evolution reaction (OER/ORR) electrocatalytic activity with onset potential and half-wave potentials of 0.980 and 0.853 V vs reversible hydrogen electrode (RHE) for ORR, and a low overpotential of 351 mV at 10 mA cm-2 for OER, superior to that of state-of-the-art commercial Pt/C and RuO2. The FeCo-NSCC presents a vigorous bifunctional OER/ORR electrocatalytic activities with the low (E1/2 - Ej=10) of 0.727 V, superior to most of the reported non-noble metal-based catalysts. Besides, the FeCo-NSCC shows remarkable durability and methanol resistance. The FeCo-NSCC based battery works at an open circuit voltage of 1.52 V and has a maximum power density of 161 mW cm-2 at current density of 246 mA cm-2, better than those of Pt/C-RuO2 based battery (1.47 V; 106 mW cm-2, 145 mA cm-2). The FeCo-NSCC based battery is stable with no obvious increased voltage gap after 60 h cycles.

Keywords: one-pot synthesis, biomass, N, S-dual dopants, FeCo alloy, bifunctional electrocatalyst