Nitrogen and Oxygen Functionalization of Multi-Walled Carbon Nanotubes for Tuning the Bifunctional Oxygen Reduction/Oxygen Evolution Performance of Supported FeCo Oxide Nanoparticles

Abstract

The combination of nanostructured transition metal oxides and carbon materials is a promising approach to obtain inexpensive, highly efficient, and stable bifunctional electrocatalysts for the oxygen reduction (ORR) and the oxygen evolution (OER) reactions. We present a strategy for improving the bifunctional ORR/OER activity of supported FeCoOx nanoparticles by tuning the properties of multi-walled carbon nanotubes (MWCNT) via nitrogen doping during their synthesis in the presence of ammonia and subsequent oxidative functionalization. In-depth structural characterization indicates that oxidative treatment provides fine control of the dispersion and localization of FeCoOx nanoparticles in MWCNT, while the optimal degree of nitrogen doping leads to increased bifunctional activity due to enhanced electrical conductivity as well as improved catalyst stability, in both OER and ORR conditions, for nanoparticles formed by two different synthesis routes. The findings reported can be strategically considered for the design of high-performance reversible ORR/OER electrocatalysts.