Cobalt and Iron Oxides Co-supported on Carbon Nanotubes as an Efficient Bifunctional Catalyst for Enhanced Electrocatalytic Activity in Oxygen Reduction and Oxygen Evolution Reactions

摘要

Developing efficient non-precious metal electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in energy conversion and storage devices is highly desirable but challenging. This report describes a general approach for preparing cobalt and iron oxide nanoparticles cosupported on nitrogen-doped carbon materials as an efficient oxygen electrode catalyst with an improved catalytic activity toward OER and ORR; these nanoparticles were obtained through pyrolysis of Co- and Fe-based metal-organic frameworks grown directly on the surface of polyvinylimidazolefunctionalized carbon nanotubes (CNTs). The Fe/Co-CNTs-800 catalyst pyrolyzed at 800 ℃ exhibited high electrocatalytic activity for ORR, with only ~50 mV lesser activity than that of Pt/C at the half-wave potential, and for OER, with only ~70 mV lesser activity than that of RuO2 at a current density of 10 mA;;cm~(-2) in a 0.1 M KOH solution. The potential difference between OER and ORR for Fe/Co-CNTs-800 (ΔE_(OER-ORR)) was 0.905 V, which was significantly lower than that for noble-metal catalysts (20 wt% Pt/C (1.137 V) and RuO2 (1.341 V)). The preparation temperature and value of Fe/Co in the catalyst composite are crucial for achieving high electrocatalytic activity for both ORR and OER.