Preparation of Cobalt/Sulfur/Graphite Electrocatalyst for Oxygen Reduction from Efficient Two-Electron Pathway

Abstract

Graphite, the most stable carbon allotrope, is widely used for various applications due to its interesting properties. In the present work, graphite surface has been partially oxidized by concentrated hydrochloric acid (37%); then, the graphite oxide surface has been modified by a low-temperature method using sulfur and cobalt atoms to obtain a Co–S–GC catalyst. The current density passing through Co–S–GC catalyst has been higher than that passing through graphite. The novel cobalt-based catalyst has been demonstrated good performance for oxygen reduction reaction (ORR) due to the unique bio-inspired structure. The number of electrons transferred for ORR vary from 2.17 to 2.41 in a wide range of over-potentials indicating an effective 2-electron pathway form O₂ to H₂O₂. The Tafel slope (≈30 mV dec^–1) indicates significant amount of cobalt oxide on the surface of the catalyst. The catalyst durability test displays a negative shift of only 11.7 mV after 10 000 cycles for its half-wave potential (E_1/2).