Co‑, Fe‑, and N‑Modified Carbon Composites for Excellent Catalytic Performances toward Electrochemical Reduction Reaction

The development of highly active noble-metal-free nitrogen-doped carbon materials is of great significance to the industrial applications of renewable and sustainable energy. In this paper, core-shell structural carbon materials composed of nitrogen-doped carbon-shell-encapsulated iron–cobalt mixed metal carbides were obtained through pyrolysis of metal organic framework precursors. Metallic (Co, Fe) carbide nanoclusters embedded in nitrogen-doped hollow carbon spheres were obtained after most of the mixed metal cores were removed by heated acid etching. The composites of carbon materials exhibited significant electrocatalytic activities toward the hydrogen evolution and oxygen reduction reactions. Hollow carbon spheres were obtained under optimized conditions for the hydrogen evolution reaction with overpotentials of 180 mV at a current density of 10 mA·cm^–2 and Tafel slope of 90 mV·dec^–1 in acidic media. The hollow carbon spheres also exhibited favorable activities toward oxygen reduction with a rather high half-wave potential of 0.82 V (vs RHE), high methanol tolerance, and robust stability. These excellent performances demonstrated their potential for applications in fuel cells, some metal-air batteries, and water splitting devices.