Fe/Fe3C Nanoparticles Embedded in Nitrogen-Doped Carbon Nanotubes as Multifunctional Electrocatalysts for Oxygen Catalysis and CO2 Reduction

Graphical All-round activity : Hybrids of Fe/Fe 3 C embedded in N-doped carbon nanotubes (Fe/Fe 3 C@NCNTs) are prepared by pyrolyzing mixtures of Fe 3 O 4 nanoparticles and dicyandiamide. Fe/Fe 3 C@NCNTs show a highly multifunctional catalytic activity for the oxygen evolution, oxygen reduction, and CO 2 reduction reactions. Hybrids of Fe/Fe 3 C embedded in N-doped carbon nanotubes (Fe/Fe 3 C@NCNTs) are prepared by pyrolyzing mixtures of Fe 3 O 4 nanoparticles and dicyandiamide. The systematic electrochemical study of Fe/Fe 3 C@NCNTs shows a decent catalytic activity toward the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The sample of Fe/Fe 3 C@NCNTs at 750 °C exhibits a remarkably high activity with an onset potential of 1.47 V for the OER, and an onset potential of 0.96 V and half-wave potential 0.88 V for the ORR, which inspired us to set up a rechargeable Zn-air battery with such Fe/Fe 3 C@NCNT nanohybrids as the cathode materials, showing a maximum power density of 198 mW cm −2 and long-term stability after 500 cycles. We also demonstrate that Fe/Fe 3 C@NCNTs present favorable electrocatalytic activity towards the CO 2 reduction reaction (CO 2 RR) with a low onset potential and good selectivity. The major products are a mixture of H 2 and CO gases that can be used for methanol production in the Fischer−Tropsch process.