Atomically Isolated Iron Atom Anchored on Carbon Nanotubes for Oxygen Reduction Reaction

Recently, electrocatalysts based on anchored dispersive/isolated single metal atoms on conductive carbon supports have demonstrated great promise to substitute costly Pt for the oxygen reduction reaction (ORR) in the field of fuel cells or metal-air batteries. However, developments of cost-efficient single-atom Fe catalysts with high activities are still facing various hardships. Here, we developed a facile way to synthesize isolated iron atoms anchored on the carbon nanotube (CNT) involving a one-pot pyrrole polymerization on a self-degraded organic template and a subsequent pyrolysis. The as-obtained electrocatalyst possessed unique characteristics of abundant nanopores in the wall of conductive CNTs to host the abundant atomic Fe-N_x active sites, showing ultrahigh ORR activity (half-wave potential: 0.93 V, kinetic current density: 59.8 mA/cm² at 0.8 V), better than that of commercial Pt/C (half-wave potential: 0.91 V; kinetic current density: 38.0 mA/cm² at 0.8 V) in an alkaline electrolyte. Furthermore, good ORR activity has been proven in acidic solution with a half-wave-potential of 0.73 V.