Coupling hollow Fe₃O₄ nanoparticles with oxygen vacancy on mesoporous carbon as a high-efficiency ORR electrocatalyst...

Designing a low-cost, high-efficiency and robust doped-carbon-based oxygen reduction reaction electrocatalyst for large-scale implementations of fuel cells is highly desirable but challenging. In this work, we report a new type of hollow Fe₃O₄ with oxygen vacancy incorporating on mesoporous carbon prepared by pyrolyzing mesoporous carbon enriched with oxygen-containing functional groups, in combination with ferric acetylacetonate. The catalysts possess high specific surface area with predominantly mesoporous architecture and ultrahigh nitrogen content (up to 7.47 wt%). Benefiting from the integration of abundant active nitrogen and Fe-N_x species, and synergistic effect between Fe₃O₄ nanoparticles cooperated with oxygen vacancy and N-doped carbon, the half-wave potential of the preparing hybrid catalyst is 30 mV more positive than that of the commercial Pt/C catalyst in alkaline medium, and exhibits a high selectivity (4 e^- process), and outstanding long-term stability. More importantly, the C-FePPDA-900 catalyst displays a high power density (106 mW cm^-2) and specific capacity of 724 mAh g_zn^-1 when it is used as an air cathode catalyst in a specifically assembling Zn-air cell, superior to those of most reported catalysts.