A Low-Cost and Facile Method for the Preparation of Fe-N/C-Based Hybrids with Superior Catalytic Performance toward Oxygen Reduction Reaction

摘要

Fe-N-doped graphitic carbon materials exhibit high efficiency and durability for oxygen reduction reaction (ORR). Although iron has relatively low price, the precursors for carbon and nitrogen used in previous studies have relatively high cost. Here reported is the preparation of highly efficient Fe-N/C-based ORR electrocatalysts by use of low-cost urea as the precursors. Fe-N/C-based hybrids are prepared through a two-step pyrolysis. During the first-step pyrolysis, the precursors convert into g-C3N4 with Fe located into the sixfold cavities, which ensures the relatively uniform distribution of Fe. The second-step pyrolysis converts Fe-g-C3N4 into Fe-N/C-based hybrids which contain multiple types of active components, Fe moieties (FeCxNy or FeNx), Fe and Fe3N nanoparticles, for ORR. The obtained Fe-N/C-based hybrids display a superior electrocatalytic performance for ORR with an onset potential of 0.940 V and half-wave potential of 0.810 V versus reversible hydrogen electrode, which are comparable to those of Pt/C at the same catalyst loading. The hybrids show higher tolerance to methanol and much greater long-term stability than commercial Pt/C. The findings provide a cost-effective approach for the preparation of high efficient and stable electrocatalysts for ORR and will be very helpful to the development of electrochemical energy storage and conversion.