Multiscale porous Fe-N-C networks as highly efficient catalysts for the oxygen reduction reaction

Non-Pt catalysts with excellent performance regarding the oxygen reduction reaction (ORR) have aroused enormous interest in recent years. Herein, we propose a dual-template method to synthesize a multiscale porous Fe-N-C (FeNC) catalyst. SiO₂ and Zn are used as co-templates to produce a multiscale porous structure. Chitosan and glutaraldehyde are used as building blocks to fabricate the frameworks of the hydrogel. After lyophilization and annealing treatments, FeNC aerogel with a multiscale porous structure could be obtained. The as-prepared FeNC catalyst annealed at 900 °C (FeNC-900) exhibits a larger electrochemically active surface area and an improved ORR activity compared to FeNC annealed at other temperatures. FeNC-900 shows a superior ORR performance in comparison with that of commercial Pt/C in terms of the onset potential and half-wave potential, i.e., 0.959 and 0.837 V, which are 28 mV and 10 mV higher than those of Pt/C, respectively. Multiscale porosity is responsible for the outstanding ORR performance of FeNC-900. The electron transfer number of FeNC-900 for the ORR was calculated to be 3.95, which is comparable with that of Pt/C. In addition, the FeNC-900 catalyst possesses an excellent long-term duration and anti-poisoning capacity against methanol crossover. All these results endow the FeNC catalyst with tremendous potential for use in fuel cells.