Nanochemistry approach for the fabrication of Fe and N co-decorated biomass-derived activated carbon frameworks: a promising oxygen reduction reaction electrocatalyst in neutral media

The sluggish nature of the cathodic oxygen reduction reaction (ORR), and the expensive price of the precious metal-based nanocatalysts are the biggest obstacles to the practical applications of cutting-edge technologies including metal–air batteries and fuel cells. Hence, it is crucial to engineering a scalable-production pathway for the fabrication of a high-performance ORR catalyst. Herein, it was aimed to boost the performance of the ORR in neutral media, especially for microbial fuel cells, by tailoring a biomass-derived ORR electrocatalyst. In this regard, with the approach of nanochemistry, which is concerned with the fabrication of building blocks that vary in size, surface, shape, and defect characteristics, iron- and nitrogen-doped activated carbon framework (Fe,N-AC) was derived from waste orange peels by a two-stage pathway comprising microwave-assisted chemical activation and the thermal annealing processes. The physicochemical characterizations confirmed the successful co-doping of iron and nitrogen atoms to the activated carbon skeleton with the hierarchically ordered porous structure. Thanks to the interdependent effects of metal and heteroatoms in the structure, as well as the enlarged specific surface area (1098 m2.g−1), Fe,N-AC catalyst offered a superior ORR activity thru the 4-electron transferring way (n = 3.969) with long-term stability (81.4% retention of initial current over the period of 7200 s). The half-wave potential was determined as 0.871 V by the introduction of iron and nitrogen to the nanoarchitecture, implying the boosting impact of the iron and nitrogen decoration. Moreover, the exceptional electrocatalytic activity of Fe,N-AC was validated by an onset potential of 0.951 V that was ca.16 mV smaller than that of Pt/C catalyst (0.967 V). The accelerated S2− poisoning test of Fe,N-AC catalyst was outperformed to Pt/C catalyst, thereby foreboding its practical utilization in MFCs. The current loss of Pt/C catalyst was determined almost five times that of Fe,N-AC catalyst at 5 mM S2− concentration. The findings paved the course for the engineering of the state-of-the-art low-cost nanocatalyst by converting agricultural biomasses to a multi-functional advanced material to be employed in sustainable energy conversion systems.Graphical abstract