Synchronized integration of iron/cobalt dual-metal in nitrogen-doped carbon hollow spheres for enriched supercapacitive and oxygen reduction reaction performances

Abstract

The development of nonprecious metals in conjunction with heteroatoms doped carbon material as an effective electrocatalyst is critical for enhanced energy storage and conversion (ESC) properties. Nonprecious metals co-doping in a nitrogen-doped carbon matrix are considered potential candidates for this purpose, but their stability and activity remain insufficient to meet the demands of practical applications. In this work, the iron‑cobalt particles integrated nitrogen-doped carbon hollow spheres (FeCoNCHSs) as an efficient electrocatalyst for electrochemical supercapacitors and oxygen reduction reaction (ORR) towards alkaline fuel cells are reported. FeCoNCHSs were prepared by Fe+3/Co+2-mediated in-situ polymerization of dopamine on modified polystyrene and later pyrolysis under N2 atmosphere at 700 °C for 3 h. The as-synthesized materials were characterized and analyzed by various electrochemical and electroanalytical techniques. Importantly, the FeCoNCHSs show remarkable supercapacitive properties with the maximum capacitance value of 287.3 F g−1 at a scan rate of 2 m Vs−1. Moreover, the FeCoNCHSs exhibited an inspiring positive half-wave potential of ~0.83 V during ORR. Density functional theory (DFT) calculations further explain that the N-coordinated metal (Fe/Co) species are the main active sites to effectively improve the charge transfer and electrochemical activities. The efficient response of the electrode material can be attributed to their meso−/macroporous intact hollow spherical morphology, large porous surface area, and high N(pyridinic/pyrrolic/graphitic)-contents. Significantly, the synergistic effects of N-doping along with N-coordinated dual-metal (Fe/Co) species are also responsible for the superior supercapacitive and ORR performances.