Metal-coordinated porous polydopamine nanospheres derived Fe₃N-FeCo encapsulated N-doped carbon as a highly efficient electrocatalyst for oxygen reduction reaction

The exploration of high-efficiency, long-durability, and cost-effectiveness transition metal doped carbon materials to replace the commercial Pt/C in oxygen reduction reaction (ORR) is greatly desirable for promoting the advancement of sustainable energy devices. Herein, the Fe₃N and FeCo alloy decorated N-doped carbon hybrid material (denoted Fe₃N-FeCo@NC) is prepared and applied as the ORR catalyst, which is derived from the two-step pyrolysis of an intriguing complex consisted of metal-coordinated porous polydopamine (PDA) nanospheres (i.e., Fe-PDA@Co) and melamine. The resulting Fe₃N-FeCo@NC delivers outstanding ORR activity with an onset potential (E_on) of 1.05 V, a half-wave potential (E_1/2) of 0.89 V, as well as excellent long-term stability and methanol resistance over Pt/C. Interestingly, the home-made Zn-air battery with Fe₃N-FeCo@NC as the air-cathode demonstrates much higher open-circuit voltage (1.50 vs. 1.48 V), power density (141 vs. 113 mW·cm⁻²) and specific capacity (806.6 vs. 660.6 mAh·g_Zn⁻¹) than those of Pt/C counterpart. Such a remarkable ORR activity of Fe₃N-FeCo@NC may stem from the synergistic effect of Fe₃N and FeCo active species, the large surface area, the hierarchical porous structure and the exceptional sphere/sheet hybridized architecture.