Multi-role graphitic carbon nitride-derived highly porous iron/nitrogen co-doped carbon nanosheets for highly...

Pyrolyzing precursors containing iron, nitrogen and carbon elements is a commonly used process for synthesizing FeNC catalysts for oxygen reduction reaction (ORR). Generally, aggregation of iron-based species is prone to occur because of a lack of chemical bonds between iron-based species and carbon matrix and synthesizing highly porous FeNC catalysts is difficult because carbon skeleton is prone to collapse during pyrolysis. Herein, highly porous FeNC catalysts with fine iron-based species are synthesized by selecting glucose as carbon source, FeCl₃ as iron source, and urea-derived g-C₃N₄ as nitrogen source, iron anchoring and stabilizing species, and pore-forming template. The multi-role g-C₃N₄-derived catalyst synthesized at 1100 °C (FeNC1100) has fine iron-based species, large specific surface area (737 m² g^-1), and extremely high pore volume (2.66 cm³ g^-1). Accordingly, FeNC1100 shows a larger half-wave potential (E_1/2 = 0.894 V), a higher stability (ΔE_1/2 = 6 mV) after 10,000 potential cycles in alkaline media, and a higher peak power density (P = 152 mW cm^-2) when employed as ORR catalyst of zinc-air battery, which are all superior to those of the commercial Pt/C catalyst (E_1/2 = 0.864 V, ΔE_1/2 = 30 mV, P = 134 mW cm^-2). The present work brings a new method for synthesizing highly porous FeNC catalysts decorated with fine active sites for ORR.