Fe–Nx moiety-modified hierarchically porous carbons derived from porphyra for highly effective oxygen reduction reaction

Abstract

The development of high-efficiency and low-cost electrocatalysts for the oxygen reduction reaction (ORR) is critical to allow large-scale application of fuel cell technologies. As promising candidates for the replacement of platinum-based electrocatalysts for the ORR, iron–nitrogen doped carbon (Fe–N–C) materials are appealing due to their outstanding ORR performances. To meet the requirements for commercial applications in fuel cells, the electrocatalytic activity and durability of the Fe–N–C electrocatalysts need to be further improved over a wide pH range. Herein, we report a facile and rational synthesis strategy for the preparation of a kind of Fe–N–C catalyst by low-temperature thermal treatment of iron phthalocyanine (FePc)-adsorbed nitrogen-doped hierarchically porous carbon (NHPC) derived from porphyra. The as-prepared electrocatalysts exhibit a superior ORR performance, even better than that of state-of-the-art Pt/C catalysts, in alkaline electrolyte (E_1/2 = 0.88 V, n = 4.0, Tafel slope = 55 mV dec⁻¹ and ca. 6 mV negative shift of E_1/2, after 3000 cycles). This work develops a low-cost, but rational and efficient, methodology for the synthesis of high-performance Fe–N–C electrocatalysts for the ORR, and also provides an effective way to design and utilize hierarchically porous carbon for other electrocatalysts.