Molecule-confined modification of graphitic C_3N_4 to design mesopore-dominated Fe-N-C hybrid electrocatalyst for oxygen reduction reaction

摘要

To design inexpensive carbon catalysts and enhance their oxygen reduction reaction (ORR) activity is critical for developing efficient energy-conversion systems. In this work, a novel Fe-N-C hybrid electrocatalyst with carbon nanolayers-encapsulated Fe3O4 nanoparticles is synthesized successfully by utilizing the molecular-level confinement of graphitic C3N4 structures via hemin biomaterial. Benefiting from the Fe-N structure prevalent on the carbon nanosheets and large mesopore-dominated specific surface area, the synthesized catalyst under optimized conditions shows excellent electrocatalytic performance for ORR with an E-ORR at 1.08 V versus reversible hydrogen electrode (RHE) and an E-1/2 at 0.87 V vs. RHE, and outstanding long-term stability, which is superior to commercial Pt/C catalysts (E-ORR at 1.04 V versus RHE and E-1/2 at 0.84 V versus RHE). Moreover, the low hydrogen peroxide yield (11%) and average electron transfer number (similar to 3.8) indicate a four-electron ORR pathway. Besides, the maximum power density of the home-made Zn-air battery using the obtained catalyst is 97.6 mW cm(-2). This work provides a practical route for the synthesis of cheap and efficient ORR electrocatalysts in metal-air battery systems. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.