Synthesis of porous nitrogen and sulfur co-doped carbon beehive in a high-melting-point molten salt medium for improved catalytic activity toward oxygen reduction reaction

摘要

The development of unique, reliable and scalable synthesis strategies for producing dual-heteroatom-doped nanostructured carbon materials with improved activity toward electrochemical oxygen reduction reaction (ORR) presents an intriguing technological challenge in the field of catalysis. Herein, we report a method to synthesize a three-dimensional (3D) N and S Co-doped carbon beehive (NS-CB) with open structure by direct pyrolysis of egg white in a high-melting-point molten salt medium, e.g. NaCl/KCl, under inert atmosphere. Physicochemical characterization shows that NS-CB possess hierarchical pores (including micro- and mesopore) with a high specific surface area of 1478 m(2) g(-1), which is obviously larger than as-prepared carbons synthesized in only NaCl (CNaCl) or KCl (CKCl) as molten salt medium. Importantly, 50% of the pore volume is contributed by micropores with average pore size of 1.4 nm, which is the ideal pore size for ORR. The remaining 50% of the pore volume is made of mesopores and open macropores, assembled in the form of interconnected carbon sheets. Due to its hierarchical structure and high specific surface area, NS-CB shows high ORR activity comparable to commercial Pt/C catalyst in KOH electrolyte in terms of the half wave potential and the onset potential of ORR. NS-CB also exhibits markedly high stability as an ORR catalyst. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.