Pudding-typed cobalt sulfides/nitrogen and sulfur dual-doped hollow carbon spheres as a highly efficient and stable oxygen reduction electrocatalyst

• Published in: Journal of power sources Vol. 348; pp. 183 - 192
• Main Authors: Xiao, Junwu, Zhao, Chen, Hu, Chencheng, Xi, Jiangbo, Wang, Shuai
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30-04-2017
• Subjects: Amorphous phase; Electro-catalysis; Metal-organic frameworks; Nitrogen and sulfur dual-doped carbon; Pudding-typed structure; Pudding-typed structure; Electro-catalysis; Metal-organic frameworks; Amorphous phase; Nitrogen and sulfur dual-doped carbon
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2017.03.011

Metal organic frameworks (MOFs) are rarely reported to be grown at the templates due to the strong inherent driving force for crystallization. Herein, we report a pathway to successfully synthesize Zeolitic imidazolate framework-67 (ZIF-67) grown at the unmodified SiO2 spheres from amorphous precursors, and further construct Pudding-typed electrocatalysts, where cobalt sulfides (CoSx) nanocrystals are embedded into nitrogen and sulfur dual-doped hollow carbon spheres (N, S-HCS). CoSx/N, S-HCS show good catalytic activity toward the oxygen reduction reaction (ORR), and the optimized performance is achieved with (CoSx/N, S-HCS)700 with the positive half-wave potentials of 0.90 V vs RHE, high selectivity, good long-term stability, and excellent tolerance against methanol-crossover effect in alkaline medium, which are even superior to that of the as-reported MOFs-derived catalysts and commercial Pt/C catalysts. The remarkable catalytic performance is originated from high reactivity of catalytic active sites composed of cobalt sulfides and nitrogen and sulfur dual-doped carbon matrices, and Pudding-typed hollow structure with proper graphitization degree to facilitate fast electron and ion transport and limit the dissolution and agglomeration of active sites during long-term operation.
[Display omitted]
•ZIF-67 is formed at the SiO2 spheres via the transformation of amorphous precursors.•ZIF-67/SiO2 are pyrolyzed into Pudding-typed CoSx/N, S-HCS via a facile process.•The optimized catalyst shows better activity and stability than Pt/C catalyst.•Highly active Co/S/N/C sites play a key role in enhancing the catalytic activity.