Multicore-shell structure CuxCoy-Fe alloy nitrogen doped mesoporous hollow carbon nanotubes composites for oxygen reduction reaction

Abstract

Carbon-based materials with transition metal modifications are the dominant materials for oxygen reduction reaction (ORR), but the synthesis in a simple and efficient way is still a great challenge. Herein, multicore-shell structure CuxCoy-Fe alloy nitrogen doped mesoporous hollow carbon nanotubes (N-MHCNT/CuxCoy-Fe@C) were designed and synthesized by a facile and environment-friendly method. In the process of pyrolysis, polypyrrole serving as the substrate to form N-doped hollow carbon nanotubes and the polydopamine (PDA) acts as the carbon and nitrogen source to form a shell structure. Additionally, the cubic CuxCoy-Fe MOFs synthesized at room temperature collapses to form multiple alloy cores. Notably, the mesoporous structure of N-MHCNT/CuxCoy-Fe@C enhances the mass transfer process, while the carbon shell protects the metal active sites. Moreover, mesoporous hollow carbon, rich M-Nx (M=Cu, Co, Fe) active sites, the synergistic effects between N-MHCNTs, CuxCoy-Fe alloys and multiple core-shell structures allowed N-MHCNT/Cu2Co1-Fe@C exhibited high activity and long-term durability in ORR. Besides, the RRDE tests confirms the reaction kinetics of N-MHCNT/Cu2Co1-Fe@C as a mainly 4-electron reaction with an electron transfer number of 3.78 (Pt/C is 3.86) and a low hydrogen peroxide yield of 16%. This work provides a new strategy for the development of non-precious metal ORR catalysts by rational structural design and metal ratio adjustment.