Single Zn atoms anchored in mesoporous N-doped carbon rods derived from metal–organic frameworks for enhanced electrocatalytic oxygen reduction reaction

Abstract

Nitrogen–carbon (N–C) materials have been recently explored to activate Fenton-reaction-inactive Zn single atoms as active sites for electrocatalytic oxygen reduction reaction (ORR). However, achieving Zn–N–C electrocatalysts with high activity and stability remains challenging. In this study, we introduce a micelle@polydopamine (PDA) layer on the surface of rod-shaped zeolitic imidazolate frameworks (ZIFs). The micelle@PDA layer could not only form a mesoporous carbon layer on the porous carbon rods after pyrolysis in Ar but also captures Zn atoms during their evaporation from the ZIF at high temperatures. As a result, the Zn single-atom catalysts anchored on hollow, multi-hierarchical porous carbon rods (Zn-MCRs) have a high content of N and Zn–N_x active sites on the mesoporous layer. Density functional theory (DFT) calculations reveal that the atomically dispersed Zn–N_x sites are the primary and most active components in N–C materials. Due to the unique one-dimensional hollow, multi-hierarchical porous structure that provides accessible Zn–N_x active sites, the catalyst exhibits an impressive half-wave potential of 873 mV in a 0.1 M KOH solution, matching the ORR activity of Pt/C with exceptional efficiency.