Cu-N4 single atoms derived from metal-organic frameworks with trapped nitrogen-rich molecules and their use as efficient electrocatalysts for oxygen reduction reaction

The development of noble-metal-free single atom electrocatalysts (SAECs) with both remarkable activity and durability for oxygen reduction reaction (ORR) are in great demand for large-scale commercialization of proton-exchange membrane fuel cells and metal-air batteries. Here, we developed a novel strategy to fabricate high-performance Cu-SAs/NSs from pyrolysis of two-dimensional (2D) Cu/Zn bimetallic MOF. Specifically, nitrogen-rich molecules (melamine) were deliberately added to intrigue the self-assembly of Cu/Zn bimetallic MOF, and contribute to the formation of highly porous structure and abundant Cu-N-4 active sites. With the enhanced accessibility of active sites and mass transport, the as-developed Cu-SAs/NSs display a remarkable ORR performance in alkaline media, outperforming the benchmark Pt/C and most of platinum group metals (PGMs)-free electrocatalysts reported to date. Notably, this facile strategy can be extended to fabricate other transition metal (TM, TM = Fe, Co, Ni)-based single atoms. This work presents a novel and general strategy to construct carbon-based SAECs towards ORR.