Stabilizing High Density Cu Active Sites with ZrO₂ Quantum Dots as Chemical Ligand in N‐doped Porous Carbon Nanofibers for Efficient ORR

Abstract The emerging transition metal‐nitrogen‐carbon (MNC) materials are considered as a promising oxygen reduction reaction (ORR) catalyst system to substitute expensive Pt/C catalysts due to their high surface area and potential high catalytic activity. However, MNC catalysts are easy to be attacked by the ORR byproducts that easily lead to the deactivation of metal active sites. Moreover, a high metal loading affects the mass transfer and stability, but a low loading delivers inferior catalytic activity. Here, a new strategy of designing ZrO₂ quantum dots and N‐complex as dual chemical ligands in N‐doped bubble‐like porous carbon nanofibers (N‐BPCNFs) to stabilize copper (Cu) by forming CuZrO_3‐x/ZrO₂ heterostructures and CuN ligands with a high loading of 40.5 wt.% is reported. While the highly porous architecture design of N‐BPCNFs builds a large solidelectrolytegas phase interface and promotes mass transfer. The preliminary results show that the half‐wave potential of the catalyst reaches 0.856 V, and only decreases 0.026 V after 10 000 cycles, exhibiting excellent stability. The proposed strategy of stabilizing metal active sites with both heterostructures and CuN ligands is feasible and scalable for developing high metal loading ORR catalyst.