Reconstruction of Highly Dense Cu-N4 Active Sites in Electrocatalytic Oxygen Reduction Characterized by Operando Synchrotron Radiation

The emerging star of single atomic site (SAS) catalyst has been regarded as the most promising Pt-substituted electrocatalyst for oxygen reduction reaction (ORR) in anion-exchange membrane fuel cells (AEMFCs). However, the metal loading in SAS directly affects the whole device performance. Herein, we report a dual nitrogen source coordinated strategy to realize high dense Cu-N-4 SAS with a metal loading of 5.61 wt% supported on 3D N-doped carbon nanotubes/graphene structure wherein simultaneously performs superior ORR activity and stability in alkaline media. When applied in H-2/O-2 AEMFC, it could reach an open-circuit voltage of 0.90 V and a peak power density of 324 mW cm(-2). Operando synchrotron radiation analyses identify the reconstruction from initial Cu-N-4 to Cu-N-4/Cu-nanoclusters (NC) and the subsequent Cu-N-3/Cu-NC under working conditions, which gradually regulate the d-band center of central metal and balance the Gibbs free energy of *OOH and *O intermediates, benefiting to ORR activity.

Automated summary

This study presents a dual nitrogen source coordinated strategy to achieve high density Cu-N-4 SAS, which exhibits superior ORR activity and stability in alkaline media. The Cu-N-4 SAS supported on 3D N-doped carbon nanotubes/graphene structure shows promising performance in H-2/O-2 AEMFC.