Boosting oxygen reduction electrocatalytic performance of Cu-Nx by modulating electron structure via construction of Cu-Nx and Cu nanocluster coupling catalyst

The utilization of atom-dispersed Cu-Nx site catalysts holds significant promise as a replacement for commercial Pt/C catalyst in the context of oxygen reduction catalysts. However, practical application of these catalysts has been hindered by their insufficient catalytic activity. It is imperative to enhance the oxygen reduction reaction (ORR) catalytic activity of the Cu-Nx catalysts by manipulating electronic structure of the Cu-Nx site. This study presents the synthesis of a composite catalyst, formed by coupling Cu nanoclusters and Cu-Nx catalysts through pyrolysis of protein-Cu2+ gel followed by acid-leaching treatment. The resultant composite catalyst demonstrates superior ORR activity as compared to isolated Cu-Nx catalysts under alkaline conditions. Through density functional theory (DFT) calculations, the synergistic mechanism of the coupled Cu nanoclusters and Cu-Nx for ORR catalytic activity is elucidated. The proximity of the Cu nanoclusters (Cu4) to the central Cu atom of Cu-Nx (CuN4) in the composite catalyst causes a shift in the d-band center of the active Cu site towards the Fermi level. This shift strengthens the binding energy of O2 adsorption, reduces ORR overpotential, and combines with favorable electron transfer from Cu nanoclusters to Cu-Nx sites, thereby enhancing ORR activity. These findings contribute novel insights into the enhancement of ORR catalysis performance through the manipulation of electron structures via nano-sized metal clusters.