Cu-based catalysts with the co-existence of single atoms and nanoparticles for basic electrocatalytic oxygen reduction reaction.

Developing efficient and stable oxygen reduction reaction (ORR) catalysts to replace the precious Pt/C is very important for the industrial application of proton-exchange membrane fuel cells. Herein, using bismuth-based metal-organic frameworks as the substrate to disperse copper ions, we prepared a catalyst containing both Cu single atoms and Cu nanoparticles (Cu SA Cu NP /BiCN) by a pyrolysis method. In 0.1 M KOH electrolyte, the electrocatalytic ORR performance of Cu SA Cu NP /BiCN was superior to that of commercial Pt/C. With a hierarchical porous architecture, Cu SA Cu NP /BiCN displayed a half-wave potential of 0.86 V vs. RHE and a diffusion-limiting current density of 5.82 mA cm -2 with a four-electron transfer process. In addition, it was stable during a 12-hour durability test. This study provides guidance for the synthesis of advanced Cu-based nano-single-atom catalytic materials for ORR applications.