Copper Isolated Sites on N-Doped Carbon Nanoframes for Efficient Oxygen Reduction

In recent years, metal isolated site catalysts with the high exposure and maximized availability of metal species provide a new route to boost the oxygen reduction performance. However, in the absence of clusters and nanoparticles, the synthesis of this catalyst with metal high-loading, especially for copper, is still a big challenge. In this work, a metal isolated site catalyst with high copper content (1.12 wt %), copper isolated sites anchored on N-doped carbon materials (donated as Cu ISs/NC-1000), was prepared by the pyrolysis of copper acetylacetone within the metal–organic framework (ZIF-8) at 1000 °C. The successful preparation of products can be demonstrated by high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption spectra. With the merits of the atomically dispersed surface metal atoms and abundant ORR-favored copper active sites, the present Cu ISs/NC-1000 exhibits an excellent ORR electrochemical activity with a half-wave potential of 0.855 V (vs RHE) and a limiting current density of 5.2 mA cm–2 in the electrochemical tests, superior to the results from commercial Pt/C and previously reported Cu-based materials. For the durability, the negligible activity decay after 10,000 continuous potential cycles and good resistance to methanol crossover can be noted. The outstanding catalytic activity from the present Cu ISs/NC-1000 demonstrates the superiority of metal isolated sites as electrocatalytic centers.