Construction of Cu Single-Atom Catalysts by Taking Spatial-Confinement and Chemical-Anchoring Effect of Hyperbranched Phthalocyanine Copper for Efficient Oxygen Reduction Reaction

Atomically dispersed nonprecious metal-based catalysts have been considered as the most promising alternatives to Pt-based catalysts since their excellent catalytic activities and almost 100 % atom utilization in oxygen reduction reaction. However, the agglomeration of metal atoms is unavoidable during pyrolysis process, thus leads to the decrease of electrocatalytic performance. Herein, hyperbranched phthalocyanine copper (HCuPc) wrapping nano-silica is synthesized via in situ polymerization and served as precursor for preparing atomically dispersed Cu-N-C electrocatalysts. Owing to the confinement effect of chemical-anchoring and spatial-hindrance, the migration and agglomeration of Cu atoms are restricted in carbonization process. The aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray photoelectron spectroscopy (XPS) are performed to confirm the atomically dispersed of as-synthesized catalyst, which is labelled as HCu-N-C/SiO2. In addition, the HCu-N-C/SiO2 possess superior ORR electrocatalytic activities with a half-wave potential of 0.874 V vs RHE and a limiting current density of 5.7 mA cm-2. The zinc-air batteries assembled with HCu-N-C/SiO2 catalyst exhibit a high specific capacity of 789 mAh g-1 as well as a maximum discharge power density of 176 mW cm-2. This work proves that hyperbranched phthalocyanine structure could be a useful confined framework to the fabrication of singles-atom catalysts. Hyperbranched phthalocyanine copper (HCuPc) wrapping nano-silica is synthesized via in situ polymerization and served as precursor for preparing atomically dispersed Cu-N-C electrocatalysts. Highly dispersed copper single-atom catalyst Cu-N-C has good electrocatalytic performance by using chemical anchoring of phthalocyanine and steric hindrance to restrict the migration and aggregation of Cu atoms. image