Plant polyphenols induced the synthesis of rich oxygen vacancies CoO/Co@N-doped carbon hollow nanomaterials for electrochemical energy storage and conversion.

Reasonable hollow structure design and oxygen vacancy defects control play an important role in the optimization of electrochemical energy storage and electrocatalytic properties. Herein, a plant polyphenol tannic acid was used to etch Co-based zeolitic imidazolate framework (ZIF-67) followed by calcination to prepare a porous CoO@Co/NC hollow nanoparticles (CoO@Co/NC-HN) with rich oxygen vacancy defects. Owing to the metal-phenolic networks (MPNs), rich oxygen vacancy defects and the synergistic effect between CoO and Co/NC, the box-like CoO@Co/NC-HN nanomaterials with large specific surface areas exhibit excellent supercapacitor performance and electrocatalytic activity. As expected, CoO@Co/NC-HN shows high specific capacity (273.9 mAh g at 1 A g) and remarkable rate performance. Moreover, the assembled Hybrid supercapacitor (HSC, CoO@Co/NC-HN//Active carbon) device obtained a maximum energy density of 57.8 Wh kg (800 W kg) and exhibited superior cycle stability of 92.6% after 4000 cycles. Notably, as an electrocatalyst, the nanocomposites exhibit small overpotential and Tafel slope. These results strongly demonstrate that both unique hollow structure and abundant oxygen vacancies designed from plant polyphenols provide superiorities for the synthesis of efficient and green multifunctional electrode materials for energy storage and conversion.