Role of Heteroatoms (N, P, O, and S) in Co3O4-Doped Carbons Derived from ZIF-67-Polyphosphazene Nanohybrids as Anode Materials for Supercapacitors

To enhance the capacity of supercapacitors, hybrid materials with diverse dopants need to be developed as they have a synergistic effect. This study was conducted to prepare the quaternary (N, P, O, and S) Co3O4-doped carbons by uniformly growing the heteroatom-holding poly(cyclotriphosphazene-co-4,4-sulfonyldiphenol) (PZS) polymer on the cobalt-containing zeolitic imidazolate framework (ZIF-67) with a polyhedral morphology. Different carbonization temperatures were used to control the contents of the elements. Co3O4-NPS-800 was found to have optimized contents of heteroatoms (N 6.13, P 2.91, O 21.37, and S 13.73 wt %), a surface area of 762 m2/g, exhibited a high specific capacity (815 F g(-1) at 1 A g(-1)) and good rate capability (617 F g-1 at 10 A g(-1)), as well as excellent long-term cyclic stability with 86% capacitance retention and 100% Coulombic efficiency over 10,000 cycles. This was attributed to the synergistic effect of heteroatoms along with Co3O4, which not only broke the inertness of the carbon structure but also increased the electron transfer tendency and produced a Lewis base surface that promoted maximum exposure to electroactive sites, resulting in a remarkable electrochemical performance.

Automated summary

This study successfully prepared quaternary doped Co3O4 carbon material with excellent electrochemical performance and long-term cyclic stability, attributed to the synergistic effect of heteroatoms and Co3O4, which made the carbon structure active and increased electron transfer tendency.