In Situ Formation of Co9S8 Quantum Dots in MOF‐Derived Ternary Metal Layered Double Hydroxide Nanoarrays for High‐Performance Hybrid Supercapacitors

Layered double hydroxides (LDHs) are promising cathode materials for supercapacitors because of the enhanced flow efficiency of ions in the interlayers. However, the limited active sites and monotonous metal species further hinder the improvement of the capacity performance. Herein, cobalt sulfide quantum dots (Co9S8‐QDs) are effectively created and embedded within the interlayer of metal‐organic‐frameworks‐derived ternary metal LDH nanosheets based on in situ selective vulcanization of Co on carbon fibers. The hybrid CF@NiCoZn‐LDH/Co9S8‐QD retains the lamellar structure of the ternary metal LDH very well, inheriting low transfer impedance of interlayer ions. Significantly, the selectively generated Co9S8‐QDs expose more abundant active sites, effectively improving the electrochemical properties, such as capacitive performance, electronic conductivity, and cycling stability. Due to the synergistic relationship, the hybrid material delivers an ultrahigh electrochemical capacity of 350.6 mAh g−1 (2504 F g−1) at 1 A g−1. Furthermore, hybrid supercapacitors fabricated with CF@NiCoZn‐LDH/Co9S8‐QD and carbon nanosheets modified by single‐walled carbon nanotubes display an outstanding energy density of 56.4 Wh kg−1 at a power density of 875 W kg−1, with an excellent capacity retention of 95.3% after 8000 charge–discharge cycles. Therefore, constructing hybrid electrode materials by in situ‐created QDs in multimetallic LDHs is promising. Cobalt sulfide quantum dots (Co9S8‐QDs) are anchored in situ within NiCoZn‐LDHs (layered double hydroxides) based on an approach of selective vulcanization of Co, and the lamellar structure of the LDHs is retained very well. Due to inheriting the characteristics of LDHs and QDs, the hybrid CF@NiCoZn‐LDH/Co9S8‐QD delivers an outstanding electrochemical performance.