Co9S8@CN Composites Obtained from Thiacalix[4]arene-Based Coordination Polymers for Supercapacitor Applications

Metal sulfides have been recognized as promising electrodes for electrochemical energy storage owing to their remarkable electrochemical properties. Here, we demonstrate the preparation of Co9S8 nanoparticles anchored on a carbon matrix (denoted as Co9S8-X@CN (X=1, 2)) from precursor sources, two 1D infinite coordination polymers 1 and 2. The two polymers were assembled by linking Co-4-TC4A secondary building blocks (SBUs) with ligands L-1 and L-2, respectively (H(4)TC4A=p-tert-butylthiacalix[4]arene, L-1=1,4-bis(2H-tetrazol-5-yl)benzene, L-2=1,3-bis(2H-tetrazol-5-yl)benzene). The composites obtained from 1D polymers showed different morphologies, that is, the Co9S8 nanoparticles of Co9S8-1@CN are octahedral with a size of ca. 140 nm, while the lamellar Co9S8 nanoparticles in Co9S8-2@CN possess different sizes (50-150 nm). The Co9S8-2@CN immobilized on nickel foam (Co9S8-2@CN/NF) show better supercapacitive performance than that of Co9S8-1@CN. Co9S8-2@CN showed exceptionally high activities, combining higher specific capacitances (445.2 F g(-1) at 2 A g(-1) and 393.9 F g(-1) and 5 A g(-1)), rate capacity (94.5% retention at 2 A g(-1)), and long-term stability (79.2% retention at 5 A g(-1) over 1000 cycles). The smaller size and larger BET surface area of Co9S8-2@CN nanoparticles can improve the electrical conductivity and provide facile pathways for charge transport, thus leading to conspicuous electrochemical performance of Co9S8-2@CN compared with its Co9S8-1@CN counterpart.

Automated summary

Metal sulfides are promising electrodes for electrochemical energy storage. In this study, Co9S8 nanoparticles anchored on a carbon matrix were prepared from precursor sources. The smaller size and larger BET surface area of Co9S8-2@CN nanoparticles improve electrical conductivity and charge transport pathways, leading to superior electrochemical performance compared to Co9S8-1@CN.