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 Co9 S8 nanoparticles anchored on a carbon matrix (denoted as Co9 S8 -X@CN (X=1, 2)) from precursor sources, two 1D infinite coordination polymers 1 and 2. The two polymers were assembled by linking Co4 -TC4A secondary building blocks (SBUs) with ligands L1 and L2 , respectively (H4 TC4A=p-tert-butylthiacalix[4]arene, L1 =1,4-bis(2H-tetrazol-5-yl)benzene, L2 =1,3-bis(2H-tetrazol-5-yl)benzene). The composites obtained from 1D polymers showed different morphologies, that is, the Co9 S8 nanoparticles of Co9 S8 -1@CN are octahedral with a size of ca. 140 nm, while the lamellar Co9 S8 nanoparticles in Co9 S8 -2@CN possess different sizes (50-150 nm). The Co9 S8 -2@CN immobilized on nickel foam (Co9 S8 -2@CN/NF) show better supercapacitive performance than that of Co9 S8 -1@CN. Co9 S8 -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 Co9 S8 -2@CN nanoparticles can improve the electrical conductivity and provide facile pathways for charge transport, thus leading to conspicuous electrochemical performance of Co9 S8 -2@CN compared with its Co9 S8 -1@CN counterpart.