Thiacalix[4]arene-supported tetradecanuclear cobalt nanocage cluster as precursor to synthesize CoO/Co₉S₈@CN composite for supercapacitor application

A new tetradecanuclear cobalt cluster [Co₁₄(TC4A)₃Cl₃(Tz)₁₂(H₂O)₆](OH)(DMF)₁₄(CH₃OH)₆(H₂O)₄ (Abbr. Co₁₄, H₄TC4A = p-tert-Butylthiacalix[4]arene, HTz = 1H-tetrazole) was obtained by the solvothermal reaction of CoCl₂·6H₂O, H₄TC4A and Htz in DMF. The cluster featured the quadrilateral planar CoII4 units housing tri-capped trigonal Co₁₂ clusters with two enclosed Co nanocages linked by Tz ligands. The uniform CoO/Co₉S₈@CN composite derived from direct annealing of Co₁₄ clusters was obtained and characterized by XRD, EDS, XPS, and Raman spectra. The composite on nickel foam (CoO/Co₉S₈@CN/NF) was used as an electrode to fabricate supercapacitors with specific capacitances of 83.7% at 2 A g^-1 and 70.0% at 5 A g^-1 at 0.5 A g^-1 (303.3 F g^-1). The composite from Co₁₄ precursor also shows high charge-discharge reversibility with a capacity retention of 96.3% and average columbic efficiency of 98.2% after 1000 cycles at 2.0 A g^-1.