Facile and Controllable One-Pot Synthesis of Hierarchical Co9S8 Hollow Microspheres as High-Performance Electroactive Materials for Energy Storage and Conversionl

Hierarchical Co9S8 hollow microspheres with nanosheet building units are synthesized via a one-step hydrothermal method. The presence of glucose in the synthesis is essential to the formation of the hollow structure and influences the size and morphology of the microspheres. Benefiting from the advantages of a hollow architecture, a conductive carbon coating and Co9S8 nanosheet units, the composite exhibits outstanding electrochemical properties. When the composite electrode is evaluated as the cathode material for supercapacitors, it exhibits a high specific capacitance of 514 Fg(-1) at 1.0 Ag-1 and a capacitance retention of circa 88% over 1000 cycles at 8 Ag-1. On the other hand, the nanosheet-constructed hollow structure can efficiently promote the electrocatalytic activity of Co9S8 toward the oxygen evolution reaction. Due to the fact that Co9S8 nanosheets impart largely exposed active sites, the composite exhibits a low Tafel slope of 66 mVdec(-1) and no obvious degradation after 12 h water oxidation.