Hierarchical hollow Co9S8 microspheres: solvothermal synthesis, magnetic, electrochemical, and electrocatalytic properties.

A simple solvothermal route in a binary solution of triethylenetetramine (TETA) and deionized water (DIW) has been used to synthesize hierarchical hollow Co(9)S(8) microspheres with high surface area (80.38 m(2) g(-1)). An appropriate volume ratio of TETA:DIW has been found to be essential for the formation of hollow Co(9)S(8) microspheres. The magnetic study indicated that the Co(9)S(8) hollow microspheres are paramagnetic at high temperature and antiferromagnetic at low temperature. The oxygen reduction reaction experiments demonstrated that the onset potential of the Co(9)S(8) sample is 0.88 V, which is comparable to the value predicted for Co(9)S(8) (0.74 V) from the theoretical simulation. The discharge capability of Co(9)S(8) hollow microspheres as cathode materials for lithium ion batteries and their electrocatalytic activity for the oxygen reduction reaction (ORR) have been studied.