The precursors were treated at 450 °C (1 °C min−1) for 2 h in an Ar atmosphere, and the final product was collected and named Co-V2O3-24. Co-V2O3-12 can be synthesized in thesame way except that the solvothermal time was changed to 12 h. For comparison, pure V2O3 was prepared under the same reaction conditions except the absence of CoIJNO3)2·6H2O and the solvothermal time of 12 h.