3.2. Synthesis of HC/NiCo Materials

The prepared HC materials (10 mg), along with the precursors of Ni [Ni(NO₃)₂·6H₂O] (12 mM) and Co [Co(NO₃)₂·4H₂O] (6 mM) in a 2:1 ratio were dispersed in a mixture of solvents containing H₂O, DMF and ethanol (equal volumetric ratios) for 1 h to attain complete dispersion of the materials. The resulting mixture was then subjected to a solvothermal reaction at 120 °C for 24 h, maintaining the volume of the solvents as one-third the volume of the autoclave, and then washed several times with DMF and ethanol, before finally being filtered and dried completely to form the HC/NiCo material. The prepared HC/NiCo material was then calcined at four different temperatures (i.e., 600, 700, 800 and 900 °C) in a tubular furnace under N₂ atmosphere to produce HC/NiCo@600, HC/NiCo@700, HC/NiCo@800 and HC/NiCo@900, respectively (Scheme 1).

Schematic diagram of the preparation of HC/NiCo at different temperatures.