4.2. Synthesis of Co(OH)F/CC and metal doped Co(OH)F/CC precursor
Co(OH)F and metal doped Co(OH)F nanowire precursor were prepared on CC by hydrothermal method. First, the CC (2 × 3 cm2) was immersed in nitric acid (HNO3) for 24 hours, aiming to improve hydrophilicity and optimize the hydrothermal growth process. Subsequently, the CC was washed with ethanol and deionized water for 5 min, which was used to grow the precursor. Second, Co(NO3)2·6H2O (1 mmol), NH4F (4 mmol) and CO(NH2)2 (5 mmol) were mixed by 20 mL of DI water and stirred for 20 min. Furthermore, the CC and precursor solution were sealed into a 25 ml Teflon-lined stainless-steel autoclave, which was used to obtain Co(OH)F/CC nanowire precursors. The preparation process of metal doped Co(OH)F was similar to that of Co(OH)F, transition metal nitrates (0.1 mmol Ni(NO3)2·6H2O, Fe(NO3)3·9H2O and Cr(NO3)3·9H2O) were added to the precursor solution mentioned above, which also results in the formation of metal doped Co(OH)F nanowires (Metal = Ni, Fe, Cr). The Teflon-lined stainless-steel autoclave containing precursor solution was placed in a hydrothermal environment, which was controlled at 120 ℃ for 6 hours.