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.