้2.1. Synthesis of porous Co3O4 nanowire arrays
Commercial nickel foils were cleaned by sonication sequentially
in acetone, and ethanol for 15 min, respectively, and then used as
the substrates. In a typical synthesis of Co3O4 nanowire arrays,
3 mmol of Co(NO3)26H2O, 2 mmol of NH4F, and 6 mmol CO(NH2)2
were dissolved in 80 mL H2O. The above solution was then
transferred into a Teflon-lined stainless autoclave and maintained
at 120 C for 9 h. After the autoclave cooled down to room
temperature, the product was collected and washed, and then
annealed at 350 C in air for 3 h.