The invention discloses a method for synthesizing a
cobalt oxide /
graphene composite wave-absorbing material and relates to nanometer wave-absorbing materials. The method comprises the following steps: (1) dissolving a
metal cobalt salt,
ammonium fluoride and
urea in water, thereby obtaining a
metal saline solution; (2) adding the
metal saline solution prepared in the step (1) into a hydrothermal kettle, and magnetically stirring to be uniform; (3) dispersing
graphene solid powder into an absolute ethyl
alcohol solution, thereby obtaining a
graphene alcohol solution; (4) adding the graphene
alcohol solution prepared by the step (3) into the metal
saline solution prepared in the step (2), mixing, stirring, putting the hydrothermal kettle into a
drying oven for reacting, thereby obtaining purple turbid liquid; and centrifuging, washing the obtained precipitate by using the
ethanol solution, thereby obtaining a subcarbonate / graphene material; and (5) heating and
drying the subcarbonate / graphene material obtained in the step (4), calcining, thereby obtaining the product
cobalt oxide / graphene composite wave-absorbing material. The method is simple, high in
operability, mild in preparation conditions, clean and
pollution-free in reaction process, high in reaction efficiency and high in reproducibility.