Nano-and micro-engineered vertical graphene/Ni for superior optical absorption

• The laser irradiation treatment has produced a “cauliflower-like” microstructure on nickel surface that enhances the light-trapping ability and greatly decreases the reflectance. • A nano-and micro-engineered structure is developed by fabricating VG on laser-modified nickel (VG/mNi), which achieves extremely low omnidirectional light reflectance. • Derived from the synergistic effect of the nano-and micro-structure, the VG/mNi exhibits a superior photothermal conversion capability. Black coatings benefit from low reflectance or high light absorption are utilized in multifarious optical applications. Due to their unique three-dimensional nanostructure and π-band optical transitions, vertical graphene (VG) has drawn great attention to the field of black coatings. However, how the morphology of VGs affects reflectance has not been comprehensively disclosed yet. In addition, the morphology of the substrate for VG growth also affects the absorption properties. Here, we report a nano-and micro-engineered VG/Ni structure based on VG and laser-modified nickel foil, which possesses omnidirectional low reflectance of ∼ 0.25% over the visible range. A larger spacing of graphene nanowalls is more conducive to the formation of light traps and improves the absorption property. Besides, the surface of nickel substrate by laser irradiation presents a “cauliflower-like” microstructure, which further enhances light-trapping ability.