Photocatalytic dye removal with ZnO/Laser-Induced graphene nanocomposite

• ZnO films were deposited by Atomic Layer Deposition (ALD) on Laser Induced Graphene (LIG) with two degrees of porosity. • The deposition was conformal down to the pores of LIG, regardless of its porosity. • The photocatalytic activity of the ZnO@LIG nanocomposites was tested on methylene blue under UV light for 120 min. • A maximum photodegradation of about 70% was found for the nanocomposites with the highest loading of ZnO. ZnO has been deposited on Laser Induced Graphene (LIG) by Atomic Layer Deposition (ALD) running up to 100, 200 and 400 number of cycles. Two different LIG substrates have been used, which differed by their porosity degree. The ALD technique allows to grow ZnO stoichiometrically on the chosen substrates down to the bottom of the pores of the material, guaranteeing an increasing coverage with increasing number of deposition cycles. The crystallinity of the deposited ZnO is also proven via XRD analysis. The photocatalytic activity of the ZnO@LIG nanocomposites has been evaluated through monitoring the discoloration of a 10 -5 M methylene blue (MB) solution upon UV irradiation (λ = 365 nm) over a time span of 120 min. Results indicate that the photocatalytic performance of the nanocomposites increases with the ZnO deposition time. For nanocomposites showing the higher ZnO coverage degree, after 120 min of irradiation a net MB photodegradation percentage of 71 ± 4 % and 69 ± 4 % is reached respectively for the less porous and more porous substrate. Conversely, the MB adsorption percentage of the samples decreases upon ZnO deposition, due to the reduced accessible porosity and the hydrophobicity of the nanocomposites. The method used to produce such solid supported nanocomposites is straightforward and represents a valuable option to obtain efficient environmental-friendly photoactive materials.