Photocatalytic characteristics of indium oxide, copper oxide and indium oxide/copper oxide thin films on plastic waste substrates for organic pollutants degradation

Abstract In this work, the characteristics of In 2 O 3 , CuO and In 2 O 3 /CuO films deposited on plastic waste substrates were investigated. The deposition was achieved using reactive dc magnetron sputtering. x-ray diffraction revealed the amorphous structure for In 2 O 3 films whereas crystalline monoclinic CuO phase was observed for CuO and In 2 O 3 /CuO films. The nano-grain sizes are in the ranges 14–48 and 12–37 nm for CuO thin film and the In 2 O 3 /CuO bilayer film, respectively. The estimated optical band gap values were 2.67, 2.20 and 2.30 eV for In 2 O 3 , CuO and In 2 O 3 /CuO films, respectively. The estimated Urbach tail values were 664, 177 and 235 meV for In 2 O 3 , CuO and In 2 O 3 /CuO films, respectively. The In 2 O 3 /CuO bilayer film has the highest refractive index and extinction coefficient values over the NIR spectral range. The degradation of methylene blue (MB) attained 86%, 74% and 96% after illumination time of 720 min for In 2 O 3 , CuO and In 2 O 3 /CuO photocatalysts, respectively. The photo electrochemical measurements of the In 2 O 3 , CuO and In 2 O 3 /CuO films were studied using Tafel plot and electrochemical impedance spectroscopy under dark and illumination conditions and they inferred the enhanced electro-conductivity of In 2 O 3 /CuO electrode. Overall, this work elucidated that depositing In 2 O 3 /CuO thin films photocatalysis on waste plastic of water drinking bottles is a workable method to degrade dyes from polluted water with low cost and high efficiency.