A Z-scheme AgI/BiOI binary nanophotocatalyst for the Eriochrome Black T photodegradation: A scavenging agents study

The increased pollution of the environment, especially the aquatic ones, requires novel techniques/catalysts with high removal efficiency and low cost. For this goal, the construction of novel visible-light heterogeneous photocatalysts attracted particular interest. The binary AgI/BiOI coupled catalyst in nano dimension was prepared and used in Eriochrome Black T (EBT) photodegradation in this research work. Photoluminescence (PL) spectra confirmed that in the coupled system, the electron-hole (e/h) production was increased concerning BiOI alone, while the e/h recombination was decreased. The modified carbon paste electrodes with semiconductors confirmed that the cyclic voltammogram (CV) peak current could change in the case of the coupled system, ensuring an internal redox process between BiOI and AgI components. By applying the Kubelka-Munk model on the UV-Vis diffuse reflectance spectra (DRS), the band gap energies of 2.8, 1.5, and 2 eV were obtained for AgI, BiOI, and AgI-BiOI samples. A boosted photocatalytic activity was observed for the coupled system, which depended on the AgI:BiOI mole ratio. The effects of some scavenging agents, including ascorbic acid, sodium bicarbonate, KI, and KNO3 were studied on the photocatalytic efficiency. Ascorbic acid drastically decreased the overall process efficiency, confirming the vital role of superoxide radicals in the photodegradation process. Based on the potential positions of the CB and VB levels, the Z-scheme mechanism was the best model to describe the photodegradation mechanism.