Comparative study on the photodegradation efficiency of organic pollutants using n-p multi-junction thin films

Abstract

The study presents comparative results of the photocatalytic removal efficiency of methylene blue (MB), phenol and imidacloprid, using spray deposited thin film heterojunctions based on (SnO2)-Cu2ZnSnS4-TiO2. The addition of the SnO2 layer increased the samples roughness, but had limited effect on their overall photocatalytic efficiency. The thicker TiO2 layer did not limit the light penetration required to activate the p-type layer as comparable or slightly higher photocatalytic efficiency values were obtained using thicker TiO2 thin films compared to the samples containing thinner ones. Adsorption appears as the most important step in the degradation mechanism, for all the investigated pollutants. Promising photocatalytic efficiencies of 20–30% for methylene blue, 15–20% for phenol and 10–12% for imidacloprid under simulated solar radiation with low irradiance (34 W/m2) and low pollutant initial concentrations (10 ppm) were obtained using the multilayered structures. The addition of the Cu2ZnSnS4 extended to VIS the activation domain of the samples, leading to improved pollutant removal compared to the reference TiO2 thin films.