Synthesis of novel direct Z-scheme heterojunction photocatalyst from WO3 nanoplates and SrTiO3 nanoparticles with abundant oxygen vacancies

Excessive use of insecticides in agriculture has raised a global concern owing to their environmental pollution. Various techniques are utilized for removal these compounds which one of the most efficient methods is photocatalytic degradation by heterojunction nanocomposites. Herein, a direct Z-scheme heterojunction nanocomposite with abundant oxygen vacancy defects was fabricated via simple hydrothermal treatment of WO3 nanoplate and SrTiO3 nanoparticle and was utilized as a powerful photocatalyst for decomposition of nitenpyram insecticide under illumination of simulated sunlight. The findings revealed that, the heterojunction nanocomposite with 30wt% of SrTiO3 has the best photocatalytic efficiency. Improvement of the photocatalytic ability may be ascribed to the existence of oxygen vacancy defects in heterojunction interfaces between two semiconductors, facilitating of charge carriers separation, and effective generation of the •O2− and •OH radicals. Furthermore, from the results of the radical capture studies, ESR techniques, and Mott-Schottky analyses, it can be concluded that the hydroxyl radical is the major oxidant for degradation of nitenpyram, and by modulating the charge carrier dynamics and regulation of the charge transfer pathways, a direct Z-scheme heterojunction nanocomposite is formed with improved photocatalytic efficiency. Additionally, the possible decomposition intermediates of nitenpyram were detected from the HPLC-MS analysis.