Carbon and oxygen co-doped phosphotungstate for high performance photocatalytic degradation of imidacloprid

Carbon and oxygen co-doped phosphotungstate were successfully prepared by one-pot thermal treatment with phosphotungstic acid (HPW) and melamine-cyanuric acid supramolecule (MCA) as precursors. Based on the results of X-ray photoelectron spectra (XPS), UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and Photoluminescence (PL) measurements, the existence of CO in CNPW-8-420 has been confirmed. Carbon and oxygen which are co-doped as CO in the Keggin structure of phosphotungstate are contributed to the separation of charge carriers and can increase the amount of the photocatalysis active sites. With the amount of HPW increasing, MCA decomposed in CNPW-8-420 and CNPW-20-420 without synthesizing g-C3N4, leading to in-situ doped of CO. Furthermore, the increase of treatment temperature can cause the supramolecular structure of MCA to overbreak, leading to carbon and nitrogen elements doped in CNPW-8-500. The photocatalytic degradation efficiency rate constant of CNPW-8-420 is 0.40 h−1 and it can be reused 3 times with no obvious change. LC−MS/MS revealed the most likely photocatalytic degradation pathway and intermediates of imidacloprid including imidacloprid olefin, guanidine-type imidacloprid, imidacloprid urea, 6-chloronicotinic acid, 5-hydroxy-imidacloprid, and 4,5-dihydroxy-imidacloprid. This study provides a promising strategy for the construction of co-doped POMs photocatalysts using different supramolecule precursors.