Photocatalytic degradation of methylene blue over N-doped MnWO4 under visible light irradiation

Abstract

In recent years, the transition-metal tungstate materials with formula MWO4 have attracted much attention in photocatalytic environmental purification due to their interesting structural and optical properties. Among the others, manganese tungstate (MnWO4) has attracted particular attention because of its appropriate bandgap energy (2.67 ​eV) with tunable optical and electrical properties, chemical stability, and low cost which makes a suitable photocatalyst. Nevertheless, the manganese tungstate (MnWO4) based materials are less explored as visible light responsive photocatalysts for wastewater purification. Hence, both parent and N-doped MnWO4 are synthesized by a hydrothermal method with different nitrogen contents (5, 10, and 15 ​mol%). The as-prepared photocatalysts were characterized by XRD, SEM-EDS, TEM-SAED, FT-IR, UV–Vis DRS, XPS and PL techniques. The photocatalytic activities of the synthesized samples were evaluated by degradation of methylene blue (MB) dye under the visible light irradiation. All the N-doped MnWO4 samples exhibited enhanced visible-light photocatalytic activity compared to the parent MnWO4, and the optimal dopant amount of nitrogen was 15 mol% for the best photocatalytic activity. The active species generated during the process of MB degradation are investigated by scavenging experiments. Further, the reusability of the 15 ​mol% N-doped MnWO4 photocatalyst was examined in three consecutive catalytic runs.