New insight on interfacial charge transfer at graphitic carbon nitride/sodium niobate heterojunction under piezoelectric effect for the generation of reactive oxygen species
Onkar Sudhir Ekande, Mathava Kumar
Abstract
Piezocatalytic removal of metronidazole (MET) using graphitic carbon nitride (g-C 3 N 4 , GCN)/sodium niobate (NaNbO 3 ) heterojunction was investigated under ultrasonication . Herein, optimized GCN(50)/NaNbO 3 heterojunction achieved 87.2% MET removal within 160 min (k = 0.0138 min −1 ). A new pathway for the generation of reactive oxygen species (ROS) via GCN(50)/NaNbO 3 piezocatalytic heterojunction was identified. The type-II heterojunction formulated using optimized GCN(50)/NaNbO 3 was found to generate hydroxyl radical ( . OH); however, it was thermodynamically not feasible. The main reasons are; (i) piezopotential generated converted type-II to S-scheme heterojunction and resulted in the participation of high oxidizing potential holes in valence band (VB) of NaNbO 3 , and (ii) formation of depletion region at the GCN-water interface and subsequent improvement in the redox potential of holes, and (iii) piezopotential generated at NaNbO 3 provided bias to GCN and established a piezo-electrocatalytic system. The higher screening of piezopotential in presence of external ions was found to reduce the generation of . OH. Overall, self-powered NaNbO 3 has great ability to improve interfacial charge transfer at GCN(50)/NaNbO 3 to form ROS.