Nb2O5/red phosphorus S-scheme heterojunction photocatalyst for removal of organic contaminant and Cr(VI): Electrochemical performance and mechanism

Abstract

Heterojunctions constructed from wide-bandgap and narrow-bandgap semiconductors with complementary functions are the most efficient structures to improve their photocatalytic performance. A niobium pentoxide (Nb2O5)/hydrothermally treated red phosphorus (HRP) S-scheme heterojunction photocatalyst was obtained via a facile one-step hydrothermal method for removal of Rhodamine (RhB) and Cr(VI). The Nb2O5/HRP heterojunction exhibited super photo-activity. The degradation rate of RhB was 95% within 9 min, and the reduction rate of Cr(VI) was 97% within 30 min. The κ of Nb2O5/HRP (0.29217 min−1) for RhB degradation was 6.4 and 20.9 times greater than that of HRP (0.04559 min−1) and Nb2O5 (0.01399 min−1), and the κ (0.11218 min−1) for Cr(VI) reduction was 7.8 and 28.8 times more than those of HRP (0.01435 min−1) and Nb2O5 (0.00390 min−1). The various electrochemical performance tests were performed, and the cyclic voltammetry (CV) test showed symmetrical redox peaks (−0.15–0.16 mA) of Nb2O5/HRP. The mechanism for photocatalytic activity of Nb2O5/HRP S-scheme heterojunction was discussed based on the active species capture experiments and molecular fluorescence spectra.