Construction of 2D/2D/2D rGO/p-C3N4/Cu3Mo2O9 heterostructure as an efficient catalytic platform for cascade photo-degradation and photoelectrochemical activity

Abstract

Well-designed heterostructure photocatalysts with effective interfacial contacts have attracted significant attention, owing to their enhanced visible-light absorption and optimal charge separation efficiency. Herein, novel visible-light-responsive heterostructure photocatalysts composed of reduced graphene oxide (rGO)/protonated g-C3N4 (p-CN)/Cu3Mo2O9 (CMO) were constructed through a facile hydrothermal method. In particular, the ternary composite with 20 wt% of CMO content (rGO/p-CN/CMO-20) was optimized as an efficient catalyst for tetracycline (TC) degradation. The TC degradation rate of the rGO/p-CN/CMO-20 catalyst was found to be ~41, 15, 22, 7, and 14 times higher than those of rGO, p-CN, CMO, p-CN/CMO-20, and rGO/CMO-20, respectively. The outstanding photocatalytic activity could be attributed to the enhanced visible-light absorption, synergistic effect among the components, high specific surface area, good interfacial contact, efficient separation and transfer of photo-generated charge-carriers as well as good photostability. In addition, reactive radical scavenging and band edge position analyses provided evidence for a possible mechanism of the enhanced photocatalytic activity exhibited by rGO/p-CN/CMO-20. Mineralization with 60% total organic carbon reduction was achieved during the 60 min treatment of the optimized sample. The kinetic analysis revealed that the photocatalytic degradation obeyed the Langmuir–Hinshelwood kinetic model. The primary intermediates were identified through liquid chromatography-mass spectrometry, and a photo-degradation pathway was tentatively proposed. This work will provide new routes for the design and construction of efficient two-dimensional rGO/p-CN-decorated heterostructures and their use in environmental decontamination.