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

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 similar to 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.