Construction of Z-scheme Cs3PMo12O40/g-C3N4 composite photocatalyst with highly efficient photocatalytic performance under visible light irradiation

Abstract

Exploitation of effective, persistent and visible-light-responsive photocatalysts is of significance for photodegrading antibiotics and organic dyes in environmental modification. Here, a novel Cs3PMo12O40/g-C3N4 (abbreviated as x% CPM/CN; x ​= ​2, 4, 6 and 8, respectively) composite was fabricated through a convenient dissolution-precipitation method. As-obtained CPM/CN composite was composed of three-dimensional (3D) CPM nanospheres and two-dimensional (2D) CN nanosheets, which was verified through SEM and TEM techniques. The interfacial interaction between CPM and CN was confirmed with XPS results, which manifested the heterojunction formation in CPM/CN composite. The prepared materials displayed excellent and durable catalytic activity for tetracycline hydrochloride (TCH), ciprofloxacin (CIP) and Rhodamine B (RhB) removal with visible light illumination (λ ​> ​420 ​nm). Particularly, 4% CPM/CN sample displayed the optimal activity, whose photodegradation rates for TCH, CIP and RhB could reach 83.11% (k ​= ​0.01255 min−1), 65.43% (k ​= ​0.00591 min−1) and 100% (k ​= ​0.64822 min−1), respectively. The improvement of photocatalytic performance was due to the enhancement in the visible light absorption and the accelerated separation and migration rate of electrons-holes. The electron spin resonance (ESR) and free radicals trapping experiments proved that superoxide radical (·O2−) and holes (h+) were dominating active species in contaminants removal. Moreover, the photocatalytic degradation pathways of TCH were detected by high performance liquid chromatography-mass spectrometry (HPLC-MS). Combined the analysis of the energy band structure and precious metal deposition test, a Z-scheme catalytic mechanism was presented in detail. This work affords novel horizons for the rational design and fabrication of Z-scheme POMs/CN-based catalysts with excellent catalytic activity for environmental protection.