Photocatalytic H2O2 production and removal of Cr (VI) via a novel Lu3NbO7: Yb, Ho/CQDs/AgInS2/In2S3 heterostructure with broad spectral response

Abstract

The low-usage of solar energy and the sluggish separation efficiency of the photogenerated electrons/holes pairs are the obstacles in the practical application of photocatalysts. The integration of upconversion and Z-scheme heterojunction is expected to break the barriers to achieve the efficient charge separation and broaden near-infrared light absorption. Herein, an effective indirect Z scheme AgInS₂/In₂S₃ heterostructure with carbon quantum dots (CQDs, as the electron conduction medium) and Lu₃NbO₇:Yb, Ho (as upconversion function) has been successfully synthesized. Consequently, the Lu₃NbO₇: Yb, Ho/CQDs/AgInS₂/In₂S₃ heterostructure exhibited superior photocatalytic activities for Cr(VI) reduction and H₂O₂ production, reducing 99.9% of Cr(VI)(20 ppm, 15 min) and 78.5% of Cr(VI) (40 ppm, 30 min) with visible light irradiation as well as 94.0% of Cr(VI) (20 ppm, 39 min) under NIR light irradiation. Simultaneously, the heterostructure could generate 902.9 μM H₂O₂ for 5 h under visible light irradiation. The intensive photocatalytic properties could primarily be attributed to the boosted light absorption capacity, the improved solar-to-energy conversion by the remarkable upconversion capacity of Lu₃NbO₇: Yb, Ho/CQDs and the faster charge transfer through a Z-schematic pathway. This work is anticipated to open a novel "window" for designing the efficient photocatalysts by coupling of Lu₃NbO₇: Yb, Ho and CQDs.

Keywords: Carbon quantum dots; Cr(VI) reduction; H(2)O(2) production; Lu(3)NbO(7): Yb, Ho; Z scheme heterostructure.