Microwave-assisted fabrication of CQDs/ZnIn₂S₄ nanocomposites for synergistic photocatalytic removal of Cr(VI) and rhodamine B

Abstract

CQDs/ZnIn₂S₄ (CQDs represents carbon quantum dots) nanocomposites were prepared via a microwave-assisted hydrothermal method. The photocatalytic activity for the reduction of Cr(VI) to Cr(III) over the as-prepared CQDs/ZnIn₂S₄ nanocomposites under visible light irradiations was studied. The study found that the reduction of Cr(VI) to Cr(III) over hexagonal ZnIn₂S₄ can be significantly increased by loading CQDs as a co-catalyst. After 60 min of visible light illumination (λ > 420 nm), almost 100% Cr(VI) can convert to Cr(III) with (NH₄)₂C₂O₄ as a scavenger. Furthermore, the CQDs/ZnIn₂S₄ nanocomposites are demonstrated to execute as bifunctional photocatalysts with appreciable activity in the hybrid systems (Cr(VI)/RhB) under visible light, which made it a potential application material for industrial wastewater treatment. Combined with photoelectrochemical analyses, it can be found that the introduction of CQDs can reduce the recombination of photogenerated electron-hole pairs. Finally, a possible photocatalytic reaction mechanism is also proposed.

Keywords:

• Photocatalysis
• CQDs/ZnIn2S4
• nanocomposites
• Cr(VI)

Additional information

Funding

This work is supported by the team of syngas catalytic conversion of Shaanxi University of Technology, Special scientific research plan of education department of Shaanxi province (Grant Nos. 20JK0552), General project of science and technology department of Shaanxi province (2019JM471).