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RESEARCH PAPER

Noble metal-free MoS2-modified In2S3 for excellent visible-NIR-light-driven photocatalytic of Cr6+ removal in alkaline wastewater Linjuan Wang & Ling Zan

Received: 1 June 2020 / Accepted: 18 October 2020 # Springer Nature B.V. 2020

Abstract MoS2-modified In2S3 (x wt.%MoS2-In2S3) samples (0 ≤ x ≤ 20) were fabricated through a facile one-pot hydrothermal process. All In2S3 samples modified by MoS2 deliver an excellent Cr6+ removal ability under visible-NIR-light-driven, and 5% MoS2-In2S3 can reduce 20 mg/L Cr6+ solution completely within 30 min with a trace photocatalyst concentration (0.27 mg/mL) which is 3.2-hold higher than that of single In2S3. Further investigations demonstrate that the loaded MoS2 can not only enhance the absorption of light scope but also promote the interfacial electron transfer from In2S3 to MoS2 and then to Cr6+, thus greatly improving the Cr6+ removal ability. ESR shows that the modifying of MoS2 can accelerate the transformation of electrons from the In2S3 to MoS2 which results in that the intensity of O2−• significantly increased. PL, photocurrent, and EIS further identified that the modification of MoS2 can greatly improve the charge carrier separation efficiency. The fabricated MoS2-In2S3 samples also exhibit characteristic features such as stable and reducing Cr6+ in the weak alkaline environment for the first time, which could always be a great challenge for wastewater purification in alkaline condition.

Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007 /s11051-020-05057-5. L. Wang : L. Zan (*) College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072, People’s Republic of China e-mail: [email protected]

Keywords Photocatalytic . Functional material . In2S3 . Cocatalyst . Cr6+ removal . Nanostructured catalysts

Introduction Hexavalent chromium [Cr(VI)] is carcinogenic and related pollution that constitutes an extremely serious threat (Kostas et al. 2017; Marikkani et al. 2019; Vellaichamy et al. 2017), especially for the precious water resources of human beings live on (Khamboonrueang et al. 2018). Cr(VI) is produced by chrome electroplating industrial revolution with decorative, corrosion-resistant chrome-layered objects in everyday life (Athanasekou et al. 2017; Zhang et al. 2019). pH with all values exists in the wastewater solution according to different manufacturing processes. However, most of the research focused on water treatment in acidic solution. The reason is probably that the potential energy is much positive in acid solution than in alkaline, and it can be reduced easily by many kinds of reagents, but it results in a waste of large amounts of acid to adjust the pH to suit any kind of medium. Therefore, it is a great significance in alkaline wastewater purification. Traditionally, chemical and bioremediation methods reducing Cr6+ with chemical reagents have higher requirements for the equipment and cost a lot (Balakumar et al. 2019; Nanda et al. 2017). Photocatalytic tre