Enhanced photocatalytic reduction of hexavalent chromium ions over S-Scheme based 2D MoS2-supported TiO2 heterojunctions under visible light

Abstract

This work demonstrates the fabrication of visible-light active nanocomposites composed of two-dimensional (2D) MoS2 decorating mesoporous TiO2 as an efficient material for the complete photoreduction of Hexavalent chromium ions Cr(VI) to less toxic trivalent state (Cr(III)). The Cr (VI) accumulation in soil and water is currently representing a crucial issue regarding environmental remediation due to its carcinogenic impacts on humans and other living organisms. The TiO2 was synthesized through the sol-gel route with the assistance of Pluronic F-68 as a growth controller. The 1.0–4.0% of 32.5 nm-sized 2D MoS2 flakes are afterwards decorated 146.2 nm TiO2 nanoparticles by chemical precipitation. The anatase TiO2 and MoS2 phases were revealed by XRD, TEM, and XPS investigations. Irrespective slight amount of MoS2, the visible-light response and bandgap energy was developed to the minimum of ~2.6 eV for the 3.0% MoS2-decorated TiO2. This photocatalyst can achieve total photoreduction of Cr(VI) at 156.89 µmol min−1, which is enhanced to 223.1 µmol min−1 by tuning the dosage at 2.0 gL−1 in just 45 min with significant reusability for five cycles. This enhanced photocatalytic performance is denoted to the magnificent carrier separation by MoS2 as proved by photoluminescence and photocurrent responses. Therefore, the MoS2 supported TiO2 photocatalysts are expected to open future research for the removal of highly toxic heavy metals by photoreduction under visible light.