Construction Of Two-dimensional MoS₂-based Heterogeneous Composites And Their Cr（Ⅵ） Photoreduction Properties

At present,environmental water pollution has become one of the intractable problems that threaten human health.But the rapid development of nanomaterials and nanotechnology has brought a new development opportunity for the remediation technology of polluted water.Photocatalytic technology is the preferred repair method because of its cleanliness,efficiency,and economy.The use of photocatalytic materials for the degradation and remediation of pollutants in water is regarded as an effective strategy to solve the problem of water pollution,which puts forward more demanding requirements for the design and synthesis of photocatalytic materials.In photocatalytic reactions,widening light absorption and accelerating the separation efficiency of the photogenerated carriers are the keys to the efficient utilization of photocatalytic materials.It is expected to promote photocatalytic performance by constructing heterogeneous structures and regulating the interface characteristics between different components to realize the rapid separation and transfer of photogenerated charge.As a typical graphene-like structure material,MoS₂ has characteristic physical and chemical properties,excellent adsorption capacity,adjustable band gap,and other advantages,which have become one of the hot spots of many photocatalytic nanomaterials.Based on this,MoS₂ is selected as the research object in this paper.From the intrinsic characteristics and microscopic morphology of the materials,two-dimensional MoS₂-based composite nanomaterials are constructed through heterogeneous engineering,and the photoreduction performance of Cr（Ⅵ）is studied.The specific research content and results are shown as follows:（1）Construction of monodisperse MoO₂nanospheres/ultra-thin MoS₂nanosheets composite system.In the presence of thioacetamide and acetic acid,uneven crystallized rutile MoO₂ nanoparticles were obtained by the hydrothermal reaction as starting materials.The shape evolution of highly monodisperse oxide nanospheres was realized by in situ vulcanization strategy using the lattice mismatch interface between oxide and sulfide nanostructures.The monodisperse MoO₂ nanospheres/ultra-thin MoS₂nanosheets composite was formed.The novel composite catalyst makes full use of the local surface plasmon resonance effect（LSPR）of MoO₂ and the visible absorption characteristics of MoS₂,which has remarkable photoreduction performance of Cr（Ⅵ）under visible light and near-infrared light irradiation.This study provides a new approach for the practical application of the LSPR effect in photocatalysis and is of great significance for the development of unique spherical monodisperse crystal nanoparticles involving chemical strategies to change the non-uniform shape of nanocrystals.（2）Self-assembly synthesis of 2D/2D MoS₂/Cu-Zn In₂S₄ composite photocatalyst.2D MoS₂/Cu-Zn In₂S₄ composite photocatalyst was synthesized by in-situ growth of 2D MoS₂ nanosheets growing on 2D Cu-doped Zn In₂S₄ nanosheets to fabricate self-assembly via a two-step solvothermal method.The incorporation of Cu broadens the optical response range and introduces receptor trap energy levels,thus accelerating the separation and migration efficiency of photogenerated electron-hole pairs.Under the condition of visible light irradiation（λ≥400 nm）and no sacrificial agent,2D/2D MoS₂/Cu-Zn In₂S₄ can achieve complete photoreduction of Cr（VI）in 4 min.In addition,the self-assembly photocatalyst showed a strikingly high tolerance to high concentrations of Cr（VI）（250 mg/L）.The photoreduction activity was virtually unaffected by wastewater containing high concentrations of inorganic ions.These merits demonstrate that 2D/2D transition metal sulfide self-assembly technology has potential application prospects in water purification and environmental remediation.