Preparation Of MoX₂?X=S,Se?/TiO₂ Nanotube Arrays And Research On Photocatalytic Purification Of Pollutant

With the progress of human social science and technology and the development of industrial civilization,energy shortage and environmental pollution turned into more and more hazardous to human health and sustainable development.Therefore,it is imperative to develop a series of methods with green and economic technologies to large-scale industrial applications to solve these problems.Photocatalysis has been highly regarded as a promising solution towards energy and environmental sustainability.As a typical photocatalyst,nanostructured TiO₂ was widely studied towards H₂-production and pollutant degradation due to its high stability,environmental friendliness,abundant availability and cost effectiveness.In this work,TiO₂ nanotube arrays?TiO₂ NTs?are employed as substrates for the assembly of graphene like layered transition metal dichalcogenide semiconductor materials during a simple hydrothermal process.The resulting composite are applied in the purification of Cr⁶⁺ or 4-NP.The research contents are summarized as follows:?1?Commercial titanium mesh serve as Ti substrate during the anodic oxidation process for the growing of TiO₂ NTs.Se powders and Na₂MoO₄·2H₂O are used as Se and Mo sources in the hydrothermal process to form the MoSe₂ nanoflower on the surface of Ti/TiO₂ NTs substrates,resulting in the MoSe₂@TiO₂ NTs composite.SEM?TEM?XRD?XPS?UV-vis?PL spectrum and photocurrent test are performed to characterize the microstructure,components and photoelectric properties of the as-prepared materials.Cr⁶⁺solution is applied as pollutant model to test the photocatalytic ability of the materials.The results show that the composites have more satisfactory performance in the photoreduction process.This phenomenon might attributed to the formation of a traditional type II heterojunction between TiO₂ and MoSe₂,which could improve the separation efficiency of the photogenerated e-and h+pairs,so that a higher quantum efficiency could be accomplished.?2?In this work,conductive,solid,soft and spiral Ti wires are used as substrates to form TiO₂ NTs.Similarly,the in-situ growth of MoSe₂ nanosheets on the Ti/TiO₂ NTs substrates is realized in the hydrothermal process,but the content of modified MoSe₂ co-catalyst is changed greatly,resulting in a direct Z-scheme MoSe₂@TiO₂NTs construction different from the traditional type II heterostructure mentioned above.The direct Z-scheme composite could not only accomplish the effectiveseparation of photogenerated e-and h+ pairs,but also could ensure the optimal oxidation and reduction capacity of each semiconductor.The photocatalytic properties of the as-fabricated composites are verified by applying in the decomposition of 4-NP.The results demonstrate that an appropriate MoSe₂ content could construct a ideal direct Z-scheme heterojunction.It is of great importance that the Ti/TiO₂ NTs substrates loaded with uniform and trace co-catalyst,and the close connection of two semiconductor is also very important.?3?In this work,the TiO₂ NTs@Ti wires are continue to be substrates in the hydrothermal procedure,and thiourea and Na₂MoO₄·2H₂O are used as S and Mo sources to form the MoS₂@TiO₂ NTs composite.High concentration Cr⁶⁺ solution is applied to test the photoclectrocatalytic?PEC?property of the obtained composite.Various low molecular weight organic acids?LOAs?are added to make up the underutilization to visible light of TiO₂ in the PEC procedure.The results show that the composite possess a superior visible-light PEC activity and excellent stability for the reduction of high concentration Cr⁶⁺?200 mg/L?with the adding LOAs,and the reduction rate reach the maximum(103.9 mg/L min^-1)when tartaric acid?TA?added as sacrificial electron donor.