Study On The Construction And Action Mechanism Of MoX₂（X=S,Se）/TiO₂NTs Photoelectrode In Antibiotic Wastewater Purification Process

With the rapid development of modern science and technology,scientific and technological achievements not only bring convenience to people’s life,but also bring a series of increasingly serious problems,such as environmental pollution,energy shortage,and ecological stability,etc.These problems have become major difficulties that endangers human health and hinders sustainable development.Therefore,it is imperative to find and study green and sustainable methods to solve these problems.In recent years,photocatalysis has been regarded as an important technology which is expected to solve these environmental pollution problems.However,TiO₂-based nanocomposites,as an efficient,stable,inexpensive and environmentally friendly photocatalytic material,have become a research hotspot for researchers.In this paper,vertically arranged and uniform TiO₂nanotube arrays were used as substrate.Transition metal sulfides with narrow band gap（e.g.MoS₂and MoSe₂）and conductive Ag nanoparticles were decorated on the nanotubes through hydrothermal method and electrochemical method to form novel Z-scheme heterojunction composite materials.They were employed as photoelectrodes in the photoelectrocatalytic degradation of antibiotics pollutants,such as tetracycline hydrochloride and cefotaxime sodium.TiO₂nanotube arrays（TiO₂NTs）were grown on three-dimensional meshes of commercial titanium grids by anodization.MoS₂/Ag/TiO₂NTs meshy photoelectrode was obtained by depositing Ag nanoparticles and MoS₂nanosheets on TiO₂NTs/Tinet through photochemical reduction and hydrothermal methods.Silver nitrate,thioacetamide and sodium molybdate were used as the source of silver,sulfur and molybdenum,respectively.The experimental results showed that the MoS₂/Ag/TiO₂NTs meshy photoelectrode exhibited excellent photocatalytic activity under the synergistic effect of visible light irradiation and applied auxiliary bias potential of1.0V.The photoelectrocatalytic degradation efficiency of tetracycline hydrochloride by MoS₂/Ag/TiO₂NTs meshy photoelectrode was 1.5 times higher than that by unmodified TiO₂NTs meshy photoelectrode.In addition,the recovery and utilization of MoS₂/Ag/TiO₂NTs based on titanium mesh is convenient.Moreover,it is also with high reusability,photoelectrocatalytic activity and stability.MoSe₂/TiO₂NTs were prepared by anodic oxidation and cyclic voltammetry using commercial titanium foil as the substrate.MoSe₂ nanoparticles were deposited on the top surface and intertublar voids of the TiO₂ nanotube arrays without shielding the tube mouth.This structure not only increase the specific surface area and adsorption capacity of the composite material,but also reduce the band gap energy and enhance the response to visible light.The photoelectrocatalytic degradation performance of MoSe₂/TiO₂NTs photoelectrode towards cefotaxime sodium was investigated under synergistic effect of the simulated solar irradiation and low applied auxiliary bias potential（0.5～3.0V）.The experimental results showed that MoSe₂/TiO₂NTs photoelectrode displayed outstanding photoelectrocatalytic activity and stability.This is because stable direct Z-scheme heterojunction was formed at the close contact interface between TiO₂NTs and MoSe₂nanoparticles.This novel heterojunction not only promote the efficient separation of photo-induced electrons and holes,but also facilitate charge carriers possess high oxidation and reduction potential,which is favorable to produce more active free radicals and accelerate the effective mineralization and decomposition of cefotaxime sodium.