| Semiconductor photocatalytic technology is an emerging high-efficiency,energy-saving modern green environmental protection technology,which provides new methods for solving social and environmental problems of today.Among many photocatalysts,titanium dioxide(TiO2)is non-toxic,harmless,stable,safe,green and cheap.It is an excellent photocatalytic material and is widely used in environmental purification,photocatalytic hydrogen production and solar photovoltaic cells.However,due to the large band gap(3.2 eV),it is difficult to be excited by visible light,which limits the practical application of TiO2.In this paper,a simple chemical oxidation method was used to successfully prepare a net-shaped TiO2 nano-grass array photocatalyst film under conditions close to normal temperature and pressure.TiO2 films under different conditions were prepared by different methods,and their surface morphology,composition,absorbance,photoelectric properties,and photocatalytic activity were characterized by various methods.The main results are summarized as follows.First,nitrogen and sulfur doping was successfully achieved by chemical oxidation.The doping amount of nitrogen increases with the extension of the chemical oxidation time,but the visible light catalytic activity is inversely proportional to the doping amount of nitrogen,and its best performance is improved by 8.6 times compared with that before doping;the doping of sulfur makes the performance further improved by 1.2 times.Nitrogen doping introduces the N 2p impurity energy level into the forbidden band of TiO2,and the electrons on it are more easily excited to transition to the conduction band by visible light,and visible light absorption is enhanced;Further sulfur doping does not enhance visible light absorption,but improves TiO2 Surface chemical ability to dissociate water.Second,the reduction of TiO2 with ethylene glycol and ammonium fluoride at lower temperatures introduced oxygen vacancy defects.The oxygen vacancy concentration increases with the reduction time,but the photocatalytic activity is not proportional to the oxygen vacancy concentration,and its optimal performance is increased by 9.6 times compared with that before doping.Oxygen vacancies create new donor levels in TiO2,and photogenerated electrons are more easily transferred to the conduction band through oxygen vacancies,which enhances visible light absorption.Third,BiOI was compounded on the surface of TiO2 using Successive Ionic Layer Adsorption and Reaction technology.The visible light catalytic activity of TiO2 adsorbed 11 times was the best,which was 4.4 times that before doping.The formation of a p-n junction produces an internal electric field that enhances the separation of photo-generated carriers;further adsorption reduces its photocatalytic activity,which may be related to the excessively thick BiOI thin film which hinders the visible light absorption of TiO2 and improves hole-electron re-electron compound rate is related.Piezoelectric photocatalysis is of great significance for the improvement of photocatalytic activity.The generation of piezoelectric potential can separate photogenerated carriers with a large driving force and prevent their recombination.This research combines photocatalytic technology,piezoelectric photocatalytic technology,and wastewater treatment technology to creatively design a photocatalytic water purification system to improve water purification efficiency. |
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