Synthesis And Regulation Of Vacant Type Defects Sulfide And Research On Its Photocatalytic Performance

Since its full utilization of solar energy and low cost of preparation,photocatalytic oxidation technology has attracted much attention has been extensively studied,which has many advantages to solve the problem of water pollution.Such as crystal defect is of growing interest,because defect or vacancy has greatly affect chemical,optical and catalytic performance of a semiconductor.To date,the simultaneously introducing double vacancies into a photocatalyst remains a big challenge.In this paper,the synthesis of materials and the regulation of vacancy type studied for Zn S and Cd S photocatalyst.The structure and morphology of samples are characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,high-resolution transmission electron microscope?HRTEM?,electron paramagnetic resonance?EPR?spectrum,X-ray photoelectron spectroscopy?XPS?,inductively coupled pasma-atomic emission apectroscopy?ICP-AES?and so on.The optical and the electrical properties of the samples are investigated by UV-DRS,EIS,SPV,etc.The photocatalytic activity of the samples is evaluated by the degradation of organic dye under visible light irradiation??>420 nm?.Two parts are mainly included as follows:?1?Double vacancy Zn S?v-Zn S,containing zinc vacancy and sulfur vacancy?are synthesized by the acid-assisted hydrothermal method,and its photocatalytic performance is evaluated by the degradation of methylene blue?MB?.It is surprising that the wide band-gap Zn S shows an interesting viable light??>420 nm?photoactivity,which is mainly attributed to the formation of double vacancies.This research shows that V_S and V_Zn lead to the formation of defect levels,which are close to conductive band?CB?bottom and valence band?VB?top,respectively.As a result,the defect levels have greatly narrowed the band gap;besides the defect levels also increase the CB and VB widths,which favor for an efficient carrier transfer.This work provides new,simple and feasible method to develop an excellent visible light photocatalyst from a wide-gap semiconductor,through simultaneously introducing double vacancies.The reported method is simple and general,which could extended to the other sulfides and mass production.To the best of our knowledge,we,for the first time,developed a simple method to simultaneously introducing double vacancies into Zn S.?2?Similarly,sulfur defect-contained Cd S are synthesized by the acid-assisted hydrothermal method through changing the acid amount added.The visible-light activity of275-Cd S with more defects is 2.1 times as high as that of Cd S with less defects for the degradation rhodamine B?Rh B?,although 275-Cd S has a larger particle size;which is mainly due to the significantly increased overall carriers to solid surface.Sulfur defects have obviously increased light absorption,but do not improve charge separation due to the offsetting effect of bulk and surface defects.This work explores the influence of surface sulfur defects on carrier concentration and proves the feasibility of the acid-assisted hydrothermal method to other sulfide besides Zn S.In addition,the study provides a simple and straightforward method to well control sulfur defects.It also provides a new idea for the development of controllable and efficient catalyst,which is promising for practical application.