Preparation And Photocatalytic Properties Based On AgIO₃ And BiOX?X=Cl,Br? Composites Photocatalyst

Highly efficient photocatalysts with visible light responsiveness have always been a research hotspot in the field of photocatalysis.Researchers always pursue narrower band gap to possess the visible light utilization performance,and hope that the photogenerated electrons and holes on the photocatalyst surface have higher separation efficiency,so as to maximize the use of photogenerated carriers.However,it is difficult for a single semiconductor material to meet the requirements of both at the same time,which was greatly restricts the application in environmental remediation.Therefore,silver iodate,a new photocatalyst,was selected as the key research object in this study.The lone pair electrons in silver iodate promote the asymmetric pyramid structure,which lead to the generation of internal electric field and polarization effect.High polarizability in internal electric field can effectively improve the separation efficiency of photogenerated electrons and holes.In addition,the band gap of silver iodate is 3.1e V,which means ultraviolet response close to the visible light.Therefore,appropriate modification of silver iodate can take into account both visible light photoabsorption and high utilization efficiency of photo-generated charge.In brief,silver iodate will be an ideal photocatalytic semiconductor material.In this study,heterojunction was introduced as the main strategy to modify silver iodate,and bismuth series photocatalyst was recommend as another component of heterojunction.The main defects of silver iodate as a photocatalyst were solved to a certain extent by surface strategy,morphology control,biomass assisted synthesis and surface plasmon effect.Tetracycline hydrochloride in liquid phase and formaldehyde in the gaseous phase were selected as degradation targets.The degradation performance of the synthesized photocatalysts to pollutants in gaseous and liquid systems was investigated,which provided a new idea for expanding the application of silver iodate and its composite photocatalysts.The main contents and achievements of this paper are summarized as follows:1.In order to overcome the shortcoming that the wide band gap and only ultraviolet response of silver iodate,Ag IO₃ and Bi VO₄ with narrow band gap were selected to construct Ag IO₃/Bi VO₄ heterojunction photocatalyst.By adjusting the two-phase composition of the heterojunction,the optimum combination was obtained after a series of physicochemical properties characterization and the photocatalytic properties of tetracycline hydrochloride?TC?and gas-phase formaldehyde in visible light degradation were tested.The photocatalytic mechanism of Ag IO₃/Bi VO₄ heterojunction was established.It was pointed out that band matching and effective separation of photogenerated electrons and holes were the reasons for the good photocatalytic performance of Ag IO₃/Bi VO₄ heterojunction.2.Ag IO₃/Ag₂O/Ag nanocomposites with high photoabsorption intensity for visible light at 500-800 nm were synthesized by a one-step coprecipitation method at room temperature,which demonstrated enhanced photocatalytic activities.The optimum hybrid of Ag IO₃/Ag₂O=1.25:1 with Ag nanoparticles?Ag NPs?loading?denoted as AA125?exhibited superior photocatalytic activity with 97.19%tetracycline?TC?degradation within 60 min under simulated solar irradiation.The advanced photocatalytic activity can be ascribed to the synergetic effects of the heterostructured Ag IO₃/Ag₂O/Ag and the strong surface plasmon resonance?SPR?effect of Ag NPs generated on the surface,which improved the efficiency of photon utilization of Ag IO₃ and promoted the separation and transfer efficiency of photoinduced electron–hole pairs.3.Sodium carboxymethyl cellulose?CMC-Na?,a biomass solvent,was used to instead of petrochemical solvent to synthesize Bi OX?X=Cl,Br?-?CMC?with{010}dominant crystal facet.Bi-functional groups of CMC-Na play an important role in coordination and crystal facets regulation in the synthesis of Bi OX.Bi OX?X=Cl,Br?-?CMC?with three-dimensional hierarchical structure exhibited significant photocatalytic performance improvement for photocatalytic degradation of TC and HCHO,which provides a suitable precursor for the construction of heterojunction with silver iodate in the next step.4.Bi OCl/diatomite composite photocatalyst was prepared to promote the adsorption and degradation of tetracycline and gaseous phase formaldehyde by synergistic photocatalysis of Bi OCl on the porous surface of diatomite.The interaction between Bi OCl and diatomite was investigated through various characterization tests.It was pointed out that diatomite not only acted as a natural porous support of of Bi OCl,but also played a dominant facets regular role in the synthesis of Bi OCl at p H=3 when the doping amount is change,owing to the surface negative electrical property of the diatomite and interaction between diatomite and Bi OCl with the Bi of[Bi₂O₂]²⁺group to O in Si-O-Si bond.5.The heterojuncted Ag/Ag IO₃/Bi OCl,Ag/Ag IO₃/Bi OCl?CMC?photocatalysts were prepared by using the synthesized Bi OCl and Bi OCl-?CMC?as the components of the heterojunctions,respectively.The formation of Ag-NPs on the surface of the heterojunction was confirmed by various characterization methods,and the surface plasmon effect of Ag-NPs promoted the separation of photogenerated electrons and holes.At the same time,it was found that the photocatalytic properties of Ag/Ag IO₃/Bi OCl?CMC?heterojunctions were better than those of Ag/Ag IO₃/Bi OCl heterojunctions for tetracycline and gas-phase formaldehyde under visible light.The reason was related to band matching,increased specific surface area and effective charge separation.The differences of reaction phase state and interfacial dispersion between gaseous phase system and liquid phase system were analyzed by the results of photocatalytic performance.6.The Ag/Ag IO₃/Bi OBr and Ag/Ag IO₃/Bi OBr?CMC?heterojunctions were prepared by using the synthesized Bi OBr and Bi OBr-?CMC?as heterojunctions of silver iodate.Based on the superior visible light response of Bi OBr,it is concluded that the heterojuncted bromine series photocatalysts are superior to the heterojuncted chlorine series photocatalysts.Among them,Bi OBr?CMC?exhibited excellent visible light response,increased specific surface area caused by 3D hierarchical structure,etc.which showed the maximum degradation activity for TC and HCHO photocatalysis after compounding with Ag IO₃.In addition,the performance differences of bismuth heterojunction and bromine heterojunction photocatalysts were compared.