Design And Synthesis Of Nano-bismuth Molybdate-based Visible-light Catalysts For Emerging Pollutants Degradation

With the development of industrialization and urbanization,environmental pollution is getting more and more attention.Organic pollutants with biotoxicity,persistence,and bioaccumulation that have not been in cluded in national management or have insufficient management measures are defined as"emerging pollutants".Chlorophenol and antibiotics are typical emerging pollutants.Emerging pollutants have seriously endangered the ecological environment and human health,the efficient degradation of environmental emerging pollutants is of great significance.Semiconductor photocatalytic technology has been considered as a potential environmental treatment technology due to its advantages of low cost,mildness and no secondary pollution.Narrow band gap semiconductor bismuth molybdate(Bi2MoO6)can realize visible light absorption,and it has diversified and tunable structure.Therefore,it becomes a photocatalyst for degrading emerging pollutants with great hope for application.However,Bi2MoO6 materials often exhibit poor photocatalytic degradation activity due to a number of issues,including poor charge separation and weak activation ability of photocatalytic electrons to O2.Therefore,it is of great significance to construct a heterojunction system with novel,broad spectral absorption and catalytic sites to improve the degradation performance of Bi2MoO6.Based on this,Bi2MoO6 two-dimensional nanosheets with different crystal faces and phases were prepared controllable,heterojunction system constructed and the introduction of catalytic components are used to improving the charge separation of Bi2MoO6 and enhance the activation ability of O2 to improve photocatalytic degradation of emerging pollutants.And the mechanism of charge transfer and separation and the mechanism of degradation were revealed.This study may broaden way to the high-efffciency degradation of typical environmental emerging pollutants using bismuth-containing oxide-based photocatalysts.This work mainly carries out from the following three aspects:(1)Preparation of facet regulated Bi2MoO6 two-dimension ultrathin sheets and photocatalytic selective dechlorination properties.Cetyltrimethylammonium bromide(CTAB)as a functional molecule,Bi2MoO6 ultrathin nanosheets with(100),(010)and(001)facets(～4 nm)were successfully prepared via a pH-controlled functional molecule assisted microwave hydrothermal method.The adsorption behavior and degradation activities of 2-CP on Bi2MoO6 with different facets were studied.The results showed that(100)Bi2MoO6 exhibited a strong adsorption capacity for 2-CP and induced a selective preferred dechlorination degradation mechanism dominated by photo-generated holes(h+).(2)Preparation of FePc/Bi2MoO6 two-dimensional Z-scheme heterojunction photocatalyst and hydrogen reduction modification.FePc/Bi2MoO6 two-dimension heterojunction was formed by controllable assembly of FePc onto the surface of Bi2MoO6 via H-bond induced assembly strategy.Furthermore,a mixed valence Fe active site was obtained by hydrogen reducing a portion of the Fe2+ in FePc.The degradation kinetic constant k of the optimal heterojunction was 0.009 min-1,which is 4.5 times higher than in the bare Bi2MoO6(0.002 min-1).This is primarily owing to the selective preferential dechlorination mechanism induced by h+on the surface of Bi2MoO6,Z-scheme charge transfer mechanism between FePc and Bi2MoO6,improves the activation of O2 via the mixed valence Fe site in FePc.(3)Preparation of FePc/phase-mixed Bi2MoO6 two-dimensional dual Z-scheme heterojunction and mechanism.The Bi3.2Mo0.807.5-Bi2MoO6 phase-mixed heterojunction nanosheets(～4 nm)were in-situ prepared using a functional molecule-assisted microwave hydrothermal method by optimizing the ratio of Bi to Mo.Moreover,the FePc/G/2.7BMO dual Z-scheme heterojunction was constructed by utilizing the abundant hydroxyl groups on the surface of G to induce the dispersion of FePc.The kinetic constants k of the optimized FePc/G/phase-mixed Bi2MoO6 heterojunction is 0.094 min1,which is 8.5 and 4.3 times that of Bi3.2Mo0.8O7.5(0.011 min-1)and Bi2MoO6(0.022min1),respectively.The improved performance is attributed to the dual Z-scheme charge transfer mechanism,the increased loading amount of highly dispersed FePc,which enhances the activation ability of O2.The degradation mechanism and pathway of TC were revealed by the free radical trapping test and intermediate substance detection.