Preparation And Properties Of Bismuth-based Catalytic Materials

Environmental pollution and energy crisis have become urgent problems to be solved in the process of rapid social development.With the progress of materials science,piezoelectric catalysis technology has become an effective means to solve global warming,environmental pollution and energy shortage.At present,the research of piezoelectric catalysis mainly focuses on two-dimensional ultra-thin materials,bismuth-based materials,hexagonal wurtzite materials and perovskite materials.Among these,layered piezoelectric materials based on bismuth have received much study due to their distinctive two-dimensional layered structure,good chemical stability,excellent piezoelectric properties and controllable synthesis technology.The catalytic efficiency can be improved by controlling the band structure,constructing heterojunction and regulating the growth direction of crystal plane.Based on this,three bismuth-based materials,Bi₂Mo O₆,BiOCl,and BiOIO₃/basic nitrate heterojunction,were designed in this paper,and their applications in the process of piezoelectric catalysis and piezoelectric photocatalysis to degrade organic dyes were studied as follows:1.Loaded Bi nanoparticles enhanced the piezoelectric catalytic activity of Bi₂Mo O₆In this work,Bi₂MoO₆ nanosheets were synthesized by hydrothermal method,and then were added to Na BH₄ solution with different concentrations for stirring reduction,and a series of Bi₂Mo O₆ loaded with Bi nanoparticles were prepared.Bi₂Mo O₆-25showed excellent piezoelectric catalytic performance and could degrade Rh B within 40minutes after loading.The band structure of Bi₂Mo O₆-25 loaded with Bi nanoparticles was tested by an electrochemical workstation.It was found that Bi₂Mo O₆-25 loaded with Bi nanoparticles has a narrower band gap,which increases its free carrier concentration,and the minimum conduction potential(E_CB)of Bi₂Mo O₆-25 is-0.38V,Bi₂Mo O₆-25 has a valence band potential(E_VB)of 2.06V,while O₂/·O₂^-has a potential of about-0.33V and OH^-/·OH has a potential of about 1.99V.Therefore,Bi₂Mo O₆-25can meet the potential requirements of oxidation-reduction reaction,and its suitable band structure is beneficial to the transition of electrons from valence band to conduction band to produce active substances for oxidation reaction.Meanwhile,piezoelectric-force microscopy also shows that Bi₂Mo O₆-25 has excellent piezoelectric properties,which provides theoretical support for its high piezoelectric catalytic activity.2.Crystal facet engineering of polar single crystal BiOCl with improved piezo-photocatalytic activitySelective exposure of highly active crystal faces is an effective strategy to improve the piezoelectric photocatalytic activity of catalysts,but the selective synthesis of highly active crystal faces is still a difficult problem.In addition,how the growth of crystal surface affects the performance of catalyst remains to be explored.In this work,BiOCl with selectively exposed（001）or（101）crystal planes were synthesized by a pot of hydrothermal method.The degradation properties of organic dyes with different exposed crystal planes under photocatalysis,piezoelectric catalysis and piezoelectric photocatalysis were investigated.In addition,it is also found that in the process of piezoelectric photocatalysis,the enrichment of reducing active centers also promotes the occurrence of catalytic reactions,and plays a greater role than smallplane charge separation.The BiOCl with a with high exposure（001）plane not only has a narrow bandgap,high charge separation efficiency,and a significant piezoelectric coefficient,but also is more prone to experience band bending under ultrasonic action,thus significantly enhancing the activity.The findings of this research will deepen our comprehension of the piezoelectric-photocoupler catalytic reactions of crystal plane regulation affecting planar charge separation and active sites.3.Promoting photocatalytic organic pollutant degradation of BiOIO₃/basic bismuth （III）nitrate by dual field effect:Built-in electric field and piezoelectric field effect Piezoelectric material polarization field engineering has gotten a lot of interest in improving photocatalytic performance.In this study,an asymmetric piezoelectric semiconductor BiOIO₃ is combined with basic bismuth（III）nitrate（BBN）to form a two-dimension heterojunction,which endows the hybrid with a built-in electric effect and a piezoelectric potential in both light and ultrasonic states.Notably,BiOIO₃/BBN1:1/3 shows a remarkable photodegradation performance.Rhodamine B dye（10 mg/L,50 m L）can be completely degraded within 3 min by 50 mg of BiOIO₃/BBN 1:1/3,and piezoelectric photocatalysis has a higher kinetic constant(2.01 min^-1)than single piezoelectricity or photocatalysis.Further experiments illustrate that such remarkable performance correlates heavily with both built-in electric field and piezoelectric field effects,which encourage the separation and transformation of photogenerated carriers.Moreover,this hybrid can also effectively degrade Congo red,methyl orange,and methylene blue.The degradation pathway of Rh B was deduced by HPLC-MS analysis and the mineralization efficiency of the reaction was tested.Our work may lay a unique foundation for the creation of extremely effective piezo-photocatalysts for wastewater purification,hydrogen production,and other piezo-optical processes,reflecting its potential for practical applications in protecting the environments.