| Modification of intercalation compounds can greatly influence the properties of materials in verified aspects,such as:specific surface area,dimensions of nanosheets,electronic structure and so on.Layered double hydroxides(LDHs)is a kind of common two-dimensional material,which possess multiple factors that can be precisely altered,such as:chemical elements in the host layers,intercalated anions,etc.By utilizing the feature,scientists have devoted themselves for years to design suitable LDHs for specific applications.Herein,we altered the intercalated anions of LDHs,achieving the efficient modulation of dimensions and electronic structures of LDHs,and the changes we made have contributed a lot to the performance of LDHs in heavy metal remediation and electrocatalytic process.Detailed content of our work is described as follows:1.Monolayer LDHs powders can easily stack and the synthesis of monolayer LDHs powders is still challenging,because of the problems existing now,we fully took the advantage of the separate nucleation and aging steps and designed a new method for synthesizing scale-up monolayer LDHs powders.[B4O5(OH)4]2-anions were intercalated in gallery to enlarge the distance between nanosheets,combining with the effect of acetone,the hydrogen bonds between layers were disrupted,as a result,monolayer LDHs with the thickness of less than 1 nm were synthesized successfully.The synthesized monolayer LDHs possessed larger specific surface area which can provide larger amount of active sites for the adsorption process,as the data of the removal results showed,monolayer LDHs can achieve the removal efficiency of more than 99%for 100 ppm solution after 1 minute,15 minutes and 180 minutes for Cu2+,Ni2+and Cd2+,respectively.Characterization for precise location of the adsorbed heavy metal ions were carried out by using XAFS,Cu2+ions were proved to be located onto the host layers of MgAl-LDH,and the most probable sites were inferred to be the Mg-vacancy site,while the adsorption sites for Ni2+were different,isomorphous substitution is considered to be the mechanism during the Ni2+adsorption process,Ni2+may have substituted Mg atoms in the host layers.The work is believed to widen the application of LDHs in mineralization,and also the investigation of adsorption sites can be a reference for more research in this area.2.Intercalation effect of different anions were investigated by synthesizing 4 different kinds of CoFe-LDH with NO3-,Cl-,BO33-and CO32-intercalated anions,repsectively.The four different kinds of LDHs we synthesized were used as electrocatalysts for hydrazine oxidation process,the catalytic performances showed good regularity of a down trend by the order of NO3-,Cl-,BO33-and CO32-.XAFS and XPS were used to show the electronic structure of the four catalysts,following the order of performance down-trend,fewer defects were detected,meanwhile,the decreasement of oxidation state for Co and increasement of Fe were illustrated.The bridge between intercalated anions and electronic structure were built in this way,while the law of the influence for electrocatalytic performance were also demonstrated by our work. |
