Preparation And Application Of Nanometer Octahedral Magnesium Oxide

Magnesium oxide?MgO?is an important inorganic functional material,which has a broad application prospect.MgO with polar?111?facet exhibits higher activity than MgO with polar?111?facet in some fields such as catalysis and adsorption fields.The preparation of MgO with?111?facet has attracted extensive attentions of many researchers.The preparation of MgO with polar?111?facet and octahedral MgO which exposed eight?111?polar facets have been reported successively.However,the preparation and application of nano octahedral MgO have been relatively less studied.Therefore,the preparation of nano octahedral MgO?N-O-MgO?is still a great challenge.We have successfully prepared nano octahedral MgO,and studied the adsorption properties of the nano octahedral MgO for methyl orange and the redox activity of the doped carbon material which used nano octahedral MgO as a template.?1?Nano octahedral MgO was successfully prepared by solvothermal method in which ethanol as solvent,urea and magnesium nitrate as solute.The nano octahedral MgO was characterized by XRD,SEM and TEM.In order to further explore the formation mechanism of the nano octahedral MgO,a single crystal?Mg?NO₃?₂·6CO?NH₂?₂?was obtained by crystal culture with the same raw materials and solvent.After calcination,the nano octahedral MgO was also successfully obtained.In general,solvothermal method can accelerate the nucleation of?Mg?NO₃?₂·6CO?NH₂?₂?in the solution system,and play an important role in obtaining nano octahedral MgO after calcination.?2?The adsorption of methyl orange on nano octahedral MgO prepared by solvothermal method was studied.The fitting results of the experimental data showed that the adsorption of methyl orange on nano octahedral MgO conform to Langmuir adsorption isotherm model and pseudo second-order kinetic equation,and the maximum adsorption capacity is 229.36 mg/g.The result of simple thermodynamic calculation showed that the adsorption process was spontaneous.The adsorption site was determined to be magnesium ion by adsorption of different dyes on nano octahedral MgO.The adsorption process of methyl orange on nano octahedral MgO:Methyl orange is hydrolyzed into methyl orange with sulfur group exposed?-SO₃^--MO?and sodium ion,and methyl orange with sulfur group exposed are adsorbed on the surface of the adsorbent via ion exchange and electrostatic interaction bond with adsorption site,magnesium ion.In the adsorption process,the adsorption sites on the adsorbent surface can be effectively utilized.?3?In this part,nano octahedral MgO was used as adsorbent and template.The mixture was carbonized at high temperature after using nano octahedral MgO adsorbed methyl orange to prepare doped carbon materials.The influence of different carbonization temperature on the doped carbon materials was studied,revealing that high temperature was helpful to the carbonization of the materials and porous structure.The doped carbon materials via nano octahedral MgO as the template showed good ORR activity.