Preparation And Application Of Ordered Mesoporous Carbon Loaded With NiCo₂O₄ Nanoparticles Material For Electrocarboxylation

Hydroxy acids（HAs）are valuable organic acids,which are widely used in food,cosmetics,pharmaceutical and other industries.They can be synthesized through enzymatic or chemical methods.Most of traditional chemical methods need to use cyanide or chlorine to react with aldehydes and ketones,then treated with acid.However,Cyanide and chlorine are both toxic reagents,which will cause serious harm to organisms and the environment.Therefore,it is the key to seek non-toxic reagents for the synthesis of hydroxy acid.As a kind of greenhouse gas,the large amount of CO₂ emission is having a negative impact on the earth’s climate.Meanwhile,it is also a rich and non-toxic resource.Using it in the synthesis of hydroxy acid instead of cyanide or chlorine not only avoids the use of toxic reagents,but also can realize the fixation of CO₂,which turn waste into treasure.Kolbe–Schmitt reaction is well known as the reaction of alkali metal phenoxides and CO₂ producing hydroxy acid,which requires high temperature and pressure,and the harsh conditions limit its application.Electrochemical method using aldehydes and ketones and CO₂ as reactants,electrons as oxidation reducing agent to synthesize hydroxy acid,not only using CO₂,but also clean and green,has mild conditions,which is an attractive method.Electrode materials play a key role in the process of electrocarboxylation to produce hydroxy acid.With the development of research,toxic Hg or Pb cathodes and expensive Pt cathodes are gradually replaced by cheap metals such as Ni.However,the contact area between the plate electrodes and the reactants is small,and the catalytic performance of single metal is limited.Therefore,the search for more efficient electrode materials has become a research hotspot.Due to its ability to accelerate electron transfer and enhance performance of gas adsorption caused by structural characteristics such as variable valence state and abundant vacancy defects,spinel metal oxidation has been widely used in energy storage,photoelectric,sensor,battery and other fields while there are few reports on the application of electrochemical organic synthesis.On the other hand,spinel metal oxidation has limited active area and are easy to aggregate,so a supporter with large specific surface area is needed to disperse it.Ordered mesoporous carbon has the characteristics of high specific surface area,uniform pore structure,good dispersibility and electrical conductivity.As a carrier in the field of electrochemistry,ordered mesoporous carbon can not only effectively reduce the agglomeration of metal nanoparticles,but also enhance the electrical conductivity of materials,making it received enormous interest.On account of the above analysis,in this dissertation,I combine the performance advantages of spinel metal oxide compound and ordered mesoporous carbon with the technology advantage of electrochemical synthesis,used ordered mesoporous carbon CMK-3 as the carrier to support spinel metal oxide.They were applied to electrocatalytic reaction of benzophenone with CO₂ to synthesize hydroxy acid.The electrocatalytic performance of electrode material in different electrolytic environments were investigated and the optimized electrolysis conditions were obtained.The electrolytic process overcomes the disadvantages of toxic and harmful,complicated steps,harsh conditions,many byproducts and poor catalytic performance of the electrode.Specific research contents are as follows:（1）NiCo₂O₄/CMK-3 electrode material was prepared by hydrothermal method,and its characterization and electrocatalytic application were carried out.The study shows that the catalytic performance of NiCo₂O₄ is due to the acceleration of electron transfer and the enhancement of CO₂ adsorption.The structure and morphology of the material（the size of NiCo₂O₄ nanoparticles,specific surface area of materials,etc.）and the electrocatalytic performance were affected by the loading amount.The effects of current density,substrate concentration and electrolytic quantity on the catalytic activity of electrode materials were also investigated to find the optimal electrolytic conditions for this reaction.The yield reached 86%under this condition.The material was reused for six times,and it was found that the material had good stability through related characterization;Through the study of the electrocarboxylation of other aromatic ketones,it was found that the material had good universality for aromatic ketones.（2）NiCo₂O₄/CMK-1,NiCo₂O₄/CMK-8 and MCo₂O₄/CMK-3 series materials were prepared by hydrothermal method in order to study the influence of carbon substrate and the type of spinel metal on the electrocatalytic performance,and their characterization and electrocatalytic application were carried out.The characterization and results of electrocatalysis show that the stronger the dispersion ability of carbon substrate and the higher the content of vacancy defects in spinel metal oxides,the better the electrocatalysis performance of the material.