Preparation And Property Study Of Bio-inspired MnO₂/rGO Aerogels

Environmental pollution and energy shortages are two major problems in the world today.On one hand,nuclear energy crisis continuously escalates while non-renewable resources,such as oil and coal,are depleting.On the one hand,the environmental pollution caused by traditional fossil energy is becoming more and more serious.Hence,it is of great demand for human beings to develop clean energy while managing deteriorating environmental pollution.The research of clean energy is important to achieve sustainable development,improve people's quality of life,and ensure national security.Herein,inspired by the natural porous structure of sponges,which is known of high filtration property,high mass exchange efficiency and high mechanical strength,various aerogels are prepared by using different materials,and their application in the environmental and energy fields has been systematically studied.In this thesis,ultrathin manganese dioxide?MnO₂?nanosheet colloids were synthesized in one step from the reaction of sodium dodecyl sulfate,manganese chloride and potassium permanganate.The synthesized MnO₂ nanosheet colloids were freeze-dried by ice-templating method to obtain the self-supporting biomimetic MnO₂ aerogel.The biomimetic MnO₂ aerogel has a 3D porous network and a crystal structure of?-MnO₂.The pore size ranges from hundreds of nanometers to tens of micrometers.This structure not only prevents 2D ultra-thin MnO₂ nanosheets from aggregating,but also allows more surface to contact organic dyes for enhanced oxidative degradation efficiency.In the test of oxidative degradation of organic dyes,the aerogel exhibits better oxidative degradation performance under acidic conditions than commercial MnO₂ powder,two-dimensional MnO₂ nanosheets and H₂O₂-based materials.We also explored the optimal amount of the aerogel and the optimal reaction pH.The experimental results showed that 0.5 g L^-1 biomimetic MnO₂ aerogel could oxidize and degrade 97.5%of rhodamine B in aqueous solution within 10minutes at a pH of 2.5.At the same time,the bionic MnO₂ aerogel also showed good performance in oxidative degradation of methylene blue in aqueous solution.Then we fabricated another aerogel starting from graphene oxide?GO?.First,the biomimetic GO aerogels with 3D porous network structure were prepared by ice-templating.Then an innovative approach of hydrothermal reduction with water vapor was used to obtain biomimetic reduced graphene oxide?rGO?aerogel with high tunability of microscopic pore size and macroscopic morphology.The resulting biomimetic rGO aerogel has a simpler preparation process,a larger volume,a smaller density and a higher formability than the other rGO aerogels reported.In the adsorption test of various organic substances,the aerogel showed good hydrophobic properties,and can stably adsorb an oily solvent to amount of about 40 times of its own weight.Meanwhile the aerogel also demonstrates a good cycling performance of repeated use.In further electrochemical characterization,the aerogel exhibited good electrical conductivity and electrochemical performance of double layer capacitance.Finally,in order to combine the advantages of ultra-thin MnO₂ nanosheets and GO nanosheets,biomimetic MnO₂/rGO hybrid aerogels were synthesized by ice-templating and hydrothermal reduction with water vapor.The ultra-thin MnO₂nanosheets are uniformly distributed between the rGO sheets,which afford the C skeleton of the aerogel,so that it has good electrical conductivity and capacitance performance in electrochemical characterization.Meanwhile,we have also prepared biomimetic Mn₃O₄/rGO hybrid aerogel by changing the temperature of hydrothermal reduction with water vapor.Through this method,ultra-thin MnO₂ nanosheets can be converted into Mn₃O₄ crystals of black manganese ore phase at a lower temperature.With the continuous development of lithium battery technology,the biomimetic Mn₃O₄/rGO aerogel holds a very bright prospect of broad application in the future energy field.