Preparation Of Manganese Dioxide Nanostructures And Their Electrochromic Properties

The rapid development of economy and the increasing progress of science and technology have brought us not only a better life but also huge energy consumption.But in the meanwhile,environmental pollution has plagued the daily life of common people.Therefore,developing energy-saving and environmental-friendly green materials became the key research.As such one kind of new materials,electrochromic materials can reduce energy consumption,complying with the trend of the development.The research of electrochromic materials with better performance and the industrialization of electrochromic devices has become a hit.In this article,nano-flower,nano-sheet and nano-wire MnO₂film preparing by hydrothermal method,are assembled with Fluorine-doped Tin Oxide(FTO)conductive glass to get electrochromic devices.The morphology of nano-flower,nano-sheet and nano-wire MnO₂film from different reaction conditions are compared respectively,and the best nano-flower,nano-sheet and nano-wire MnO₂film are selected for electrochemical test.Then,the complementary electrochromic devices composed of best nano-flower MnO₂film(nano-sheet MnO₂film and nano-wire MnO₂ film)and WO₃ film are tested about electrochromic properties.The main research results obtained in this paper are as follows:(1)The nano-flower MnO₂ film and nano-sheet MnO₂film were prepared from KMnO₄by hydrothermal method and heat treatment.Then the nanostructure morphologies of MnO₂from different concentrations were analyzed.The results show that 0.10 mol/L KMnO₄precursor solution was heated by water at 160 ^oC for 9 h and heat-treated at 200 ^oC for 3 h to obtain nanoscale flower-like MnO₂films with complete morphology,uniform dispersion and no large agglomeration.The diameter of the flower-like structure was about400 nm.After adding HCl and making the precursor solution acidic,the flower-like structure gradually disintegrated,and the nanoscale MnO₂film was obtained.Further experiments revealed that the prepared nano-flower MnO₂film and FTO conductive glass were assembled into electrochromic device that had the maximum transmittance modulation(?37.0%)with colored state response time of 13.3 s,color fading state response time of 18.4s at 452 nm.In a similar way,the prepared nano-sheet MnO₂film and FTO conductive glass were assembled into electrochromic device that has the maximum transmittance modulation(?26.4%)with colored state response time of 18.8s,color fading state response time of 28.4s at 548 nm.(2)The nano-wire MnO₂ film were prepared by hydrothermal method using KMnO₄and Mn SO₄·H₂O.And the effect of the concentration of reactants on its morphology is discussed.The results show that,0.35 g of KMnO₄and 0.15 g of Mn SO₄·H₂O was dissolved in deionized water to prepare a solution,which was under hydrothermal condition at 160 ^oC,12h and normal pressure then dried at 80 ^oC and 30 min to obtain the best nano-wire MnO₂film.Furthermore,it had complete structure morphology,uniform dispersion and a diameter of about 20 nm and length of about 1?m.Next,The prepared nano-wire MnO₂film and FTO conductive glass were assembled into electrochromic device that had the maximum transmittance modulation(?25.1%)with colored state response time of 12.7 s,color fading state response time of 23.2 s at 551 nm.(3)The above nano-flower MnO₂ film,nano-sheet MnO₂film and nano-wire MnO₂film were assembled with WO₃film prepared by electro-deposition method,respectively,to get complementary type electrochromic devices.The nano-flower MnO₂/WO₃complementary type electrochromic device had better electrochemical performance than simple the nano-flower MnO₂electrochromic device.According to the test,the above nano-flower MnO₂/WO₃electrochromic device had the maximum transmittance modulation(?46.2%)with colored state response time of 2.5 s,color fading state response time of 3.0 s.The nano-sheet MnO₂/WO₃complementary type electrochromic device had the maximum transmittance modulation(?42.7%)with colored state response time of 5.9 s,color fading state response time of 29.6 s.The nano-wire MnO₂/WO₃complementary type electrochromic device had faster response time and greater transmittance modulation than simple the nano-wire MnO₂electrochromic device.The above nano-wire MnO₂/WO₃electrochromic device had the maximum transmittance modulation(?38.3%)with colored state response time of 5.8 s,color fading state response time of 8.2 s.