With using manganese sulfate monohydrate as manganese source and ammonium persulfate as oxidant,five MnO2 products were prepared by a hydrothermal synthesis method at the reaction temperature of 100,120,140,160 and 180℃,respectively.The results of XRD,SEM and supercapacitor performance tests shown that the reaction temperature directly affected the crystal form,morphology and supercapacitor properties of MnO2 products.When the reaction temperature was in the range of 100～120℃,the as-prepared MnO2 (S1 and S2) were consisted of α+γ crystal and in the morphology of aggregated spheres.As the temperature was in the range of 140～180℃,MnO2 products (S3～S5) with the crystal form of α+β and the morphology of rods were synthesized;furthermore,with the increasing of reaction temperature from 140 to 180℃,the rod diameter was found to be gradually increased from 0.18 to 0.51 μm,as well as the α-form content was proved to be gradually decreased from 77.8% to 57.5%.As far as supercapacitor properties are concerned,the rod-like products (S3-S5) exhibits higher specific capacitance,coulombic efficiency and capacitance retention than those aggregated sphere-like products (S1 and S2).Among the rod-like products,product S3 which with the smallest rod diameter and the highest α-form content appeared the best supercapacitor behavior.
[1] Jang J H,Han S,Hyeon T,et al.Electrochemical capacitor performance of hydrous ruthenium oxide/mesoporous carbon composite electrodes[J].Journal of Power Sources,2003,123(1):79-85.
[2] Simon P,Gogotsi Y.Materials for electrochemical capacitors[J].Nature Materials,2008,7(11):845-854.
[3] Wang Y,Song Y,Xia Y.Electrochemical capacitors:mechanism,materials,systems,characterization and applications[J].Chemical Society Reviews,2016,45(21):5925-5950.
[4] Wang J,Xu Y,Chen X,et al.Electrochemical supercapacitor electrode material based on poly(3,4-ethylenedioxythiophene)/polypyrrole composite[J].Journal of Power Sources,2007,163(2):1120-1125.
[5] Bhalerao A B,Bulakhe R N,Deshmukh P R,et al.Chemically synthesized 3D nanostructured polypyrrole electrode for high performance supercapacitor applications[J].Journal of Materials Science Materials in Electronics,2018(7):1-9.
[6] Hao Y,Yunmeng L,Xiaoya G,et al.Synergistic supercritical water ‘wet’ activated biomass carbon as high performances electrode materials for supercapacitor[J].Journal of The Electrochemical Society,2018,165(10):A2075-A2083.
[7] Li Q,Hu M,Kang W,et al.One-step approach for fabrication of 3D porous carbon/graphene composites as supercapacitor electrode materials[J].Catalysis Today,doi.org/10.1016/j.cattod,2018.02.031.
[8] Zhao Y,Wen Y,Xu B,et al.Fe2O3 hollow sphere nanocomposites for supercapacitor applications[C].Iop Conference Series:Earth & Environmental Science,2018.
[9] Wu X,Meng L,Wang Q,et al.A flexible asymmetric fibered-supercapacitor based on unique Co3O4@PPy core-shell nanorod arrays electrode[J].Chemical Engineering Journal,2017,327:193-201.
[10] Ye C,Lin Z M,Hui S Z.Electrochemical and capacitance properties of rod-shaped MnO2 for supercapacitor[J].Journal of the Electrochemical Society,2005,152(6):A1272-A1278.
[11] Kalubarme R S,Jadhav H S,Park C J.Electrochemical characteristics of two-dimensional nano-structured MnO2 for symmetric supercapacitor[J].Electrochimica Acta,2013,87(1):457-465.
[12] Poonguzhali R,Shanmugam N,Gobi R,et al.Effect of thermal annealing on the structural,morphological and super capacitor behavior of MnO2 nanocrystals[J].Materials Science in Semiconductor Processing,2014,27:553-561.
[13] Yu Z,Duong B,Abbitt D,et al.Highly ordered MnO2 nanopillars for enhanced supercapacitor performance[J].Advanced Materials,2013,25(24):3302-3306.
[14] Kim H,Popov B N.Characterization of hydrous ruthenium oxide/carbon nanocomposite supercapacitors prepared by a colloidal method[J].Journal of Power Sources,2002,104(1):52-61.
[15] Feng L,Zhu Y,Ding H,et al.Recent progress in nickel based materials for high performance pseudocapacitor electrodes[J].Journal of Power Sources,2014,267:430-444.
[16] Li Y,Xie H,Wang J,et al.Preparation and electrochemical performances of α-MnO2 nanorod for supercapacitor[J].Materials Letters,2011,65(2):403-405.
[17] Wang H Q,Yang G,Li Q Y,et al.Porous nano-MnO2:large scale synthesis via a facile quick-redox procedure and application in a supercapacitor[J].New Journal of Chemistry,2011,35(2):469-475.
[18] Zhang X,Sun X,Zhang H,et al.Microwave-assisted reflux rapid synthesis of MnO2,nanostructures and their application in supercapacitors[J].Electrochimica Acta,2013,87(1):637-644.
[19] Wang H Q,Li Z S,Huang Y G,et al.A novel hybrid supercapacitor based on spherical activated carbon and spherical MnO2 in a non-aqueous electrolyte[J].Journal of Materials Chemistry,2010,20(19):3883-3889.
[20] Devaraj S,Munichandraiah N.Effect of crystallographic structure of MnO2 on its electrochemical capacitance properties[J].Journal of Physical Chemistry C,2008,112(11):4406-4417.
[21] Li D,Yang J,Tang W,et al.Controlled synthesis of hierarchical MnO2 microspheres with hollow interiors for the removal of benzene[J].RSC Advances,2014,4(51):26796-26803.
[22] Xu H,Qu Z,Zhao S,et al.Different crystal-forms of one-dimensional MnO2 nanomaterials for the catalytic oxidation and adsorption of elemental mercury[J].Journal of Hazardous Materials,2015,299:86-93.
[23] Ranjusha R,Nair A S,Ramakrishna S,et al.Ultra-fine MnO2 nanowire based high performance thin film rechargeable electrodes:effect of surface morphology,electrolytes and concentrations[J].Journal of Materials Chemistry,2012,22(38):20465-20471.
[24] Su D,Ahn H J,Wang G.β-MnO2 nanorods with exposed tunnel structures as high-performance cathode materials for sodium-ion batteries[J].NPG Asia Materials,2013,5,e70.DOI:10.1038/am.2013.56.
[25] 王歌,赵晓昱,张瑾,等.不同晶型二氧化锰的可控制备条件研究[J].无机盐工业,2017(8):16-20.
[26] 周武艺,唐绍裘,万隆,等.制备条件对纳米TiO2晶型及其晶相含量影响的研究[J].稀有金属,2004,28(4):631-634.
[27] Zhang H,Wang Y,Wang C.Influence of surfactant on the capacitive performance of manganese dioxide prepared at different temperatures[J].Energy Conversion & Management,2013,74(5):286-292.
[28] Chen C,Yu D,Zhao G,et al.Three-dimensional scaffolding framework of porous carbon nanosheets derived from plant wastes for high-performance supercapacitors[J].Nano Energy,2016,27:377-389.
[29] Bello A,Fashedemi O O,Barzegar F,et al.Microwave synthesis:characterization and electronhemical properties of amorphous activated carbon-MnO2 nanocomposite electrodes[J].Journal of Alloys and Compounds,2016,681:293-300.
[30] Shao J,Li W,Zhou X,et al.Magnetic-field-assisted hydrothermal synthesis of 2×2 tunnels of MnO2,nanostructures with enhanced supercapacitor performance[J].CrystEngComm,2014,16(43):9987-9991.
