高锰酸钾与盐酸在100℃回流反应制备层状水钠锰矿,改变盐酸用量调控水钠锰矿的锰平均氧化度(AOS),即Mn(Ⅳ)与Mn(Ⅲ)的相对含量.采用X射线衍射、扫描电镜、X射线吸收光谱等表征产物晶体结构、微观形貌、价态组成和键长等,考察锰平均氧化度对水钠锰矿理化性质与电容性能的影响.结果表明,随着盐酸用量增加,三维花球状水钠锰矿AOS降低,氧化度可调控为4．02,3．88和3．72,且组成花球的片层厚度有降低趋势,比表面积随之增大,层间K＋和结晶水含量降低；水钠锰矿比电容量随氧化度升高而增大,其充放电过程中晶体内层间离子扩散速率显著影响电容性能.氧化度为4．02的水钠锰矿电化学性能最佳,比容量最大为232 F/g,200周循环保持为222 F/g,容量保持率为95．7％.
Layered birnessites were prepared by reflux reaction of concentrated hydrochloric acid and KMnO4 at 100 ℃.The Mn average oxidation state (AOS),affected by the relative content of Mn(Ⅳ)and Mn(Ⅲ),was controlled by adjusting the molar ratio of hydrochloric acid and KMnO4 .The crystal structures,micromorphol-ogies,compositions and bond length were characterized using X-ray diffractometer (XRD),scanning electron microscope (SEM),X-ray absorption spectroscopy (XAS),and the influence of Mn AOS on the electrochemical performance of birnessites was studied by cyclic voltammetry and charge/discharge test.Results indicated that birnessites with three-dimension hierarchical microspheres composed of disk-shaped plates were formed.Mn AOSs were obtained as 4.02,3.88 and 3.72 when the molar ratios of concentrated hydrochloric acid and KMnO4 were controlled as 1.35∶1,1.66∶1,and 2∶1,respectively.The particle size of microspheres and the thickness of plates decreased,and the corresponding specific surface area increased with a decrease of Mn AOS.The measured interlayer distances of (001)crystal plane and the content of K+ and crystal water increased due to the increasing of Mn AOS.The supercapacitor performance increased with an increase in Mn AOS,and the interlay-er distances of (001)crystal plane,the content of K+ and crystal water possibly played an important role in im-proving the electrochemical performance of birnessite.Birnessite with Mn AOS of 4.02 exhibited the best elec-trochemical performance with initial discharge capacity of 232 F/g,and it decreased to 222 F/g with retention rate about 95.7% after 200 cycles.
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