纳米Ni(OH)_2的质子扩散行为研究

Studies on proton diffusion behavior of nanometer size Ni(OH)_2

用沉淀转化法制备了纳米Ｎｉ（ＯＨ）２ 超微粉，ＸＲＤ谱图显示为β（Ⅱ）相，用Ｓｃｈｅｒｒｅｒ公式估算的粒径大小为２０ｎｍ 。将Ｎｉ（ＯＨ）２ 超微粉与微米级的球形Ｎｉ（ＯＨ）２ 对照，分别作为活性物质涂填进泡沫镍基体中制成电极，研究了充放电性能，发现纳米Ｎｉ（ＯＨ）２ 微粉放电比容量要高于球形Ｎｉ（ＯＨ）２ ，而且放电电位高，充电电位低，说明纳米Ｎｉ（ＯＨ）２ 填充的电极有较小的极化。另外，采用粉末微电极技术测定了两种Ｎｉ（ＯＨ）２ 活性物质的质子扩散系数：纳米Ｎｉ（ＯＨ）２ 为１．１×１０－ １０ ｃｍ ２ ／ｓ，球形Ｎｉ（ＯＨ）２ 为３．５×１０－ １１ ｃｍ ２／ｓ。探讨了其质子扩散行为差异的原因，纳米Ｎｉ（ＯＨ）２ 的粒径小，有更大的比表面积，可以增加与电解质溶液的接触，而且纳米微粒可减小质子在固相中的扩散距离，从而提高了其质子扩散性能。

Nanometer size nickel hydroxide powder was prepared by precipitation transformation method.The sample was in β(Ⅱ)phase and its particle size was about 20 nm estimated by Scherrer Formula.In order to contrast nanometer size nickel hydroxide powder with micron size spherical Ni(OH) 2,the charge/discharge properties of the foam nickel electrodes filled with the two samples as active materials respectively were studied.It was found that the discharge capacity of nanometer size Ni(OH) 2 is higher than that of spherical Ni(OH) 2,and the charge potential of the electrode filled with nanometer Ni(OH) 2 is lower as well as its discharge potential is higher.All of the results show that the polarization of the electrode filled with nanometer size Ni(OH) 2 is lower.Moreover,the proton diffusion coefficients of the two samples were measured by powder microelectrode technique and the results show that nanometer size Ni(OH) 2 indicates 1.1×10 -10 cm 2/s as well as the spherical Ni(OH) 2 indicates 3.5×10 -10 cm 2/s.The differences of proton diffusion behavior between the two samples were also discussed.Nanometer size Ni(OH) 2 has smaller particle size,so it has larger specific surface area and is easier for the active material to contact with electrolyte solution.Moreover,the smaller particle can decrease the distance for proton diffusion thus the ability of proton diffusion is improved.