水在Ag电极上取向与结构的SERS研究──不同电极电位和NaClO_4浓度的影响

SERS Studies on the Orientation and Structure of Absorbed Water at Ag Electrodes──Effects of Electrode Potential and NaClO_4 Concentrations

将特殊的ＯＲＣ方法、薄层溶液技术和差谱方法相结合，在较宽的电位区间（－０．７～－２．０Ｖ），获得了不含任何（类）卤素离子的ＮａＣｌＯ４／Ａｇ体系中水的ＳＥＲＳ谱。结果表明，不同浓度的ＮａＣｌＯ４体系中，尽管体相水的结构有很大差别，但电极表面的吸附水有相似的结构特征，即由于电场作用而使有序性较高；并且随电极电位由极负电位向零电荷电位（ＰＺＣ）变化时可能都经历着由单氢端吸附转变为双氢端吸附，继而又转向氧端吸附的取向变化过程。利用ＳＥＲＳ技术特有的检测表面物种的高灵敏度，可观察到ＮａＣｌＯ４浓度引起的表面水的ＳＥＲＳ谱的一些细微差异，依此较详细讨论了ＮａＣｌＯ４浓度对表面水的结构和取向变化过程的影响。

Combining with the special procedure of roughing surface and the difference spectra technique,one can obtain the surface enhanced Raman scattering(SERS) spectra of water adsorbed on Ag electrodes in a wide potential range(-0.7--2.0V) from NaClO4 solutions with various concentrations(0.1-8.0 mol/L).It has been shown that the absorbed water has much higher ordered structure than that in the bulk solutions.The concentration of NaClO4 has much less effect on water molecules adsorbed on the surface,especially in the relatively negative potential region,in comparison with that in the bulk solutions.With changing the potential form-2.0 V to-0.9 V,the adsorbed water is reoriented from one hydrogen ending to the surface to two hydrogens then to the oxygen ending.The concentration effect of ions on the reorientation of the absorbed water is discussed in detail.