锰欠电位沉积的密度泛函计算与循环伏安实验的研究

Study on Underpotential Deposition of Manganese by Density Functional Calculation and Cyclic Voltammetry

用密度泛函计算和循环伏安法研究了锰在金和铅表面的欠电位沉积(UPD)行为.理论计算,假设生成紧密的二维相(2D)欠电位沉积层,用基于密度泛函理论的DMol3软件计算在金与铅表面生成2D相锰层的欠电位偏移值△fE2DMe,证明锰在金表面可发生欠电位沉积,而在铅表面不能发生欠电位沉积.循环伏安实验结果与理论计算不一致:金电极析氢电位高不利于研究锰的还原沉积反应,没有发现锰的欠电位沉积现象;铅电极在MnCl2溶液中有锰的欠电位沉积现象.这种理论计算与电化学实验结果的差异,主要是因为理论计算没有考虑溶剂与阴离子特性吸附作用的影响,理论计算模型是电化学实验体系的一种理想模型.

Underpotential deposition （UPD） of manganese on gold and lead was studied by density functional calculation and cyclic voltammetry. The theoretical calculation is on the hypothesis of formation of a condensed two-dimensional （2D） phase of the UPD metal on the substrate metal （S）. Underpotential shifts △fE2DMe for manganese UPD on gold and lead were calculated by using DMol3 that is based on the density functional theory. The results show that Mn/Au is a UPD system but Mn/Pb is not a UPD system. By contraries, cyclic voltammograms （CV） show that no phenomenon of manganese UPD occurs on gold since evaluation of hydrogen easily occurs on gold, while manganese UPD occurs on lead from ammonium-chloride solution. This difference between theoretical calculation and CV experiments is likely to be due to solvent effects and/or anion adsorption which were not included in the model of the theoretical calculation.