应用循环伏安法和计时安培法研究了铋在玻碳电极上的电结晶行为.循环伏安曲线显示了铋在玻碳电极上成核的典型特征,并表明其于玻碳电极上的电结晶是一个扩散控制过程.根据计时安培法响应曲线分析阐明了铋的浓度和过电势对成核生长机理的影响.进一步的定量测试表明该成核速率常数A和活化点密度N0随过电势增加呈现指数增大规律;扩散系数D随过电势增加呈指数衰减.以上实验结果至今未见报道.同时表明:Scharifker公式和Heerman公式均可用于本实验的理论解释.
The electrocrystallization of bismuth on glassy carbon electrodes (GCEs) from nitrate solutions was studied by cyclic voltammetry and chronoamperometry. Cyclic voltammograms exhibit a crossover between the cathodic and anodic branches, characteristic of the formation of bismuth nuclei on GCEs, and show that the bismuth electrocrystallization on GCEs is a diffusion-controlled reaction. The current transients were analyzed with the Scharifker and the Heerman equations. With the increaseof Bi~(3+)concentration, the non-dimensional plots leaned to the theoretical curve for 3D instantaneous nucleation and growth. The overpotential dependence of nucleation and growth mechanism was also found. With the increase of overpotential, the non-dimensional curve approaches closer the limit for 3D instantaneous nucleation and growth. A quantitative analysis further shows that the nucleation rate constant (A) and the number density of active sites (N_(0 )) exponentially grow with the increase of overpotential, and the diffusion coefficient (D)decays in an exponential mode, which was not reported before. A comparison between the kinetic parameter values obtained from the Scharifker equation and those from the Heerman equation was made, showing the very close N_0 and Dvalues and the distinct Avalues (especially at -300 and -350 mV). However, under the experimental conditions of this work, both of the equations can be used for describing the electrocrystallization of bismuth on GCEs.
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