非化学计量的混合价态氧化钼(Ⅵ,Ⅴ)修饰微电极的电化学制备

Electrochemical Preparation of Microelectrodes Modified with Non-Stoichiometric Mixed-Valent Molybdenum Oxides

在新鲜配制的Na_2MoO_4的弱酸性水溶液中,通过循环电位扫描在碳纤维微电极表面可沉积一层均匀的蓝色氧化钼(VI,V)薄膜,膜的厚度通过电量进行控制.在电沉积之前,电极的阳极化处理不仅可以加快氧化钼的电沉积,而且可以改善膜的伏安行为.溶液的pH值对膜的电沉积和伏安行为有极大的影响.膜的阴极过程被认为是产生青钼铜:H_xMoO_3(0<x<2),或次化学计量的较低氧化钼MoO_(3-y)(0<y<1);阳极过程是青钼铜/Mo(V)中心[或可能是膜中进一步被还原的Mo(IV)]可逆氧化到Mo(VI).通过X射线光电子能谱和扫描电镜获得膜的组成及价态.

A compact non - stoichiometric molybdenum (VI, V) oxide of blue film was grown on carbon fiber (CF) microelectrode surface by cycling the potential between + 0. 2V and - 0.70V ina freshly prepared Na2MoO4 solution containing 5 × 10-3mol/L H2SO4. The quantity of the oxide is controlled by the charge passing the electrode. The electrochemical pretreatment of CF microelectrode not only raises the deposition velocity of molybdenum oxide on CF surface, but also improves greatly the cyclic voltammetric behavior of the molybdenum oxide film prior to the electrodeposition. The cathodic processes are believed to yield the hydrogen molybdenum oxide bronzes, HxMoO3(0< x < 2), or substoichiometric lower molybdenum oxides with the formula MoO3-y(0 <y< 1). The anodic response results from the reversible oxidation of molybdenum bronze/Mo(V) centers [or perhaps Mo(IV) in more reduced coatings], to Mo(VI). Further information was gained about the chemical composition and valent state of Mo from XPS and SEM.