Kosov Alexander V, Grishenkova Olga V, Semerikova Olga L, Vakarin Sergey V, Zaikov Yuriy P
Institute of High Temperature Electrochemistry, Ural Branch of the Russian Academy of Sciences, Yekaterinburg 620990, Russia.
Materials (Basel). 2023 Nov 17;16(22):7207. doi: 10.3390/ma16227207.
A comprehensive study concerning the phase formation mechanism and growth/dissolution kinetics of sodium tungsten bronze crystals during the electrolysis of a 0.8NaWO-0.2WO melt was carried out. The regularities of deposit formation on a Pt(111) working electrode were investigated experimentally using cyclic voltammetry, chronoamperometry, scanning electron microscopy, and X-ray diffraction analysis. Models have been developed to calculate the current response during the formation, growth and dissolution of a two-phase deposit consisting of NaWO and metallic tungsten or two oxide tungsten bronzes with different sodium content. These models consider mass transfer to the electrode and nuclei; chemical and electrochemical reactions with the participation of polytungstate ions, Na, Na, and O; as well as the ohmic drop effect. The approach was proposed to describe the dissolution of an NaWO crystal with a nonuniform sodium distribution. The fitting of cyclic voltammograms was performed using the Levenberg-Marquardt algorithm. The NaWO formation/growth/dissolution mechanism was determined. Concentration profiles and diffusion coefficients of [WO], reaction rate constants, number density of nuclei, and time dependencies of crystal size were calculated. The proposed approaches and models can be used in other systems for the cyclic voltammogram analysis and study of the mechanism and kinetics of electrode processes complicated by phase formation; parallel and sequential electrochemical and chemical reactions; as well as the formation of a deposit characterized by a nonuniform phase and/or chemical composition.
对0.8NaWO-0.2WO熔体电解过程中钠钨青铜晶体的相形成机制及生长/溶解动力学进行了全面研究。使用循环伏安法、计时电流法、扫描电子显微镜和X射线衍射分析等实验方法研究了Pt(111)工作电极上沉积物形成的规律。已开发出模型来计算由NaWO和金属钨或两种钠含量不同的氧化钨青铜组成的两相沉积物形成、生长和溶解过程中的电流响应。这些模型考虑了向电极和晶核的传质；多钨酸根离子、Na、Na和O参与的化学和电化学反应；以及欧姆降效应。提出了描述钠分布不均匀的NaWO晶体溶解的方法。使用Levenberg-Marquardt算法对循环伏安图进行拟合。确定了NaWO的形成/生长/溶解机制。计算了[WO]的浓度分布和扩散系数、反应速率常数、晶核数密度以及晶体尺寸的时间依赖性。所提出的方法和模型可用于其他系统，用于循环伏安图分析以及研究因相形成、平行和顺序的电化学和化学反应以及形成具有不均匀相和/或化学成分的沉积物而复杂化的电极过程的机制和动力学。
