Electrochemical mechanism and kinetics of electrodissolution-coupled hafnium alkoxide synthesis in tetraethylammonium-chloride-based anhydrous system

Electrodissolution-coupled hafnium alkoxide synthesis (EHS) is a promising pathway for efficient electro- synthesis. It employs simultaneous heterogeneous reactions of Hf dissolution and ethanol dehydrogenation, and spontaneous solution-based combination reaction between Hf4+ cations and alkoxy anions. To elucidate the mechanism and kinetics of EHS process, the electrochemical behaviors of anodic Hf dissolution and cathodic ethanol dehydrogenation were explored through electrochemical measurements, SEM observations, gas chromatography, and micro-kinetics modeling. The results indicated the supporting electrolytes of tetraethylammonium chloride (Et4NCl) to be preferable, which facilitated a passive-film-punctured pitting mechanism for Hf dissolution and a two-stage dehydrogenation mechanism. Three indicators related to passive rate, sensitivity towards puncture of the passive film, and pitting rate were extracted to quantify the kinetics of passive puncture and Hf corrosion. Micro-kinetics models were developed to evaluate the Et4NCl-based EHS process, which achieved electric energy requirements of 1.53–1.83 kW·h/kg Hf(OC2H5)4.