Anodic Behavior of Hafnium in Anhydrous Electrodissolution-Coupled Hafnium Alkoxide Synthesis

Abstract

The electrodissolution-coupled hafnium alkoxide (Hf(OR)4, R is alkyl) synthesis (EHS) system, which has significant environmental and economic advantages over conventional thermal methods, serves as a promising system for green and efficient Hf(OR)4 electro-synthesis. The EHS system is operated based on the simultaneous heterogeneous reactions of hafnium dissolution and ethanol dehydrogenation, as well as the spontaneous solution-based reaction of Hf4+ and OR−. Employing green ethanol and Hf as feedstocks, the anodic hafnium corrosion/dissolution electrochemical behavior of the Et4NCl or Et4NHSO4 based anhydrous system was investigated through electrochemical measurements combined with SEM observations. The results demonstrated that the Et4NCl-based anhydrous ethanol system exhibited an efficient mechanism of passive film pitting corrosion breakdown and metal hafnium dissolution, while the Et4NHSO4-based anhydrous ethanol system reflected the weak corrosion mechanism of the anodic hafnium under the passive film. The polarization resistance of the Et4NCl system was dramatically lower than that of the Et4NHSO4 system, which indicated that the Et4NCl system had superior anodic hafnium corrosion performance compared to the Et4NHSO4 system. Overall, the investigation of the electrochemical behaviors of anodic hafnium corrosion/dissolution provides theoretical guidance for the efficient operation of EHS electrolysis.