Electrochemical Behavior of Tetraethylammonium-Hydrogen Sulfate-Based Electrodissolution-Coupled Hafnium Alkoxide Synthesis

Currently, the conventional halide synthesis method of preparing hafnium alkoxides [Hf(OR) 4 , R is an alkyl] has problems of inefficiency, a heavy CO 2 emission footprint, and substantial solid and gas waste, which severely hinders its wide deployment. Herein, we propose an electrodissolution-coupled Hf(OR) 4 synthesis system using an alcohol solvent and Hf metal as feedstock for the efficient, low-carbon and waste-free electro-synthesis of Hf(OR) 4 . The electrochemical behavior of the tetraethylammonium-hydrogen sulfate (Et 4 NHSO 4 )-based EHS process is investigated by cyclic voltammetry, linear sweep voltammetry, Tafel, and electrochemical impedance spectroscopy, complemented with SEM observation. The anodic hafnium dissolution/corrosion occurs inside the passive film while the cathodic ethanol dehydrogenation occurs in a two-stage pathway. Tafel extrapolation and numerical fitting analysis acquires important kinetics parameters, such as corrosion current density, exchange current density, and apparent activation energy as well as solution, polarization and “Warburg” resistances, etc. This work can provide theoretical guidance for the efficient operation of EHS.