Deep potential molecular dynamic and electrochemical experiments to reveal the structure and behavior of Mn(II) in magnesium electrolysis

Abstract

Magnesium (Mg) production via electrolysis can offer an efficient and sustainable alternative to conventional metallothermic processes. However, electrolytic systems contain impurities like manganese (Mn) that significantly influence efficiency and product quality. This study investigates the local structure of Mn²⁺ and the intricate electrochemical behavior of Mn(II) within MgCl₂-NaCl-KCl melts, aiming to explore its impacts on electrode kinetics. Deep Potential Molecular Dynamics (DPMD) method is applied for structure introduction, and a strange chloride layer around Mn²⁺ is observed. Furthermore, cyclic voltammetry, chronopotentiometry, and other techniques are employed for study using tungsten electrodes with introduced MnCl₂. Results reveal the quasi-reversible reduction of Mn(II) on tungsten. The diffusion coefficients (D) of Mn(II) at different temperatures are summarized, and an activation energy of 30.60 kJ·mol^-1 for diffusion is found. Mn electrodeposition follows instantaneous nucleation. While limited in scope, these findings provide important insights into Mn(II) interactions that could inform efforts to optimize Mg electrolysis. Further research on Mn(II) effects on melt structure is still needed to understand electrolytic systems comprehensively. This work significantly furthers the fundamental comprehension of Mn(II) electrochemistry within industrial Mg production.