Operando probing and adjusting of the complicated electrode process of multivalent metals at extreme temperature

A Deep Insight into the Microscopic Dynamics of the Electrode-Electrolyte Interface under Extreme Operating Conditions

Understanding the interfacial dynamics during operation is critical for electrochemistry to make great advancements. However, breakthroughs on this topic under extreme conditions are very scarce. Here, as an example, we employ operando Raman spectroscopy to decode the interfacial dynamics of titanium electrolysis using a tailored instrument. Direct spectral evidence not only confirms the two-step reduction pathway and the key intermediate (TiF52-) in molten fluorides with high-temperature and strong-corrosion conditions but also unravels the origins of the undesirable shuttling effect of TiF52-, which are the sluggish reduction kinetics and outward diffusion behavior of TiF52-. Moreover, an insightful atomic scenario of the electric double layer (EDL) under varied potentials has been established. These quantitative understandings guide us to design economical-feasible regulation protocols─the rational combination of a high-concentration, low-valence Ti-ion electrolyte with appropriate applied potential. Impressively, the current efficiency is greatly promoted from 27.7 to 81.8% using our proposed protocols. Finally, this work also demonstrates a bottom-up technological research paradigm for extreme electrochemistry based on mechanism insights rather than phenomenological findings, which will accelerate the advancement of extreme electrochemistry.

Effect of electric fields on tungsten distribution in Na2WO4-WO3 molten salt

Tungsten coatings have unique properties such as high melting points and hardness and are widely used in the nuclear fusion and aviation fields. In experiments, compared to pure Na2WO4 molten salt, electrolysis with Na2WO4-WO3 molten salt results in a lower deposition voltage. Herein, an investigation combining experimental and computational approaches was conducted, involving molecular dynamics simulations with deep learning, high-temperature in situ Raman spectroscopy and activation strain model analysis. The results indicated that the molten salt system's behaviour, influenced by migration and polarization effects, led to increased formation of Na2W2O7 in the Na2WO4-WO3 molten salt, which has a lower decomposition voltage and subsequently accelerated the cathodic deposition of tungsten. We analyzed the mechanism of the effect of the electric field on the Na2W2O7 structure based on the bond strength and electron density. This research provides crucial theoretical support for the effect of electric field on tungsten in molten salt and demonstrates the feasibility of using machine learning-based DPMD methods in simulating tungsten-containing molten salt systems.