Quantificational 4D Visualization of Industrial Electrodeposition

Abstract

Electrodeposition is a fundamental technology in modern society and has been widely used in metal plating and extraction, etc. However, extreme reaction conditions, including wide operation temperature ranges and corrosive media (molten salt/oxide systems as a particular example), inhibit direct in situ observation of the electrodeposition process. To visualize the electrode kinetics in such "black box," X-ray tomography is employed to monitor the electrochemical processes and three-dimensional (3D) evolution of morphology. Benefiting from the excellent penetration of X-ray, a non-destructive and non-contact in situ four-dimensional (4D) visualization of Ti deposition is realized. Real-time 3D reconstructed images reveal that the counterintuitive nucleation and growth process of a mesoscale Ti dendrite at both solid and liquid cathodes. According to 3D morphology evolution, unusual mechanism based on synergetic effect of the diffusion of metallic Ti and local field enhancement is achieved utilizing a simulation method based on a finite element method. This approach allows for timely and accurately regulating the electrodeposition process upon in situ monitored parameters. More importantly, the 4D technique upon operando X-ray tomography and numerical simulation can be easily applied to other electrodeposition systems, which will help deeply understand the internal kinetics and the precise optimization of the electrodeposition conditions.

A 4D x-ray computer microtomography for high-temperature electrochemistry

“…Following procedures previously described in ( 25 ), NaCl, KCl, and LiCl (99.9%) were purchased from Alfa Aesar. Anhydrous titanium tetrachloride (TiCl 4 , 99.99%) were purchased from Tokyo Chemical Industry.…”

“…The mixed electrolyte was predried under vacuum at 200°C for 48 hours. All experiments were conducted in a sealed vessel under Ar atmosphere at 500°C, and the temperature was measured by a thermocouple (protected by a steel tube) inserted into the melt ( 25 ).…”

“…Two electrode arrangement modes were developed: In the first mode, the Ti and Ni wires were used as anode and cathode, respectively, with the same initial area. In the second mode, a Ti sheet was rolled into an 8-mm-diameter cylinder as the anode, and Ni wire was the cathode ( 25 ).…”

“…The electrodes were taken out of the melt and washed with anhydrous ethanol to remove any residual electrolyte. The collected Ni electrodes were characterized by SEM (JSM-6701F, JEOL) equipped with an EDS probe (NS7, Thermo Fisher Scientific) ( 25 ).…”

“…The second 3D results were collected by scanning the electrodes after electrorefining. As an analogy, we eventually got the dynamic evolution of 3D morphology and material components of Ti anodes and Ni cathodes during electrorefining ( 25 ).…”