High Temperature Electrochemistry IV: Session V
Sponsored by: TMS Extraction and Processing Division, TMS: Nuclear Materials Committee, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Prabhat Tripathy, Batelle Energy Alliance (Idaho National Laboratory); Guy Fredrickson, Idaho National Laboratory
Wednesday 2:00 PM
March 17, 2021
Room: RM 40
Location: TMS2021 Virtual
Session Chair: Hojong Kim, The Pennsylvania State University
2:00 PM
Advances in Solid Oxide Membrane Based Electrolysis for Solar-grade Silicon Deposition
: Michelle Sugimoto1; Haoxuan Yan1; Federico Coppo1; Adam Powell2; Uday Pal1; 1Boston University; 2Worchester Polytechnic Institute
Currently, photovoltaic (PV) cells, which utilize available solar energy with zero end-user emissions, are dominated by polycrystalline silicon designs. The cost of PV has dropped drastically in the last several decades. However, the current solar-grade Si production process is highly energy and cost intensive, and is not easily scaled up. In this work, an alternate production route, akin to the Hall-Héroult process used for aluminum production, has been developed. Here, we present a high-temperature, molten oxide-fluoride bath electrolysis cell capable of depositing a planar layer of Si starting from abundantly sourced silica onto a Si wafer cathode. An optimized alternating square wave signal was developed and applied across the cell in order to periodically redissolve any dendritic growth back into the molten salt. This ensured a uniform, planar deposition of Si. Finally, an optimized rare-earth nickelate anode was developed, removing costly and/or volatile precious metals from the system.
2:30 PM
Feasibility of Potentiometry for Monitoring Activity of GdCl3 in Molten LiCl-KCl Salt: Guoping Cao1; Steven Herrmann1; Guy Fredrickson1; Robert Hoover1; Kevin Tolman1; 1Idaho National Laboratory
In pyroprocessing spent nuclear fuels by electrorefining in LiCl-KCl salt, it is desired to monitor the UCl3 concentration for safeguard purposes. A potentiometry approach was evaluated herein for real time monitoring of GdCl3, a surrogate for UCl3, in LiCl-KCl salt, using a Gd metal electrode and a Ag/AgCl reference electrode (RE). The open circuit potential (OCP) of a Gd metal electrode versus the Ag/AgCl RE was measured, while GdCl3 salt was incrementally added into the LiCl-KCl salt, followed by additions of LaCl3, CeCl3 and NdCl3. It was shown that (1) the potentiometry measurement using Gd metal and Ag/AgCl RE can be used to measure the GdCl3 concentration in the tested 0.05--1.7 mol% GdCl3 range and (2) the addition of a small amount of LaCl3 and CeCl3 did not affect the activity of GdCl3 in the LiCl-KCl-GdCl3 salt system, but the addition of NdCl3 did affect potentiometry measurements of LiCl-KCl-GdCl3.
3:00 PM
First-principles Molecular Dynamics and CALPHAD Modeling of the CaF2-MgF2-SiO2 Molten Salt System: Yifan Zhang1; Uday Pal2; Adam Powell1; Michael Gao3; Yu Zhong1; 1Worcester Polytechnic Institute; 2Boston University; 3National Energy Technology Laboratory
In order to study the transport properties of ions and phase transformations in CaF2-MgF2-SiO2 molten salt system, this work provides extensive simulations from both molecular dynamics and CALPHAD approaches. The local structures, ionic self-diffusion coefficients, and viscosity of this system are investigated by classical interatomic potential molecular dynamics (IPMD) and first-principles molecular dynamics (FPMD). In addition, the thermodynamic database of CaF2-MgF2-SiO2 molten salt system is also established by using the CALPHAD approach and phase diagrams are predicted at different temperatures. All calculated properties are compared with experimental data from existing literature.