Abstract
Enhancing the solar energy storage and power delivery afforded by emerging molten salt-based technologies requires a fundamental understanding of the complex interplay between structure and dynamics of the ions in the high-temperature media. Here we report results from a comprehensive study integrating synchrotron X-ray scattering experiments, ab initio molecular dynamics simulations and rate theory concepts to investigate the behavior of dilute Cr3+ metal ions in a molten KCl–MgCl2 salt. Our analysis of experimental results assisted by a hybrid transition state-Marcus theory model reveals unexpected clustering of chromium species leading to the formation of persistent octahedral Cr–Cr dimers in the high-temperature low Cr3+ concentration melt. Furthermore, our integrated approach shows that dynamical processes in the molten salt system are primarily governed by the charge density of the constituent ions, with Cr3+ exhibiting the slowest short-time dynamics. These findings challenge several assumptions regarding specific ionic interactions and transport in molten salts, where aggregation of dilute species is not statistically expected, particularly at high temperature.
Highlights
Simple inorganic molten salts have emerged as important media for the development of modern concentrating solar power (CSP) plants and next-generation molten salt nuclear reactors (MSRs) having signi cant potential to provide sustainable, carbon-free energy for the future.[1,2,3,4] Among different salt formulations, mixtures of potassium chloride (KCl) and magnesium chloride (MgCl2) hold special promise for these technologies, owing to their stability under hightemperature regimes and their exceptional thermal characteristics.[5,6,7,8,9] In addition, chloride salts are abundant and relatively inexpensive
X-ray absorption spectroscopy (XAS) is a powerful tool to investigate metal ion speciation,[15,16,17,18] but provides reliable information only about the rst coordination sphere, and recent XAS experiments were unable to determine the local structure of Cr3+ in a KCl–MgCl2 molten salt mixture at the high temperatures (>973 K)[19] that are relevant to technological processes in CSP and MSR applications
The dynamic structural behaviour of dilute Cr3+ species in a high-temperature ionic chloride medium was investigated by means of high-energy X-ray scattering and ab initio molecular dynamics (AIMD) simulations
Summary
Simple inorganic molten salts have emerged as important media for the development of modern concentrating solar power (CSP) plants and next-generation molten salt nuclear reactors (MSRs) having signi cant potential to provide sustainable, carbon-free energy for the future.[1,2,3,4] Among different salt formulations, mixtures of potassium chloride (KCl) and magnesium chloride (MgCl2) hold special promise for these technologies, owing to their stability under hightemperature regimes and their exceptional thermal characteristics.[5,6,7,8,9] In addition, chloride salts are abundant and relatively inexpensive. We demonstrate a highly integrated approach combining theory, simulations and high-energy synchrotron Xray scattering experiments to elucidate the atomic-scale structure and dynamics of dilute Cr3+ species in the KCl–MgCl2 molten salt at 1073 K.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
