Molten-Salt Electrochemical-Assisted Synthesis of the CeO2-OV@GC Composite-Supported Pt Clusters with a Pt-O-Ce Structure for the Oxygen Reduction Reaction.

Highly active and robust Pt-based electrocatalysts for an oxygen reduction reaction (ORR) are of crucial significance for the development of proton exchange membrane fuel cells (PEMFCs). Herein, the high-loading and well-dispersive Pt clusters on graphitic carbon-supported CeO2 with abundant oxygen vacancies (PtAC/CeO2-OV@GC) were successfully fabricated by a molten-salt electrochemical-assisted method. The bonding of Pt with the highly electronegative O induces charge redistribution through the Pt-O-Ce structure, thus reducing the adsorption energies of oxygen-containing species. Such a PtAC/CeO2-OV@GC electrocatalyst exhibits a greatly enhanced ORR performance with a mass activity of 0.41 ± 0.02 A·mg-1Pt at 0.9 V versus a reversible hydrogen electrode, which is 2.7 times the value of a commercial Pt/C catalyst and shows negligible activity decay after 20000 cycles of accelerated degradation tests. It is anticipated that this work will provide enlightening guidance on the controllable synthesis and rational design of high-performance Pt-based electrocatalysts for PEMFCs.

One-Step Molten-Salt-Assisted Approach for Direct Preparation and Regeneration of LiNi0.6Co0.2Mn0.2O2 Cathode.

Single-crystal lithium-nickel-manganese-cobalt-oxide (SC-NMC) is attracting increasing attention due to its excellent structural stability. However, its practical production faces challenges associated with complex precursor preparation processes and severe lithium-nickel cation mixing at high temperatures, which restricts its widespread application. Here, a molten-salt-assisted method is proposed using low-melting-point carbonates. This method obviates the necessity for precursor processes and simplified the synthetic procedure for SC-NMC down to a single isothermal sintering step. Multiple characterizations indicate that the acquired SC-LiNi0.6Mn0.2Co0.2O2 (SC-622) exhibits favorable structural capability against intra-granular fracture and suppressive Li+/Ni2+ cation mixing. Consequently, the SC-622 exhibits superior electrochemical performance with a high initial specific capacity (174 mAh g-1 at 0.1 C, 3.0-4.3 V) and excellent capacity retention (87.5% after 300 cycles at 1C). Moreover, this molten-salt-assisted method exhibits its effectiveness in directly regenerating SC-622 from spent NMC materials. The recovered material delivered a capacity of 125.4 mAh g-1 and retained 99.4% of the initial capacity after 250 cycles at 1 C. This work highlights the importance of understanding the process-structure-property relationships and can broadly guide the synthesis of other SC Ni-rich cathode materials.

Intercalation of Metal into Transition Metal Dichalcogenides in Molten Salts.

Van der Waals (vdW)-layered materials have drawn tremendous interests due to their unique properties. Atom intercalation in the vdW gap of layered materials can tune their electronic structure and generate unexpected properties. Here a chemical-scissor-mediated method that enables metal intercalation into transition metal dichalcogenides (TMDCs) in molten salts is reported. By using this approach, various guest metal atoms (Mn, Fe, Co, Ni, Cu, and Ag) are intercalated into various TMDC hosts (such as TiS2 , NbS2 , TaS2 , TiSe2 , NbSe2 , TaSe2 , and Ti0.5 V0.5 S2 ). The structure of the intercalated compound and intercalation mechanism are investigated. The results indicate that the vdW gap and valence state of TMDCs can be modified through metal intercalation, and the intercalation behavior is dictated by the electron work function. The adjustable charge transfer and intercalation endow a channel for rapid mass transfer to enhance the electrochemical performances. Such a chemical-scissor-mediated intercalation provides an approach to tune the physical and chemical properties of TMDCs, which may open an avenue in functional application ranging from energy conversion to electronics.

Self-Assembly of Silicon Nanotubes Driven by a Biphasic Transition from the Natural Mineral Montmorillonite in Molten Salt Electrolysis.

Silicon nanotubes (SNTs) have been considered as promising anode materials for lithium-ion batteries (LIBs). However, the reported strategies for preparing SNTs generally have special requirements for either expensive templates or complex catalysts. It is necessary to explore a cost-effective and efficient approach for the preparation of high-performance SNTs. In this work, a biphasic transformation strategy involving "solid-state reduction" and "dissolution-deposition" in molten salts is developed to prepare SNTs using montmorillonite as a precursor. The rod-like intermediate of silicon-aluminum-calcium is initially reduced in solid state, which then triggers the continuous dissolution and deposition of calcium silicate in the inner space of the intermediate to form a hollow structure during the subsequent reduction process. The transition from solid to liquid is crucial for improving the kinetics of deoxygenation and induces the self-assembly of SNTs during electrolysis. When the obtained SNTs is used as anode materials for LIBs, they exhibit a high capacity of 2791 mAh g-1 at 0.2 A g-1, excellent rate capability of 1427 mA h g-1 at 2 A g-1, and stable cycling performance with a capacity of 2045 mAh g-1 after 200 cycles at 0.5 A g-1. This work provides a self-assembling, controllable, and cost-effective approach for fabricating SNTs.

High-Index NiO Particle Synthesis in Alkali Chloride Salts: Nonclassical Crystallization Pathways and Thermally-Induced Surface Restructuring.

The formation mechanism(s) of high-index facets in metal oxides is not widely understood but remains a topic of interest owing to the challenges of stabilizing high-energy surfaces. These metal oxide crystal surfaces are expected to provide unique physicochemical characteristics; therefore, understanding crystallization pathways may enable the rational design of materials with controlled properties. Here the crystallization of NiO via thermal decomposition of a nickel source in excess of alkali chlorides is examined, focusing on KCl, which produces trapezohedral NiO (311) particles that are difficult to achieve through alternative methods. Trapezohedral NiO crystals are confirmed to grow via a molten eutectic where NiO nucleation is followed by nonclassical crystallization through processes resembling colloidal assembly. Aggregates comprised of NiO nanocrystals form mesostructures that ripen with heating time and exhibit fewer grain boundaries as they transition into single-crystalline particles. At temperatures higher than those of NiO crystallization, there is a restructuring of (311) facets into microfacets exposing (111) and (100) surfaces. These findings illustrate the complex crystallization processes taking place during molten salt synthesis. The ability to generate metal oxide particles with high-index facets has the potential to be a more generalized approach to unlock the physicochemical properties of materials for diverse applications.

Spatially confined synthesis of large-sized MoS2nanosheets in molten KSCN toward efficient hydrogen evolution.

Low-temperature KSCN molten salt is a promising technique to synthesize defect-rich MoS2catalysts for hydrogen evolution reaction (HER). However, owing to the fast ion diffusion rate for rapid crystal growth, the resultant catalysts show a morphology of microsphere, which aggregates from MoS2nanosheets, to suppress the catalytic performance. In this work, large-sized few-layer MoS2nanosheets are synthesized via a spatial confinement strategy by adding inert NaCl into the KSCN molten salt. With the NaCl spacer to physically block the long-distance ion diffusion and isolate the chemical reaction, the MoS2nucleation and subsequent crystal growth could be controlled, guiding the nanosheets to grow along the narrow gap between the NaCl crystals to avoid aggregation. As a result, ultrathin MoS2nanosheets with a large geometry size are constructed. Profiting from the architecture to expose active sites and boost charge transfer kinetics, the large-sized few-layer MoS2nanosheets exhibit an impressive HER performance, showing a smallη10of 160 mV and a low Tafel slope of 53 mV dec-1with excellent stability. This work provides not only an efficient HER catalyst but also a facile spatial confinement technique to design and synthesize a large spectrum of transition metal sulfides for broad uses.

Preparation and properties of two-dimensional Ti2CTxMXene based on electroetching method.

The continuous advancements in wearable electronics have drawn significant attention toward 2D MXenes materials for energy storage owing to their abundant availability, adaptability, and distinctive physicochemical properties. Two unresolved concerns currently revolve around environmental pollution by F-containing etching and finite kinetics caused because of re-stacking of nanosheets. In this study, Al was electrochemically etched from porous Ti2AlC electrodes without the use of fluorine, through a selective electrochemical etching process in dilute hydrochloric acid. Subsequently, Ti2CTxMXene was vertically grown on carbon fiber (CF) substrates. The resulting Ti2CTx@CF electrodes are lightweight, thin, and flexible, exhibiting a surface capacitance of 330 mF cm-2at a constant current density of 1 mA cm-2after 2000 cycles. They display a surface capacitance retention of 96.16% and a high energy density of 45.3µWh cm-2at a power density of 0.497 mW cm-2. These metrics underscore the Ti2CTx@CF electrode's commendable multifunctionality, electrochemical performance, ion transport efficiency, and charge storage capacity. Moreover, a flexible energy storage electrode material with a high area capacity was developed by combining Ti2CTxMXene nanosheets, possessing a large specific surface area, with a flexible carbon fabric substrate.

Spontaneous formation of multilayer refractory carbide coatings in a molten salt media.

Refractory materials hold great promise to develop functional multilayer coating for extreme environments and temperature applications but require high temperature and complex synthesis to overcome their strong atomic bonding and form a multilayer structure. Here, a spontaneous reaction producing sophisticated multilayer refractory carbide coatings on carbon fiber (CF) is reported. This approach utilizes a relatively low-temperature (950 °C) molten-salt process for forming refractory carbides. The reaction of titanium (Ti), chromium (Cr), and CF yields a complex, high-quality multilayer carbide coating composed of 1) Cr carbide (Cr3C2), 2) Ti carbide, and 3) Cr3C2 layers. The layered sequence arises from a difference in metal dissolutions, reactions, and diffusion rates in the salt media. The multilayer-coated CFs act as a permeable oxidation barrier with no crystalline degradation of the CFs after extreme temperature (1,200 °C) and environment (oxyacetylene flame) exposure. The synthesis of high-quality multilayer refractory coating in a fast, efficient, easy, and clean manner may answer the need for industrial applications that develop cheap and reliable extreme environment protection barriers.

A Highly Selective Acetone Sensor Based on Coal-Based Carbon/MoO2 Nanohybrid Material.

High temperature represents a critical constraint in the development of gas sensors. Therefore, investigating gas sensors operating at room temperature holds significant practical importance. In this study, coal-based porous carbon (C-700) and coal-based C/MoO2 nanohybrid materials were synthesized using a simple one-step vapor deposition and sintering method, and their gas-sensing performance was investigated. The gas-sensing performance for several VOC gases (phenol, ethyl acetate, ethanol, acetone, triethylamine, and toluene) and a 95% RH high-humidity environment were tested. The results indicated that the C/MoO2-450 sample sintered at 450 °C exhibited excellent specific selectivity towards acetone at room temperature, with a response value of 4153.09% and response/recovery times of 10.8 s and 2.9 s, respectively. Furthermore, the C/MoO2-450 sample also demonstrated good repeatability and long-term stability. The sensing mechanism of the synthesized materials was also explored. The superior gas-sensing performance can be attributed to the synergistic effect between the porous carbon and MoO2 nanoparticles. Given the importance of enhancing the high-tech and high-value-added utilization of coal, this study provides a viable approach for utilizing coal-based carbon materials in detecting volatile organic compounds at room temperature.

Loading of Single Atoms of Iron, Cobalt, or Nickel to Enhance the Electrocatalytic Hydrogen Evolution Reaction of Two-Dimensional Titanium Carbide.

The rational design of advanced electrocatalysts at the molecular or atomic level is important for improving the performance of hydrogen evolution reactions (HERs) and replacing precious metal catalysts. In this study, we describe the fabrication of electrocatalysts based on Fe, Co, or Ni single atoms supported on titanium carbide (TiC) using the molten salt method, i.e., TiC-FeSA, TiC-CoSA, or TiC-NiSA, to enhance HER performance. The introduction of uniformly distributed transition-metal single atoms successfully reduces the overpotential of HERs. Overpotentials of TiC-FeSA at 10 mA cm-2 are 123.4 mV with 61.1 mV dec-1 Tafel slope under acidic conditions and 184.2 mV with 85.1 mV dec-1 Tafel slope under alkaline conditions, which are superior to TiC-NiSA and TiC-CoSA. TiC samples loaded with transition-metal single atoms exhibit high catalytic activity and long stability under acidic and basic conditions. Density functional theory calculations indicate that the introduction of transition-metal single atoms effectively reduces the HER barrier of TiC-based electrocatalysts.

Regulating Spin Polarization via Axial Nitrogen Traction at Fe-N5 Sites Enhanced Electrocatalytic CO2 Reduction for Zn-CO2 Batteries.

Single Fe sites have been explored as promising catalysts for the CO2 reduction reaction to value-added CO. Herein, we introduce a novel molten salt synthesis strategy for developing axial nitrogen-coordinated Fe-N5 sites on ultrathin defect-rich carbon nanosheets, aiming to modulate the reaction pathway precisely. This distinctive architecture weakens the spin polarization at the Fe sites, promoting a dynamic equilibrium of activated intermediates and facilitating the balance between *COOH formation and *CO desorption at the active Fe site. Notably, the synthesized FeN5, supported on defect-rich in nitrogen-doped carbon (FeN5@DNC), exhibits superior performance in CO2RR, achieving a Faraday efficiency of 99% for CO production (-0.4 V vs. RHE) in an H-cell, and maintaining a Faraday efficiency of 98% at a current density of 270 mA cm-2 (-1.0 V vs. RHE) in the flow cell. Furthermore, the FeN5@DNC catalyst is assembled as a reversible Zn-CO2 battery with a cycle durability of 24 hours. In-situ IR spectroscopy and density functional theory (DFT) calculations reveal that the axial N coordination traction induces a transformation in the crystal field and local symmetry, therefore weakening the spin polarization of the central Fe atom and lowering the energy barrier for *CO desorption.

Tailoring Oxygen-Depleted and Unitary Ti3C2Tx Surface Terminals by Molten Salt Electrochemical Etching Enables Dendrite-Free Stable Zn Metal Anode.

Two-dimensional Ti3C2Tx MXene materials, with metal-like conductivities and versatile terminals, have been considered to be promising surface modification materials for Zn-metal-based aqueous batteries (ZABs). However, the oxygen-rich and hybridized terminations caused by conventional methods limit their advantages in inhibiting zinc dendrite growth and reducing corrosion-related side reactions. Herein, -O-depleted, -Cl-terminated Ti3C2Tx was precisely fabricated by the molten salt electrochemical etching of Ti3AlC2, and controlled in situ terminal replacement from -Cl to unitary -S or -Se was achieved. The as-prepared -O-depleted and unitary-terminal Ti3C2Tx as Zn anode coatings provided excellent hydrophobicity and enriched zinc-ionophilic sites, facilitating Zn2+ horizontal transport for homogeneous deposition and effectively suppressing water-induced side reactions. The as-assembled Ti3C2Sx@Zn symmetric cell achieved a cycle life of up to 4200 h at a current density and areal capacity of 2 mA cm-2 and 1 mAh cm-2, respectively, with an impressive cumulative capacity of up to 7.25 Ah cm-2 at 5 mA cm-2//2 mAh cm-2. These findings provide an effective electrochemical strategy for tailoring -O-depleted and unitary Ti3C2Tx surface terminals and advancing the understanding of the role of specific Ti3C2Tx surface chemistry in regulating the plating/stripping behaviors of metal ions.

High-Performance Li-CO2 Battery Based on Carbon-Free Porous Ru@QNFs Cathode.

Lithium-carbon dioxide (Li-CO2 ) batteries have attracted much attention due to their high theoretical energy density. However, due to the existance of lithium carbonate and amorphous carbon in the discharge products that are difficult to decompose, the battery shows low coulombic efficiency and poor cycle performance. Here, by adjusting the adsorption of carbon dioxide (CO2 ) on ruthenium (Ru) catalysts surface, this work reports an ultralow charge overpotential and long cycle life Li-CO2 battery that consists of typical lithium metal, ternary molten salt electrolyte (TMSE), and Ru-based cathode. Experimental results show that the Ru catalysts deposited on quartz nanofiber (QF) can suppress the four-electron conversion of CO2 to lithium carbonate (Li2 CO3 ). As a result, the battery shows a long-cycle-life of over 457 cycles at 1.0 A g-1 with a limited capacity of 500 mAh g-1 Ru . Remarkably, a recorded low discharge potential of ≈3.0 V has been achieved after 35 cycles at 0.5 A g-1 , with a charge potential retention of over 99%. Moreover, the battery can operate over 25 A g-1 and recover 96% potential. This battery technology paves the way for designing high-performance rechargeable Li-CO2 batteries with carbon neutrality.

Functional Tailoring of Multi-Dimensional Pure MXene Nanostructures for Significantly Accelerated Electromagnetic Wave Absorption.

Transition metal carbide (Ti3 C2 Tx MXene), with a large specific surface area and abundant surface functional groups, is a promising candidate in the family of electromagnetic wave (EMW) absorption. However, the high conductivity of MXene limits its EMW absorption ability, so it remains a challenge to obtain outstanding EMW attenuation ability in pure MXene. Herein, by integrating HF etching, KOH shearing, and high-temperature molten salt strategies, layered MXene (L-MXene), network-like MXene nanoribbons (N-MXene NRs), porous MXene monolayer (P-MXene ML), and porous MXene layer (P-MXene L) are rationally constructed with favorable microstructures and surface states for EMW absorption. HF, KOH, and KCl/LiCl are used to functionalize MXene to tune its microstructure and surface state (F- , OH- , and Cl- terminals), thereby improving the EMW absorption capacity of MXene-based nanostructures. Impressively, with the unique structure, proper electrical conductivity, large specific surface area, and abundant porous defects, MXene-based nanostructures achieve good impedance matching, dipole polarization, and conduction loss, thus inheriting excellent EMW absorption performance. Consequently, L-MXene, N-MXene NRs, P-MXene ML, and P-MXene L enable a reflection loss (RL ) value of -43.14, -63.01, -60.45, and -56.50 dB with a matching thickness of 0.95, 1.51, 3.83, and 4.65 mm, respectively.

Unveiling Superior Capacitive Behaviors of One-Pot Molten Salt-Engineered B, N Co-Doped Porous Carbon Sheets.

Heteroatom-doped porous carbon materials with distinctive surface properties and capacitive behavior have been accepted as promising candidates for supercapacitor electrodes. Currently, the researches mainly focus on developing facile synthetic method and unveiling the structure-activity relationship to further elevate their capacitive performance. Here, the B, N co-doped porous carbon sheet (BN-PCS) is constructed by one-pot pyrolysis of agar in KCl/KHCO3 molten salt system. In this process, the urea acts as directing agent to guide the formation of 2D sheet morphology, and the decomposition of KHCO3 and boric acid creates rich micro- and mesopores in the carbon framework. The specific capacitance of optimized BN-PCS reaches 361.1 F g-1 at a current density of 0.5 A g-1 in an aqueous KOH electrolyte. Impressively, the fabricated symmetrical supercapacitor affords a maximum energy density of 43.5 Wh kg-1 at the power density of 375.0 W kg-1 in 1.0 mol L-1 TEABF4 /AN electrolyte. It also achieves excellent long-term stability with capacitance retention of 91.1% and Columbic efficiency of 100% over 10 000 cycles. This study indicates one-pot molten salt method is effective in engineering advanced carbon materials for high-performance energy storage devices.

Molten-Salt Electrochemical Preparation of Co2 B/MoB2 Heterostructured Nanoclusters for Boosted pH-Universal Hydrogen Evolution.

Boosting the hydrogen evolution reaction (HER) activity of α-MoB2 at large current densities and in pH-universal medium is significant for efficient hydrogen production. In this work, Co2 B/MoB2 heterostructured nanoclusters are prepared by molten-salt electrolysis (MSE) and then used as a HER catalyst. The composition, structure, and morphology of Co2 B/MoB2 can be modulated by altering the stoichiometries of raw materials and synthesis temperatures. Impressively, the obtained Co2 B/MoB2 at optimized conditions exhibits a low overpotential of 297 and 304 mV at 500 mA cm-2 in 0.5 m H2 SO4 and 1 m KOH, respectively. Moreover, the Co2 B/MoB2 catalyst possesses a long-term catalytic stability of over 190 h in both acidic and alkaline medium. The excellent HER performance is due to the modified electronic structure at the Co2 B/MoB2 heterointerface where electrons are accumulated at the Mo sites to strengthen the H adsorption. Density functional theory (DFT) calculations reveal that the formation of the Co2 B/MoB2 heterointerface decreases the H adsorption and H2 O dissociation free energies, contributing to the boosted HER intrinsic catalytic activity of Co2 B/MoB2 . Overall, this work provides an experimental and theoretical paradigm for the design of efficient pH-universal boride heterostructure electrocatalysts.

Molten-Salt Electrochemical Deoxidation Synthesis of Platinum-Neodymium Nanoalloy Catalysts for Oxygen Reduction Reaction.

Platinum-rare earth metal (Pt-RE) nanoalloys are regarded as a potential high performance oxygen reduction reaction (ORR) catalyst. However, wet chemical synthesis of the nanoalloys is a crucial challenge because of the extremely high oxygen affinity of RE elements and the significantly different standard reduction potentials between Pt and RE. Here, this paper presents a molten-salt electrochemical synthetic strategy for the compositional-controlled preparation of platinum-neodymium (Pt-Nd) nanoalloy catalysts. Carbon-supported platinum-neodymium (Ptx Nd/C) nanoalloys, with distinct compositions of Pt5 Nd and Pt2 Nd, are obtained through molten-salt electrochemical deoxidation of platinum and neodymium oxide (Pt-Nd2 O3 ) precursors supported on carbon. The Ptx Nd/C nanoalloys, especially the Pt5 Nd/C exhibit a mass activity of 0.40 A mg-1 Pt and a specific activity of 1.41 mA cm-2 Pt at 0.9 V versus RHE, which are 3.1 and 7.1 times higher, respectively, than that of commercial Pt/C catalyst. More significantly, the Pt5 Nd/C catalyst is remarkably stable after undergoing 20 000 accelerated durability cycles. Furthermore, the density-functional-theory (DFT) calculations confirm that the ORR catalytic performance of Ptx Nd/C nanoalloys is enhanced by compressive strain effect of Pt overlayer, causing a suitable weakened binding energies of O* Δ E O ∗ $\Delta {E}_{{{\rm{O}}}^*}$ and Δ E OH ∗ $\Delta {E}_{{\rm{OH}}^*}$ .

Dopant Site Engineering on 2D Co3O4 Enables Enhanced Toluene Oxidation in a Wide Temperature Range.

Development of cost-effective oxide catalysts holds the key to the removal of toluene, one of the most important volatile organic compounds. However, the catalysts follow varied working mechanisms at different reaction temperatures, posing a challenge to achieving efficient toluene removal over a wide temperature range. Here we report an agitation-assisted molten salt method, which achieves the rational doping on a two-dimensional Co3O4 catalyst and forms two different structures of active sites to enhance catalytic oxidation of toluene in specific temperature intervals, enabling a facile tandem design for working in a wide temperature range. Specifically, Co3O4 is doped with Cu at the octahedral site (Cu-Co3O4) and Zn at the tetrahedral site (Zn-Co3O4) to form CuOh-O-CoTe and ZnTe-O-CoOh structures on the surface, respectively. Mechanistic studies reveal the different working mechanisms of these two active sites toward remarkable performance enhancement at specific temperature intervals, and the improved performance derived from accelerated consumption of intermediates adsorbed on the catalyst surface. Taken together, Cu-Co3O4 and Zn-Co3O4 achieve excellent toluene purification performance over a wide temperature range. This work provides insights into the mechanism-oriented design of active sites at the atomic level.

Molten salts for efficient removal of radioactive contaminants from stainless steel surface: Mechanisms and applications.

Here, we have demonstrated an innovative decontamination strategy using molten salts as a solvent to clean stubborn uranium contaminants on stainless steel surfaces. The aim of this work was to investigate the evolutionary path of contaminants in molten salts to reveal the decontamination mechanism, thus providing a basis for the practical application of the method. Thermodynamic analysis revealed that alkali metal hydroxides, carbonates, chlorides and nitrates can react with uranium oxides (UO3 and U3O8) to form various uranates. Notably, the decontamination mechanism was elucidated by analyzing the chemical composition of the contaminants in the molten salts and the surface morphology of the specimens considering NaOH-Na2CO3-NaCl melt as the decontaminant. The decontamination process involved two stages: a rapid decontamination stage dominated by the thermal effect of molten salt, and a stable decontamination stage governed by the chemical reactions and diffusion of molten salt. Subsequently, a multiple decontamination strategy was implemented to achieve high decontamination rates and low residual radioactivity. Within the actual cleaning time of 30 min, the decontamination efficiency (DE) of UO3-contaminated specimens reached 97.8% and 93.0% for U3O8-contaminated specimens. Simultaneously, the radioactivity levels of all specimens were reduced to below the control level for reuse in the nuclear domain. Particularly, the actual radioactive waste from the nuclear industry reached a reusable level of radioactivity after decontamination. The NaOH-Na2CO3-NaCl melt outperforms conventional chemical solvents and may be one of the most rapid and efficient decontaminants for stubborn uranium contamination of metal surfaces, which provides insights in regard to handling nuclear waste.

Novel Calibration Approach for Monitoring Aerosol Hydrogen Isotopes Using Laser-Induced Breakdown Spectroscopy for Molten Salt Reactor Off-Gas Streams.

Online monitoring is a key challenge for the continued development of molten salt reactor (MSR) technology. Laser-induced breakdown spectroscopy (LIBS) has previously been demonstrated to be a viable tool for monitoring aerosolized species and noble gases in real time, but the ability to discern varying isotopes in these streams has not yet been investigated for MSR applications. Tritium will form in MSRs from ternary fission and from (n,α)-reactions occurring in lithium-containing salts. This study compares three spectrometers of varying resolutions and types for measuring hydrogen isotope shifts in LIBS spectra of wetted filter paper. For each spectrometer, multivariate models were built (i.e., principal component regression, partial least squares regression, and multivariate curve resolution) to quantify the isotope ratio. The top models were then modified and corrected to apply the models to aerosol samples with varying isotope ratios. This novel calibration strategy offers an 82% reduction in volume of the calibration samples needed and is a more viable pathway for calibrating deployable LIBS systems. Lastly, this calibration model was compared with an all-aerosol trained model for monitoring hydrogen isotopes during a real-time test where the protium/deuterium ratio, along with representative salt species (i.e., lithium, sodium, and potassium) were adjusted dynamically. Results of this test validated the predictive capabilities of the transferred model and highlighted the capabilities of LIBS for real-time monitoring of MSR effluent streams.