Methods for performing electrolytic reactions in the presence of a plasma and associated systems

Abstract

Methods of performing electrolytic reactions in the presence of a plasma and associated systems are generally provided. Some methods described herein may comprise employing a system described herein to perform one or more steps and / or may be capable of being performed (partially or fully) in a system described herein. Similarly, some systems described herein may be capable of performing and / or may be configured to perform (partially or fully) a method described herein. In some embodiments, a system described herein comprises an electrolytic cell that is capable of performing and / or configured to perform (partially or fully) a method described herein.

Description

[0001] METHODS FOR PERFORMING ELECTROLYTIC REACTIONS IN THE PRESENCE OF A PLASMA AND ASSOCIATED SYSTEMS

[0002] RELATED APPLICATIONS

[0003] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 633,663, filed April 12, 2024, and entitled “Methods for Performing Electrolytic Reactions in the Presence of a Plasma and Associated Systems,” which is incorporated herein by reference in its entirety for all purposes.

[0004] TECHNICAL FIELD

[0005] Methods of performing electrolytic reactions in the presence of a plasma, and associated systems, are generally described.

[0006] SUMMARY

[0007] Methods of performing electrolytic reactions in the presence of a plasma, and associated systems, are generally described. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles.

[0008] Certain embodiments relate to methods of performing electrolytic reactions in a molten salt. In some embodiments, a method of performing electrolytic reactions in a molten salt comprises generating a plasma between a first current collector and a first surface of the molten salt; oxidizing an anion present in the molten salt to form a gaseous byproduct, wherein the oxidation occurs at an interface between the first surface and the plasma; and reducing a cation present in the molten salt at to form a metal, wherein the molten salt electronically insulates the metal from the plasma.

[0009] Certain embodiments relate to systems for performing electrolytic reactions in a molten salt. In some embodiments, a system for performing electrolytic reactions in a molten salt comprises a vessel; a first current collector; a second current collector comprising a surface positioned inside the vessel; a shield positioned around the first current collector; and a source of gas positioned to supply a gas between the current collector and the shield.

[0010] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

[0013] FIG. 1 is a schematic illustration of a system, in accordance with certain embodiments.

[0014] FIG. 2 is a schematic illustration of a system comprising a vessel containing a molten salt, in accordance with certain embodiments.

[0015] FIG. 3 is a schematic illustration of a system comprising a vessel containing a molten salt and a metal, in accordance with certain embodiments.

[0016] FIG. 4 is a schematic illustration of a system in which a plasma is generated, in accordance with certain embodiments.

[0017] FIG. 5 is a schematic illustration of a system in which a species formed during the performance of an electrolytic reaction is contained in a vessel, in accordance with certain embodiments.

[0018] FIG. 6 is a schematic illustration of a system comprising various components, in accordance with certain embodiments.

[0019] FIGs. 7-9 are schematic illustrations of a current collector and a shield, in accordance with certain embodiments.

[0020] FIG. 10 is a schematic illustration of a current collector, a shield, and a source of gas, in accordance with certain embodiments.

[0021] FIG. 11 is a schematic illustration of the use of a current collector to generate a plasma, in accordance with certain embodiments.

[0022] FIG. 12 is a schematic illustration of a method, in accordance with certain embodiments. DETAILED DESCRIPTION

[0023] Methods of performing electrolytic reactions in the presence of a plasma and associated systems are generally provided. Some methods described herein may comprise employing a system described herein to perform one or more steps and / or may be capable of being performed (partially or fully) in a system described herein. Similarly, some systems described herein may be capable of performing and / or may be configured to perform (partially or fully) a method described herein. In some embodiments, a system described herein comprises an electrolytic cell that is capable of performing and / or configured to perform (partially or fully) a method described herein.

[0024] In some embodiments, a method comprises performing one or more electrolytic reactions in a molten salt and in the presence of a plasma. In such embodiments, the plasma may be employed to conduct electrons generated or consumed during an electrolytic reaction between the molten salt and a first current collector. The first current collector may be positioned such that it does not contact the molten salt and / or metal generated during the electrolytic reactions.

[0025] In some embodiments, the use of a first current collector positioned in this manner may be particularly advantageous for performing electrolytic reactions in molten salts with particularly high melting temperatures (e.g., those from which liquid iron may be recovered) and / or in molten salts that are particularly oxidizing (e.g., molten oxide salts). Without wishing to be bound by any particular theory, it is believed that many current collectors, upon exposure to high temperature environments and / or environments that are highly oxidizing, undesirably undergo degradation. Additionally, in some instances, degradation products generated by such degradation that would otherwise be present at the surfaces of such current collectors and thereby protect the current collector from further degradation may undesirably be soluble in such environments. This may result in the continual exposure of fresh portions of the current collector to such environments, causing accelerated current collector degradation. Such degradation may disadvantageously reduce the lifetime of the system in which the electrolytic reactions are occurring, result in the generation of greenhouse gases (e.g., for electrodes that degrade to form carbonaceous byproducts), and / or result in the inclusion of impurities in metal generated by the electrolytic reactions (e.g., impurities that take the form of a species generated upon degradation of the first current collector and / or a reaction products of such species).

[0026] It is thus believed that it may be beneficial to perform electrolytic reactions under conditions in which a first current collector is positioned such that it is still capable of serving its current-collecting function but is not in contact with a molten salt in which the electrolytic reactions are taking place. The use of a plasma as a pathway that facilitates electron transport between a first current collector spatially separated from a molten salt in which electrolytic reactions are occurring, and which is positioned between the first current collector and the molten salt, may therefore be advantageous.

[0027] In some embodiments, a system is provided that facilitates the performance of electrolytic reactions in the presence of a plasma. As one example, in some embodiments, a system comprises one or more components that assist with shielding a first current collector (e.g., a current collector that does not contact a molten salt and / or a metal generated during electrolytic reactions) from one or more species present during an electrolytic reaction described herein and / or generated during such an electrolytic reaction. For instance, a system may comprise one or more components that assist with shielding a first current collector from one or more oxidizing gases generated during an electrolytic reaction.

[0028] One non-limiting example of a combination of components that can assist with shielding a first current collector is a shield positioned around the first current collector and a source of gas positioned to supply a gas between the first current collector and the shield. The shield may serve as a physical barrier that prevents access to the first current collector through pathways other than openings therein. Gas supplied between the first current collector and the shield may flow between the first current collector and the shield and / or may flow out of the shield through any openings therein. This flow may prevent and / or substantially reduce flow of gas generated outside the shield through such openings, especially if the gas is supplied at a pressure higher than the pressure external to the shield. This flow may therefore desirably further reduce the exposure of the first current collector to species present during electrolytic reactions and / or generated during electrolytic reactions, such as oxidizing gases (e.g., O2), generated during electrolytic reactions.

[0029] FIG. 1 shows one non-limiting example of a system described herein. The system 100 shown in FIG. 1 comprises a vessel 102, a first current collector 104, and a second current collector 106 comprising a surface 108 positioned inside the vessel 102. As shown in FIG. 1, it is possible for a second current collector to comprise a surface positioned inside a vessel but to not be fully contained in the vessel (i.e., it may comprise one or more portions and / or surfaces that are positioned external to the vessel). As also shown in FIG. 1, it is possible for a first current collector to be positioned external to a vessel. In some embodiments, a first current collector is partially or fully contained in a vessel (not shown).

[0030] In some embodiments, the system 100 comprises an electrolytic cell and / or may be a location in which one or more electrolytic reactions are performed. The term “electrolytic cell,” as used herein, refers to a device in which electrical energy is input into the device to drive a non- spontaneous redox reaction. The reactions that occur upon the input of such electrical energy may also be referred to as electrolytic reactions, and the process of operating an electrolytic cell to perform such reactions may be referred to as electrolysis. Operation of an electrolytic cell may comprise generating a voltage difference between one or more anodes (and / or anodic current collectors) present in the electrolytic cell with respect to one or more cathodes (and / or cathodic current collectors) present therein, which may cause the anode(s) (and / or anodic current collectors) to exhibit a positive charge and the cathode(s) (and / or cathodic current collectors) to exhibit a negative charge. The voltage difference may cause an oxidation reaction to occur at the anode (and / or anodic current collector) and / or a reduction reaction to occur at the cathode (and / or cathodic current collector).

[0031] As described herein, a “first current collector” may be an anodic current collector and a “second current collector” may be a cathodic current collector.

[0032] In some instances, during electrolysis and / or electrolytic reactions, the anode(s) and cathode(s) (and / or anodic and cathodic current collectors) present in an electrolytic cell do not react as a result of the redox reactions and / or otherwise during the redox reactions and may remain unconsumed by these redox reactions. The redox reactions may comprise reducing cations present in the molten salt to generate, as a desired product, elemental and / or alloyed metal (e.g., a metal having a zero oxidation state). The redox reactions may comprise oxidizing anion counter ions to form a gaseous byproduct.

[0033] During the performance of an electrolytic reaction, a molten salt may be contained in the vessel shown in FIG. 1. This is depicted schematically in FIG. 2, which further depicts the molten salt 110. As can be seen in FIG. 2, the molten salt 110 may contact the second current collector 106 (e.g., via the surface 108 of the second electrode that is positioned inside the vessel 102 and via the surface 112 of the molten salt). As can also be seen in FIG. 2, it is also possible for the molten salt and the first current collector to be spatially separated and / or not in contact with each other. In some embodiments, one or more species formed during an electrolytic reaction may also be contained in the vessel shown in FIG. 1. For instance, in some embodiments, an electrolytic reaction may result in the formation of a metal. In such embodiments, the metal may also be contained in the vessel. This is further depicted schematically in FIG. 3, which shows both a molten salt 110 and a metal 114 contained in the vessel 102. When the metal is denser than the molten salt, the metal may be positioned beneath the molten salt. In such embodiments, the second current collector may contact the metal (e.g., but not the molten salt). With respect to FIG. 3, it can be seen that the surface 108 of the second current collector contacts the surface 116 of the metal.

[0034] During the performance of an electrolytic reaction, it is also possible for a plasma to be generated between the first current collector shown in FIGs. 1-3 and the molten salt shown in FIGs. 2 and 3, such as between a surface of the molten salt and the first current collector. This is shown schematically in FIG. 4, in which the plasma 118 is generated between the surface 120 of the molten salt 110 and the first current collector 104. As shown in FIG. 4, the plasma may contact a surface of a molten salt and / or may contact a surface of the first current collector. In such embodiments, the plasma may be capable of conducting electrons therebetween.

[0035] As shown in FIG. 4, a plasma positioned between a first current collector and a surface of a molten salt may contact some or all of the surface of the molten salt and / or some or all of a surface of a first current collector proximate to a molten salt. Additionally, a plasma may be “between” a first current collector and a surface of a molten salt even if the plasma extends laterally beyond the first current collector and / or the surface of the molten salt. Similarly, a plasma may be “between” a first current collector and a surface of a molten salt even if one or more portions of the first current collector and / or the surface of the molten salt extend laterally beyond the plasma.

[0036] In some embodiments, and as shown in FIG. 4, during the performance of an electrolytic reaction in the presence of plasma (e.g., at the beginning of the performance of such an electrolytic reaction), very few or no species formed during the electrolytic reaction (e.g., metal(s), gas(es)) are present in a vessel containing a molten salt. In such embodiments, the molten salt may contact a second current collector present in the system.

[0037] As noted above, it is also possible for one or more species formed during the performance of an electrolytic reaction to be contained in a vessel. In such embodiments, during the performance of an electrolytic reaction, one or more such species (e.g., a metal formed during the performance of the electrolytic reaction) may contact a second current collector, may be positioned between the molten salt and the second current collector, and / or may block contact between the molten salt and the second current collector. This is shown schematically in FIG. 5.

[0038] Similarly, in some such embodiments, during the performance of an electrolytic reaction, a molten salt may be positioned between a species formed during the performance of an electrolytic reaction (e.g., a metal formed during the performance of the electrolytic reaction) and a plasma and / or may block contact between the species formed during the performance of the electrolytic reaction and the plasma. This is also shown schematically in FIG. 5.

[0039] In some embodiments, a molten salt present during an electrolytic reaction may have a relatively low electronic conductivity, such as an electronic conductivity that does not allow for the formation of an appreciable electronic current therethrough under the conditions present during the performance of certain electrolytic reactions. For instance, under such conditions, minimal or no electronic current may be generated from the plasma, through the molten salt, and to a current collector and / or a product of an electrolytic reaction separated from a plasma by the molten salt. Thus, blocking contact between the plasma and certain products of electrolytic reactions (e.g., conductive products of electrolytic reactions, such as metals) may prevent the formation of an electrical breakdown (also sometimes referred to as a discharge) between first and second current collectors positioned in a system, such as an electrical breakdown that passes through the plasma and a metal formed by an electrolytic reaction. In some such embodiments, the molten salt may electronically insulate a metal formed during an electrolytic reaction from the plasma.

[0040] It should be understood that molten salts having one or more properties provided in the preceding paragraph (e.g., a low electronic conductivity), may still have an appreciable ionic conductivity. In such embodiments, the molten salt may allow for ion conduction to occur therethrough even while not allowing for appreciable electronic conduction therethrough. For instance, a molten salt may electronically insulate a metal formed during an electrolytic reaction from a plasma while still allowing ionic conduction therebetween. During the application of a plasma, ions (e.g., anions) may be conducted through the molten salt to an interface between the first surface of the molten salt and the plasma. Similarly, during the application of a plasma, ions (e.g., cations) may be conducted through the molten salt to an interface between the molten salt and a surface of a second current collector and / or to an interface between the molten salt and a metal generated by an electrolytic reaction. In some embodiments, a molten salt described herein performs in a manner akin to a selective membrane that allows for electrolytic reactions to occur via ionic conduction therethrough.

[0041] In some embodiments, a system comprises one or more ports through which species may be introduced into and / or removed therefrom. For instance, a system may comprise some or all of the following ports: a gas outlet port through which a gaseous byproduct generated during an electrolytic reaction (as described in further detail below) may be removed, a molten salt feed port through which a molten salt may be introduced, a molten salt outlet port through which molten salt may be removed, and a metal outlet port through which metal (e.g., metal generated during an electrolytic reaction) may be removed.

[0042] Additionally, the systems described herein may comprise one or more further components that assist with the performance of electrolytic reactions, such as anode and cathode bussing and a voltage supply. FIG. 6 shows one non-limiting example of a system comprising such components in addition to the components described above. In FIG. 6, the gas outlet port is labeled as “Gas Outlet,” the molten salt feed port is labeled as “Feed Port,” the molten salt outlet port is labeled “Molten Oxide Tap,” the metal outlet port is labeled as “Molten Iron Tap,” and the electrode is labeled as “Cathodic Current Collector.” It should be understood that a system described herein may comprise all of the components shown in FIG. 6 or any desired subset of the components shown in FIG. 6. Similarly, it should be understood that a system may comprise a component shown in FIG. 6 that has a different chemistry and / or design than that shown in FIG. 6 (e.g., a system may comprise a molten salt other than a molten oxide and / or be employed to generate a metal other than iron). Additionally, it should be understood that a system may comprise a component shown in FIG. 6 but that is positioned in a different location than the location shown in FIG. 6 (e.g., a system may comprise a metal outlet port that is positioned such that metal may be syphoned out of the system therethrough and / or may be placed at a location above a vessel containing the metal and / or above any metal present in a vessel containing the metal).

[0043] In some embodiments, a system described herein further comprises one or more components that assist with maintaining the temperature of one or more system components. As an example, in some embodiments, a system comprises a cooling system in thermal communication with a first current collector described herein. In some embodiments, the cooling system may be a water-based cooling system. As can also be seen in FIG. 6, and as described above, in some embodiments, a system comprises a shield that is positioned around a first current collector. One example of a combination of a first current collector and a shield with this design is shown in FIG. 7. In FIG.

[0044] 7, the shield 122 is positioned around the first current collector 104.

[0045] Shields that are positioned around first current collectors may be positioned such that they form a closed loop (and / or occupy at least 50%, 75%, 80%, 90%, 95%, and / or 99% of a closed loop) that encloses a portion of the first current collector. FIG. 8 shows this concept with further clarity. In FIG. 8, the shield 122 is positioned such that it occupies the entirety of the closed loops 124 and 126 enclosing the current collector 104. As can be appreciated from FIG.

[0046] 8, it is possible for a shield to occupy multiple closed loops that enclose a first current collector and it is possible for there to exist one or more closed loops enclosing a first current collector that are not occupied appreciably by a shield that is positioned around a first current collector (e.g., the closed loop 128 enclosing the current collector 104).

[0047] In some embodiments, a first current collector includes a long axis (e.g., a longest principal axis), and a shield may be positioned (e.g., concentrically) around certain portions of the long axis but not others. For instance, with respect to FIG. 9, the shield 122 is positioned concentrically around the portion 130 of the long axis 132 but not around the portion 134 of the long axis 132. It is also possible for a shield to be positioned concentrically around all portions of a long axis of a current collector and / or for a shield to extend beyond the current collector in the direction of the long axis. In some embodiments, a shield is positioned such that it forms at least 50% of a closed loop (and / or at least 75%, at least 80%, at least 95%, at least 99%, or 100% of a closed loop) around the first current collector along at least 50%, at least 75%, at least 80%, at least 95%, or at least 99% of the length of the long axis of the first current collector.

[0048] In some embodiments, a shield is positioned such that it forms a closed loop (and / or occupies at least 50%, at least 75%, at least 80%, at least 95%, and / or at least 99% of a closed loop) around the first current collector in a plane perpendicular to the long axis of the first current collector.

[0049] In some embodiments, a system comprises a source of gas positioned to supply a gas between a first current collector and a shield. A current collector, shield, and source of gas having this design are shown schematically in FIG. 10. In FIG. 10, the source of gas 136 is positioned to supply a gas between the first current collector 104 and the shield 122. The source of gas may also be positioned such that the gas supplies flows in the space between the first current collector and the shield, occupies a relatively high percentage of the space between the first current collector and the shield (e.g., at least 50%, 75%, 80%, 90%, 95%, and / or 99% of this space), and / or flows in a direction that has a component parallel to a long axis of the first current collector. As noted above, such gas flow may reduce the flow of any gases present external to the shield into the space between the first current collector and the shield. In some embodiments, such gas flow may also assist with cooling the first current collector.

[0050] FIG. 11 shows one non-limiting example of a first current collector around which a shield is positioned. FIG. 11 also shows the flow of a gas parallel to the long axis of the first current collector in the space between the first current collector and the shield. FIG. 11 also shows the use of the first current collector to generate a plasma that contacts both the first current collector and a surface of a molten salt spatially separated from the first current collector. It should be noted that although FIG. 11 depicts the flow of a particular gas and a particular type of first current collector, other types of gases and first current collectors may also be employed in system components having the design shown in FIG. 11.

[0051] As noted above, some embodiments are related to methods. FIG. 12 shows one nonlimiting example of a method described herein. The method 1238 shown in FIG. 12 comprises the steps 1240, 1242, 1244, 1246, 1248, 1250, 1252, and 1254. It should be noted that, although these steps are shown as being sequential, they may be performed in an order other than that shown in FIG. 12. Similarly, a method may comprise performing some or all of the steps during periods of time that partially or fully overlap.

[0052] The first step shown in FIG. 12 is the optional step 1240, which comprises introducing a molten salt into a vessel (e.g., through a molten salt feed port). The vessel may be positioned in a system described elsewhere herein (e.g., that is suitable for performing electrolytic reactions). When the step 1240 is performed, the molten salt may be introduced in molten form or may be introduced in solid form and subsequently heated once contained in the vessel. When this step is performed, some or all of the subsequent steps of the method shown in FIG. 12 may be performed while the molten salt is contained in the vessel.

[0053] The second step shown in FIG. 12 is the step 1242, which comprises generating a plasma between a first current collector and a first surface of a molten salt. While step 1242 is not shown as being optional in the method shown in FIG. 12, in other embodiments, step 1242 could be optional. The plasma may be generated by generating a potential difference between the first surface of the molten salt and the first current collector sufficient to cause the formation of an electrical arc. This potential difference may be generated by selecting an appropriate electrical potential for the first current collector and / or a second current collector. In some embodiments, a plasma is generated prior to the formation of any metal. For instance, a plasma may be generated between a molten salt contained in a vessel and the vessel may lack any metal (and / or any metal generated by an electrolytic reaction) prior to the occurrence of any electrolytic reactions caused by the presence of the plasma and / or described elsewhere herein.

[0054] The third step shown in FIG. 12 is the optional step 1244, which comprises supplying a gas between the first current collector and a shield. When this step is performed, the gas may flow through the space between the first current collector and the shield. As described above, this may assist with reducing or preventing the exposure of the first current collector to one or more species present during the performance of the method (e.g., a gaseous byproduct generated during the performance of an electrolytic reaction). In some embodiments, a gas supplied between the first current collector and the shield may, subsequent to flowing out of the shield, undergo a phase transition to form the plasma described in the preceding paragraph. In other words, the electric arc described in the preceding paragraph may form through gas that is supplied between the first current collector and the shield and subsequently flows out of the shield and between the first current collector and the first surface of the molten salt.

[0055] The fourth step shown in FIG. 12 is the step 1246, which comprises oxidizing an anion present in the molten salt to form a gaseous byproduct. While step 1246 is not shown as being optional in the method shown in FIG. 12, in other embodiments, step 1246 could be optional. The oxidation may occur at the interface between the plasma and the first surface of the molten salt. In such embodiments, this interface may serve as the anode in an electrolytic cell. Advantageously, this may allow for the oxidation of the anion without contact between the anion and the first current collector, which may prevent the formation of deleterious byproducts that would be generated by such contact.

[0056] The fifth step shown in FIG. 12 is the optional step 1248, which comprises removing the gaseous byproduct. The gaseous byproduct may be removed by flowing out of the system in which the electrolytic reactions are occurring through a port, such as out of a gas outlet port. Some gaseous byproducts may be corrosive or otherwise undesirably reactive with certain system components, and so removing them from the systems described herein may advantageously reduce system lifetime by decreasing the degradation caused by their interaction with such system components. The sixth step shown in FIG. 12 is the step 1250, which comprises reducing a cation present in the molten salt to form a metal. While step 1250 is not shown as being optional in the method shown in FIG. 12, in other embodiments, step 1250 could be optional. This reduction may occur at an interface between the molten salt and a second current collector (e.g., in such embodiments, the second current collector may serve as a cathode in an electrolytic cell), at an interface between the molten salt and a component in the system that is in electronic communication with a second current collector, and / or at an interface between the molten salt and a species contained in the system that is in electronic communication with a second current collector. One example of the latter is at an interface between the molten salt and a metal positioned between the molten salt and the second current collector (e.g., in such embodiments, the metal may serve as a cathode in an electrolytic cell). In such embodiments, the metal, because it is a conductor, may be at the same potential as the second current collector with which it is in electronic communication, which may be a potential sufficient to reduce a cation present in the molten salt.

[0057] The seventh step shown in FIG. 12 is the optional step 1252, which comprises removing the metal. In some embodiments, it may be desirable to perform a method described herein in order to form a metal from a starting material comprising metallic ions. After the metal is formed, it may then be removed from the system and recovered for further use and / or to undergo further downstream processing. The metal may be removed, for instance, via a metal outlet port. In some embodiments, the metal may be a liquid (e.g., it may be molten) and so may be removed by flowing out of the metal outlet port.

[0058] The last step shown in FIG. 12 is the optional step 1254, which comprises removing the molten salt from the vessel (e.g., through a molten salt outlet port). The molten salt may be removed while molten or may be cooled and then removed once in solid form.

[0059] In some embodiments, a method described herein may be performed at a relatively high temperature, such as a temperature in excess of the melting point of Fe.

[0060] As noted above, some embodiments relate to the performance of electrolytic reactions in a molten salt. A “molten salt,” as used herein, is a liquid-phase salt. In some embodiments, a molten salt may comprise, consist essentially of, and / or consist of a salt that is present at a temperature above its melting point. It is also possible for a molten salt to further comprise a dissolved metal and / or a dissolved gas (e.g., a dissolved metal and / or a dissolved gas, such as a gaseous byproduct, that is produced by an electrolytic reaction). A molten salt is not the same as a solubilized salt (which is a salt that has been solubilized into its constituent ions within a solvent). In some embodiments, the molten salt is a salt that is in a solid phase when at a temperature of 25 °C and a pressure of 1 atmosphere but that melts to form a liquid phase when heated to or above its melting point. In some embodiments, the molten salt is a salt that is formed upon the melting of a solid introduced into a system and / or vessel described herein.

[0061] In some embodiments, a molten salt comprises a metallic cation and / or a metal is formed upon reduction of a cation present in a molten salt. In some embodiments, a molten salt comprises two or more different types of metallic cations. Metallic cations present in the molten salts described herein may have a variety of suitable oxidation states (e.g., +1, +2, +3, +4, +5, +6, and / or +7).

[0062] In some embodiments, a molten salt comprises a transition metal cation ion, a transition metal is formed upon reduction of a cation present in a molten salt, and / or an alloy comprising a transition metal is formed upon reduction of a cation present in a molten salt. The “transition metals,” as used herein, are scandium (Sc), yttrium (Y), lanthanum (La), actinium (Ac), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), manganese (Mn), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe), ruthenium (Ru), osmium (Os), hassium (Hs), cobalt (Co), rhodium (Rh), iridium (Ir), meitnerium (Mt), nickel (Ni), palladium (Pd), platinum (Pt), darmstadtium (Ds), copper (Cu), silver (Ag), gold (Au), roentgenium (Rg), zinc (Zn), cadmium (Cd), mercury (Hg), and copemicium (Cn). In some embodiments, a molten salt comprises an Fe cation.

[0063] The molten salts described herein may comprise a variety of types of anions. In some embodiments, a molten salt comprises two or more different types of anions. Anions present in the molten salts described herein may have a variety of suitable oxidation states (e.g., -1, -2, and / or -3). In some embodiments, a molten salt comprises an oxygen (e.g., an O2) anion. In some embodiments, the molten salt includes relatively few or zero sulfur anions and / or relatively few or zero non-oxygen anions. It is also possible for the molten salt to include sulfur anions.

[0064] In some embodiments, a molten salt comprises an iron oxide.

[0065] Gaseous byproducts generated during the electrolytic reactions described herein may include a relatively low amount of carbon. In some embodiments, carbon makes up less than or equal to 10 wt%, less than or equal to 7.5 wt%, less than or equal to 5 wt%, less than or equal to 2 wt%, less than or equal to 1 wt%, less than or equal to 0.75 wt%, less than or equal to 0.5 wt%, less than or equal to 0.2 wt%, or less than or equal to 0.1 wt% of the gaseous byproducts. In some embodiments, carbon makes up greater than or equal to 0 wt%, greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.5 wt%, greater than or equal to 0.75 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 5 wt%, or greater than or equal to 7.5 wt% of the gaseous byproducts. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 10 wt% and greater than or equal to 0 wt%). Other ranges are also possible. In some embodiments, carbon makes up identically 0 wt% of the gaseous byproducts.

[0066] In some embodiments, a gaseous byproduct generated during an electrolytic reaction comprises oxygen gas (O2).

[0067] In some embodiments, a gas outlet port may be in fluidic communication with a source of reduced pressure, which may facilitate the removal of gaseous byproducts from the systems described herein. For instance, a gas outlet port may be in fluidic communication with a source that has a pressure of less than or equal to -0.25 inches of H2O with respect to the pressure in the system (e.g., a source that has a pressure of less than or equal to -5 inches of H2O with respect to the pressure in the system).

[0068] The current collectors described herein may have a variety of suitable compositions. In some embodiments, a current collector described herein comprises, consists of, and / or consists essentially of one or more refractory materials. In some embodiments, a current collector described herein comprises, consists of, and / or consists essentially of one or more refractory metals, non-limiting examples of which include W, Nb, and Mo. In some embodiments, a current collector described herein comprises, consists of, and / or consists essentially of one or more refractory ceramics, non-limiting examples of which include carbides (e.g., tungsten carbide, silicon carbide) and borides (e.g., titanium diboride).

[0069] The shields described herein may have a variety of suitable compositions. In some embodiments, a shield described herein comprises, consists of, and / or consists essentially of one or more refractory materials. In some embodiments, a shield described herein comprises, consists of, and / or consists essentially of one or more refractory ceramics, one non-limiting example of which is a refractory oxide.

[0070] A variety of suitable gases may be employed in the systems described herein (e.g., that are supplied between a current collector and a shield, in which a plasma is generated). In some embodiments, an inert gas is employed, such as argon (Ar). The vessels described herein may have a variety of suitable compositions. In some embodiments, a vessel described herein comprises, consists of, and / or consists essentially of one or more refractory materials. In some embodiments, a vessel described herein comprises, consists of, and / or consists essentially of one or more refractory metals, non-limiting examples of which include W, Nb, and Mo. In some embodiments, a vessel described herein comprises, consists of, and / or consists essentially of one or more refractory ceramics, non-limiting examples of which include oxides (e.g., magnesium oxide, zirconium oxide, calcium oxide) and high- temperature refractory bricks.

[0071] The following example is intended to illustrate certain embodiments of the present invention, but does not exemplify the full scope of the invention.

[0072] EXAMPLE 1

[0073] 6.51 grams of a magnesium oxide-iron oxide mixture was put into a firebrick container with a hole in the bottom. The firebrick container had an additional, dense layer of magnesium oxide to fill the porosity. A welding rod weighing 8.28 grams was bent into the hole and surrounded by the magnesium oxide-iron oxide mixture to act as a cathode. A welder was configured with a pure tungsten electrode, a gas lens, and a ceramic shield. Argon gas was passed around the tungsten electrode to shield the electrode from oxidation. The grounding electrode was applied to the welding rod, making the welding rod the negative electrode and the gas-shielded tungsten electrode positive. The welder was activated and passed current for 45 seconds, creating a molten oxide and liquid metal pool with the liquid metal shielded from the atmosphere by the container vessel on the sides and the molten oxide on the top. After cooling, the metal cathode was removed from the firebrick vessel and all produced metal was extracted from the molten oxide. The final measured mass of metal was 9.10 grams, indicating the reduction of 0.82 grams of metal. Collected metal was found to be iron without magnesium or tungsten impurities after EDS analysis.

[0074] While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention.

[0075] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0076] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0077] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0078] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0079] As used herein, “wt%” is an abbreviation of weight percentage. As used herein, “at%” is an abbreviation of atomic percentage. Unless context indicates to the contrary, the amounts described herein are based on mass and the percentage amounts described herein are based on mass percentages.

[0080] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0081] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

CLAIMSWhat is claimed is:

1. A method of performing electrolytic reactions in a molten salt, comprising: generating a plasma between a first current collector and a first surface of the molten salt; oxidizing an anion present in the molten salt to form a gaseous byproduct, wherein the oxidation occurs at an interface between the first surface and the plasma; and reducing a cation present in the molten salt at to form a metal, wherein the molten salt electronically insulates the metal from the plasma.

2. A system for performing electrolytic reactions in a molten salt, comprising: a vessel; a first current collector; a second current collector comprising a surface positioned inside the vessel; a shield positioned around the first current collector; and a source of gas positioned to supply a gas between the current collector and the shield.

3. A method or system as in any preceding claim, wherein the cation is a transition metal cation.

4. A method or system as in any preceding claim, wherein the transition metal is iron.

5. A method or system as in any preceding claim, wherein the anion is O2'.

6. A method or system as in any preceding claim, wherein the molten salt further comprises another, different cation.

7. A method or system as in any preceding claim, wherein the molten salt further comprises another, different anion.

8. A method or system as in any preceding claim, carbon makes up less than or equal to 10 wt% of the gases generated during the electrolytic reactions.

9. A method or system as in any preceding claim, wherein the first current collector comprises and / or consists essentially of one or more refractory metals.

10. A method or system as in any preceding claim, wherein the refractory metal(s) comprise tungsten, niobium, and / or molybdenum.

11. A method or system as in any preceding claim, wherein the gas is an inert gas.

12. A method or system as in any preceding claim, wherein the gas is Ar.

13. A method or system as in any preceding claim, wherein the shield comprises and / or consists essentially of one or more refractory ceramics.

14. A method or system as in any preceding claim, wherein the refractory ceramic(s) comprise a refractory oxide.

15. A method or system as in any preceding claim, further comprising a cooling system in thermal communication with the first current collector.

16. A method or system as in any preceding claim, wherein the molten salt is contained in a vessel.

17. A method or system as in any preceding claim, wherein the vessel comprises a gas outlet port through which the gaseous byproduct may be removed.

18. A method or system as in any preceding claim, wherein the vessel comprises a molten salt feed port through which the molten salt may be introduced.

19. A method or system as in any preceding claim, wherein the vessel comprises a molten salt outlet port through which the molten salt may be removed.

20. A method or system as in any preceding claim, wherein the vessel comprises a metal outlet port through which the metal may be removed.

21. A method or system as in any preceding claim, wherein the vessel comprises and / or consists essentially of a refractory material.

22. A method or system as in any preceding claim, wherein the refractory material is tungsten.

23. A method or system as in any preceding claim, wherein the molten salt allows ionic conduction between the metal and the plasma.

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