Systems and methods for high-rate electrochemical arsine generation

A system and method for generating arsine are disclosed. The system may include a shell having a top interior surface. The system may also include a cathode-anode assembly positioned in the shell and forming an elongated structure substantially parallel to the top surface. The cathode-anode assembly may include a first electrode and a second electrode surrounding the first electrode and forming a gap therebetween. The second electrode may include a plurality of channels along a length of the second electrode. The plurality of channels may allow circulation of electrolyte within and around at least a portion of the cathode-anode assembly and allow gases generated in response to current applied to the cathode-anode assembly to escape from the cathode-anode assembly. Such gases may be used as precursor gases for a high-volume metal-organic chemical vapor deposition (MOCVD) operation.

BACKGROUND

Technical Field

The present disclosure relates generally to generating gases for semiconductor processing operations, and more particularly, to systems and methods for high-rate electrochemical arsine generation.

Introduction

Arsine, in the form of arsine gas, may be employed for growth of gallium-arsenide (GaAs) and other compound semiconductors by metal-organic chemical vapor deposition (MOCVD). Techniques for synthesis of arsine include aqueous reduction of various arsenic compounds, and extensive purification thereafter. These techniques typically use an arsine manufacturing facility separate from arsine utilization facilities (e.g. semiconductor manufacturing facility).

Various approaches have been suggested to generate arsine at or near the point of use. Some techniques involve the use of dissolved ionic moieties as sources for arsenic, which may allow supplies of a precursor to be stored separately from an electrochemical chamber and pumped into the electrochemical chamber when needed. However, preferred precursors, such as oxides of arsenic, are roughly ten times more toxic than elemental arsenic. Further, most of the work from this technique produces relatively modest yield of arsine versus hydrogen, and thus results in a low overall current efficiency.

As another example, some techniques involve the use of elemental arsenic sacrificial electrodes in alkaline electrolytes. This technique may use arrays of electrodes along with a single cathode to generate arsine in hydrogen. Efficient utilization of the arsenic cathode is important in an economically-viable process, due to the high cost of ultrapure arsenic required to provide high arsine yield. Such efficient utilization has been demonstrated for vertically-oriented cylindrical cathodes without the aid of forced electrolyte flow at low current densities, such as 14 mA/cm2, as described, for example, in U.S. Pat. No. 8,021,536 to Machado et. al. However, single-cathode arrangements may not be scalable for high output rates of arsine and additionally may result in uncontrolled (or undesirable) temperature increases.

An array of vertically-disposed electrodes may be used. Even when an array of vertical electrodes is available, higher current densities, such as 100 to 300 mA/cm2, must be employed to construct a practical gas generator. However, vertical electrodes operated at high current density may be consumed non-uniformly along their height due to combined effects of heat transport and bubble accumulation and may lead to reduced arsenic cathode utilization, even with the addition of forced electrolyte flow.

Accordingly, there exists a need for further improvements to systems and methods for arsine generation.

SUMMARY

In an aspect, a gas generator is presented. The gas generator may include a shell having a top interior surface and a bottom interior surface opposite the top interior surface. The gas generator may also include a cathode-anode assembly horizontally positioned in the shell and forming an elongated structure substantially parallel to the top interior surface and the bottom interior surface. The cathode-anode assembly may include a first electrode and a second electrode surrounding the first electrode and forming a gap between the second electrode and the first electrode. The second electrode may include a plurality of channels along a length of the second electrode, one or more first channels of the plurality of channels being open towards the top interior surface of the shell, wherein the plurality of channels allow circulation of electrolyte within and around at least a portion of the cathode-anode assembly, and the one or more first channels allow gases, generated in response to current applied to the cathode-anode assembly and directed towards the one or more first channels, to escape from the cathode-anode assembly.

In another aspect, a cathode-anode assembly is presented. The cathode-anode assembly may include a first electrode forming an elongated structure. The cathode-anode assembly may also include a second electrode forming a second elongated structure surrounding the first electrode and forming a gap between the second electrode and the first electrode, the second electrode including a plurality of channels along a length of the second electrode, one or more first channels of the plurality of channels open towards a first direction which is substantially vertical, wherein the plurality of channels allow circulation of electrolyte within and around at least a portion of the cathode-anode assembly and the one or more first channels allow gases, generated in response to current applied to the cathode-anode assembly and directed towards the one or more first channels, to escape from the cathode-anode assembly in the first direction.

In another aspect, a method for generating gas is presented. The method may include providing current to a cathode-anode assembly horizontally positioned within an gas generator having a top interior surface, wherein a length of the cathode-anode assembly is arranged substantially parallel to the top interior surface. The method may also include rotating a first electrode of the cathode-anode assembly along a center axis of a length of the first electrode, the first electrode being rotated inside a second electrode of the cathode-anode assembly that surrounds the first electrode. The method may also include circulating electrolyte through the gas generator and the cathode-anode assembly, wherein the operation of the cathode-anode assembly generates the gas.

DETAILED DESCRIPTION

The present disclosure describes an array (plurality or set) of electrode rods (or arsenic rods or arsenic electrode rods) acting as sacrificial cathodes. In an example, each of the electrode rods is formed around a conductive metallic core, such as an iron core. Each of the electrode rods may be mounted with its axis horizontal to a surface such as a surface of a table, a floor, or the Earth (e.g., the electrode rods are horizontally mounted). Each of the electrode rods may be mounted within close proximity to a metallic anode. In some examples, each of the electrode rods may be shaped to minimize a variation in electrolyte spacing between an anode and a cathode. In some examples, each of the electrode rods may be shaped differently at an end of the electrode rod, where one or more gaps are provided in the electrode rod for electrolyte circulation and for gas generated from the electrode rod to escape.

Bubbles of gas (e.g., arsine or hydrogen) generated along the surfaces of the cathodes are provided with a direct path to gas collection at the top of the cell (described in more detail herein), that depends on angular position but not position along the rod length. Typically, electrochemical reactors employ electrodes that are not eroded or are eroded very slowly during gas generation. In contrast, the sacrificial cathodes described by the present disclosure are eroded whenever gas is generated, and their cost is a significant fraction of the total cost of operation. In vertical gas evolution surfaces, bubble formation and transport can be complex and dependent on vertical position within the reactor, leading to variations in effective voltage and current density with location, as described, for example, in Taqieddin et. al., J. Electrochem. Soc. V. 164 p. E448 (2017). Uniform erosion of arsenic cathodes may be difficult to achieve in these circumstances, leading to poor utilization of the arsenic cathode and greatly increased cost. In the exemplary horizontal arrangement of the electrodes, bubble formation and transport are substantially uniform along the length of the cathodes, promoting length-independent gas generation and cathode erosion.

In an aspect, each of the plurality of electrode rods may be supported on one or more rotatable fixtures to provide electrical contact and allow periodic or continuous rotation of the cathode rods within the anodes rods. Rotation of the electrode rods may ensure uniform azimuthal consumption of the arsenic material on the electrode rods thereby maximizing an overall arsenic utilization.

In an aspect, the plurality of electrode rods may be contained within a cell (structure or shell or case or body) formed of a nonreactive-coated metal, such as a polytetrafluoroethene (PTFE)-coated stainless steel, or other materials with similar characteristics or properties. The cell may be configured to provide an open region above the array of electrode rods through which electrolyte may be circulated. While the electrolyte is circulated, a continuous supply of electrolyte may be provided and filtered of precipitates and impurities that may accumulate in the electrolyte during operation.

In some examples, integral components, structures, and/or devices may be used for electrolyte pumps and electrode rotation without seals to rotating surfaces penetrating the envelope of the cell, to ensure safe operation at high pressure. Supplemental components, structures, and/or devices for recovery of arsine gas dissolved in the electrolyte may be incorporated into a circulation path.

In an aspect, the cell may be scalable to allow multiple cells to be connected in electrical series or parallel, and to employ either separate electrolyte reservoirs and pumps or a common single electrolyte distribution / purification system.

Referring toFIGS.1A and1B, views of an example of a cathode-anode assembly102of an gas generator100(or cell) is depicted. The gas generator100may be configured to generate gas (e.g., arsine) based on a current applied to the cathode-anode assembly102and a electrochemical reaction between a first electrode104(e.g., cathode) and a second electrode110(e.g., anode) of the cathode-anode assembly102. As shown, the cathode-anode assembly102may be horizontal to a plane of the Earth (or substantially perpendicular to a general rising direction of gas bubbles160that result from the electrochemical reaction).

The first electrode104(arsenic rod, arsenic electrode rod) may be a sacrificial cathode, or a cathode that is consumed during generation of arsine, AsH3(i.e., operation of the gas generator100). The first electrode104may include an outer layer106aand a core106b, where the outer layer106ais deposited on at least a portion of the core106b. In an example, the first electrode104may be in the form of a tube or rod. In an example, the first electrode104may be elongated, form a cylindrical structure, and/or form a concentric cylindrical structure, as shown byFIGS.1A-1B. In an example, the first electrode104may have a diameter of 1.5 to 3 centimeters (cm) and a length of 30-80 cm.

In an aspect, the outer layer106amay be formed of elemental arsenic (As). In an aspect, the core106bmay be configured to provide mechanical support, electrical contact, and/or rotational motion for the first electrode104. In an example, the core106bmay be a solid or hollow core that extends the length of the first electrode104and, in some examples, past the ends of the outer layer106a, as shown byFIG.1B. The core106bmay be formed of a conductive-metallic material such as iron, stainless steel, or tungsten. In an example, the core106bmay have a diameter (e.g., 3 to 5 millimeters (mm) diameter) that is less than a diameter of the first electrode104.

In an aspect, the cathode-anode assembly102may include the second electrode110. In an example, the second electrode110may be a sacrificial anode, or an anode that oxidizes itself during generation of the gas (i.e., operation of the gas generator100). The second electrode110may be formed of an oxidizable material or metal such as molybdenum, tungsten, or a hydrogen-oxidation anode. The second electrode110may form a hollow tube to surround the first electrode104. In an example, the second electrode110may be elongated, form a cylindrical structure, and/or form a concentric cylindrical structure, as shown byFIGS.1A-1B. The second electrode110may be spaced from the first electrode104to form a gap108. In an example, an initial spacing of the gap108may be chosen to be as small as tolerances allow to reduce a voltage drop and power consumption during arsine generation. In an example, the second electrode110may be the about the same length as the first electrode104(and/or about the same length of the outer layer106a), however, aspects of the present disclosure are not limited to these lengths. Instead, the second electrode110may be a length different (e.g., shorter or longer) from the length of the first electrode104.

While the above descriptions have envisioned the use of a sacrificial anode (e.g., second electrode110) such as molybdenum or tungsten, some examples of the cathode-anode assembly102may also be configured with any anode that does not evolve oxygen, such as a hydrogen-oxidation anode, using a sintered mixture of molybdenum and nickel or cobalt, as described for example in “Polarization of Cobalt-Molybdenum and Nickel-Molybdenum Hydrogen Electrodes for Alkaline Fuel Cells”, C. Fan et. al., Int. J. Hydrogen Energy, v. 19, p. 529 (1994). The use of a molybdenum-based hydrogen-oxidation anode may provide the advantage of the anode will erode and release molybdate ions if a portion of the anode is not supplied with adequate hydrogen, but will not produce oxygen, thereby preserving the purity of the evolved arsine gas stream.

The second electrode110may include one or more channels (e.g.,118,120) to allow the gas bubbles160to exit the cathode-anode assembly102and/or to allow for the electrolyte150to enter, circulate through, and exit the cathode-anode assembly102. In an example, the one or more channels (e.g.,118,120) may form circular apertures and/or elongated slots in the second electrode110.

The gas bubbles160generated at the surface of the first electrode104will tend to rise due to their buoyancy relative to the electrolyte150. If the gas bubbles160are transported to the surface of the second electrode110, some gas (e.g., arsine) may be lost due to unintended oxidation; this phenomenon is known as crossover, which may be minimized by various measures. For example, a width of one or more of the first channels118may be increased, but this may impact the uniformity of consumption of the second electrode110and the current density thereon. The convective flow through the one or more of the second channels120may be increased, which will be effective if the gas bubbles160have small diameters. Hydrogen gas may be dispensed through the one or more of the second channels120to form gas bubbles that help displace the gas bubbles160from the surface of the second electrode110, albeit at the possible cost of increasing the effective resistivity of the electrolyte150.

In some aspects, a screen170may be placed to direct the flow of gas bubbles160towards the one or more first channels118, as shown byFIG.1A. Further, the screen170may be porous to allow the flow of the electrolyte150to circulate through the gap108with minimal impediment to transport of reactants and ions. In an example, the porosity of the screen170may be chosen to minimize an impediment of the transport of hydroxyl ions from the first electrode104to the second electrode110. Examples of the screen170may include, a mesh, a polymer sheet with one or more openings, a permeable membrane, or an ion-conductive porous membrane. In an example, the screen170includes one or more supporting members (not shown) to retain the screen170in a fixed position within the gap108.

In some examples, the second electrode110may include a first segment112(upper segment) and a second segment114(lower segment). The second electrode110may include one or more alignment pins116or other provisions to ensure mechanical position of the first segment112with the second segment114and electrical continuity between the first segment112and the second segment114. In an example, the alignment pins116may be supplemented by polymeric or other seals to prevent flow of the electrolyte150in a region between the first segment112and the second segment114.

The first segment112may include one or more first channels118to allow for the gas bubbles160, generated during the operation of the gas generator100, to escape from the gap108and be collected in the gas generator100.

In some examples, an exterior surface of the second electrode110may be covered by a PTFE (e.g., Teflon) or other protective films to minimize corrosion from the electrolyte150

In an example as illustrated inFIGS.1A and1B, the cathode-anode assembly102may be at least partially submerged in electrolyte150and the gap108may contain the electrolyte150. In an example, the electrolyte150may be formed of a conductive material suitable for generation of gas (e.g., arsine) such as potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), or Caesium hydroxide (CsOH). Further, the electrolyte150may optionally contain various additives, such as surfactants, ammonium hydroxide (NH4OH), and/or coordinating agents, such as ethylene diamine tetraacetate (EDTA), chosen to optimize performance in generating arsine.

The electrolyte150may provide temperature control of the cathode-anode assembly102and remove contaminants, generated during the operation of the gas generator100, from the gap108. As explained in more detail below, the electrolyte150may be circulated through the cathode-anode assembly102via the one or more first channels118of the first segment112and one or more second channels120of the second segment114. As shown byFIG.1A, in an example, the electrolyte150may flow into the gap108via the one or more second channels120and exit the gap108via the one or more first channels118. Other flow patterns, however, may also be implemented.

In some examples, the gas generator100may also include a base130configured to support the cathode-anode assembly102. For example, as shown byFIG.1A, the support base130may be positioned below the second electrode110(e.g., below the second segment114of the second electrode110). In addition to, or aside from, supporting the cathode-anode assembly102, the one or more second channels120may extend into the support base130such that the electrolyte150may flow into the cathode-anode assembly102via the support base130.

Based on implementations of the present disclosure, gas bubbles160(e.g., arsine or hydrogen bubbles) generated along the surface of the outer layer106aof the first electrode104may be provided with a path to gas collection at the top of a shell (described in more detail below) via the cathode-anode assembly102. In comparison with vertically placed cathodes/anodes, which may result in complex bubble formation and transport and may be dependent on vertical position of the cathodes/anodes within a generator, leading to variations in effective voltage and current density with location, implementations of the present disclosure allow bubble formation and transport to be substantially similar along the length of the cathode-anode assembly102, promoting length-independent gas generation and cathode erosion.

While examples of sizes and dimensions of the cathode-anode assembly102and components of the cathode-anode assembly102are described herein, the selection of the dimensions of the cathode-anode assembly102and respective component elements may proceed from the following considerations. In the discussion below, the following notation is adopted:

Rc=radius of the core106b;

Roi=initial radius of the outer layer106a;

R0f=final radius of the outer layer106awhen a maximum allowed consumption of the cathode is reached;

Ho=length of the outer layer106aexposed to the electrolyte150;

Nrod=number of cathode-anode assemblies102in a single gas generator100;

Q(AsH3)=total mass of arsenic that could be produced before replacement of the first electrode 104;

Fstd(AsH3)=output flow of arsine in standard liters per minute;

RTP0=conversion constant from standard liters per minute to moles per second, about 7.4×104;

Y(AsH3)=% of AsH3in the produced mixture of AsH3:H2;

Igen=total generation current provided to all the cathode-anode assemblies102of a single gas generator100, where the current supplied to the various cathode-anode assemblies102is treated as electrically in parallel;

ne=number of electrons required to produce an arsine molecule,3in this case; and

The largest quantity of arsine that may be produced by a gas generator100before replacement of the first electrode104is needed is based on the following equation:

The current required to produce a given output flow of arsine, assuming the yield Y is known, is based on the following equation:

The exposed surface area at the start of process with a new set of first electrodes104is based on the following equation:
Asi=2πRoiH0Nrod

The corresponding surface area at the termination of processing with a given set of cathode-anode assemblies102is based on the following equation:
Asf=2πRofH0Nrod

The initial current density at the first electrode104is based on the following equation:

at the initiation of processing with a new set of first electrodes104, and

at the termination of processing with that set of cathode-anode assemblies102. The procedure for determining the dimensions of the reactor elements is then:

(A) Set constraints on the design based on final performance requirements. In an example, such requirements might be the maximum allowed size for the generator envelope based on the facility in which it will be installed, the largest arsenic samples the vendor can fabricate, the uptime requirements of the use facility, and the flow requirements of MOCVD processes. From these external limitations, one may obtain the maximum allowed length of a single rod maximum allowed radius Roirequired total output arsine before rod change Q(AsH3), required output flow rate Fstd.

(B) Establish the maximum allowed current density from experiment or simulation for the specific geometry in use and measure the arsine yield at that current density.

(C) Establish the required current Igen from Fstd for the arsine yield measured above.

(D) From the requirement on Q(AsH3), the allowed starting radius Roi, and the maximum allowed value of Hc, determine the number of rods Nrod.

(E) Determine the radius at which processing of the rod set is terminated, Rof, from the current density constraint Jcf.

(F) Set the core radius Rc, to be slightly less than Rof, such as 90% of Rof.

(G) Choose the inner diameter of the anode (e.g., second electrode110) to create a channel (e.g., gap108) sufficiently large at the initiation of processing with a new set of rods (e.g., first electrode104) to permit the target minimum electrolyte flow.

Referring toFIGS.2A-2D, different views of an example of the gas generator100are depicted.FIG.2Aillustrates a top-down view of an example of the gas generator100,FIG.2Billustrates a cross-sectional side view of the example of the gas generator100ofFIG.2Aalong the line2B-2B, andFIGS.2C and2Dillustrate a cross-sectional side views of an example of a rotational system220of the gas generator100ofFIG.2A.

As shown inFIG.2A, the gas generator100may include an outer shell202(housing, case, or container) forming a housing with a cavity configured to contain the contents of the gas generator100. The outer shell202may be constructed of one or more materials suitable for use with high differential pressure, such as stainless steel. In an example, at least the inside surface of the outer shell202may be coated with PTFE (e.g., Teflon) or other protective films to minimize corrosion from the electrolyte150.

The gas generator100may also include partition walls204to form an isolated area206within the outer shell202. The isolated area206may be configured to isolate (or seal or contain) one or more of the cathode-anode assemblies102and the electrolyte150from remaining areas within the outer shell202. The partition walls204may be formed of a stainless steel material or other material that is not corroded by contact with the electrolyte150. The partition walls204may contain openings for the cores106bof each of the first electrodes104and conductor rods212of each of the second electrodes110to pass through. In an example, any equivalent means of making electrical contact to the second electrodes110may be used, including, but not limited to, using mechanical supports for the second electrodes110as ground connections. In the case of using mechanical supports, a positive potential may be held at ground and the first electrodes104may be held at a negative potential with respect to ground. Gaskets244(see e.g.,FIG.2C), such as PTFE gaskets or other suitable gaskets, may be used in the openings of the partition walls204to allow rotation of the cores106band to prevent or minimize electrolyte leakage to the remaining areas within the outer shell202.

As shown byFIG.2D, in some examples, the partition walls204may be assembled from multiple sections such as a first section240and a second section242(e.g., upper and lower sections) to allow assembly of the cathode rods. In an example, one or more alignment pins250or other means may be provided to ensure accurate assembly of the multiple sections of the partition walls204. In some examples, a region between the first section240and the second section242of the partition walls204may include a flexible gasket or other means for preventing leakage of the electrolyte150.

In an aspect, each of the first electrodes104and the second electrodes110may couple with one or more electrical cables210aand210b(or wires). In an example, the electrical cables210amay couple with ends of the cores106bto provide a flow of current to the first electrodes104during gas generation, and the electrical cables210bmay couple with the conductor rods212to return the current to the current source270during gas generation. While only one end of the first electrodes104and one end of the second electrodes110are shown as being connected to the electrical cables210aand210b, aspects are not limited to this configuration. Instead, other configurations may be used, for example, both ends of the first electrodes104and the second electrodes110may couple with the electrical cables210aand210b, respectively, to reduce the effect of series resistances. Further, while only some of the first electrodes104and the second electrodes110are illustrated as being coupled with the electrical cables210aand210b, respectively, each cathode-anode assembly102may be coupled with the electrical cables210aand210b.

In an aspect, each of the first electrodes104may be rotationally coupled to a rotational system220(see e.g.,FIG.2A). Rotation of the first electrodes104may ensure uniform erosion in azimuth around a surface of the first electrodes104. In an example, the rotational system220may rotate the first electrodes104at a rate comparable to a rate at which the first electrodes104are consumed. In some examples, the rotational system220may rotate the first electrodes104continuously during gas generation, or in periodic steps. In some examples, by limiting the extent of rotation to a small number of approximate multiples of degrees (e.g., 15, 30, 45, 60, 90 or 180), symmetric erosion around the first electrodes104may be obtained while minimizing the stress on the electrical cables210a, allowing simple provisions for electrical connection without the need for sliding or rotating contacts between the electrical cables210aand the first electrodes104.

In an aspect, the rotational system220may include a rack-and-pinion system, as shown, to provide rotation movement of the first electrodes104. In an example, the rotational system220may include one or more drive gears222, racks224, and/or bellows226for rotational movement (see e.g.,FIGS.2A-2D) . The drive gears222may couple with one or more ends of the cores106b, and the racks224may rotationally engage the drive gears222to rotate the first electrodes104. The bellows226may cause the racks224to move linearly. In an example, the bellows may cause to racks224to move linearly in a first direction and then linearly in a second direction opposite the first direction. The bellows226may include a bellows-sealed impeller in order to avoid rotating seals between the isolated area206containing the generated gas and other portions of the gas generator100. The extent of linear motion of the racks224may be selected to ensure uniform azimuthal consumption of the first electrodes104. If consumption of the first electrode104is bilaterally symmetric with respect to the vertical direction, 180 degrees or less of rotation of the first electrodes104may be sufficient. Multiples of degrees (e.g., 15, 30, 45, 60, 90 or 180) may also be employed to account for asymmetries in the construction or operation of the cathode-anode assemblies102.

In an aspect, the rotational system220may also include one or more rack supports228configured to provide support for the racks224. In an example, the rack supports228may mount to or be a part of the partition walls204. However, in other examples, the rack supports228may be mounted to a base of the gas generator100.

As previously described, the initial spacing of the gap108may be chosen to be as small as tolerances allow to reduce a voltage drop and power consumption during operation. During arsine generation, the first electrode104may be consumed. If the first electrode104orientation was fixed during operation, consumption of the first electrode104would vary with respect to an angle from the vertical, due to mass transport within the electrolyte150, non-uniform bubble accumulation, variations in temperature, and other asymmetries. However, the rotational system220may allow rotation of the first electrodes104while the second electrodes110remain fixed.

Accordingly, the rotational system220may ensure uniform erosion or consumption of the first electrodes104and provide maximal utilization of the elemental arsenic on the first electrodes104with minimum changes in performance of the gas generator100.

During operation, the second electrodes110may also erode or be consumed. However, a radius of the first electrode104decreases due to erosion of arsenic, which may reduce an exposed surface area of the first electrode104and increase the current density, whereas internal radius of the second electrode110may increase, which may increase an exposed surface area of the second electrode110and reduce the current density. Accordingly, the decrease of surface area of the first electrode104may dominate the change in a size of the gap108and behavior of the gas generator100.

In an aspect, the gas generator100may also include an electrolyte circulation system230(see e.g.,FIG.2A) configured to circulate or distribute the electrolyte150uniformly through the gas generator100and remove or clean particulates or contaminants generated during the operation of the gas generator100from the cathode-anode assembly102. The electrolyte circulation system230may also maintain control of composition (by adding one or more additives to the electrolyte150and/or filtering contaminants) and control of temperature of the electrolyte150in the cathode-anode assembly102.

The electrolyte circulation system230may include one or more pumps/filters232to pump the electrolyte into the isolated area206and to filter the electrolyte150that exits the isolated area206. In an example, the pumps/filters232may control circulation of the electrolyte150. The pumps/filters232may be located outside of the isolated area206, as shown. In an example, the pumps/filters232may be electrically driven and controlled to avoid use of rotating seals, or the pumps/filters232may include magnetically-coupled pumps. In some examples, the pumps/filters232may filter the electrolyte150to remove any particulates from the electrolyte150. In an some examples, the gas generator100may include one or more reservoirs (not shown) to add one or more compounds to the electrolyte150via the pumps/filters232. For example, the pumps/filters232may incorporate a reservoir to add potassium hydroxide, or any other appropriate solute, to the electrolyte150during arsine generation to compensate for the consumption of hydroxide resulting from the formation of potassium molybdate.

In an example, the electrolyte circulation system230may include one or more electrolyte supply lines234which may receive the electrolyte150from the pump/filters232and provide the electrolyte150to the cathode-anode assemblies102via the one or more second channels120. As shown byFIG.2B, the electrolyte supply lines234may be positioned below the support base130.

The electrolyte circulation system230may also include one or more electrolyte drains236, which provide an opening for the electrolyte150to drain from the isolated area206. In operation, the pumps/filters232may push the electrolyte150up through the cathode-anode assembly102such that the electrolyte150may pass into the space above the cathode-anode assemblies102and drain through the electrolyte drains236.

The electrolyte circulation system230may also include one or more electrolyte return lines238, which may receive the electrolyte150from the electrolyte drains236and provide the electrolyte150to the pumps/filters232.

In an aspect, the gas generator100may also include gas vents260which provide a path for the generated gas to leave the outer shell202. In an example, the gas vents260are connected to one or more gas reservoirs or tanks (not shown) for storing the generated gas. In an example, the gas vents260may be coupled to demisting and purification modules (not shown) for removing water vapor and other contaminants from the gas stream.

In an aspect, the gas generator100may also include a current source270(see e.g.,

FIG.2A) configured to provide current to each of the cathode-anode assemblies102. In an example, the current source270may couple with each of the cores106bof the first electrodes104via the electrical cables210aand with each of the second electrodes110via the conductor rods212and the electrical cables210b. The current source270may include a positive connection and a negative connection. In an example, the positive connection of the current source270may couple with the first electrodes104and the negative connection of the current source270may couple with the second electrodes110. In this arrangement, during gas generation, current may flow from the positive connection of the current source270towards the negative connection of the current source270via the electrical cables210a, the first electrodes104, the second electrodes110, the conductor rods212, and the electrical cables210b. In an example, the current source270may be mounted to the outer shell202(either interior or exterior), or located external to the outer shell202.

In an aspect, the gas generator100may also include a controller290(see e.g.,FIG.2A) for controlling one or more components of the gas generator100including the rotational system220, the electrolyte circulation system230, and/or the current source270. The controller290may be electrically coupled with the components via one or more buses280. In an example, the controller290may cause the current source270to provide current to the cathode-anode assembly102. The current may cause an electrochemical reaction between the first electrode104and the second electrode110to generate gas. In another example, the controller290may control the bellows226of the rotational system220to cause the racks224to move and the first electrode104to rotate. In another example, the controller290may control the pumps/filters232of the electrolyte circulation system230to circulate the electrolyte through the cathode-anode assemblies102. In an example, the controller290may be mounted to the outer shell202(either interior or exterior), or located external to the outer shell202.

While the present disclosure discloses a single gas generator100, aspects of the present disclosure are not limited to being a single gas generator100. Instead, a plurality of gas generators100, including gas generators100of varying numbers and sizes, may be interconnected to provide larger arsine generation capacities than a single gas generator100.

Further, the gas generator100may include additional features for facilitating the generation and removal of the generated gas. For example, the gas generator100may also include a demisting device (not shown) configured to remove and return electrolyte droplets captured within the outer shell202. The demisting device may be positioned at the top of the cavity of the outer shell202or in the gas vents260. In some examples, the gas generator100may include a means for purging the gas generator100and the electrolyte150before use to remove air or oxygen, and after use to remove toxic gases. In some examples, the gas generator100may also include a temperature controller (not shown) to control an external temperature of a surface temperature of the outer shell202over a sufficiently large area exposed to the electrolyte150(e.g. bottom of outer shell202). In some examples, the gas generator100may also include a gas purifier (not shown) to purify the arsine gas by removing water vapor and/or contaminants from the generated arsine gas. In some examples, the gas generator100may also include a gas injector (not shown) to provide an additional gas such as hydrogen to be combined with the generated gas. While the overall pressure of the gas generator100may be controlled by varying the electrical current provided to the gas generator100to control the rate of gas generation, the gas injector may ensure constant composition of the delivered gas stream.

Referring toFIG.3, an example of a method300for generating arsine by the gas generator100according to aspects of the present disclosure is illustrated. Various aspects of the method300may be controlled or coordinated by, for example, the controller290, which may include one or more processors and/or one or more memories with instructions to coordinate the operations of the gas generator100.

At302, the method300may include providing current to a cathode-anode assembly of an gas generator having a top interior surface, wherein a length of the cathode-anode assembly is arranged substantially parallel to the top interior surface. For example, the controller290may control the current source270to provide the current to the cathode-anode assembly102. In an example, the current source270may provide the current to the first electrode104via the electrical cable210aand the current may return to the current source270via the second electrode110, the conductor rods212, and the electrical cable210b.

At304, the method300may include rotating a first electrode of the cathode-anode assembly along a center axis of a length of the first electrode. For example, the controller290may control the rotational system220to rotate the first electrode104via the core106b. In an example, the rotational system220may include the one or more bellows226which linearly moves the rack224causing the drive gear222, coupled with the first electrode104via the core106b, to rotate. In an example, the controller290may continually rotate the first electrode104. In another example, the controller290may rotate the first electrode104according to a periodic step.

At306, the method300may include circulating electrolyte through the gas generator100and the cathode-anode assembly. For example, the controller290may control the electrolyte circulation system230to circulate the electrolyte150through the gas generator100and the cathode-anode assembly102. In an example, controller290may control the pumps/filters232to circulate the electrolyte150. The pumps/filters232may pump the electrolyte150to the cathode-anode assembly102via the electrolyte supply line234and the one or more second channels120. The electrolyte may be pushed around the first electrode104and through the one or more first channels118to an exterior of the cathode-anode assembly102. The electrolyte150may then drain via the one or more drains236to the one or more electrolyte return lines238, which returns the electrolyte to the pumps/filters232.

At308, the method300may optionally include filtering the electrolyte. For example, the controller290may control the electrolyte circulation system230to filter the electrolyte150while being circulated through the gas generator100and the cathode-anode assembly102. In an example, the pumps/filters232may filter the electrolyte150.