Patent Description:
It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems and methods may be implemented using any number of techniques, whether currently known or not yet in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, but may be modified within the scope of the appended claims.

The disclosure includes systems and methods for determining characteristics of an electrolyte in an electrochemical sensor. Electrochemical gas sensors that operate based on aqueous electrolytes (such as sulfuric acid) may exhibit changes in electrolyte concentration due to water uptake or water loss with the ambient environment. The resulting change in concentration affects the performance of the sensor, for example resulting in changes in gas sensitivity and/or the resulting output signal values from the sensor, or in extreme cases can result in the sensor bursting (too much water uptake) or failing due to the electrolyte becoming too dry or too concentrated. It may therefore be desirable to be able to measure the electrolyte concentration so that suitable remedial action may be taken, for example compensating for sensitivity loss or flagging impending failure.

Systems and methods disclosed herein may allow for direct electrochemical measurement of the electrolyte concentration. Typical methods for determining electrolyte concentration may involve impedance measurement. However, impedance measurements do not give a unique result, and there are two possible electrolyte concentrations for any given impedance (as would be known to one skilled in the art). The impedance of the electrolyte is also affected by geometrical factors and the physical location of the electrolyte within the sensor. The disclosed methods and systems may allow for sensors to be operated over a wider environmental range with reduction in the need for recalibration.

Embodiments involve performing cyclic voltammetry on an electrode located within the sensor. In embodiments, the CV is performed on the working electrode. This may involve applying a ramped waveform to the electrode over a range of potentials between the onsets of electrolysis of the electrolyte. The resulting measured current vs voltage trace exhibits peaks due to generation and removal of adsorbed hydrogen, and also due to generation and removal of platinum oxide on the electrode surface. Surprisingly, the disclosed embodiments illustrate that the potential difference between one of the hydrogen peaks and the platinum oxide removal (stripping) peak is a function of electrolyte concentration or pH.

There may be a number of end purposes for the concentration determination. The resulting electrolyte concentration measurement can be used to correct an output value from the signal to provide a more accurate reading of a concentration of one or more gases, where compensation is applied to the sensor output. This would be applied along with the offset and amplification. Additionally, an error may be flagged because the concentration has gotten to a level where compensation can no longer be accurately applied but the sensor may recover. The other uses would be to identify an abnormal concentration, i.e. too high or too low of a concentration that could result in an error and/or permanent failure of the sensor. The sensor may be considered to have completely failed and is not recoverable when the electrolyte has gotten so concentrated that components in the sensor have been irreversibly degraded or the volume has increased to the extent that the sensor is likely to have leaked or burst.

Referring now to <FIG>, an electrochemical sensor may typically have some or all of the elements shown. <FIG> illustrates an exploded view of an exemplary electrochemical sensor <NUM>. The sensor <NUM> may comprise a housing <NUM>, a separator <NUM>-<NUM> near a working electrode <NUM>, and a separator <NUM>-<NUM> between a reference electrode <NUM> and a counter electrode <NUM>. The electrodes <NUM>, <NUM>, and <NUM> along with the electrolyte E are carried in a housing <NUM>. Housing <NUM> can include a vent <NUM> as would be understood by those of skill in the art. Sensor <NUM> can be carried by a gas detector 10a, in an external housing 10b. Electrolyte E is contained in the housing <NUM>.

Electrical connecting elements, indicated at <NUM>-<NUM>, carried by housing <NUM> are coupled to the various electrodes in the housing <NUM>. A power supply <NUM>-<NUM>, which could be implemented as a rechargeable battery, could be carried in external housing 10b to energize the gas detector 10a.

External housing 10b can also carry control circuits 10c which are coupled to the connector elements <NUM>-<NUM> to receive signals from and coupled signals to the electrodes <NUM>, <NUM>, <NUM> so as to sense conditions in the sensor <NUM>, or to control the operation of one or more electrodes <NUM>, <NUM>, <NUM> to carry out the operational and diagnostic methods described herein.

The gas detector 10a can communicate via interface circuits 10d, coupled to control circuits 10c, via a medium M (which could be wired, or wireless), with displaced monitoring systems. The control circuits 10c can be implemented, at least in part, with a programmable processor 10e which executes pre-stored control instructions 10f. Other elements of the sensor <NUM>, illustrated in <FIG>, are conventional and would be known to those of skill in the art.

Cyclic voltammetry may be completed on one or more of the electrodes <NUM>, <NUM>, <NUM> to provide one or more diagnostic scans. Cyclic voltammetry is an electrochemical technique which measures the current that develops in an electrochemical cell under conditions where voltage is in excess of that predicted by the Nernst equation. CV is performed by cycling the potential of an electrode, and measuring the resulting current. In cyclic voltammetry, the electrode potential may ramp linearly versus time in cyclical phases. In some embodiments, other waveforms may be used to complete the cyclic voltammetry. The rate of voltage change over time during each of these phases is known as the experiment's scan rate (V/s). The results of a CV scan on one or more of the electrodes <NUM>, <NUM>, <NUM> may generate diagnostic information about the sensor <NUM>. In embodiments, the CV scans is completed on the working electrode <NUM>.

<FIG> illustrates a cross-section drawing of an electrochemical sensor <NUM>. The sensor <NUM> generally comprises a housing <NUM> defining a cavity or reservoir <NUM> designed to hold an electrolyte solution. A working electrode <NUM> can be placed between an opening <NUM> and the reservoir <NUM>. A counter electrode <NUM> and a reference electrode <NUM> are positioned within the reservoir <NUM>. When the gas reacts at the interface between the working electrode <NUM> and the electrolyte in the separator <NUM>, an electrical current and/or potential can be developed between the electrodes to provide an indication of the concentration of the gas. A reference electrode <NUM> is positioned within the reservoir <NUM> to provide a reference for the potential between the working electrode <NUM> and the counter electrode <NUM>.

The housing <NUM> defines the interior reservoir <NUM>, and one or more openings <NUM> can be disposed in the housing <NUM> to allow a gas to be detected to enter the housing <NUM> into a gas space <NUM>. The housing <NUM> can generally be formed from any material that is substantially inert to the electrolyte and gas being measured. In an embodiment, the housing <NUM> can be formed from a polymeric material, a metal, or a ceramic. For example, the housing can be formed from a material including, but not limited to, acrylonitrile butadiene styrene (ABS), polyphenylene oxide (PPO), polystyrene (PS), polypropylene (PP), polyethylene (PE) (e.g., high density polyethylene (HDPE)), polyphenylene ether (PPE), or any combination or blend thereof.

One or more openings <NUM> can be formed through the housing <NUM> to allow the ambient gas to enter the gas space <NUM> and/or allow any gases generated within the housing to escape. In an embodiment, the electrochemical sensor <NUM> may comprise at least one inlet opening <NUM> to allow the ambient gas to enter the housing <NUM>. The opening <NUM> can be disposed in a cap when a cap is present and/or in a wall of the housing <NUM>. In some embodiments, the opening <NUM> can comprise a diffusion barrier to restrict the flow of gas (e.g., carbon monoxide, hydrogen sulfide, oxygen, etc.) to the working electrode <NUM>. The diffusion barrier can be created by forming the opening <NUM> as a capillary, and/or a film or membrane can be used to control the mass flow rate through the one or more openings <NUM>.

In an embodiment, the opening <NUM> may serve as a capillary opening to provide a rate limited exchange of the gases between the interior and exterior of the housing <NUM>. In an embodiment, the opening <NUM> may have a diameter between about <NUM> and about <NUM>, where the opening <NUM> can be formed using a conventional drill for larger openings and a laser drill for smaller openings. The opening <NUM> may have a length between about <NUM> and about <NUM>, depending on the thickness of the cap or housing <NUM>. In some embodiments, two or more openings <NUM> may be present for the inlet gases. When a membrane is used to control the gas flow into and/or out of the housing <NUM>, the opening diameter may be larger than the sizes listed above as the film can contribute to and/or may be responsible for controlling the flow rate of the gases into and out of the housing <NUM>.

The reservoir <NUM> comprises the counter electrode <NUM>, the reference electrode <NUM>, and the working electrode <NUM>. The electrolyte can be contained within the reservoir <NUM>, the counter electrode <NUM>, the reference electrode <NUM>, and the working electrode <NUM> being in electrical contact through the electrolyte. One or more porous separators <NUM>, <NUM> or other porous structures are used to retain the electrolyte in contact with the electrodes <NUM>, <NUM>, <NUM>. The separators <NUM>, <NUM> can comprise a porous member that acts as a wick for the retention and transport of the electrolyte between the reservoir <NUM> and the electrodes <NUM>, <NUM>, <NUM> while being electrically insulating to prevent shorting due to direct contact between any two electrodes. One or more of the porous separators <NUM>, <NUM> extend into the reservoir <NUM> to provide the electrolyte a path to the electrodes <NUM>, <NUM>, <NUM>. In an embodiment, a separator <NUM> can be disposed between the counter electrode <NUM> and the reference electrode <NUM>, and a separator <NUM> can be disposed between the reference electrode <NUM> and the working electrode <NUM>.

One or more of the separators <NUM>, <NUM> can comprise a nonwoven porous material (e.g., a porous felt member), a woven porous material, a porous polymer (e.g., an open cell foam, a solid porous plastic, etc.), or the like, and is generally chemically inert with respect to the electrolyte and the materials forming the electrodes <NUM>, <NUM>, <NUM>. In an embodiment, the separators <NUM>, <NUM> can be formed from various materials that are substantially chemically inert to the electrolyte including, but not limited to, glass (e.g., a glass mat), polymer (plastic discs), ceramics, or the like.

The electrolyte can be any conventional aqueous acidic electrolyte such as sulfuric acid, phosphoric acid, or a neutral ionic solution such as a salt solution (e.g., a lithium salt such as lithium chloride, etc.), or any combination thereof. For example, the electrolyte can comprise sulfuric acid having a molar concentration between about <NUM> to about <NUM>. Since sulfuric acid is hygroscopic, the concentration can vary from about <NUM> to about <NUM> wt% (<NUM> to <NUM> molar) over a relative humidity (RH) range of the environment of about <NUM> to about <NUM>%. In an embodiment, the electrolyte can comprise phosphoric acid having a concentration in an aqueous solution between about <NUM>% to about <NUM>% H<NUM>PO<NUM> by weight. As another example, the electrolyte can include a lithium chloride salt having about <NUM>% to about <NUM>% LiCl by weight, with the balance being an aqueous solution.

In some embodiments, the electrolyte may be in the form of a solid polymer electrolyte which comprises an ionic exchange membrane. In some embodiments, the electrolyte can be in the form of a free liquid, disposed in a matrix or slurry such as glass fibers (e.g., the separator <NUM>, the separator <NUM>, etc.), or disposed in the form of a semi-solid or solid gel.

The working electrode <NUM> is disposed within the housing <NUM>. The gas entering the sensor <NUM> can contact one side of the working electrode <NUM> and pass through the working electrode <NUM> to reach the interface between the working electrode <NUM> and the electrolyte. The gas can then react to generate the current indicative of the gas concentration. As disclosed herein, the working electrode <NUM> can comprise a plurality of layers. The base or substrate layer can comprise a hydrophobic material or a hydrophobically treated material. A catalytic material can be formed as an electrode on one side of the working electrode <NUM> and placed in contact with the electrolyte.

In an embodiment, the working electrode <NUM> can comprise a porous substrate or membrane as the base layer. The substrate can be porous to the gas of interest, which in some embodiments can comprise hydrogen sulfide, carbon monoxide, or oxygen. In an embodiment, the substrate can comprise a carbon paper formed of carbon or graphite fibers. In some embodiments, the substrate can be made to be electrically conductive through the addition of a conductive material such as carbon. The use of carbon may provide a sufficient degree of electrical conductivity to allow the current generated by the reaction of the gas with the electrolyte at the surface of the working electrode <NUM> to be detected by a lead coupled to the working electrode <NUM>. Other electrically conductive substrates may also be used such as carbon felts, porous carbon boards, and/or electrically conductive polymers such as polyacetylene, each of which may be made hydrophobic as described below. Alternatively, an electrically conductive lead can be coupled to the catalytic layer to electrically couple the catalytic material to the external circuitry, as described in more detail herein. In an embodiment, the substrate can be between about <NUM> mils to about <NUM> mils thick in some embodiments.

The porous substrate can be hydrophobic to prevent the electrolyte from passing through the working electrode <NUM>. The substrate can be formed from a hydrophobic material, or the substrate can be treated with a hydrophobic material. In an embodiment, the substrate can be made hydrophobic through the impregnation of the substrate with a hydrophobic material such as a fluorinated polymer (e.g., PTFE, etc.). In some embodiments, the substrate or membrane can comprise GEFC-IES (e.g., the copolymer of perfluorosulfonic acid and PTFE, which is commercially available from Golden Energy Fuel Cell Co. ), Nafion® (a copolymer of polytetrafluoroethylene and perfluoro-<NUM>,<NUM>-dioxa-<NUM>-methyl-<NUM>-octene-sulfonic acid, which is commercially available from Dupont™), or pure or nearly pure polytetrafluoroethylene (PTFE). The impregnation process can include disposing a hydrophobic material containing solution or slurry on the substrate using a dipping, coating, or rolling process. Alternatively, a dry composition such as a powder can be applied to the substrate. In some embodiments, an optional sintering process can be used to infuse the hydrophobic material into the substrate to create the hydrophobic base layer for the working electrode <NUM>, where both sides of the hydrophobic base layer are hydrophobic. The sintering process can cause the hydrophobic polymer to bond or fuse with the carbon of the substrate to securely bond the hydrophobic material to the substrate.

The resulting substrates can contain about <NUM>% to about <NUM>% by weight of the hydrophobic polymer. The amount of hydrophobic material added to the substrate can affect the electrical conductivity of the substrate, where the electrical conductivity tends to decrease with an increased amount of the hydrophobic material. The amount of the hydrophobic polymer used with the substrate may depend on the degree of hydrophobicity desired, the porosity to the target gas, and the resulting electrical conductivity of the working electrode.

The catalytic layer can be formed by mixing the desired catalyst with a binder and depositing the mixture on the substrate material. The binder can comprise a solution of perfluorinated ion electrolyte solution (e.g., GEFC-1ES, Nafion®, etc.), a hydrophobic material such as PTFE, mixtures thereof, or the like. When used as a binder, the GEFC-IES Nafion® and/or PTFE can affect the gas diffusion parameters while supporting the electrocatalyst and maximizing the interfaces between catalyst, gas, and electrolyte at which the electrochemical processes occur. Glycol or other similar chemicals can be used as a diluent to form a catalyst slurry, recipe, or catalyst system, which can be printed on a substrate by a printer.

The catalytic layer might be deposited onto the substrate by, for example, screen printing, filtering in selected areas from a suspension placed onto the substrate, by spray coating, or any other method suitable for producing a patterned deposition of solid material. Deposition might be of a single material or of more than one material sequentially in layers, so as, for example, to vary the properties of the electrode material through its thickness or to add a second layer of increased electrical conductivity above or below the layer which is the main site of gas reaction. Once deposited, the printed element can optionally be sintered at an elevated temperature to form the electrode.

The working electrode comprises platinum. In the working electrode <NUM>, the catalytic layer can comprise carbon (e.g., graphite) and/or one or more metals or metal oxides such as copper, silver, gold, nickel, palladium, platinum, ruthenium, iridium, and/or oxides of these metals. The catalyst used can be a pure metal powder, a metal powder combined with carbon, or a metal powder supported on an electrically conductive medium such as carbon, or a combination of two or more metal powders either as a blend or as an alloy. The materials used for the individual electrodes can be the same or different. In an embodiment, the working electrode <NUM> comprises a platinum electrode. The catalyst material can have a weight loading per square centimeter (cm<NUM>) of the surface area of the working electrode <NUM> of between about <NUM>/cm<NUM> and about <NUM>/cm<NUM>, or between about <NUM>/cm<NUM> and about <NUM>/cm<NUM>, or about <NUM>/cm<NUM>.

The counter electrode <NUM> is disposed within the housing <NUM>. The counter electrode <NUM> can comprise a substrate or membrane such as a PTFE membrane, a GEFC-IES membrane, a Nafion® membrane, or the like having a catalytic material disposed thereon. In an embodiment, the catalytic material can be mixed and disposed on the membrane using any suitable process such as rolling, coating, screen printing, or the like to apply the catalytic material on the membrane, as described in more detail herein. The catalyst layer can then be bonded to the membrane through a sintering process as described herein.

In an embodiment, the catalytic material for the counter electrode can comprise a noble metal such as gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), Iridium (Ir), oxides thereof, or any combination thereof. In an embodiment, the catalytic material comprises a platinum ruthenium (Pt-Ru) mixture that is screen printed on the membrane, where the membrane can be a GEFC-IES membrane. The catalyst loading for the counter electrode <NUM> can be within any of the ranges described herein for the working electrode <NUM>. In an embodiment, the catalyst loading for the counter electrode <NUM> can be the same or substantially the same as the catalyst loading for the working electrode <NUM>, the catalyst loading can also be greater than or less than that of the working electrode <NUM>.

Similarly, the reference electrode <NUM> is disposed within the housing <NUM>. The reference electrode <NUM> can comprise a substrate or membrane such as a PTFE membrane, a GEFC-IES membrane, a Nafion® membrane, or the like having a catalytic material disposed thereon. In an embodiment, the catalytic material can be mixed with a hydrophobic material (e.g., PTFE, etc.) and disposed on the PTFE membrane. Any of the methods used to form the working electrode <NUM> or the counter electrode <NUM> can also be used to prepare the reference electrode <NUM>. In an embodiment, the catalytic material used with the reference electrode <NUM> can comprise a noble metal such as gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), Iridium (Ir), oxides thereof, or any combination thereof. In an embodiment, the catalytic material used to form the reference electrode <NUM> can comprise a Pt-Ru mixture that is screen printed on the membrane, where the membrane can be a GEFC-IES membrane. The catalyst loading for the reference electrode <NUM> can be within any of the ranges described herein for the working electrode <NUM>. In an embodiment, the catalyst loading for the reference electrode <NUM> can be the same or substantially the same as the catalyst loading for the working electrode <NUM>, the catalyst loading can also be greater than or less than that of the working electrode <NUM>. While illustrated in <FIG> as having the reference electrode <NUM>, some embodiments of the electrochemical sensor <NUM> may not include a reference electrode <NUM>.

In order to detect the current and/or potential difference across the electrodes <NUM>, <NUM>, <NUM> in response to the presence of the target gas, one or more leads or electrical contacts can be electrically coupled to the working electrode <NUM>, the reference electrode <NUM>, and/or the counter electrode <NUM>. The lead contacting the working electrode <NUM> can contact either side of the working electrode <NUM> since the substrate comprises an electrically conductive material. In order to avoid the corrosive effects of the electrolyte, the lead contacting the working electrode <NUM> can contact the side of the working electrode <NUM> that is not in contact with the electrolyte. Alternatively, the electrode material may comprise a corrosion resistant material such as platinum and it is in contact with the electrolyte. Leads may be similarly electrically coupled to the counter electrode <NUM> and the reference electrode <NUM>. The leads can be electrically coupled to external connection pins to provide an electrical connection to external processing circuitry. The external circuitry can detect the current and/or potential difference between the electrodes <NUM>, <NUM>, <NUM> and convert the current into a corresponding target gas concentration.

In use, the sensor <NUM> can detect a target gas concentration. In use, the ambient gas can diffuse into the sensor <NUM> through the opening <NUM>, which serves as the intake port for the sensor <NUM>. The ambient gas can comprise a concentration of the target gas, which may include hydrogen sulfide, oxygen, and/or carbon monoxide. The gas can contact the working electrode and pass through the fine pores of the porous substrate layer to reach the surface of the working electrode <NUM> treated with the catalyst layer. The electrolyte is in contact with the surface of the working electrode <NUM>, and the target gas may react and result in an electrolytic current forming between the working electrode <NUM> and the counter electrode <NUM> that corresponds to the concentration of the target gas in the ambient gas. By measuring the current, the concentration of target gas can be determined using, for example, the external detection circuitry.

In embodiments, one or more elements of the sensor (as described above in <FIG> and <FIG>) is scanned using cyclic voltammetry to observe the effects of changing concentration in the electrolyte (E above).

An electrochemical sensor may be scanned using one or more of the electrodes. According to the invention, the scanning is done on the working electrode. The scan may generate a graph that contains a plurality of peaks due to adsorption, desorption, formation, and/or reduction of certain elements. The scanning is completed at a plurality of electrolyte concentrations, wherein the graphs for each of the concentrations may be compared. In embodiments, the graph shows one or more peaks that are consistent for each concentration, which may be considered reference peaks. Additionally, the graph shows one or more peaks that change with concentration. The difference in voltage between the concentration dependent peaks and the reference peaks may provide a correlation for electrolyte concentration. In some embodiments, this correlation may be approximately linear, where the axes may be electrolyte concentration and voltage difference between the two peaks. In other embodiments, the correlation may comprise a non-linear graph.

Once a correlation is established, the electrolyte concentration for similar electrochemical sensors may be determined by completing a CV scan on the sensor, and then identifying the relevant peaks to the correlation. Once the voltage difference between the peaks is identified, the electrolyte concentration may be determined. The determined electrolyte concentration may be used to correct sensor readings, and/or to identify any other errors with the sensor.

The disclosure having been generally described, the following examples are given as particular embodiments of the disclosure and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification or the claims in any manner.

<FIG> illustrates a cyclic voltammogram of an exemplary electrode. To investigate the effects of the changing concentration of acid in the sensor cells, cyclic voltammetry may be performed in a range of N<NUM> purged, H<NUM>SO<NUM> solutions (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>) and the results are shown in <FIG>. Using the same electrode, acid concentration was varied between pH <NUM> and -<NUM> (<NUM> - <NUM>).

The cyclic voltammogram shown in <FIG> illustrates a plot generated from an exemplary electrode with a PTFE backing and PTFE binder measured at a scan rate of <NUM> Volts per second (V/s). The electrochemical cell was purged with N<NUM> (for approximately <NUM>). The reference may comprise saturated mercurous sulfate electrode (SMSE) and the counter electrode may comprise platinum (Pt) gauze. In another embodiment, the calibration may be completed on an assembled gas sensor. In each case the electrode was conditioned in the new solution for <NUM> scans between the same limits at <NUM> mV/s prior to the measurement, each CV shown is the 3rd of <NUM> scans at <NUM> mV/s.

The section of the CV plot which is more negative than (or to the left of) -<NUM> V vs SMSE, where hydrogen adsorption and desorption (Hads) occurs is relatively similar and only changes a small amount. For this reason it has been used as a reference point. The Pt-Oxide formation and reduction which is all more positive than (or to the right of) <NUM> V vs SMSE changes a large amount.

<FIG> shows a plot of the potential difference between the strong Hads peak and Pt-Oxide reduction peak vs. the pH of the electrolyte, where the electrolyte has been purged with N<NUM>. <FIG> shows that there is a strong correlation between the potential difference between the two peaks (Hads and Pt-Oxide reduction) and the pH of the electrolyte. Therefore, this measurement could therefore be used as an indicator of the pH of the electrolyte.

<FIG> shows a plot of the potential difference between the strong Hads peak and Pt-Oxide reduction peak vs. the pH of the electrolyte, where the electrolyte has been purged with O<NUM>. An oxygen saturated electrolyte may be indicative of the working conditions for a sensor. <FIG> shows that there is a strong correlation between the potential difference between the two peaks (Hads and Pt-Oxide reduction) and the pH of the electrolyte. Therefore, this measurement could therefore be used as an indicator of the pH of the electrolyte.

<FIG> illustrates the sensor <NUM> in the context of a larger circuit. The circuit can include a circuit board <NUM>, which can comprise a separate component from the sensor <NUM>, a portion of the housing, or in some embodiments, an extension of the substrate such that the sensor <NUM> is formed on a single substrate that the other components are also disposed on. In this embodiment, the leads <NUM> may extend through a wall of the housing, and contact various external circuitry such as various sensing circuitry <NUM> (e.g. sensors, meters, etc.), a potentiostat <NUM>, operating and control circuitry <NUM>, communication circuitry <NUM>, and the like. The sensor <NUM> and meters can comprise additional sensors such as temperature and/or pressure sensors, which may allow for compensation of the sensor <NUM> outputs such that the compensation measurements are taken at or near the sensor <NUM> itself. Further, the location of the sensing circuitry <NUM> at or near the sensor <NUM> may allow smaller currents to be detected without intervening resistance, current loss, or electrical noise in longer electrical conductors. The control circuitry <NUM> may comprise a processor <NUM> and a memory <NUM> for performing various calculations and control functions, which can be performed in software or hardware. The communication circuitry <NUM> may allow the overall sensor results or readings to be communicated to an external source, and can include both wired communications using, for example, contacts on the board, or wireless communications using a transceiver operating under a variety of communication protocols (e.g., WiFi, Bluetooth, etc.). In some embodiments, the sensor <NUM> can be a separate component that is electrically coupled to external operating circuitry.

The control circuitry <NUM> of the sensor <NUM> may be operable to control the potentiostat <NUM> to complete the CV scans of the sensor <NUM>. The control circuitry <NUM> may also receive the readings from the sensor <NUM> that are generated during the CV scans, and may be configured to analyze the readings, as described above.

While various embodiments in accordance with the principles disclosed herein have been shown and described above, modifications thereof may be made by one skilled in the art. The embodiments described herein are representative only and are not intended to be limiting. Many variations, combinations, and modifications are possible. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also possible. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention(s). Furthermore, any advantages and features described above may relate to specific embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages or having any or all of the above features.

Use of broader terms such as "comprises," "includes," and "having" should be understood to provide support for narrower terms such as "consisting of," "consisting essentially of," and "comprised substantially of. " Use of the terms "optionally," "may," "might," "possibly," and the like with respect to any element of an embodiment means that the element is not required, or alternatively, the element is required, both alternatives being within the scope of the embodiment(s). Also, references to examples are merely provided for illustrative purposes, and are not intended to be exclusive.

While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the scope of the invention as defined by the appended claims. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted or not implemented.

Claim 1:
A method for identifying a concentration of an aqueous acidic electrolyte in an electrochemical sensor, the method comprising:
scanning a working electrode of the electrochemical sensor using cyclic voltammetry, wherein the working electrode is in contact with the electrolyte, wherein a porous separator retains the electrolyte in contact with the working electrode, and wherein the working electrode comprises platinum;
generating a set of readings from the cyclic voltammetry;
identifying positions of at least two peaks in the set of readings, wherein one peak is a reference peak corresponding to adsorption or desorption of hydrogen and the other peak is due to Pt-oxide formation or reduction; and
determining the electrolyte concentration of the electrolyte of the electrochemical sensor by applying a predetermined correlation to a voltage difference between the identified positions of the at least two peaks.