Hydrogen sulfide sensor based on Pt-Au alloy nano catalytic material and preparation method thereof

Abstract

The invention relates to the technical field of pollution monitoring equipment, in particular to a Pt-Au alloy nano catalytic material-based hydrogen sulfide sensor and a preparation method thereof, AgCl nano cube is used as a sacrificial template to successfully synthesize a Pt-Au bimetallic alloy catalyst, and the catalyst is loaded on a pretreated conductive carbon black XC-72 carrier to obtain the hydrogen sulfide sensor based on the Pt-Au alloy nano catalytic material. A water-based silk-screen printing technology is utilized to further prepare a membrane electrode group, a device model constructed by combining a 3D printing technology is combined to assemble a gas sensor, and due to the synergistic effect between Pt and Au bimetals, the alloy catalyst shows excellent gas-sensitive performance superior to that of a single-metal catalyst, and particularly, the gas-sensitive performance of the alloy catalyst is greatly improved. The introduction of Au effectively alleviates the poisoning phenomenon of a Pt-based catalyst to H2S and the poisoning effect of CO, so that the constructed H2S sensor has excellent repeatability and stability, and realizes a low detection limit.

Description

Technical Field

[0001] The present invention relates to the technical field of pollution monitoring equipment, in particular to a hydrogen sulfide sensor based on a Pt-Au alloy nanocatalytic material and a preparation method thereof. Background Art

[0002] Increased levels of air pollutants lead to a decline in air quality. Airborne pollutants, toxic gases, and volatile organic compounds (VOCs) pose a threat to human health. Sensitive monitoring of their concentrations can maximize the protection of animals and humans from these harmful gases. Common hazardous gases in our daily lives include NH3, H2S, CO2, CH4, and CO. H2S is a colorless, toxic, and flammable gas, and its biotoxicity depends primarily on its concentration. The Occupational Safety and Health Administration (OSHA) sets a maximum 10-minute exposure limit for H2S at 10 ppm. Exposure to H2S concentrations above 100 ppm can be fatal in an instant. Given the widespread use of H2S in manufacturing industries, from petrochemicals and natural gas to chemical manufacturing, online monitoring of its concentration is essential to protect healthy employees and warehouse workers. Therefore, to effectively detect trace amounts of H2S, it is necessary to develop a small, portable, fast, and practical H2S gas sensor capable of online monitoring.

[0003] Electrochemical gas sensors are also a type of applied gas sensor. They are attracting increasing attention due to their fast response, good accuracy, cost-effectiveness, simple manufacturing process, and flexible configuration capabilities. Platinum-based metals are widely used in sensing gases such as H2S, CO, and NO2 due to their excellent catalytic sensing properties, including accurate detection, fast response, and recovery time. In industrial production, electrochemical gas sensors are used as consumables. On the one hand, this is due to electrolyte loss, which can be improved by using colloidal electrolytes / ionic electrolytes to extend the lifespan and avoid electrolyte leakage. On the other hand, the nano-sized precious metal catalysts in the core electrode membrane of electrochemical gas sensing elements gradually deactivate during long-term use, mainly manifested in catalyst agglomeration and performance degradation or even loss due to long-term poisoning of the catalyst. For electrochemical gas sensors, the membrane electrode is the core component, and its catalyst cost and detection durability are important parameters. In order to develop high-performance and stable electrochemical gas sensors, it is necessary to explore new high-performance catalytic materials and study their application and detection in the field of gas sensing. Summary of the Invention

[0004] The object of the present invention is to provide a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material, comprising a catalyst, wherein the catalyst is a Pt-Au / C nanocatalyst, and the Pt-Au / C nanocatalyst is prepared by loading a Pt-Au bimetallic alloy catalyst on pretreated conductive carbon black XC-72.

[0006] A method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material comprises the following steps:

[0007] Step S1, taking 300 mg of commercial conductive carbon black XC-72 and adding it to a mixed solution of 30% hydrogen peroxide and 10% nitric acid, after ultrasonic dispersion for 0.5 h, transferring it to an oil bath and heating under reflux for 5 h, then transferring it to a centrifuge to obtain a precipitate, drying it at 60° C. overnight, and then grinding it to obtain a modified conductive carbon black of equal mass;

[0008] Step S2: 200 mg of PVP and 250 mg of AgNO3 were dissolved in 25 mL of ethylene glycol and stirred until fully dissolved to obtain solution A. 36 mL of FeCl3 ethylene glycol solution was prepared, ultrasonically dispersed for 10 min, and stirred for 30 min until the FeCl3 was completely dissolved to obtain solution B.

[0009] Step S3: Solutions A and B were mixed and immediately transferred to an oil bath at 130°C for reaction under magnetic stirring for 5 h. After the reaction, the mixture was immediately cooled in an ice-water bath, and the solvent and PVP were removed. The resulting AgClNCs were dispersed in 8 mL of ethanol / water solution.

[0010] Step S4: Using the prepared AgCl-NCs as a template, a Pt-Au / C bimetallic nanocatalyst was prepared in an oil phase EG. 1 mL of the AgCl-NCs solution was dispersed in 20 mL of EG and stirred at 60°C for 30 min. 20 μL of HAuCl4 solution and 4 mL of a 20 mM K2PtCl4 solution were then added dropwise thereto. The mixture was stirred at 60°C for 3 h to obtain a black suspension that could be separated by standing.

[0011] Step S5, centrifuge and wash with water or alcohol, and let the supernatant stand. Remove AgCl and Ag from the prepared solid catalyst powder, dry and grind the product, record it as Pt-Au-1, take 5 mg of Pt-Au-1 and disperse it in 45 mg of pretreated XC-72. After stirring overnight, centrifuge and dry to obtain Pt-Au-1 / C catalyst, and assemble the obtained catalyst into a gas sensor.

[0012] Preferably, in step S1, the amount of 30% hydrogen peroxide used is 10 mL, and the amount of 10% nitric acid mixed solution used is 20 mL.

[0013] Preferably, in step S1, the temperature of the oil bath during the heating and reflux process is set to 60°C.

[0014] Preferably, in step S2, the molecular weight of PVP is selected as: MW=58000.

[0015] Preferably, in step S2, the concentration of the FeCl3 ethylene glycol solution is 0.6 mM.

[0016] Preferably, in step S3, the process of removing the solvent and PVP is as follows:

[0017] Step S3.1, adding a certain amount of acetone to the material after water bath cooling, and letting it stand overnight to extract the off-white AgCl nanocube precipitate;

[0018] Step S3.2: The upper layer of solution was removed, and the lower layer of precipitate was centrifuged at 4000 rpm for 5 min, and washed with deionized water and ethanol several times to remove the solvent and PVP.

[0019] Preferably, in step S4, after the HAuCl4 solution is dripped, a certain amount of AA solution is dripped to reduce the precursor solution and inhibit the electrochemical replacement reaction between silver and the noble metal precursor.

[0020] Preferably, in step S5, the mass fraction of the obtained Pt-Au-1 / C catalyst is 10%.

[0021] Preferably, in step S5, the prepared solid catalyst powder is washed with a 1M ammonia solution and a 6M nitric acid solution in sequence to remove AgCl and Ag.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention successfully synthesized a Pt-Au bimetallic alloy catalyst using AgCl nanocubes as a sacrificial template. This catalyst was then loaded onto a pretreated conductive carbon black XC-72 carrier to prepare a Pt-Au / C nanocatalyst. A membrane electrode assembly was further prepared using water-based screen printing technology, and a device model constructed using 3D printing technology was assembled into a gas sensor. Thanks to the synergistic effect between the Pt and Au bimetallics, the alloy catalyst exhibited superior gas-sensing performance that surpassed that of single metal catalysts. In particular, the introduction of Au effectively alleviated the poisoning of the Pt-based catalyst on H2S and the poisoning of CO, resulting in the constructed H2S sensor with excellent repeatability and stability, and a low detection limit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the morphology and structure characterization of Pt-Au nanocatalyst;

[0025] Figure 2 Schematic diagram of the structure of membrane electrode and test kit;

[0026] Figure 3 X-ray diffraction patterns of different materials;

[0027] Figure 4 is the cyclic voltammetry curve of the hydrogen sulfide sensor based on Pt-Au-1 catalyst;

[0028] Figure 5 Optimize the curve graph for experimental conditions;

[0029] Figure 6 This is the response recovery signal curve of the gas sensor based on Pt-Au / C-1;

[0030] Figure 7 The graph of the gas sensor response signal based on Pt-Au-1 catalyst is shown;

[0031] Figure 8 Repeatability curve and response time summary statistics of the Pt-Au / C-1 based sensor.

[0032] Figure 9 Schematic diagram of the effect of different temperatures on sensor sensitivity;

[0033] Figure 10 Schematic diagram of the sensor's working stability. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The invention relates to a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material, comprising a catalyst, wherein the catalyst is a Pt-Au / C nanocatalyst, and the Pt-Au / C nanocatalyst is prepared by loading a Pt-Au bimetallic alloy catalyst on pretreated conductive carbon black XC-72.

[0036] A method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material comprises the following steps:

[0037] Step S1, taking 300 mg of commercial conductive carbon black XC-72, adding it to a mixed solution of 10 mL of 30% hydrogen peroxide and 20 mL of 10% nitric acid, after ultrasonic dispersion for 0.5 h, transferring it to an oil bath, heating and refluxing at 60° C. for 5 h, then transferring it to a centrifuge to obtain a precipitate, drying it at 60° C. overnight, and then grinding it to obtain a modified conductive carbon black of equal mass;

[0038] Step S2: 200 mg of PVP and 250 mg of AgNO3 were dissolved in 25 mL of ethylene glycol and stirred to fully dissolve to obtain solution A. 36 mL of 0.6 mM FeCl3 ethylene glycol solution was prepared, ultrasonically dispersed for 10 min, and stirred for 30 min until the FeCl3 was completely dissolved to obtain solution B, wherein the molecular weight of PVP was selected: MW = 58000;

[0039] Step S3: Solutions A and B were mixed and immediately transferred to an oil bath at 130°C for reaction under magnetic stirring for 5 h. After the reaction, the mixture was immediately cooled in an ice-water bath, a certain amount of acetone was added, and the mixture was allowed to stand overnight to extract the off-white AgCl nanocube (NCs) precipitate. The upper layer of the solution was removed, and the lower precipitate was centrifuged at 4000 rpm for 5 min and washed several times with deionized water and ethanol to remove the solvent and PVP. The resulting AgCl NCs were dispersed in 8 mL of ethanol / water solution with a volume ratio of 1:1 and stored in the dark.

[0040] Step S4: Using the prepared AgCl-NCs as a template, a Pt-Au / C bimetallic nanocatalyst was prepared in an oil phase EG. 1 mL of the AgCl-NCs solution was dispersed in 20 mL of EG and stirred at 60°C for 30 min. 20 μL of HAuCl4 solution and 4 mL of a 20 mM K2PtCl4 solution were sequentially added dropwise thereto. A certain amount of AA solution was added dropwise to reduce the precursor solution and inhibit the electrochemical replacement reaction (GRR) between silver and the noble metal precursor. The suspension was stirred at 60°C for 3 h to obtain a black suspension, which could be separated by standing.

[0041] Step S5, centrifuge and wash with water or alcohol, and let the supernatant stand. The prepared solid catalyst powder is washed with 1M ammonia solution and 6M nitric acid solution in sequence to remove AgCl and Ag. The product is vacuum dried at 60°C, the yield is calculated, and the product is ground into powder, recorded as Pt-Au-1. 5 mg of Pt-Au-1 is dispersed in 45 mg of pretreated XC-72, stirred overnight, centrifuged, and dried in an oven at 60°C to obtain a Pt-Au-1 / C catalyst with a mass fraction of 10%. The obtained catalyst is prepared into an electrode film and assembled into a gas sensor to obtain the sensor.

[0042] Example:

[0043] ①、Morphology and structural characterization of Pt-Au nanocatalysts:

[0044] Under the same reaction conditions, Pt / C and Au / C single metal catalysts without HAuCl4 / K2PtCl4 and Pt-Au-2 / C without AgClNCs as template were prepared as control groups. Figure 1 Schematic diagram of the morphology and structural characterization of Pt-Au nanocatalysts, morphology and structural characterization of Pt-Au nanocatalysts, where the scanning electron microscope images of Pt-Au-2 are AB, the scanning electron microscope images of AgCl nanocubes are CD, and the scanning electron microscope image of Pt-Au-1 composite material is EF.

[0045] like Figure 1 As shown in Figure 2, the micromorphology of the prepared AgCl, Pt-Au-1 and Pt-Au-2 composite materials was characterized by scanning electron microscopy (SEM). Figure 1 The AB graph in the middle shows the morphology of the prepared Pt-Au-2 nanomaterial. The catalyst nanoparticles are about 100 nm in size and agglomerated, which is not conducive to maintaining the H2S sensing performance. Figure 1 The CD sub-figure in the figure shows the SEM image of AgCl nanoparticles prepared by the polyol method. The prepared AgCl has sharp edges and corners and presents the shape of nanocubes. Except for some particles with a larger side length of about 1μm, the side length of most particles can be controlled within 500nm, and a small part can be controlled within 100nm. The microscopic morphology of AgCl nanocubes can effectively prevent the performance degradation caused by the agglomeration of the catalyst. Figure 1 Figures EF in the figure show the microscopic morphology of the Pt-Au-1 composite material prepared using silver chloride nanocubes as templates. The prepared Pt-Au nanoparticles are attached to the vicinity of AgClNCs and are about 20 nm in size. More importantly, due to the spatial confinement of AgClNCs, the nanoparticles hardly agglomerate.

[0046] The prepared Pt-Au catalyst was loaded onto conductive carbon black, and a film was coated by screen printing to prepare a gas sensor. Figure 2 Figure A shows 20 groups of gas-sensitive films prepared from the same batch. The catalysts adhere tightly to the PTFE films and are evenly distributed. The printing consistency of the electrode films in the same batch is good, ensuring that there will not be too large a gap in gas-sensitive performance due to individual differences in the gas-sensitive films. Figure 2 The B part of the figure shows the prepared three-component membrane electrode, which is the working electrode, the counter electrode and the reference electrode from left to right. Figure 2The C part of the diagram shows the corresponding dimensions, where the diameter ratio of PTFE membrane: working electrode: counter electrode: reference electrode is 1.8:1.2:1.2:0.6cm. All gas sensors are assembled and tested using this parameter. Figure 2 The D part in the middle shows a scanning electron microscope image of the cross section of the prepared working electrode. The porous and breathable thick film at the bottom of the figure is a base PTFE film with a thickness of 200 μm, on which is a coated Pt-Au catalyst. Figure 2 The E part in the middle is an enlarged image of the catalyst membrane electrode, which shows that its membrane thickness is about 8-9μm. Figure 2 The middle F figure shows the actual optical image of the gas sensor and the optical image of the test kit. The gas sensor housing is made of 3D-printed resin material, which is acid, alkali and corrosion-resistant. The tightly fitting sealing device can prevent the loss of sensing performance due to the volatilization of the electrolyte solution.

[0047] In order to prove the successful preparation of catalytic materials, X-ray diffraction (XRD) patterns were used to characterize the elements of various prepared catalysts, such as Figure 3 As shown, Figure 3 Figure 3 is the X-ray diffraction pattern of AgCl-NCs (a), Au / C (b), Pt / C (c), Pt-Au-1 (d) and Pt-Au-2 (e), and the XRD standard spectra of different elements: red (platinum), green (gold), blue (silver chloride). Curve a is the XRD pattern of the prepared AgCl-NCs. It can be seen that the prepared AgCl has good crystallinity, which is consistent with its XRD standard pattern (blue vertical line), proving the successful preparation of AgCl. The large broad peak near 25° can be attributed to the carbon peak. The five characteristic peaks at 38.1°, 44.3°, 64.3°, 77.5° and 81.5° appearing in curve b correspond to the five peaks of Au (111), (200), (220), (311), (222) Different crystal planes prove that gold nanoparticles are successfully prepared and do not contain other impurities. The sharp peak at 26.5° in curve c may be attributed to the residual AgCl particles that have not been removed. The five characteristic peaks at 39.5°, 46.1°, 67.4°, 81.2° and 85.7° correspond to the (111), (200), (220), (311) and (222) crystal planes of Pt, proving the successful preparation of Pt nanoparticles. Furthermore, the XRD spectra of the prepared Pt-Au-1 and Pt-Au-2 are studied. As shown in curves d and e, the peak types of the two are almost the same. In addition to the five characteristic absorption peaks belonging to Pt, characteristic peaks belonging to Au nanoparticles can be observed, proving the successful preparation of Pt-Au nanoparticles.

[0048] ②. Detection feasibility of electrochemical H2S gas sensor:

[0049] Figure 4 (A) is the cyclic voltammetry curve of the hydrogen sulfide sensor based on Pt-Au-1 catalyst under (a) nitrogen and (b) 20 ppm hydrogen sulfide atmosphere, and (B) is the detection sensitivity of the prepared catalyst to 10 ppm H2S: (a) Au / C, (b) Pt / C, (c) PtAu-2, (d) PtAu-1.

[0050] Figure 4 The cyclic voltammograms of the sensor based on Pt-Au-1 catalyst in nitrogen (a) and 20ppmH2S (b) atmospheres with a voltage window between -0.4V and 0.8V are shown. It can be seen that the cyclic voltammogram profiles in the two cases are similar because there is a certain amount of charging current in the membrane electrode of the sensor and no obvious oxidation or reduction peaks appear. Figure 4 The enlarged inset at 0.4V in the A curve in the middle graph shows that the oxidation current in the presence of H2S is approximately 2μA higher than in the presence of nitrogen. This indicates that under the applied forward bias, H2S is indeed electrolyzed at the electrode, resulting in an increased current, allowing H2S to be detected according to Faraday's law of electrochemical electrolysis. Figure 4 The middle B part is a bar graph showing the sensitivity of various catalytic materials prepared. The detection sensitivity of the prepared Au / C and Pt / C to hydrogen sulfide is 38nA / ppm respectively. -1 and 51nA / ppm -1 The effect of adding AgCl on gas sensing performance was also tested. The performance of Pt-Au / C-1 with added AgCl was significantly better than that of Pt-Au / C-2 without AgCl. This may be because the presence of AgCl template effectively dispersed the Pt-Au catalyst, avoiding the reduction of catalytic performance and active sites caused by catalyst agglomeration. At the same time, the sensitivity of Pt-Au-1 catalyst was 138nA / ppm. - , which is 1.6 times that of the single metal catalyst, which can be attributed to the synergistic effect of the bimetallic catalyst leading to the improvement of gas sensing performance.

[0051] ③. Optimization of experimental parameters of electrochemical H2S gas sensor:

[0052] Before the experimental test begins, it is necessary to optimize the experimental conditions and two important parameters that affect the detection performance of the H2S sensor, namely: the operating voltage of the sensor and the concentration of the electrolyte sulfuric acid solution. Figure 5 As shown in the A part of the figure, as the applied voltage increases, the detection zero point also increases. In the voltage range of 0-0.5V, the detection sensitivity of the sensor first increases and then decreases and reaches a peak at 0.4V, with a sensitivity of up to 170nA / ppm. -1In the range of 0-0.4V, as the bias voltage increases, the catalytic activity of the catalyst continues to improve, reaching the best performance at 0.4V. As the operating voltage of the sensor continues to increase, the detection sensitivity decreases. This may be because the catalyst aggregates and the stability deteriorates after aging of the sensor, resulting in a decrease in the detection ability of hydrogen sulfide. Therefore, the optimal operating voltage of the sensor is controlled to be 0.4V. In addition, the concentration of the electrolyte sulfuric acid solution is optimized in the range of 0.1-7mol / L -1 Within the concentration range, different concentrations of electrolyte lead to different sensor performances, such as Figure 5 As shown in the figure B, as the electrolyte concentration increases, the detection sensitivity of the sensor gradually increases and reaches 5 mol / L. -1 The peak value is 170nA / ppm -1 When the concentration continues to increase, the performance of the sensor will be reduced. At the same time, it was found in actual operation that the electrolyte with a lower concentration is very easy to lose water and cause the electrolytic cell to dry up, and the electrolyte with a higher concentration will absorb water during use and cause the sensor to swell. Therefore, according to the actual detection situation, 5mol / L -1 The following tests were carried out using sulfuric acid as the electrolyte solution.

[0053] ④. Gas sensing performance of electrochemical H2S gas sensor:

[0054] Figure 6 Figure 2 shows the (A) response recovery signal curve and (B) selectivity of the Pt-Au / C-1-based gas sensor for 10 ppm H2S. The constructed sensor was used to detect 10 ppm H2S. The sensor was exposed to a 10 ppm H2S atmosphere for 10 minutes to evaluate its poisoning performance. The sensor's detection response time and recovery time for 10 ppm H2S were also calculated. Figure 6 As shown in the figure A in the middle, after 10 minutes of H2S exposure experiment, the response signal value of the sensor decreased slightly, but still maintained a detection performance of 98.4%, indicating that the prepared sensor has strong anti-poisoning function and detection stability. In addition, the response time of the sensor to 10ppmH2S is short, at 127.9s, but its recovery time is slightly longer than the response time of 169.9s. After the test, the detection zero point of the sensor returned to the initial value without significant change, indicating that the sensor has good detection stability. Figure 6 Figure B shows the sensor's detection selectivity for H2S. Even 100ppm of SO2 produces a response of 156nA, which is much lower than the response signal of 10ppm H2S (1382nA). Therefore, interfering gases such as SO2, CO, NH3, and H2 have low cross-sensitivity, proving that the sensor has good detection selectivity.

[0055] Figure 7 The response signal curve (A) and the detection linear fitting curve (B) of the gas sensor based on Pt-Au-1 catalyst to 1-20ppmH2S are shown. The detection linearity and detection range of the sensor are explored. Figure 7 As shown in the figure A in the middle, within the detection range of 1-20ppm, as the gas concentration increases, the detection signal of the sensor increases linearly. Figure 7 The B figure shows the linear fitting curve of the sensor. The linear equation is y = 139.3 × x + 50.4, where y is the detection signal difference and x is the H2S concentration. The detection sensitivity value is the same as the slope of the sensor, which is 139.3nA / ppm. -1 , its R 2 It reached 0.999, proving that its detection linearity is good and it has excellent linear detection capability for H2S. According to 3σ calculation, the theoretical detection limit is as low as 83ppb, which can achieve sub-ppm level H2S detection.

[0056] Figure 8 The repeatability curve (A) and response time summary (B) of the Pt-Au / C-1 based sensor for detecting 10ppmH2S. The repeatability of the sensor was investigated by repeatedly injecting 10ppmH2S 11 times. Figure 8 As shown in the figure A in the middle, during the 11 repeated tests, the sensor's response value to 10ppmH2S remained basically consistent, and the sensitivity was basically stable at 140nA / ppm. -1 , the detection RSD value is only 4.28%, indicating that the sensor has good repeatability. In addition, the response time of 20 groups of samples in the detection process was statistically analyzed, such as Figure 8 As shown in Figure B, the H2S sensor's response time initially was relatively fast, only 95 seconds. However, as the number of tests increased, the response time gradually increased and eventually stabilized at around 125 seconds, demonstrating that the sensor's response time is related to the number of tests and ultimately stabilizes at a specific value. This is likely due to the fact that the newly fabricated sensing catalytic layer undergoes partial pre-poisoning upon contact with the H2S target. As the number of tests increases, the sensor's catalytic electrode gradually reaches its optimal state, achieving stable response time and detection sensitivity.

[0057] Figure 9 In the range of 20℃-40℃, (A) the effect of temperature on the sensor's detection zero point and detection sensitivity (H2S concentration is 10ppm), (B) the relative sensitivity of the sensor based on 25℃. In order to adapt to actual application scenarios with variable temperatures, the temperature characteristics of the sensor were explored, mainly to detect the changes in the sensor's detection baseline and detection sensitivity under different temperature conditions. Figure 9As shown in the figure A in the middle, the gas sensing performance changes of Pt-Au nanocatalysts in the range of -20℃ to 40℃ were explored. With the increase of temperature, the detection zero point of the sensor also increased, the electron transfer rate became faster, and the internal resistance decreased, resulting in an increase in the baseline. The detection sensitivity of the sensor showed a trend of first increasing and then decreasing, reaching a maximum value of 179nA / ppm-1 at 15℃, indicating that the optimal storage and operating temperature of the sensor is 15℃. Taking the detection sensitivity at 25℃ as the benchmark, Figure 9 Panel B shows the sensor's relative sensitivity. Its H2S detection sensitivity decreases to varying degrees with temperature, ranging from -20% to 40% overall. The optimal temperature, reaching 40%, is 15°C. This H2S sensor exhibits excellent temperature sensitivity and is expected to adapt to temperature fluctuations in real-world environments.

[0058] exist Figure 10 The figure shows the working stability of the H2S sensor (A) and the test stability of 10ppmH2S for 60 consecutive days (B). The stability of the sensor's detection target is one of the important parameters for verifying sensor reliability. The sensor's continuous working stability and intermittent working stability for H2S detection are tested. Figure 10 As shown in the figure A in the middle, the online stability of the sensor is tested 100,000 seconds after power-on. Since a certain bias voltage needs to be applied, the sensor needs a certain amount of preparation time. As can be seen from the figure, after 1 hour of power-on, the current value of the sensor has dropped to 99.5% of the change value, which basically meets the test standard. In the following period, excluding changes in ambient temperature, the detection zero point of the sensor basically does not fluctuate. The signal value of the sensor remains stable for more than 90,000 seconds, proving that its continuous working stability is good in a short period of time. In order to test the H2S detection stability of the gas sensor, its detection sensitivity to 10ppmH2S is tested at fixed intervals within 60 days. The results can be seen in Figure 10 In panel B, the sensor's sensitivity remained within 140 ± 5 nA / ppm⁻¹. Some data exceeding the standard were attributed to performance degradation or slight increase due to changes in the laboratory ambient temperature. These results demonstrate the sensor's excellent continuous and intermittent operating stability, demonstrating promising prospects for H₂S detection applications.

[0059] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material, characterized in that: The catalyst comprises a Pt-Au / C nano catalyst, which is prepared by loading a Pt-Au bimetallic alloy catalyst on pretreated conductive carbon black XC-72.

2. A method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material, characterized in that: The method comprises the following steps: Step S1, taking 300 mg of commercial conductive carbon black XC-72 and adding it to a mixed solution of 30% hydrogen peroxide and 10% nitric acid, after ultrasonic dispersion for 0.5 h, transferring it to an oil bath and heating under reflux for 5 h, then transferring it to a centrifuge to obtain a precipitate, drying it at 60° C. overnight, and then grinding it to obtain a modified conductive carbon black of equal mass; Step S2: 200 mg of PVP and 250 mg of AgNO3 were dissolved in 25 mL of ethylene glycol and stirred until fully dissolved to obtain solution A. 36 mL of FeCl3 ethylene glycol solution was prepared, ultrasonically dispersed for 10 min, and stirred for 30 min until the FeCl3 was completely dissolved to obtain solution B. Step S3: Solutions A and B were mixed and immediately transferred to an oil bath at 130°C for reaction under magnetic stirring for 5 h. After the reaction, the mixture was immediately cooled in an ice-water bath, and the solvent and PVP were removed. The resulting AgClNCs were dispersed in 8 mL of ethanol / water solution. Step S4: Using the prepared AgCl-NCs as a template, a Pt-Au / C bimetallic nanocatalyst was prepared in an oil phase EG. 1 mL of the AgCl-NCs solution was dispersed in 20 mL of EG and stirred at 60°C for 30 min. 20 μL of HAuCl4 solution and 4 mL of a 20 mM K2PtCl4 solution were then added dropwise thereto. The mixture was stirred at 60°C for 3 h to obtain a black suspension that could be separated by standing. Step S5, centrifuge and wash with water or alcohol, and let the supernatant stand. Remove AgCl and Ag from the prepared solid catalyst powder, dry and grind the product, record it as Pt-Au-1, take 5 mg of Pt-Au-1 and disperse it in 45 mg of pretreated XC-72. After stirring overnight, centrifuge and dry to obtain Pt-Au-1 / C catalyst, and assemble the obtained catalyst into a gas sensor.

3. The method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material according to claim 2, characterized in that: In step S1, the amount of 30% hydrogen peroxide used is 10 mL, and the amount of 10% nitric acid mixed solution used is 20 mL.

4. The method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material according to claim 2, characterized in that: In step S1, the temperature of the oil bath is set to 60° C. during the heating and reflux process.

5. The method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material according to claim 2, characterized in that: In step S2, the molecular weight of PVP is selected as MW=58000.

6. The method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material according to claim 2, characterized in that: In step S2, the concentration of the FeCl3 ethylene glycol solution is 0.6 mM.

7. The method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material according to claim 2, characterized in that: In step S3, the process of removing the solvent and PVP is as follows: Step S3.1, adding a certain amount of acetone to the material after water bath cooling, and letting it stand overnight to extract the off-white AgCl nanocube precipitate; Step S3.2: The upper layer of solution was removed, and the lower layer of precipitate was centrifuged at 4000 rpm for 5 min, and washed with deionized water and ethanol several times to remove the solvent and PVP.

8. The method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material according to claim 2, characterized in that: In step S4, after the HAuCl4 solution is dripped, a certain amount of AA solution is dripped to reduce the precursor solution and inhibit the electrochemical replacement reaction between silver and the noble metal precursor.

9. The method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material according to claim 2, characterized in that: In the step S5, the mass fraction of the obtained Pt-Au-1 / C catalyst is 10%.

10. The method for preparing a hydrogen sulfide sensor based on Pt-Au alloy nanocatalytic material according to claim 2, characterized in that: In step S5, the prepared solid catalyst powder is washed with a 1M ammonia solution and a 6M nitric acid solution in sequence to remove AgCl and Ag.

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