A bipolar hydrogen-producing acid-base hybrid fuel cell

Abstract

This invention discloses a bipolar hydrogen-producing acid-base hybrid fuel cell, belonging to the field of fuel cell technology. The bipolar hydrogen-producing acid-base hybrid fuel cell of this invention includes bipolar plates, a negative electrode, a positive electrode, a cation exchange membrane, a positive electrode electrolyte, and a negative electrode electrolyte; wherein the positive electrode electrolyte is an acidic electrolyte; the negative electrode electrolyte is an alkaline electrolyte; the alkaline electrolyte contains formaldehyde; the negative electrode is supported with an alkaline formaldehyde selective electrocatalytic oxidation catalyst; and the positive electrode is supported with an acidic electrocatalytic hydrogen evolution catalyst. The bipolar hydrogen-producing acid-base hybrid fuel cell of this invention does not require external oxidants or high-temperature conditions, and can directly utilize the low redox potential (-0.2V vs. RHE) of formaldehyde to achieve efficient conversion, thus avoiding secondary pollution and carbon emissions at the source.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a bipolar hydrogen-producing acid-base hybrid fuel cell. Background Technology

[0002] Green hydrogen has attracted much attention as a clean energy carrier, but its large-scale application is still limited by the high energy consumption bottleneck of water electrolysis for hydrogen production. Meanwhile, formaldehyde waste liquid and waste gas absorption liquid generated in industrial sectors (such as resin synthesis, wood processing, textile printing and dyeing, and pharmaceutical chemicals) have become prominent environmental pollutants. Traditional treatment processes (such as chemical oxidation, advanced oxidation, and catalytic combustion) can degrade formaldehyde, but they rely on high-energy-consuming reaction conditions or generate secondary pollution, accompanied by large amounts of carbon emissions. Based on the characteristics of formaldehyde molecules—low redox potential (-0.2V vs. RHE) and high hydrogen storage density (8.4wt%)—formaldehyde can be selectively converted into high-value-added formate through electrochemical oxidation, simultaneously releasing hydrogen. Using it as the anode reactant to replace the traditional oxygen evolution reaction (OER) can significantly reduce the theoretical voltage requirement for water electrolysis for hydrogen production from 1.23V to below 0V, significantly reducing energy consumption. However, existing research is mostly limited to anion exchange membrane (AEM) electrolysis systems, and the kinetics of the hydrogen evolution reaction (HER) at the cathode are slow under alkaline conditions, requiring the application of high overpotentials, which limits the overall energy efficiency improvement. Therefore, there is an urgent need to find a water electrolysis method for hydrogen production that is low in energy consumption, high in efficiency, and low in pollution. Summary of the Invention

[0003] The purpose of this invention is to provide a bipolar hydrogen-producing acid-base hybrid fuel cell to solve the problems existing in the prior art.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] One of the technical solutions of the present invention is a bipolar hydrogen-producing acid-base hybrid fuel cell, comprising a bipolar plate, a negative electrode, a positive electrode, a cation exchange membrane, a positive electrode electrolyte, and a negative electrode electrolyte;

[0006] The positive electrode electrolyte is an acidic electrolyte;

[0007] The negative electrode electrolyte is an alkaline electrolyte; the alkaline electrolyte contains formaldehyde;

[0008] The negative electrode is supported by an alkaline formaldehyde selective electrocatalytic oxidation catalyst (i.e., an alkaline negative electrode);

[0009] The positive electrode is supported on an acidic electrocatalytic hydrogen evolution catalyst (i.e., an acidic positive electrode).

[0010] This invention's bipolar hydrogen-producing acid-base hybrid fuel cell overcomes the limitations of a single pH environment. Utilizing the Nernst potential difference between the alkaline negative electrode and the acidic positive electrode, it converts the chemical potential energy of the acid and base in the positive and negative electrode electrolytes into a driving voltage (directly converting chemical energy into electrical energy), thereby achieving efficient formaldehyde conversion and energy-free hydrogen production. Furthermore, this bipolar hydrogen-producing acid-base hybrid fuel cell can also output stored chemical energy as electrical energy, forming a multi-generation closed loop of "pollutant treatment - green hydrogen production - energy storage and power generation".

[0011] This invention not only provides a low-carbon pathway for the treatment of industrial aldehyde-containing wastewater, but also promotes the innovation of hydrogen production technology through a material-energy synergistic conversion mechanism, which is of great significance to resource recycling and sustainable energy development.

[0012] Furthermore, the concentration of hydroxide ions in the alkaline electrolyte is 0.1–10 mol / L, and the concentration of formaldehyde is 0.05–2 mol / L.

[0013] Furthermore, the hydrogen ion concentration in the acidic electrolyte is 0.1–10 mol / L.

[0014] Furthermore, the acidic electrocatalytic hydrogen evolution catalyst comprises Pt / C.

[0015] Furthermore, the positive electrode comprises a hydrophilic carbon felt loaded with Pt / C, wherein the Pt loading is 0.1–1 mg / cm³. 2 .

[0016] Furthermore, the alkaline formaldehyde selective electrocatalytic oxidation catalyst comprises a copper-silver alloy; the negative electrode is foamed copper containing a copper-silver alloy electroplating layer.

[0017] Furthermore, the molar ratio of copper to silver in the copper-silver alloy is 1:9 to 9:1.

[0018] The second technical solution of the present invention: an application of the above-mentioned bipolar hydrogen-producing acid-base hybrid fuel cell in formaldehyde waste liquid treatment.

[0019] The third technical solution of the present invention: the application of the above-mentioned bipolar hydrogen-producing acid-base hybrid fuel cell in electrolytic hydrogen production.

[0020] The fourth technical solution of the present invention: a method for reusing formaldehyde waste liquid, wherein an alkaline electrolyte is prepared from formaldehyde waste liquid as the negative electrode electrolyte, and an acidic solution is used as the positive electrode electrolyte to prepare a bipolar hydrogen-producing acid-base hybrid fuel cell for electrolytic hydrogen production.

[0021] The present invention discloses the following technical effects:

[0022] (1) The bipolar hydrogen-producing acid-base hybrid fuel cell of the present invention does not require external oxidants or high temperature conditions. It can directly utilize the low oxidation-reduction potential of formaldehyde (-0.2V vs. RHE) to achieve efficient conversion, thus avoiding secondary pollution and carbon emission problems from the source.

[0023] (2) Traditional water electrolysis for hydrogen production (such as alkaline electrolyzers, AEMWE, PEMWE, etc.) relies on the high-energy-consuming oxygen evolution reaction. However, the bipolar hydrogen-producing acid-base hybrid fuel cell of the present invention replaces OER with formaldehyde oxidation and converts formaldehyde into high-value chemicals (formate salts) and hydrogen through an electrocatalytic pathway. This not only completely eliminates pollutants but also achieves efficient resource recovery (i.e., significantly improves energy utilization efficiency) and greatly enhances overall economic efficiency.

[0024] At 0V, the formate production over half an hour is approximately 9.5 mmol / cm³. 2 Electrode yield can reach approximately 190 mol / (m 2 h); at -0.4V, the formate production in half an hour is approximately 5 mmol / cm³. 2 Electrode yield can reach approximately 100 mol / (m 2 h).

[0025] (3) Traditional water electrolysis for hydrogen production is costly, mainly due to high electricity consumption (electricity costs account for 70% of the total cost). Currently, the production cost of green hydrogen is approximately RMB 3.5–5 per Nm³. 3 This invention utilizes formaldehyde oxidation to assist in hydrogen production, eliminating the need for electricity input, significantly reducing the cost of electrolytic hydrogen production, greatly improving economic efficiency, and making it more competitive in the market.

[0026] (4) Traditional formaldehyde waste liquid treatment methods (such as chemical oxidation degradation) emit about 2.5 tons of CO2 for every ton of formaldehyde treated, while the bipolar hydrogen-producing acid-base hybrid fuel cell of the present invention can achieve zero carbon emissions.

[0027] Furthermore, because green hydrogen replaces traditional gray hydrogen (based on natural gas or coal), approximately 10 tons of CO2 emissions can be reduced for every ton of hydrogen produced. Simultaneously, the green synthesis of formate avoids the carbon emissions of traditional petrochemical routes (approximately 3 tons of CO2 per ton of product). Taking the annual treatment of 100,000 tons of formaldehyde waste as an example, this technology can reduce direct carbon emissions by 250,000 tons and indirectly reduce CO2 emissions by 1 million tons through green hydrogen and formate production. The total carbon reduction is equivalent to the annual carbon sequestration capacity of planting 6.5 million trees. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a cross-sectional view of the bipolar hydrogen-producing acid-base hybrid fuel cell in Embodiment 1 of the present invention, wherein 1 is a bipolar plate, 2 is a serpentine flow channel, 3 is a sealed end of the outlet, 4 is a sealed end of the inlet, 5 is the positive electrode, 6 is a cation exchange membrane, and 7 is the negative electrode.

[0030] Figure 2 The polarization curve of the bipolar hydrogen-producing acid-base hybrid fuel cell prepared in Example 1;

[0031] Figure 3 The power density curve of the bipolar hydrogen-producing acid-base hybrid fuel cell prepared in Example 1;

[0032] Figure 4 The positive and negative electrode hydrogen production of the bipolar hydrogen-producing acid-base hybrid fuel cell prepared in Example 1 was determined to be at the voltage value (-0.4V) under the maximum output power density condition.

[0033] Figure 5 The polarization curves of the bipolar hydrogen-producing acid-base hybrid fuel cell in Comparative Example 1 are shown.

[0034] Figure 6 The power density curve is shown for the bipolar hydrogen-producing acid-base hybrid fuel cell in Comparative Example 1. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0041] An exemplary bipolar hydrogen-producing acid-base hybrid fuel cell includes a bipolar plate, a negative electrode, a positive electrode, a cation exchange membrane, a positive electrode electrolyte, and a negative electrode electrolyte.

[0042] The positive electrolyte is on the positive electrode side, and the negative electrolyte is on the negative electrode side;

[0043] The cation exchange membrane is placed between the negative and positive electrodes and completely covers both electrodes.

[0044] The bipolar plate is provided with a feed port and a discharge port, and the inner side of the bipolar plate (facing the electrode) has a flow channel for the flow of electrolyte and gas-liquid mixture;

[0045] The feed port and discharge port of the bipolar plate are connected to the water pipe and the water pump, respectively, to transfer the positive and negative electrolytes stored in the liquid storage tank, and to separate the gas phase and transfer it to the hydrogen storage tank when transferring the gas-liquid mixture; the transferred gas-liquid mixture enters the hydrogen storage tank, where gas-liquid separation is performed and the gas is collected.

[0046] A bipolar hydrogen-producing acid-base hybrid fuel cell consists of, from the outside in, bipolar plates, a positive or negative electrode, and a cation exchange membrane.

[0047] A bipolar hydrogen-producing acid-base hybrid fuel cell also includes electronic components such as load resistors, inductors, capacitors, or electronic controllers, which are electrically connected to the fuel cell and used to regulate the output voltage of the fuel cell and match it with an external load or energy storage system.

[0048] Optional materials for bipolar plates include graphite, stainless steel, or platinum-plated titanium, which are conductors with good electrical conductivity and resistance to acid and alkali corrosion.

[0049] Optionally, the liquid reservoir can be made of acid and alkali resistant materials such as polytetrafluoroethylene, silicon carbide, and phenolic vinyl resin, and is used to hold the positive and negative electrolytes.

[0050] Optionally, a hydrogen storage device is used for gas-liquid separation and to collect hydrogen generated at the positive and negative electrodes.

[0051] Optionally, the feed port and discharge port of the bipolar plate need to be connected to a sealed port made of stainless steel or platinum-plated titanium.

[0052] Optionally, the bipolar hydrogen-producing acid-base hybrid fuel cell can be cylindrical or cubic in shape.

[0053] Optionally, the output voltage of the bipolar hydrogen-producing acid-base hybrid fuel cell can be controlled from the open-circuit voltage to approximately 0V; the output current density can be controlled from 0 to 0.54 A / cm². 2 .

[0054] Example 1

[0055] A bipolar hydrogen-producing acid-base hybrid fuel cell:

[0056] (1) Preparation of the negative electrode:

[0057] A. Cleaning of the substrate material: 1×1×3cm 3 Commercially available copper foam was sequentially immersed in 0.5 mol / L hydrochloric acid solution, anhydrous ethanol, and deionized water and sonicated for 15 min to clean the oxide layer and organic matter on its surface, thus obtaining pretreated copper foam.

[0058] B. Electroplating solution preparation: Dissolve CuSO4·5H2O, Ag2SO4, H2SO4 and trisodium citrate in 25 mL of deionized water to obtain the electroplating solution. The concentration of CuSO4·5H2O in the electroplating solution is 6 mmol / L, the concentration of Ag2SO4 is 14 mmol / L, the concentration of H2SO4 is 1.5 mol / L, and the concentration of trisodium citrate is 0.1 mol / L.

[0059] C. Using pretreated foamed copper as the working electrode and a commercial graphite rod as the counter electrode, both electrodes are immersed in the electroplating solution. An electrochemical workstation or DC power supply at -3A / cm² is used. 2 Electrodeposition was performed at a current density for 60 seconds, followed by rinsing with deionized water and drying to obtain copper foam loaded with a copper-silver alloy (the molar ratio of copper to silver in the copper-silver alloy was 3:7), which is the negative electrode.

[0060] (2) Preparation of the positive electrode:

[0061] A. Cleaning of the substrate material: 1×1×3cm 3 Commercial hydrophilic carbon felt was sequentially immersed in anhydrous ethanol and deionized water and sonicated for 15 minutes to clean its surface impurities, thus obtaining pretreated hydrophilic carbon felt.

[0062] B. Preparation of catalyst slurry: 12 mg of commercial 5% Pt / C powder (Pt loading on C is 5%), 267 μL of 5 wt% Nafion solution, 133 μL of isopropanol and 33 μL of deionized water were mixed and sonicated for 5 h to obtain catalyst slurry.

[0063] C. The catalyst slurry is drop-cast onto the surface of a pretreated hydrophilic carbon felt, air-dried overnight, and then used to obtain a Pt / C-loaded hydrophilic carbon felt, i.e., the positive electrode, with a Pt loading of 0.5 mg / cm³. 2 .

[0064] (3) Assembly of bipolar hydrogen-producing acid-base hybrid fuel cells

[0065] A cation exchange membrane 6 is placed between the positive electrode 5 and the negative electrode 7, and is completely attached to the positive electrode 5 and the negative electrode 7. A bipolar plate 1 is placed outside the positive electrode 5 and the negative electrode 7. A serpentine flow channel 2 is etched on the inner side of the bipolar plate 1 (towards the electrode). The bipolar plate 1 is provided with a feed port and a discharge port. The feed port of the bipolar plate is connected to a sealing port of acid and alkali resistant material (such as polytetrafluoroethylene), which is the feed port sealing end 4. The discharge port is connected to a sealing port of acid and alkali resistant material (such as polytetrafluoroethylene), which is the discharge port sealing end 3. The feed port of the bipolar plate 1 is connected to a water pipe and a liquid storage tank. The discharge port of the bipolar plate 1 is connected to a water pipe and a water pump. The water pump is used to draw in the electrolyte and draw out the gas-liquid mixture to pass into the hydrogen storage tank.

[0066] Among them, the material of bipolar plate 1 is a metal material with good conductivity and acid and alkali resistance, such as 316L stainless steel.

[0067] The liquid reservoir is made of acid and alkali resistant materials, such as polytetrafluoroethylene;

[0068] The bipolar hydrogen-producing acid-base hybrid fuel cell has a cylindrical shape.

[0069] The fuel cell is connected to electronic components such as load resistors, inductors, capacitors, or electronic controllers to regulate its output voltage and match it to an external load or energy storage system. This allows the fuel cell's output voltage to be controlled from the open-circuit voltage (1.3V) to approximately 0V, and the output current density to be controlled from 0 to 0.54 A / cm². 2 It can achieve the electrochemical production of hydrogen and formate without the application of voltage.

[0070] A cross-sectional view of a bipolar hydrogen-producing acid-base hybrid fuel cell is shown below. Figure 1 .

[0071] (4) Pass an alkaline electrolyte into the serpentine channel 2 inside the negative electrode 7 (the concentration of potassium hydroxide in the alkaline electrolyte is 1 mol / L and the concentration of formaldehyde is 0.5 mol / L).

[0072] An acidic electrolyte (with a sulfuric acid concentration of 0.5 mol / L) is introduced into the serpentine channel 2 inside the positive electrode 5.

[0073] Electrolysis was carried out by controlling the flow rate of the alkaline electrolyte to 0.2 L / min and the flow rate of the acidic electrolyte to 0.2 L / min.

[0074] The polarization curves and corresponding power density curves of the bipolar hydrogen-producing acid-base hybrid fuel cell prepared in this embodiment were measured at a scan rate of 10 mV / s. The results are shown in [Figure number missing]. Figure 2 and Figure 3 .

[0075] from Figure 2 and Figure 3 As can be seen from the data, the bipolar hydrogen-producing acid-base hybrid fuel cell prepared in this embodiment can output a maximum current density of approximately 540 mA / cm². 2 The corresponding maximum output power is approximately 97mW / cm². 2 .

[0076] The electrolyte conditions were controlled as above. The hydrogen production at the positive and negative electrodes of the bipolar hydrogen-producing acid-base hybrid fuel cell prepared in this embodiment was measured at the voltage value (-0.4V) under the maximum output power density condition (electrolysis time 30 min). The results are shown below. Figure 4 .

[0077] from Figure 4 As can be seen, at the maximum output power density, the bipolar hydrogen production can reach approximately 5 mmol / cm³ within half an hour. 2 The yield can reach approximately 100 mol / (m 2 (h), the production of formate can reach approximately 5 mmol / cm³ within half an hour. 2 The yield can reach approximately 100 mol / (m 2 h).

[0078] Comparative Example 1

[0079] When the pH gradient between the positive and negative electrode electrolytes decreases, it will lead to a decline in the performance of the prepared fuel cell. For example... Figure 5 and Figure 6 As shown, when the positive electrode electrolyte is replaced from 1M H2SO4 to 0.1M H2SO4, the maximum current density of the fuel cell can only reach about 300 mA / cm². 2 The maximum output power is only about 71mW / cm. 2 .

[0080] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A bipolar hydrogen-producing acid-base hybrid fuel cell, characterized in that, It includes bipolar plates, negative electrode, positive electrode, cation exchange membrane, positive electrode electrolyte, and negative electrode electrolyte; The positive electrode electrolyte is an acidic electrolyte; The negative electrode electrolyte is an alkaline electrolyte; the alkaline electrolyte contains formaldehyde; The negative electrode is supported by an alkaline formaldehyde selective electrocatalytic oxidation catalyst. The positive electrode is supported with an acidic electrocatalytic hydrogen evolution catalyst.

2. The bipolar hydrogen-producing acid-base hybrid fuel cell according to claim 1, characterized in that, The concentration of hydroxide ions in the alkaline electrolyte is 0.1–10 mol / L, and the concentration of formaldehyde is 0.05–2 mol / L.

3. The bipolar hydrogen-producing acid-base hybrid fuel cell according to claim 1, characterized in that, The hydrogen ion concentration in the acidic electrolyte is 0.1–10 mol / L.

4. The bipolar hydrogen-producing acid-base hybrid fuel cell according to claim 1, characterized in that, The acidic electrocatalytic hydrogen evolution catalyst includes Pt / C.

5. The bipolar hydrogen-producing acid-base hybrid fuel cell according to claim 4, characterized in that, The positive electrode comprises a hydrophilic carbon felt loaded with Pt / C, wherein the Pt loading is 0.1–1 mg / cm³. 2 .

6. The bipolar hydrogen-producing acid-base hybrid fuel cell according to claim 1, characterized in that, The alkaline formaldehyde selective electrocatalytic oxidation catalyst comprises a copper-silver alloy.

7. The bipolar hydrogen-producing acid-base hybrid fuel cell according to claim 6, characterized in that, The molar ratio of copper to silver in the copper-silver alloy is 1:9 to 9:

1.

8. The application of a bipolar hydrogen-producing acid-base hybrid fuel cell according to any one of claims 1 to 7 in the treatment of formaldehyde waste liquid.

9. The application of a bipolar hydrogen-producing acid-base hybrid fuel cell according to any one of claims 1 to 7 in the electrolytic production of hydrogen.

10. A method for reusing formaldehyde waste liquid, characterized in that, A bipolar hydrogen-producing acid-base hybrid fuel cell was prepared by using formaldehyde waste liquid to prepare an alkaline electrolyte as the negative electrode electrolyte and an acidic solution as the positive electrode electrolyte for hydrogen electrolysis.

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