Flowing membrane electrode for electrolytic hydrogen production coupled alcohol oxidation and electrolytic hydrogen production coupled alcohol oxidation method

Abstract

The invention provides a flowing membrane electrode for electrolytic hydrogen production coupled alcohol oxidation and an electrolytic hydrogen production coupled alcohol oxidation method. The flowing membrane electrode comprises an anode, an electrochemical diaphragm and a cathode; the anode and the cathode are arranged on the two sides of the electrochemical diaphragm respectively and are attached to the electrochemical diaphragm to form a sandwich structure; the thickness of the electrochemical diaphragm is 200 to 500 [mu] m; the anode and the cathode are respectively prepared by immobilizing a catalytic material in a conductive substrate; the conductive substrate has a porous structure, and the pore diameter of the porous structure is 100-500 [mu] m. By adopting an alcohol fed-batch feeding mode, through optimizing the alcohol concentration in a reaction fluid and combining with a porous structure flowing membrane electrode, relatively high selectivity of organic acid, Faraday current efficiency of an anode and hydrogen yield are realized in a long-term continuous electrolytic hydrogen production coupling alcohol oxidation reaction; the problems of low reaction rate and low accumulation amount of organic acid products are solved.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic hydrogen production coupled with alcohol oxidation, and relates to a flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation and a method for electrolytic hydrogen production coupled with alcohol oxidation. Background Technology

[0002] The high cost of water electrolysis for hydrogen production using renewable energy has become a major bottleneck restricting its development. One major reason is the slow kinetics of the oxygen evolution reaction at the anode and the low oxygen utilization rate during water electrolysis. To address this issue, replacing the oxygen evolution process at the anode with an industrially important alcohol oxidation reaction can not only significantly reduce the anode oxidation overpotential and improve the hydrogen production efficiency at the cathode, but also enable the green synthesis of high-value chemicals, thereby solving the problem of improving efficiency and reducing costs in water electrolysis for hydrogen production.

[0003] The "serpentine / corrugated flow channels" on the electrode plate, parallel and independent of the electrode, are currently the main structure of electrolytic hydrogen production coupled with anodic oxidation membrane electrodes. This type of membrane electrode has three main problems: 1) At the anode, because the electrolyte only flows on the electrode surface, the thickness of the diffusion layer is generally in the range of tens to hundreds of micrometers; when the current density exceeds the limiting current density, the anodic oxidation reaction is diffusion-controlled, resulting in severe concentration polarization, leading to low mass transfer rate and uneven residence time; 2) At the cathode, the hydrogen bubbles generated by electrolysis overcome the adhesion between the bubbles and the electrode through buoyancy, resulting in a large mass transfer overpotential; 3) The portion of the electrode plate occupied by the flow channels cannot contact the electrode, resulting in a large contact resistance. Furthermore, most current research on alcohol electrooxidation reactions is conducted in diluted alcohol solutions (millimolar level), leading to low reaction rates and extremely low organic acid accumulation, limiting its industrial application.

[0004] In existing technologies, Luo et al. (Ruipeng Luo, Yuyang Li, Lixin Xing, A dynamic Ni(OH)2-NiOOH / NiFeP heterojunction enabling high-performance E-upgrading of hydroxymethylfurfural, Applied Catalysis B: Environmental 311(2022)121357.) loaded NiFeP heterojunction catalysts onto nickel foam (NF) via electrodeposition and used them for the electrochemical oxidation of 5-hydroxymethylfurfural (HMF). In this method, the working electrode (NiFeP-NF) was located in the anode chamber, while the reference electrode (Ag / AgCl) and the counter electrode (graphite electrode) were located in the cathode chamber. The anode and cathode chambers were filled with 15 mL of 1M KOH + different concentrations of HMF and 15 mL of 1M KOH, respectively. Luo et al. tested the linear sweep voltammetry curves of NiFeP-NF in the electrolyte under different HMF concentrations, with and without stirring. Test results show that without stirring, when the HMF concentration in the electrolyte is low, local HMF deficiency occurs, HMF electro-oxidation is diffusion-controlled, and the oxygen evolution reaction gradually becomes dominant. Increasing the HMF concentration in the electrolyte or increasing mass transfer through stirring provides more HMF to the electrode surface, thereby inhibiting the oxygen evolution reaction. However, even with enhanced mass transfer through stirring, the electro-oxidation of HMF ultimately still exhibits diffusion control, until the HMF concentration in the electrolyte is increased to infinity, indicating that enhancing mass transfer through stirring is not effective enough.

[0005] Li et al. (Zhenhua Li, Yifan Yan, Si-Min Xu, Alcohols electrooxidation coupled with H2 production at high current densities promoted by a cooperative catalyst, Nature Communications 13(2022)147.) conducted a two-electrode test of electrolytic hydrogen production coupled with benzyl alcohol oxidation in a self-made membrane-free flowing electrolyzer. They used an Au / CoOOH catalyst as the anode and nickel foam as the cathode, with a working area of ​​30 cm². 2Electrochemical tests were conducted under industrial-grade conditions (70°C and 3M KOH + 0.2M benzyl alcohol). The linear sweep voltammetry curves showed that the onset potential for benzyl alcohol oxidation was 0.7V, significantly lower than the onset potential of the oxygen evolution reaction. As the voltage increased, the current for benzyl alcohol oxidation increased until it temporarily decayed at approximately 2.5V, then increased again from approximately 2.7V. This technique employed a self-made membrane-free flow electrolyzer for electrolytic hydrogen production coupled with benzyl alcohol oxidation. In this electrolyzer, the electrolyte flowed through a self-made flow channel across the electrolytic surface, while simultaneously diffusing into the porous electrode. However, the trend of increasing-decreasing-increasing current in the linear sweep voltammetry curves indicates a significant mass transfer control phenomenon in the benzyl alcohol electrooxidation process. This suggests that the electrolyte-surface-flowing operation mode still suffers from insufficient mass transfer at the electrode surface.

[0006] Therefore, how to simultaneously achieve high selectivity and high accumulation of organic acids in the electro-oxidation reaction of alcohols, and effectively enhance mass transfer, current density and electrode activity, is one of the key issues facing the electrolytic hydrogen production coupled with alcohol oxidation. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a flowing membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation and a method for electrolytic hydrogen production coupled with alcohol oxidation. By designing a membrane electrode with a porous flow structure, when used for electrolytic hydrogen production coupled with alcohol oxidation in a fed-batch alcohol manner, the membrane electrode can effectively improve the accumulation of organic acids, Faraday current efficiency, organic acid selectivity, and hydrogen production.

[0008] To achieve the above objectives, the present invention provides a flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation, wherein the flow membrane electrode includes an anode, an electrochemical membrane, and a cathode; the anode and cathode are respectively disposed on both sides of the electrochemical membrane and are bonded to the electrochemical membrane to form a sandwich structure; the thickness of the electrochemical membrane is 200-500 μm; the anode and cathode are respectively prepared by immobilizing catalytic materials in a conductive substrate; the conductive substrate has a porous structure with a pore size of 100 to 500 μm.

[0009] In this invention, the cathode and anode are tightly bonded to both sides of the electrochemical membrane, thereby reducing the distance between the cathode and anode, which can effectively shorten the mass transfer distance between the two stages, reduce the solution resistance, and increase the current density.

[0010] In some specific implementations, preferably, the method for supporting the catalytic material includes hydrothermal synthesis support method, electrodeposition method, flow synthesis support method, thermal spraying method, etc.

[0011] In some specific embodiments, preferably, the loading of the catalytic material is 50-100 mg·g. -1 .

[0012] According to a specific embodiment of the present invention, preferably, the catalytic material of the anode includes an alcohol oxidation catalytic material; and the catalytic material of the cathode includes a hydrogen evolution catalytic material.

[0013] According to a specific embodiment of the present invention, preferably, the alcohol oxidation catalyst includes, but is not limited to, one or a combination of two or more of MnO2, Co3O4, Ni(OH)2, and Co(OH)2, more preferably a combination of Ni(OH)2 and Co(OH)2, such as Co 0.1 Ni 0.9 (OH)2.

[0014] According to a specific embodiment of the present invention, preferably, the hydrogen evolution catalyst material includes, but is not limited to, one or more combinations of platinum, Co(OH)2, Ni, Mo, CoFe bimetal, CoMo bimetal, NiMo bimetal, Raney nickel, etc.

[0015] In some specific embodiments, preferably, the morphology of the catalytic material includes one or more combinations of nanoparticles, nanowires, nanorods, etc.

[0016] According to a specific embodiment of the present invention, preferably, the conductive substrate is a porous medium with good conductivity, including one or more of sintered titanium (Ti), sintered stainless steel (SS), nickel foam (Ni), carbon cloth, and graphite.

[0017] According to a specific embodiment of the present invention, preferably, the material of the electrochemical membrane includes one or a combination of two or more of the following: polyetheretherketone membrane (PEEK), polyphenylene sulfide membrane (PPS), polytetrafluoroethylene resin modified asbestos membrane, asbestos membrane, and polysulfone membrane (PSF).

[0018] According to a specific embodiment of the present invention, preferably, the shape of the channels in the conductive substrate includes one or a combination of two or more of the following: through-holes, mesh-like holes, and stepped holes. In this invention, the conductive substrate with porous microstructure flow has significant advantages in promoting fluid flow, mass transfer, and electron transfer. After loading catalytic materials with alcohol oxidation and hydrogen evolution functions into its channels, it can be used as an electrode for electrolytic hydrogen production coupled with alcohol oxidation.

[0019] According to a specific embodiment of the present invention, preferably, the shape of the membrane electrode includes one or more combinations of tubular, sheet-plate, and hollow fiber structures, more preferably a tubular membrane structure. If a tubular membrane electrode is used, the outer tube serves as the anode and the inner tube serves as the cathode; if a sheet-plate membrane electrode is used, either side of the membrane can serve as the anode.

[0020] This invention also provides a method for electrolytic hydrogen production coupled with alcohol oxidation, wherein the method includes: forcibly flowing an electrolyte through the channels of a flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation in a direction perpendicular to the electrode thickness; the electrolyte flowing out of the channels is circulated and then re-enters the membrane electrode for reaction. The forced flow process is achieved by a fluid transfer pump.

[0021] According to a specific embodiment of the present invention, preferably, the electrolyte comprises an alcohol and an electrolyte.

[0022] According to a specific embodiment of the present invention, preferably, the alcohol is added to the electrolyte by a fed-batch method, wherein the interval between each feeding is 15-120 minutes. The fed-batch method is carried out at room temperature and pressure.

[0023] In this invention, the feed strategy is based on Faraday's law, and its key lies in determining the feeding interval and feed rate, with the aim of maintaining the alcohol at a relatively constant concentration.

[0024] According to a specific embodiment of the present invention, preferably, the concentration of the alcohol in the electrolyte is 0.1M to 0.4M; more preferably, it is 0.2M. The lower the initial concentration of the alcohol, the shorter the corresponding feeding interval; the higher the initial concentration of the alcohol, the longer the corresponding feeding interval.

[0025] According to a specific embodiment of the present invention, preferably, the concentration of alcohols in the electrolyte is maintained relatively constant during the reaction process. The concentration of alcohols is maintained at a relatively constant value through a fed-batch operation. The feed rate is determined based on the amount of alcohol consumed; the amount of alcohol consumed can be estimated by current density and reaction time, or by directly measuring the concentration of alcohols in the electrolyte to obtain the amount of alcohol consumed; the alcohol is fed in a fed-batch manner according to the amount of alcohol consumed to maintain the alcohol concentration at a relatively constant level.

[0026] The inventors of this invention discovered that, in order to enhance current density and electrode activity, alcohol electro-oxidation is usually carried out in a strongly alkaline electrolyte. However, typical alcohols (such as ethanol, benzyl alcohol, glycerol, etc.) accumulate corresponding aldehyde intermediates during electro-oxidation, and these aldehyde intermediates are prone to undergo a series of non-Faraday side reactions (such as Cannizzaro rearrangement, aldol condensation, and base-catalyzed dehydration reactions) in alkaline media. Therefore, the inventors believe that the increase in non-Faraday side reactions is caused by the increase in alcohol reactant concentration, which leads to the inability to obtain higher product concentrations. However, directly reducing the alcohol reactant concentration will also reduce the reaction rate, resulting in a decrease in the accumulation of organic acid products. Based on the above findings, this invention, in order to suppress the occurrence of side reactions and maintain high selectivity for organic acids, adopts an alcohol feed-in method. By optimizing the alcohol concentration in the reaction fluid, the reaction rate and the selectivity of organic acids are balanced, thereby achieving long-term continuous operation of electrolytic hydrogen production coupled with alcohol oxidation, increasing the accumulation of organic acids, and effectively promoting the quality and efficiency improvement of the electrolytic hydrogen production coupled with alcohol oxidation process.

[0027] According to a specific embodiment of the present invention, preferably, the alcoholic substance includes one or a combination of two or more of methanol, ethanol, propanol, and benzyl alcohol.

[0028] According to a specific embodiment of the present invention, preferably, the voltage range of the electrolytic hydrogen production coupled alcohol oxidation method is 0-3V; it is powered by an electrochemical workstation or DC power supply, and the applied potential is lower than the oxygen evolution potential.

[0029] In some specific implementation schemes, the rate at which the electrolyte flows through the membrane electrode can be controlled by adjusting external forces (such as by adjusting the speed of the fluid transfer pump), and can be adjusted automatically according to experiments.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) The flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation provided by the present invention has a sandwich structure in which the anode, electrochemical membrane and cathode are tightly bonded together, reducing the distance between the two stages and forming a porous microstructure flow-catalysis integrated structure for electrolytic hydrogen production coupled with alcohol oxidation. When the electrolyte is forced to flow through the pores of the electrode, the flow, transport, alcohol oxidation and hydrogen evolution reaction are all confined within the pores with microscale structure, thereby significantly shortening the transport distance, reducing the transport resistance, and improving the uniformity of the field distribution and the selectivity of the products.

[0032] (2) The flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation provided by this invention significantly shortens the mass transfer distance at the anode due to the porous structure, reduces the mass transfer resistance in the reaction process, and increases the rate of alcohol oxidation. In addition, the fluid micro-elements within the pores undergo mixing due to the dispersion effect, thereby achieving good flow uniformity characteristics and resulting in a uniform distribution of residence time, concentration field, and temperature field, which can effectively improve the electrolytic reaction rate and the selectivity of organic acids.

[0033] (3) The flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation provided by the present invention, at the cathode, the porous structure flow can quickly remove bubbles in the electrode channels, reduce the mass transfer overpotential caused by bubbles, reduce hydrogen production energy consumption, and increase hydrogen production. In addition, since the entire electrode plate can be in contact with the electrode, the contact overpotential between the electrode and the electrode plate is reduced.

[0034] (4) By adopting an alcohol-feed feed method, the appropriate concentration of alcohol in the electrolyte can be determined by balancing the reaction rate and the selectivity of organic acids. By optimizing the alcohol concentration in the reaction fluid and combining it with a porous flow membrane electrode, high selectivity of organic acids, Faraday current efficiency of the anode, and hydrogen production are achieved in long-term continuous electrolytic hydrogen production coupled with alcohol oxidation reaction, solving the problems of low reaction rate and low accumulation of organic acid products in alcohol solution electrocatalytic oxidation coupled with hydrogen production. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a porous flow membrane electrode.

[0036] Figure 2 This is a comparison of the selectivity of acetic acid at different ethanol concentrations during non-feed operation.

[0037] Figure 3 This is a comparison of the acetic acid selectivity of the membrane electrode under different ethanol concentrations during fed-batch operation.

[0038] Figure 4 This is a comparison of the cumulative acetic acid concentration and Faraday current efficiency of the membrane electrode under different ethanol concentrations during fed-batch operation.

[0039] Figure 5 This is a comparison chart of cumulative hydrogen production under non-feed and fed-batch operation. Detailed Implementation

[0040] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0041] Raw material or equipment sources: Potassium hydroxide and ethanol were purchased from Chengdu Kelong Chemical Co., Ltd., and acetic acid was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Main testing equipment includes: DC power supply, electrochemical workstation, gas chromatograph, fluid transfer pump, constant temperature water bath, etc.

[0042] Evaluation and analysis method: During the electrochemical test, the prepared electrode with alcohol oxidation function is used as the working electrode, and the electrode with hydrogen evolution function is used as the counter electrode. The two electrodes are connected through a DC power supply to perform constant voltage or constant current electrolysis.

[0043] Electrolytic hydrogen production coupled with alcohol oxidation produces anolyte and cathodic products. The anolyte is a liquid phase present in the electrolyte, while the cathodic product is a gas phase. Gas chromatography (GC) or liquid chromatography (LC) is used to analyze the anode and cathode products to determine the type, yield, and hydrogen production of the anolyte. When analyzing the liquid phase products using GC, an internal standard method is used to determine the sample concentration. An FFAP capillary column (30 m × 0.32 mm × 1.0 μm) is used for sample separation, and a flame ionization detector (FID) is used for detection. Nitrogen is used as the carrier gas at a flow rate of 24 mL / min. -1 The column oven temperature was programmed. For gaseous product testing, the external standard method was used to determine hydrogen production. A TDX 01 column (2m × 3mm) was used for sample separation, and a thermal conductivity detector (TCD) was used for detection. Nitrogen was used as the carrier gas at a flow rate of 24 mL / min. -1 The column oven temperature is kept constant.

[0044] Calculation method: The Faraday current efficiency of the product acetic acid is calculated based on the corresponding electron transfer during molecular oxidation, using the following equation:

[0045]

[0046] Where, n product The product yield is expressed in mol, z is the number of electrons transferred (z = 4 for the conversion of ethanol to acetic acid), and F is the Faraday constant (96485 C mol). -1 ), where I is the current value (A) and t is the reaction time (s).

[0047] Example 1

[0048] This embodiment provides a porous flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation, without a fed-batch reaction system. The specific process is as follows:

[0049] Nickel foam with a pore size of 230 μm and a porosity of 98% was selected as the conductive substrate, and Co was immobilized by electrodeposition. 0.1 Ni 0.9The anode of the membrane electrode was prepared in nickel foam using (OH)2 with a loading of 65 mg·g. -1 The cathode of the membrane electrode was prepared by electrodepositing elemental platinum onto nickel foam using nickel foam of the same specifications as the conductive substrate, with a loading of 60 mg·g. -1 This is used for electrolytic hydrogen production coupled with ethanol oxidation. A diagram of the specific experimental setup is shown below. Figure 1 As shown, Co 0.1 Ni 0.9 The (OH)2 / Ni electrode (electrode area of ​​2cm×2cm) and the Pt / Ni electrode are placed in the electrolytic cell. The anode and cathode are separated by a ZIRFON UTP 500+ membrane (membrane thickness of 500μm) to form a sandwich structure in which the anode-electrochemical membrane-cathode are tightly bonded, thus obtaining a porous flow membrane electrode.

[0050] In the process of electrolytic hydrogen production coupled with alcohol oxidation, 100 mL of ethanol containing different concentrations and 6 mol·L⁻¹ is delivered via a fluid transfer pump. -1 The electrolyte solution of potassium hydroxide is prepared at a concentration of 4.08 L·h⁻¹. -1 The flow rate simultaneously passes through the anode and cathode before returning to the storage tank. The electrolytic cell is powered by a DC power supply via an injection pump, and the reaction temperature is controlled at 25°C by a constant temperature water bath. The reaction products are tested and analyzed by a gas chromatograph.

[0051] This embodiment tested the Co content at an initial ethanol concentration of 0.1M with a power supply constant voltage output of 1.75V. 0.1 Ni 0.9 The selectivity of (OH)2 / Ni anodic oxidation of ethanol to the product acetic acid is shown in the following results. Figure 2 As shown: When the initial concentration of ethanol is 0.1M, the current density increases from 220 mA·cm⁻¹ within a 15-minute reaction time. -2 Reduced to 150 mA·cm -2 The selectivity for acetic acid is 98%, the cumulative concentration of acetic acid is only 0.027 M, and the Faraday current efficiency for producing acetic acid is 74%.

[0052] Example 2

[0053] This embodiment is the same as Example 1 under the same conditions, except that the initial concentration of ethanol is changed to 0.2M for testing. Figure 2 As shown, when the initial concentration of ethanol is 0.2M, during a reaction time of 45 minutes, with the power supply constant voltage output at 1.75V, the current density increases from 330 mA·cm⁻¹. -2 Reduced to 207 mA·cm -2 The selectivity for acetic acid is 90%, the cumulative concentration of acetic acid is only 0.078 M, and the Faraday current efficiency for producing acetic acid is 89%.

[0054] Example 3

[0055] This embodiment is the same as Embodiment 1 under the same conditions, except that the initial concentration of ethanol is changed to 0.4M for testing. Figure 2 As shown, when the ethanol concentration is 0.4M, during a reaction time of 120 minutes, with a constant power supply output of 1.75V, the current density increases from 400 mA·cm⁻¹. -2 Reduced to 240 mA·cm -2 The selectivity for acetic acid was 74%, the cumulative concentration of acetic acid was only 0.179 M, and the Faraday current efficiency for producing acetic acid was 62%.

[0056] Examples 1-3 above were used to determine the optimal alcohol concentration. The results showed that a higher ethanol concentration resulted in a higher oxidation current density and a faster reaction rate. However, although increasing the initial ethanol concentration could accelerate the reaction rate (reflected in an increase in current density), a higher initial ethanol concentration also resulted in lower acetic acid selectivity. Therefore, in electrolytic hydrogen production coupled with ethanol oxidation, balancing the reaction rate and product selectivity is a crucial criterion for determining the optimal ethanol concentration. It is necessary to weigh both the reaction rate and acetic acid selectivity to comprehensively determine the optimal ethanol concentration. When the ethanol concentration was 0.2 M, both the reaction rate and acetic acid selectivity remained at relatively high levels, which can be considered the optimal reactant concentration.

[0057] Examples 4-6 below investigate the effects of ethanol feed addition on the cumulative concentration of organic acids, Faraday current efficiency, and organic acid selectivity. The specific process is as follows:

[0058] Example 4

[0059] This embodiment, compared to Embodiment 1, adds the operation of adding ethanol to the electrolyte via a fed-batch method. Other conditions remain the same as in Embodiment 1. The concentration of ethanol was maintained at approximately 0.1 M using a fed-batch method, and the power supply output voltage was 1.75 V. The Co... 0.1 Ni 0.9 The selectivity, cumulative acetic acid concentration, and Faraday current efficiency of (OH)2 / Ni anodic electro-oxidation of ethanol to acetic acid are detailed in the following results and analysis:

[0060] The specific parameters for the feed flow are as follows: under normal temperature and pressure conditions, feed is added every 15 minutes, and each feed increases the reactant concentration by about 0.01M, so that as the reaction proceeds, the reactant concentration is always maintained at about 0.1M.

[0061] like Figure 3 and Figure 4As shown, under fed-batch operation, when the reactant concentration is maintained at around 0.1 M, the selectivity of acetic acid remains at 95%-100%, the cumulative concentration of acetic acid reaches 0.08 M, and the Faraday current efficiency for producing acetic acid reaches 77%.

[0062] Example 5

[0063] This embodiment is the same as embodiment 4 in other conditions, except that the concentration of ethanol is maintained at around 0.2M by feed-in method.

[0064] The specific parameters for the feed flow are as follows: under normal temperature and pressure conditions, feed is added every 30 minutes, and each feed increases the reactant concentration by about 0.05M, so that as the reaction proceeds, the reactant concentration is always maintained at about 0.2M.

[0065] like Figure 3 and Figure 4 As shown, under fed-batch operation, when the reactant concentration is maintained at around 0.2 M, the selectivity of acetic acid remains above 90%, the cumulative concentration of acetic acid reaches 0.2 M, and the Faraday current efficiency for producing acetic acid is 92%.

[0066] Example 6

[0067] This embodiment is the same as embodiment 4 in other conditions, except that the concentration of ethanol is maintained at around 0.4M by feed-in method.

[0068] The specific parameters for the feed flow are as follows: under normal temperature and pressure conditions, feed is added every 120 minutes, and each feed increases the reactant concentration by about 0.2M, so that as the reaction proceeds, the reactant concentration is always maintained at about 0.4M.

[0069] like Figure 3 and Figure 4 As shown, under fed-batch operation, when the reactant concentration is maintained at around 0.4 M, the selectivity of acetic acid remains at around 70%, the cumulative concentration of acetic acid reaches 0.43 M, and the Faraday current efficiency for producing acetic acid is 64%.

[0070] Comparing the test results of Examples 4-6 with those of Examples 1-3, it can be seen that by increasing the feed rate to maintain a relatively constant ethanol concentration during the reaction, the reaction time can be extended and the cumulative amount of acetic acid can be increased. That is, at the same reactant concentration, the examples using the feed rate ultimately achieve a higher cumulative acetic acid concentration. Furthermore, the acetic acid selectivity of Examples 4-6 remains at 95%-100%, above 90%, and approximately 70%, respectively. Therefore, the feed rate operation has no significant effect on the acetic acid selectivity at specific reactant concentrations and remains essentially unchanged.

[0071] Examples 4-6, through systematic adjustment of reactant concentrations, revealed that the highest Faraday current efficiency was achieved at an ethanol concentration of 0.2 M, maximizing the cumulative acetic acid concentration while maintaining high acetic acid selectivity. In contrast, when the ethanol concentration decreased to 0.1 M, insufficient mass transfer during electrolysis easily occurred, leading to oxygen evolution and a decrease in Faraday current efficiency. When the ethanol concentration increased to 0.4 M, the large-scale accumulation of acetaldehyde during electrolysis resulted in non-Faraday side reactions, reducing acetic acid selectivity and similarly lowering Faraday current efficiency. Therefore, considering various indicators, an ethanol concentration of 0.2 M is relatively suitable for continuous, highly selective, and efficient production of acetic acid at industrial current density in an alkaline medium environment, yielding a high cumulative concentration of acetic acid.

[0072] Examples 7-8 below investigate the effect of ethanol fed-batch processing on increasing hydrogen production. The specific process is as follows:

[0073] Example 7

[0074] This embodiment also uses the porous flow membrane electrode structure from Embodiment 1. When the power supply output voltage is 1.75V, the Co content was tested under the "no ethanol feed" method. 0.1 Ni 0.9 The cumulative hydrogen production from (OH)₂ / Ni anodic electro-oxidation of ethanol to acetic acid and co-production of hydrogen is shown in the following results and analysis:

[0075] like Figure 5 As shown, without ethanol feed operation, and with an initial reactant concentration of 0.2M, the total conversion time to ethanol was 122 minutes, and the maximum cumulative hydrogen production was 0.69L.

[0076] Example 8

[0077] This embodiment is the same as embodiment 7 in other conditions, except that it combines the "ethanol feed" method for testing.

[0078] The specific parameters for the feed flow are as follows: under normal temperature and pressure conditions, feed is added every 30 minutes, and each feed increases the reactant concentration by about 0.05M, so that as the reaction proceeds, the reactant concentration is always maintained at about 0.2M.

[0079] like Figure 5 As shown, compared with Example 7, this example, by combining ethanol feed, can increase the maximum cumulative hydrogen production to 0.90L within the same reaction time (122 minutes).

[0080] This shows that increasing the feed of reactant ethanol can improve hydrogen production.

[0081] Comparative Example 1

[0082] This comparative example provides an electrode for electrolytic hydrogen production coupled with alcohol oxidation. The electrocatalytic oxidation of n-propanol is carried out using a manganese dioxide catalyst immobilized on a porous titanium membrane. The specific process is as follows:

[0083] First, the titanium membrane was pretreated with oxalic acid to remove surface impurities and etch the membrane surface. Next, a 0.8 mol / L manganese sulfate solution was permeated into the titanium membrane using a peristaltic pump, followed by membrane drying. Then, a 0.2 mol / L potassium permanganate solution was permeated into the pores of the titanium membrane using a peristaltic pump; during this process, the potassium permanganate solution reacted with the manganese sulfate in the membrane pores in a redox reaction to synthesize MnO2. Finally, the above manganese sulfate and potassium permanganate permeation steps were repeated four times to increase the manganese oxide loading to 16 mg / g. -1 MnO2@Ti electrode was obtained.

[0084] The electrocatalytic oxidation of n-propanol was carried out under constant current, with sodium sulfate solution as the electrolyte, and the flow rate was set to 89.3 L / min. -2 ·h -1 The reaction was carried out at room temperature for 19 hours. The products were quantitatively analyzed by gas chromatography, and the generated hydrogen gas was collected and quantified by water displacement. The MnO2@Ti electrode prepared by loading MnO2 catalyst into the pores of a Ti membrane in this comparative example was used as the anode, and a stainless steel mesh surrounding the anode served as the cathode. The distance between the anode and cathode was fixed at 17.5 mm. The entire device was connected to the electrolytic cell via a peristaltic pump hose for cyclic oxidation. The peristaltic pump provided a constant negative pressure, allowing the n-propanol solution to flow through the MnO2@Ti electrode for oxidation.

[0085] The electrode prepared in this comparative example can be used for the electrolysis of n-propanol to co-produce hydrogen and propionic acid. When the concentration of n-propanol is 0.16 M and the cell voltage is 2.45 V, the measured current density is 2.55 mA·cm⁻¹. -2 The overall current is 120mA.

[0086] The data above shows that, due to the large distance between the anode and cathode in Comparative Example 1, the required cell voltage for electrolyzing n-propanol to co-produce hydrogen and propionic acid is high, resulting in low overall current and low current density. In contrast, in the embodiments of this invention, the anode and cathode are respectively disposed on both sides of the electrochemical membrane and tightly bonded to it to form a sandwich structure. The distance between the anode and cathode is only 500 μm of the membrane's thickness. Therefore, based on the test results of Examples 1-3, a current density of 200 mA·cm⁻¹ can be achieved at a cell voltage of 1.75 V. -2The above initial current density indicates that the sandwich structure designed in this invention has a good effect on the coupling of hydrogen evolution in alcohol electrolysis.

Claims

1. A flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation, wherein, The flow membrane electrode includes an anode, an electrochemical membrane, and a cathode; the anode and cathode are respectively disposed on both sides of the electrochemical membrane and are bonded to the electrochemical membrane to form a sandwich structure; The thickness of the electrochemical membrane is 200-500 μm; The anode and cathode are respectively prepared by immobilizing catalytic materials in a conductive substrate; The conductive substrate has a porous structure with a pore size of 100 to 500 μm.

2. The flow membrane electrode according to claim 1, wherein, The catalytic material of the anode includes an alcohol oxidation catalytic material; the catalytic material of the cathode includes a hydrogen evolution catalytic material. The alcohol oxidation catalyst includes one or more of MnO2, Co3O4, Ni(OH)2, and Co(OH)2; The hydrogen evolution catalyst material includes one or more of the following: platinum, Co(OH)2, Ni, Mo, CoFe bimetal, CoMo bimetal, NiMo bimetal, and Raney nickel.

3. The flow membrane electrode according to claim 1, wherein, The conductive substrate includes one or more of sintered titanium, sintered stainless steel, nickel foam, carbon cloth, and graphite.

4. The flow membrane electrode according to claim 1, wherein, The electrochemical membrane is made of one or more of the following materials: polyetheretherketone membrane, polyphenylene sulfide membrane, polytetrafluoroethylene resin modified asbestos membrane, asbestos membrane, and polysulfone membrane.

5. A method for electrolytic hydrogen production coupled with alcohol oxidation, wherein, The method includes: forcing an electrolyte to flow through the channels of a flow membrane electrode for electrolytic hydrogen production coupled with alcohol oxidation as described in any one of claims 1-4 in a direction perpendicular to the electrode thickness, wherein the electrolyte flowing out of the channels is circulated and then re-enters the membrane electrode for reaction.

6. The method according to claim 5, wherein, The electrolyte comprises alcohols and electrolytes; The alcohols are added to the electrolyte by a feed-feed method, with each feeding interval being 15-120 minutes.

7. The method according to claim 6, wherein, The concentration of the alcohol in the electrolyte is 0.1M to 0.4M.

8. The method according to claim 7, wherein, During the reaction, the concentration of alcohols in the electrolyte remains relatively constant.

9. The method according to claim 6, wherein, The alcohols include one or more of methanol, ethanol, propanol, and benzyl alcohol.

10. The method according to claim 5, wherein, The voltage range of the electrolytic hydrogen production coupled with alcohol oxidation method is 0-3V.

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