A medium- and high-temperature methanol electrolysis hydrogen production reactor

Abstract

A medium-high temperature methanol electrolysis hydrogen production reactor includes an end plate, an anode plate, an anode gas diffusion layer, a medium-high temperature membrane electrode, a cathode gas diffusion layer, and a cathode plate. The medium-high temperature membrane electrode mainly consists of a medium-high temperature acidic electrolyte membrane, a dual-catalytic layer anode, and a cathode. The dual-catalytic layer anode includes an outer catalytic layer and an inner catalytic layer. The operating temperature of the medium-high temperature methanol electrolysis hydrogen production reactor is 160℃-250℃. During operation, a methanol aqueous solution introduced to the anode side passes sequentially through the anode plate and the anode gas diffusion layer to reach the dual-catalytic layer anode. After applying a certain potential, methanol undergoes an electrochemical oxidation reaction in the outer and inner catalytic layers to generate carbon dioxide, protons, and electrons. The protons pass through the medium-high temperature acidic electrolyte membrane to reach the cathode and combine with electrons to generate hydrogen gas.

Description

Technical Field

[0001] This invention relates to the fields of methanol reforming for hydrogen production and high-temperature proton exchange membranes, and particularly to a medium- and high-temperature methanol electrolysis hydrogen production reactor. Background Technology

[0002] Current methanol reforming technologies for hydrogen production mainly include thermochemical reforming and methanol electrolysis. Thermochemical reforming primarily involves steam reforming, partial oxidative reforming, and autothermal reforming. The hydrogen-rich gas produced by thermochemical reforming often contains impurities such as carbon monoxide and formic acid, requiring multiple purification stages including low-temperature steam-water conversion, selective oxidation, pressure swing adsorption, and Pd membrane separation to obtain pure hydrogen for use in proton exchange membrane fuel cells (PEMFCs). This process is complex and energy-intensive. In contrast, the hydrogen-rich gas produced by methanol electrolysis does not contain impurities such as carbon monoxide and formic acid, requires no multi-stage purification, and can be directly used as a hydrogen source for PEMFCs.

[0003] However, most current methanol electrolysis hydrogen production reactors use Nafion membranes, which operate at relatively low temperatures, typically 60℃-80℃. This low operating temperature results in slow methanol electrochemical oxidation kinetics, significant anodic polarization losses, higher operating voltages, lower efficiency, higher Pt usage, and higher costs. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a medium- and high-temperature methanol electrolysis hydrogen production reactor, which improves the rate of methanol electrochemical oxidation reaction in the anode and the utilization rate of the catalyst, reduces methanol permeation, reduces anode polarization loss, thereby reducing the operating voltage of the electrolyzer, improving energy conversion efficiency and power density, and reducing costs.

[0005] The technical solution of this invention is: A medium- and high-temperature methanol electrolysis hydrogen production reactor includes an end plate, an anode plate, an anode gas diffusion layer, a medium- and high-temperature membrane electrode, a cathode gas diffusion layer, a cathode plate, and an end plate connected in sequence. The medium- and high-temperature membrane electrode includes an electrolyte membrane, a double-catalytic layer anode, and a cathode. The electrolyte membrane is a phosphoric acid-doped PBI membrane. The operating temperature of the reactor is 160℃-250℃.

[0006] The electrolyte membrane is a phosphoric acid-doped PBI membrane, primarily serving to block methanol permeation and conduct protons. This choice of electrolyte membrane allows the medium-to-high temperature methanol-to-hydrogen electrolysis reactor to operate at temperatures between 160℃ and 250℃. This accelerates the reactor's reaction kinetics and reduces the electrolyzer's operating voltage.

[0007] During operation, the methanol-water solution introduced into the anode side passes sequentially through the anode plate and the anode gas diffusion layer to the double-catalytic layer anode. After a certain potential is applied, methanol undergoes an electrochemical oxidation reaction in the outer and inner catalytic layers to generate carbon dioxide, protons, and electrons. The protons pass through the medium-high temperature acidic electrolyte membrane to the cathode and combine with electrons to generate hydrogen gas.

[0008] The PBI film is pure PBI or a PBI film modified by grafting, cross-linking, or inorganic doping; the pure PBI film includes mPBI, OPBI, or ABPBI; the thickness of the PBI film is 30μm-150μm, and the phosphoric acid doping amount is 200%-450%.

[0009] The dual-catalytic-layer anode comprises an outer catalyst layer and an inner catalyst layer. The outer catalyst layer comprises PtRu / C or PtW / C and PTFE. In the outer catalyst layer, the mass fraction of noble metals in the PtRu / C or PtW / C is 10%–90%, and the loading of noble metals in the outer catalyst layer is 0.05–2.0 mg / cm³. 2 The PTFE content is 5%–25% of the total mass of the outer catalyst layer; The inner catalyst layer consists of PtRu black or PtW black and PTFE, with a noble metal loading of 0.05-5.0 mg / cm³. 2 The PTFE content is 5%–40% of the total mass of the inner catalyst layer.

[0010] The ratio of the loading of noble metals in the inner catalyst layer to the outer catalyst layer is 1 / 8 to 10 / 1, and the ratio of the thickness of the inner catalyst layer to the outer catalyst layer is 1 / 5 to 5 / 1.

[0011] The PTFE content in the outer catalyst layer is lower than that in the inner catalyst layer.

[0012] The cathode comprises Pt / C, Pd / C, or PtPd / C with PTFE; in the cathode, the mass fraction of noble metals in the Pt / C, Pd / C, or PtPd / C is 5%–80%, and the noble metal loading in the cathode is 0.02–3.0 mg / cm³. 2 The PTFE content is 5%–35% of the total cathode mass.

[0013] The anode gas diffusion layer includes a support layer and a microporous layer; the support layer is carbon paper, carbon cloth, carbon felt, titanium mesh, or stainless steel mesh, and the microporous layer includes carbon powder and PTFE. The carbon powder is any one or more of activated carbon, graphitized carbon, carbon nanotubes, carbon nanoribbons, and carbon nanospheres, and the PTFE content in the microporous layer is 5%-30%.

[0014] The cathode gas diffusion layer includes a support layer and a microporous layer; the support layer is carbon paper, carbon cloth, carbon felt, titanium mesh, or stainless steel mesh, and the microporous layer includes carbon powder and PTFE. The carbon powder is any one or more of activated carbon, graphitized carbon, carbon nanotubes, carbon nanoribbons, and carbon nanospheres, and the PTFE content in the microporous layer is 10%-40%.

[0015] The anode and cathode plates are made of graphite resin composite or stainless steel, aluminum alloy, or titanium alloy with gold, tantalum, and / or niobium plating on the surface; the flow fields of the cathode and anode plates are multi-channel serpentine, parallel, point-like, porous, or combined flow fields.

[0016] The sealing gaskets of the anode and cathode plates are made of PTFE, FEP, PFA or fluororubber; the end plates are made of gold-plated stainless steel, aluminum alloy or titanium alloy plates; electric heating elements are attached to the surface of the end plates for start-up; the end plates are also equipped with inlet and outlet devices for the inflow of reactants and the outflow of products.

[0017] In summary, this application includes at least the following beneficial technical effects: Compared to methanol thermochemical reforming hydrogen production reactors, the hydrogen-rich gas produced by the electrolytic methanol hydrogen production reactor of this application does not contain impurities such as carbon monoxide and formic acid, eliminating the need for multi-stage purification and allowing it to be directly used as a hydrogen source for PEMFCs. The electrolytic methanol hydrogen production reactor uses a phosphoric acid-doped PBI electrolyte membrane, with an operating temperature typically between 120℃ and 180℃. The reaction is a single-phase flow, requiring no humidification. Compared to traditional Nafion system electrolyzers, the methanol electrochemical oxidation reaction rate at the anode is faster, hydrothermal management is simpler, and efficiency is higher. The anode of the electrolytic methanol hydrogen production reactor employs a dual-catalyst layer structure. By controlling the type of catalyst and the PTFE content in the inner and outer catalyst layers, differences in pore structure and hydrophilicity / hydrophobicity are created, improving the distribution of phosphoric acid, effectively constructing a three-phase interface, enhancing the utilization rate of the precious metal catalyst, and reducing costs. Attached Figure Description

[0018] Figure 1 A schematic diagram of a medium- and high-temperature methanol electrolysis hydrogen production reactor; Figure 2 Schematic diagram of medium- and high-temperature membrane electrode structure; Figure 3 Polarization curves of membrane electrodes for methanol-to-hydrogen electrolysis with different anode structures.

[0019] Appendix Figure 1 , Figure 2 Markings: 1. End plate; 2. Anode plate; 3. Anode gas diffusion layer; 4. Medium-high temperature membrane electrode; 5. Cathode gas diffusion layer; 6. Cathode plate; 7. Electrolyte membrane; 8. Double catalyst layer anode; 9. Inner catalyst layer; 10. Outer catalyst layer; 11. Cathode.

[0020] Appendix Figure 3 Labeling: 1. Comparative Example 1; 2. Comparative Example 2; 3. Comparative Example 3; 4. Comparative Example 4; 5. Example 1. Detailed Implementation

[0021] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments: Example 1 See Figure 1 The present invention is a medium- and high-temperature electrolytic methanol-to-hydrogen reactor, comprising an end plate 1, an anode plate 2, an anode gas diffusion layer 3, a medium- and high-temperature membrane electrode 4, a cathode gas diffusion layer 5, a cathode plate 6, and an end plate 1 connected in sequence.

[0022] End plate 1 is made of 316L stainless steel with a gold-plated surface for current collection. It has heating elements and inlet / outlet devices for reactant entry and product exit. Anode plate 2 is a graphite resin composite bipolar plate with a thickness of 2mm. The plate has a 3-channel serpentine flow field, and the edge sealing gasket is a fluororubber high-temperature resistant gasket. Cathode plate 6 is also a graphite resin composite bipolar plate with a thickness of 2mm. It has a point flow field, and the edge sealing gasket is a fluororubber high-temperature resistant gasket. The anode gas diffusion layer 3 has a support layer made of SGL carbon paper with a thickness of 180μm, and a microporous layer composed of carbon powder and PTFE, with a PTFE content of 20%. The cathode gas diffusion layer 5 has a support layer made of Torray carbon paper with a thickness of 150μm, and a microporous layer composed of carbon powder and PTFE, with a PTFE content of 25%.

[0023] See Figure 2 The medium-high temperature membrane electrode 4 includes an electrolyte membrane 7, a double-catalyst anode 8 and a cathode 9 located on both sides of the electrolyte membrane 7. The double-catalyst anode 8 includes an outer catalyst layer 10 and an inner catalyst layer 9. The electrolyte membrane is a modified PBI membrane with a thickness of 50 micrometers and a phosphoric acid doping amount of 350%. After acid doping, the membrane thickness is 90 micrometers, and the typical operating temperature is 160℃-180℃. The outer catalyst layer is composed of 40wt% PtRu / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The inner catalyst layer is composed of PtRu black and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 20%. The cathode of the medium-high temperature membrane electrode is composed of 40wt% Pt / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%.

[0024] Comparative Example 1 Compared to Example 1, the membrane electrode assembly (MEA) of the methanol-to-hydrogen electrolysis reactor in Comparative Example 1 uses a Nafion 117 membrane as the electrolyte membrane, and the operating temperature is 80°C. The anode in the MEA has a double-catalytic-layer structure, and the cathode has a single-catalytic-layer structure. The outer catalytic layer of the anode consists of 40 wt% PtRu / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The inner catalyst layer is composed of PtRu black and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 20%. The cathode is composed of 40wt% Pt / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The electrode plates, gas diffusion layer, and end plates of this electrolyzer are the same as those in Example 1.

[0025] Comparative Example 2 Compared to Example 1, in Comparative Example 2, the anode and cathode of the high-temperature membrane electrode in the methanol-to-hydrogen electrolysis reactor both have a single catalytic layer structure, and the operating temperature is 160°C. The anode catalytic layer consists of 40 wt% PtRu / C and PTFE, with a noble metal loading of 2.5 mg / cm³. 2 The PTFE content is 10%. The cathode is composed of 40wt% Pt / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The electrodes, phosphate-doped PBI electrolyte membrane, gas diffusion layer, and end plates of this electrolyzer are the same as those in Example 1.

[0026] Comparative Example 3 Compared to Example 1, in Comparative Example 3, the membrane electrode assembly of the methanol-to-hydrogen electrolysis reactor features a double-catalytic-layer structure at the anode and a single-catalytic-layer structure at the cathode, with an operating temperature of 160°C. The outer catalytic layer of the anode consists of 40 wt% PtRu / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 20%. The inner catalyst layer is composed of PtRu black and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The cathode is composed of 40wt% Pt / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The electrodes, phosphate-doped PBI electrolyte membrane, gas diffusion layer, and end plates of this electrolyzer are the same as those in Example 1.

[0027] Comparative Example 4 Compared to Example 1, in Comparative Example 4, the membrane electrode assembly of the methanol-to-hydrogen electrolysis reactor features a double-catalytic-layer structure at the anode and a single-catalytic-layer structure at the cathode, with an operating temperature of 160°C. The outer catalytic layer of the anode is composed of PtRu black and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The inner catalyst layer consists of 40wt% PtRu / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The cathode is composed of 40wt% Pt / C and PTFE, with a noble metal loading of 0.5 mg / cm³. 2 The PTFE content is 10%. The electrodes, phosphate-doped PBI electrolyte membrane, gas diffusion layer, and end plates of this electrolyzer are the same as those in Example 1.

[0028] Performance testing The polarization curves of the membrane electrodes for methanol-to-hydrogen electrolysis with different anode structures were detected. The specific operating conditions were as follows: the operating temperature of the methanol-to-hydrogen electrolysis reactor in Comparative Example 1 was 80℃, and the operating temperature of the methanol-to-hydrogen electrolysis reactors in Comparative Examples 2, 3, 4 and the examples was 160℃; the anode was fed with a methanol aqueous solution with a concentration of 4 mol / L, and the cathode hydrogen outlet pressure was atmospheric pressure.

[0029] The reactors of the above embodiments and comparative examples were subjected to the following tests: A high-precision DC power supply was used to perform the methanol-to-hydrogen electrolysis reaction, and the voltage and current were recorded in real time.

[0030] The products from the anodes of the methanol electrolysis hydrogen generators in the examples and comparative examples were collected, and the purity of the hydrogen was determined by gas chromatography. The results are shown in Table 1.

[0031] According to Table 1 and Figure 3 It can be seen that, compared to the low-temperature Nafion system methanol-to-hydrogen reactor with an operating temperature of 80℃ (Comparative Example 1), the methanol-to-hydrogen reactor using a phosphoric acid-doped PBI electrolyte membrane (Example 1) with an operating temperature of 160℃ exhibits lower electrolysis voltage, higher electrolysis efficiency, and higher hydrogen purity in the product at the same current density. This is mainly because, on the one hand, the electrochemical oxidation reaction rate of methanol increases with temperature, resulting in less electrochemical polarization loss; on the other hand, since the reaction is a single-phase flow at high temperatures, humidification is unnecessary, reducing the permeation of methanol, carbon dioxide, etc., into the phosphoric acid-doped PBI electrolyte membrane, thus leading to higher hydrogen purity in the product.

[0032] The detection results of Example 1 and Comparative Example 2 are shown below. Figure 3 Under these conditions, it can be seen that using a low platinum loading (1.0 mg / cm³) is effective. 2Double-catalytic-layer anode (Example 1) with high platinum loading (2.5 mg / cm³) 2 The performance of the membrane electrode assembly (MEA) in the dual-catalytic-layer anode reactor for methanol-to-hydrogen electrolysis is comparable, at 0.02 A cm⁻¹. -2 The voltages reached 160mV and 163mV respectively, at 0.3 A cm. -2 The voltages reached 275mV and 277mV respectively at 0.5 A cm. -2 The voltages reached 310mV and 313mV respectively, indicating that the double catalyst layer structure of the anode is more conducive to the uniform distribution of phosphoric acid, avoiding acid flooding caused by excessive local phosphoric acid and low three-phase interface area caused by insufficient phosphoric acid, thereby reducing activation polarization loss and ohmic polarization loss, improving catalyst utilization, reducing platinum loading, and reducing cost.

[0033] The detection results of Example 1 and Comparative Example 3 are shown in [reference]. Figure 3 Under these conditions, it can be seen that compared to the dual-catalyst anode structure with an inner catalyst layer containing 10 wt% PTFE and an outer catalyst layer containing 20 wt% PTFE, the membrane electrode constructed with the inner catalyst layer containing 20 wt% PTFE and the outer catalyst layer containing 10 wt% PTFE exhibits higher performance and lower voltage at the same electrical density, specifically at 0.02 A cm⁻¹. -2 The voltages reached 160mV and 185mV respectively, at 0.3 A cm. -2 The voltages reached 275mV and 305mV respectively at 0.5 A cm. -2 The voltages reached 310mV and 353mV respectively, indicating that the anode double catalyst layer structure with an inner catalyst layer of 20wt% PTFE and an outer catalyst layer of 10wt% PTFE is more conducive to the uniform distribution of phosphoric acid, avoiding acid flooding caused by excessive local phosphoric acid and low three-phase interface area caused by insufficient phosphoric acid, thereby reducing activation polarization loss and ohmic polarization loss, reducing the actual electrolysis voltage and improving efficiency.

[0034] The detection results for Example 1 and Comparative Example 4 are shown below. Figure 3 Under these conditions, it can be seen that compared to the dual-catalyst anode structure with an inner catalyst layer of 40wt% PtRu / C and PTFE and an outer catalyst layer of PtRu black and PTFE, the membrane electrode structure with an inner catalyst layer of PtRu black and PTFE and an outer catalyst layer of 40wt% PtRu / C and PTFE exhibits higher performance and lower voltage at the same dielectric constant, specifically at 0.02 A cm⁻¹. -2 The voltages reached 160mV and 175mV respectively, at 0.3 A cm. -2 The voltages reached 275mV and 290mV respectively at 0.5 A cm. -2The voltages reached 310mV and 332mV respectively, indicating that the anode double catalyst layer structure with 40wt%PtRu / C inner catalyst layer and 40wt%Pt / C outer catalyst layer is more conducive to constructing a lower three-phase interface area of ​​the electrode reaction, thereby reducing activation polarization loss and ohmic polarization loss, reducing electrolysis voltage, and improving efficiency.

[0035] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A medium-to-high temperature methanol electrolysis hydrogen production reactor, characterized in that: It includes end plate A, anode plate (2), anode gas diffusion layer (3), medium and high temperature film electrode (4), cathode gas diffusion layer (5), cathode plate (6) and end plate B connected in sequence; The anode gas diffusion layer (3) includes a support layer and a microporous layer; the support layer is carbon paper, carbon cloth, carbon felt, titanium mesh, or stainless steel mesh, and the microporous layer includes carbon powder and PTFE. The carbon powder is any one or more of activated carbon, graphitized carbon, carbon nanotubes, carbon nanoribbons, and carbon nanospheres. The PTFE content in the microporous layer is 5% to 30% of the total mass of the microporous layer. The medium-high temperature membrane electrode (4) includes an electrolyte membrane (7), a double-catalytic layer anode (8), and a cathode (9); wherein, the electrolyte membrane (7) is a phosphoric acid-doped PBI membrane, and the reactor operating temperature is 160℃~250℃; the phosphoric acid doping amount of the PBI membrane is 200%-450%; the double-catalytic layer anode (8) includes an outer catalyst layer (10) and an inner catalyst layer (11); the outer catalyst layer (10) is composed of PtRu / C and PTFE or PtW / C and PTFE; in the outer catalyst layer (10), the mass fraction of noble metal in PtRu / C or PtW / C is 10%~90%, and the loading of noble metal in the outer catalyst layer (10) is 0.05~2.0 mg / cm³. 2 The PTFE content is 10% of the total mass of the outer catalyst layer (10); the inner catalyst layer (11) is composed of PtRu black and PTFE or PtW black and PTFE; the loading of noble metals in the inner catalyst layer (11) is 0.05~5.0 mg / cm³. 2 The PTFE content is 20% of the total mass of the inner catalyst layer (11); the ratio of the noble metal loading in the inner catalyst layer (11) to the outer catalyst layer (10) is 1 / 8; the cathode (9) is composed of one of Pt / C, Pd / C or PtPd / C and PTFE; in the cathode (9), the mass fraction of noble metal in Pt / C, Pd / C or PtPd / C is 5%~80%, and the noble metal loading in the cathode (9) is 0.02~3.0 mg / cm³. 2 The PTFE content is 10% of the total mass of the cathode (9); The cathode gas diffusion layer (5) includes a support layer and a microporous layer; the support layer is carbon paper, carbon cloth, carbon felt, titanium mesh, or stainless steel mesh, and the microporous layer includes carbon powder and PTFE. The carbon powder is any one or more of activated carbon, graphitized carbon, carbon nanotubes, carbon nanoribbons, and carbon nanospheres, and the PTFE content in the microporous layer is 10% to 40%.

2. The medium-high temperature methanol electrolysis hydrogen production reactor according to claim 1, characterized in that: The thickness of the PBI membrane ranges from 30 μm to 150 μm.

3. The medium-high temperature methanol electrolysis hydrogen production reactor according to claim 1, characterized in that: The thickness ratio of the inner catalyst layer to the outer catalyst layer is 1 / 5.

4. The medium-high temperature methanol electrolysis hydrogen production reactor according to claim 1, characterized in that: End plates A and B are made of 316L stainless steel and are gold-plated to achieve the purpose of flow collection. Electric heating elements are attached to end plates A and B and inlet and outlet devices are provided for the entry of reactants and the discharge of products.

5. A medium-high temperature methanol electrolysis hydrogen production reactor according to claim 1, characterized in that: The anode plate (2) is a graphite resin composite bipolar plate with a 3-channel serpentine flow field and a fluororubber high-temperature resistant sealing gasket at the edge of the plate.

6. The medium-high temperature methanol electrolysis hydrogen production reactor according to claim 1, characterized in that: The cathode plate (6) is a graphite resin composite bipolar plate. The plate flow field is a point flow field, and the edge sealing gasket is a fluororubber high-temperature resistant sealing gasket.

Images