Direct ammonia fuel cell chip, method of manufacture and stack module

Abstract

The application provides a direct ammonia fuel cell chip, which comprises an anode current collecting substrate, an anode catalytic layer, a proton exchange membrane, a cathode catalytic layer and a cathode current collecting substrate which are vertically and layerwisely arranged; the anode current collecting substrate and the cathode current collecting substrate comprise a Ti3AlC2 MAX phase ceramic core layer, a nano diamond gradient composite layer and a passivation layer; and the application further provides a preparation method of the direct ammonia fuel cell chip and a direct ammonia fuel cell chip stacking module. The Ti3AlC2 MAX phase composite ceramic material substrate has excellent corrosion resistance; the power density is greatly increased by setting a pulse electric field; compared with traditional noble metal catalysts, the catalyst cost is greatly reduced; the direct ammonia fuel cell chip adopts parallel main reaction flow channels as an anode flow field and parallel cathode oxidation gas flow channels as a cathode flow field, and a trace ammonia recovery channel is arranged between the main reaction flow channels and the cathode oxidation gas flow channels, so that most of ammonia gas is separated and recovered, thereby improving the ammonia utilization rate.

Description

Technical Field

[0001] This invention relates to the field of direct ammonia fuel cell technology, and more particularly to direct ammonia fuel cell chips, fabrication methods, and stacking modules. Background Technology

[0002] Driven by dual carbon objectives, green ammonia has become a core carrier for grid-scale long-term energy storage and zero-carbon power in the transportation sector due to its low storage and transportation costs, high volumetric energy density (more than 10 times that of 70MPa high-pressure hydrogen), and zero carbon emissions throughout its entire life cycle. Direct ammonia fuel cells (DAFCs) can directly convert the chemical energy of ammonia into electrical energy without the need for online reforming to produce hydrogen. With a simpler system structure and higher energy conversion efficiency, DAFCs represent the core technological path for the large-scale utilization of green ammonia.

[0003] For example, Chinese invention patent CN116230995A discloses a direct ammonia fuel SOFC and PEMFC combined system, including a solid oxide fuel cell (SOFC) and proton exchange membrane fuel cell (PEMFC) combined system using liquid ammonia as fuel, including a liquid ammonia tank, SOFC, PEMFC, burner, condenser, ammonia removal device, multiple heat exchangers and vaporizer; the core scheme is that ammonia is decomposed into nitrogen and hydrogen mixture on the nickel-based anode of SOFC at 600-800℃, and the high-temperature tail gas of SOFC anode is heat exchanged, condensed and ammonia removed, and the remaining hydrogen is sent to PEMFC for secondary power generation, and the waste heat of tail gas combustion is used for SOFC intake preheating. Chinese invention patent CN115224295A discloses a fuel cell bipolar plate with a corrosion-resistant film and its preparation method. The method includes using a 316L stainless steel sheet with dense pores on its surface as a substrate, preparing a graphitized hexagonal carbon layer network film on the surface of the fuel cell bipolar plate, and forming a corrosion-resistant carbon film on the stainless steel surface through electrochemical etching, impregnation with a polyamic acid precursor, high-temperature imidization, and carbonization. After carbonization at 900℃, the corrosion current density of the bipolar plate in a simulated fuel cell environment at room temperature is 2.75 μA / cm². 2 .

[0004] The above technical solutions, along with other current direct ammonia fuel cell technologies, all reference solid oxide fuel cells, using bipolar plates, catalyst layers, and proton exchange membranes to achieve the reaction. However, this approach still has the following problems:

[0005] Existing DAFCs generally adopt a split splicing structure of graphite / metal bipolar plates. Graphite bipolar plates are brittle, have high microchannel processing costs, and poor airtightness. Metal bipolar plates are prone to corrosion and passivation under high-temperature ammonia atmosphere, and their continuous operating life is less than 5,000 hours. The split structure has high interlayer contact resistance and mismatched thermal expansion coefficients of heterogeneous materials, which can easily lead to sealing failure and interface delamination during thermal cycling.

[0006] Under medium and low temperature conditions, the energy barrier for AOR reaction is extremely high, and the reaction rate is two orders of magnitude slower than that of hydrogen hydroxide. Existing technologies must rely on precious metal catalysts such as Pt and Ir, and the cost of fuel cell stack catalysts accounts for more than 60%, resulting in high costs.

[0007] Ammonia molecules can easily permeate through the proton exchange membrane to the cathode, leading to irreversible poisoning of the cathode oxygen reduction (ORR) catalyst and rapid decay of battery power. Currently, the utilization rate of ammonia fuel is generally below 85%, and the continuous operating life of the cathode is less than 3,000 hours.

[0008] Existing DAFCs are all custom-built stacks / system-level structures. During power amplification, they suffer from severe flow field inhomogeneity, temperature inhomogeneity, and performance degradation. The amplification effect is significant, making modular and automated production impossible. Large-scale application is costly and has a long implementation cycle. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a direct ammonia fuel cell chip, a fabrication method, and a stacking module, which solves problems such as high cost, short service life, and difficulty in scaling up existing technologies.

[0010] In a first aspect, the present invention proposes a direct ammonia fuel cell chip, comprising a vertically stacked anode current collector substrate, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, and a cathode current collector substrate.

[0011] The anode current collector and cathode current collector are composite ceramic substrates, including a Ti3AlC2MAX phase ceramic core layer, a nanodiamond gradient composite layer grown in situ on the surface of the core layer, and a passivation layer grown in situ on the surface of the gradient composite layer. The anode current collector and cathode current collector are integrally formed with a flow field on opposite sides, and the inner wall of the flow field is respectively attached with an anode catalyst layer and a cathode catalyst layer.

[0012] The anode catalyst layer includes an ammonia oxidation catalyst, and the cathode catalyst layer includes an oxygen reduction catalyst;

[0013] A pulsed electric field control unit is integrated on the anode current collector and the cathode current collector. The pulsed electric field control unit uses the anode current collector and the cathode current collector as electrodes to form an adjustable high-frequency pulsed electric field at both ends of the anode catalyst layer and the cathode catalyst layer.

[0014] The anode current collector and / or cathode current collector are provided with fluid interfaces, electrical interfaces, and mechanical interfaces on their sides, and an encapsulation frame is integrally formed on the outer edge; so that the anode current collector, proton exchange membrane and cathode current collector are stacked in sequence to form an overall closed structure, thereby constituting a chip; a sensor module is integrated inside the anode current collector and / or cathode current collector.

[0015] Furthermore, the thickness of the Ti3AlC2MAX phase ceramic core layer is 0.2-0.8 mm; in the nanodiamond gradient composite layer, the diamond content increases in four steps from near the core layer to the outside, from 0%, 30%, 70%, and 100%.

[0016] Furthermore, the flow field on the anode current collector includes a main reaction channel and an ammonia capture channel, which are arranged adjacent to each other and separated by a hydrophobic all-silica molecular sieve membrane, wherein the hydrophobic all-silica molecular sieve membrane is an ammonia selective permeation membrane.

[0017] Furthermore, the main reaction channel is a three-level self-similar fractal microchannel, including a primary main channel, a secondary sub-channel, and a tertiary micro / nano channel. The primary main channel has a width of 2 mm, the secondary sub-channel has a width of 0.8 mm, and the tertiary micro / nano channel has a width of 40-60 μm. An anode catalyst layer is grown in situ on the inner wall of the primary main channel, the secondary sub-channel, and the tertiary micro / nano channel.

[0018] Furthermore, the flow fields of the anode current collector and the cathode current collector are provided with in-situ grown nitrogen-defective graphene support layers, and the anode catalyst layer and the cathode catalyst layer are anchored on the graphene support layer; the ammonia oxidation catalyst is a Fe / Ni / Mo dual single-atom catalyst, and the oxygen reduction catalyst is a Mn / Co single-atom oxygen reduction catalyst.

[0019] Furthermore, the electric field strength applied by the pulse electric field control unit is 0-8V / cm and the frequency is 1-20kHz.

[0020] Furthermore, the fluid interface includes an ammonia fuel inlet, an oxidant inlet, a tail gas outlet, and a circulating ammonia return inlet; the electrical interface includes an elastic conductive post; and the mechanical interface includes a positioning pin hole.

[0021] Secondly, this invention proposes a method for preparing a direct ammonia fuel cell chip, comprising the following steps:

[0022] S1. The Ti3AlC2 raw material powder was dry-pressed into a green body, and the Ti3AlC2MAX phase ceramic matrix was prepared by high-temperature sintering in an argon atmosphere. The flow field, encapsulation frame, interface structure and mechanical positioning structure were integrally formed by laser milling. Then, the nanodiamond gradient composite layer was grown in situ by MPCVD process, and a passivation layer was generated on the surface of the gradient composite layer by oxygen plasma treatment. Finally, the in-situ hydrophilic and hydrophobic partitions were generated in the flow field by laser induction. Finally, the anode current collector matrix and the cathode current collector matrix were prepared respectively.

[0023] S2. Nitrogen-deficient graphene support layers are grown in situ on the inner walls of the flow channels of the anode current collector and the cathode current collector using PECVD process. Then, an equal-volume impregnation process is used to calcine the graphene support layers under an argon atmosphere, thereby anchoring the ammonia oxidation catalyst and the oxygen reduction catalyst on the graphene support layers respectively, forming the anode catalyst layer and the cathode catalyst layer.

[0024] S3. After positioning and aligning the anode current collector, proton exchange membrane, and cathode current collector through a mechanical interface, they are stacked and then hot-pressed to achieve integrated packaging.

[0025] S4. The pulse electric field control unit is integrated at the edge of the anode current collector or cathode current collector using LTCC process. Then, the sensor module is fabricated using magnetron sputtering / photolithography process. The electrical interface, fluid interface and mechanical interface are assembled in accordance with the interface structure position to complete the chip fabrication.

[0026] Furthermore, in step S2, after processing the catalyst, a full-silicon molecular sieve membrane is prepared on a porous alumina support using a secondary growth method. After being modified by trimethylchlorosilane vapor phase hydrophobicity, it is laser-cut to the designed size, installed in the flow field, and the main reaction channel and ammonia collection channel are separated. It is then sealed and fixed using high-temperature resistant ceramic slurry.

[0027] Thirdly, the present invention also proposes a direct ammonia fuel cell chip stacking module, which consists of several of the above-mentioned direct ammonia fuel cell chips, which are positioned by mechanical interfaces and tightly stacked by cooperating connectors, and are connected in parallel to electrical and fluid inlet and outlet components through electrical interfaces and fluid interfaces.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The anode current collector and cathode current collector in this invention are composite ceramic substrates, comprising a Ti3AlC2MAX phase ceramic core layer, a nanodiamond gradient composite layer grown in situ on the surface of the core layer, and a passivation layer grown in situ on the surface of the gradient composite layer. The overall structure is an integrated, non-adhesive architecture, which greatly increases the overall structural strength and interfacial bonding force. The interfacial bonding force is ≥40MPa. After 1000 thermal cycles, there is no cracking or delamination. The corrosion current density under acidic conditions at 120℃ is <0.05μA / cm². 2 Compared to existing stainless steel materials, the corrosion current density is significantly reduced, and there is almost no risk of coating peeling, resulting in a rated service life of more than 10,000 hours, which is more than doubled.

[0030] 2. This invention incorporates a pulsed electric field control unit in both the anode and cathode current collectors. Using the anode and cathode current collectors as electrode plates, an electric field is applied, and the reaction is achieved in situ with the catalyst. This reduces the activation energy of the AOR reaction from 120 kJ / mol to below 38 kJ / mol, and the peak power density of the non-platinum catalyst is ≥850 mW / cm². 2 It improves upon commercial 20wt% Pt / C catalysts by more than 48%, and reduces costs by more than 97% compared to traditional precious metal catalysts such as Pt and Ir.

[0031] 3. The anode current collector and cathode current collector of the present invention are provided with parallel main reaction channels and ammonia capture channels. During the reaction process, the remaining ammonia gas is directly separated by selective permeation membrane and returned for reuse, eliminating the contact between ammonia and cathode catalyst, thereby avoiding cathode poisoning problems and increasing cathode life by more than 3 times. At the same time, the ammonia utilization rate is increased from 85% in the prior art to more than 98.5%, which greatly reduces operating costs.

[0032] 4. This invention replaces the traditional direct ammonia fuel cell with a standardized chip design, and with standardized electrical, fluid and mechanical interfaces, it can achieve automated modular stacking with a power expansion linearity of >99%, which solves the bottleneck of large-scale stacking of traditional technology and can significantly reduce mass production costs. Attached Figure Description

[0033] Figure 1 This is a cross-sectional schematic diagram of an embodiment of the present invention.

[0034] Figure 2 This is a diagram illustrating ammonia separation and circulation in an embodiment of the present invention.

[0035] In the above figures: 1. Anode current collector substrate; 2. Anode catalyst layer; 3. Proton exchange membrane; 4. Cathode catalyst layer; 5. Cathode current collector substrate; 6. Flow field. Detailed Implementation

[0036] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] The present invention provides a standard direct ammonia fuel cell chip. It includes, in a vertically stacked manner, an anode current collector substrate, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, and a cathode current collector substrate.

[0038] Specifically, the anode current collector 1 and the cathode current collector 5 are composite ceramic substrates, including a Ti3AlC2MAX phase ceramic core layer, a nanodiamond gradient composite layer grown in situ on the surface of the core layer, and a passivation layer grown in situ on the surface of the gradient composite layer. The anode current collector and the cathode current collector are integrally formed with a flow field on opposite sides, and the inner wall of the flow field is respectively attached with an anode catalyst layer and a cathode catalyst layer.

[0039] The Ti3AlC2MAX phase ceramic core layer has an electrical conductivity ≥5×10⁻⁶ at 25℃. 6 With a current-to-weight ratio (S / m) comparable to metallic copper, efficient current collection can be achieved without an additional conductive layer; thermal conductivity ≥170W / (m·K) ensures uniform temperature distribution on the chip, preventing localized overheating; coefficient of thermal expansion 9.0×10⁻⁶. -6 The coefficient of thermal expansion (CTE) matches that of the perfluorosulfonic acid proton exchange membrane by ≥95%, and the CTEs of the positive and negative electrode substrates are 100% consistent, completely eliminating thermal stress during the -40℃ to 150℃ thermal cycling process. The nanodiamond gradient composite layer and the Ti3AlC2MAX phase ceramic core layer are metallurgically bonded with a bonding strength ≥40MPa, eliminating the risk of detachment. After 1000 thermal cycles, the interfacial bonding strength retention rate is ≥98%. The passivation layer combines high conductivity and corrosion resistance, exhibiting a corrosion current density of <0.05μA / cm under acidic fluorine-containing conditions at pH 2-3, 80℃, and 1.0V vs. RHE in the negative electrode of a fuel cell. 2 Surface contact resistance <1mΩ·cm 2 .

[0040] The main reaction channel and the ammonia trapping channel are integrally formed and arranged in parallel on the anode current collector substrate 1, and are separated by a 500nm thick hydrophobic modified S-1 all-silicon molecular sieve membrane. The main reaction channel is a three-level self-similar fractal microchannel, with a first-level main channel width of 2mm, a second-level sub-channel width of 0.8mm, and a third-level micro-nano channel width of 50μm. An AOR catalyst layer is grown in situ on the inner wall of the channel. The side ammonia trapping channel is a continuous serpentine microchannel with an internal microneedle-shaped cold trap reinforcement structure and a channel width of 0.5mm.

[0041] Unreacted ammonia molecules in the main reaction channel can selectively permeate into the trapping channel through the 0.55nm pores of the S-1 membrane. After hydrophobic modification, the S-1 membrane has a permeability selectivity of ≥99% for ammonia and completely blocks nitrogen and water vapor. The trapping channel achieves a low-temperature cold trap effect of -20℃ to 50℃ through low-temperature liquid ammonia, which instantly liquefies and enriches the permeated ammonia. The ammonia is then recycled back into the main reaction channel through a microfluidic loop, increasing the ammonia utilization rate from 85% in the existing technology to over 98.5%.

[0042] The cathode oxidation gas flow channel and the trace ammonia recovery channel, which are integrally formed and arranged on the cathode current collector 5, are also separated by the S-1 membrane. A very small amount of ammonia that has permeated through the proton exchange membrane is selectively captured and sent to the anode circulation system, completely eliminating the contact between ammonia and the cathode ORR catalyst.

[0043] The anode catalyst layer 2 includes an ammonia oxidation catalyst, and the cathode catalyst layer 4 includes an oxygen reduction catalyst. The inner walls of the flow field of the anode current collector 1 and the cathode current collector 5 are in-situ grown with nitrogen-deficient graphene support layers via PECVD. C-Ti chemical bonds are formed between the graphene support layer and the substrate, with a bonding force ≥35MPa and no risk of detachment. The graphene nitrogen-deficient sites are in-situ anchored to Fe / Ni / Mo dual single-atom non-platinum catalysts, with metal atoms forming MNC chemical bonds with the nitrogen-deficient sites. The single-atom particle size is <0.5nm, and there is no aggregation. At 200℃, the catalyst's AOR half-wave potential reaches 0.58V (vs RHE), a positive shift of 32mV compared to a commercial 20wt% Pt / C catalyst, demonstrating intrinsic activity significantly superior to noble metal catalysts such as Pt and Ir.

[0044] A pulsed electric field control unit is integrated on the anode current collector 1 and the cathode current collector 5. This control unit uses the anode and cathode current collectors as electrodes to form an adjustable high-frequency pulsed electric field at both ends of the anode and cathode catalyst layers. Specifically, the pulse voltage is 4V and the pulse frequency is 10kHz. By directionally polarizing the NH bonds of the NH3 molecule with the electric field, the bond dissociation energy is reduced from 435kJ / mol to below 180kJ / mol, and the activation energy of the AOR reaction is reduced from 120kJ / mol to below 38kJ / mol, increasing the reaction rate by more than 6 times. Using a high-frequency narrow-pulse electric field instead of a constant-voltage electric field completely avoids water electrolysis side reactions and electrochemical degradation of the proton exchange membrane, ensuring long-term operational stability.

[0045] The anode current collector 1 and / or cathode current collector 5 are provided with fluid interfaces, electrical interfaces, and mechanical interfaces on their sides, and an encapsulation frame is integrally formed along their outer edge; thus, the anode current collector, proton exchange membrane, and cathode current collector are stacked sequentially to form an integral closed structure, thereby constituting a single chip; a sensor module is integrated inside the anode current collector and / or cathode current collector. Preferably, the pulse electric field control unit includes an STM32 main control chip, a DC-DC adjustable pulse power supply module, a hardware-based PID operational amplifier, and a signal acquisition module. The operational amplifier uses an OPA2277 chip with a response delay of <1μs. The sensor module is a MEMS-based sensor array that can output power, ammonia concentration, and temperature data in real time. Combined with the pulse electric field control unit, it dynamically adjusts the electric field parameters to achieve adaptive enhancement of the AOR reaction without the need for an external controller.

[0046] The fabrication method of the direct ammonia fuel cell chip in this embodiment is as follows:

[0047] (1) Using 99.2% pure Ti3AlC2 powder, 3wt% yttrium oxide sintering aid was added. Anhydrous ethanol was used as solvent and PVB as binder. The mixture was ball-milled for 24 hours to prepare a uniform slurry with a ball-to-powder ratio of 5:1 and a ball milling speed of 300 rpm. After spray granulation, a 0.6 mm thick green body was prepared by dry pressing. The forming pressure was 200 MPa and the holding time was 30 s. The anode and cathode flow channel contours, main-side channel isolation grooves, encapsulation frame, and interface positioning structure were pre-etched on the surface of the green body using ultraviolet laser with a positioning accuracy of ±10 μm. The green body was placed in a graphite crucible and protected with a high-purity argon atmosphere. The temperature was raised to 1350℃ at a heating rate of 3℃ / min and sintered at a constant temperature for 4 hours. Then, it was cooled to room temperature with the furnace at a rate of 2℃ / min to obtain a MAX phase ceramic with a thickness of 0.5 mm and a density of ≥99.2%. The substrate was machined using a five-axis femtosecond laser (1030nm laser wavelength, 300fs pulse width, 100kHz repetition frequency) to integrally machine the main reaction channel, side ammonia capture channel, cathode reaction channel, fluid interface, and positioning pin hole on the substrate with a machining accuracy of ±5μm. After machining, the substrate was ultrasonically cleaned with anhydrous ethanol for 10 min and dried with high-purity nitrogen. An 8μm thick nanodiamond gradient composite layer was grown in situ on all surfaces of the substrate using MPCVD technology. The microwave power was 3kW, the deposition temperature was 800℃, the working pressure was 150Torr, and the deposition was carried out in four gradient stages with a total deposition time of 1.5h. The substrate surface was treated with oxygen plasma for 10 min at a power of 200W and an oxygen flow rate of 50sccm to generate a CO-Ti passivated self-corrosion-resistant conductive interface in situ, thus completing the preparation of the substrate core.

[0048] (2) Nitrogen-defect graphene layers were grown in situ on the inner walls of the anode current collector and the cathode current collector using PECVD process. The methane flow rate was 30 sccm, the nitrogen flow rate was 10 sccm, the hydrogen flow rate was 50 sccm, the microwave power was 2 kW, the deposition temperature was 700 ℃, the deposition time was 30 min, and the vacuum degree was 50 Pa. An equal-volume impregnation method was used to immerse the graphene-loaded anode current collector substrate in an ethanol-water solution of ferric nitrate, nickel nitrate, and ammonium molybdate (ethanol:water volume ratio 1:1), with a total metal concentration of 0.05 mol / L and a molar ratio of ferric nitrate, nickel nitrate, and ammonium molybdate of 2:2:1. The substrate was impregnated under vacuum at 25°C for 12 h. After impregnation, the substrate was rinsed three times with anhydrous ethanol and dried under vacuum at 60°C for 12 h. Subsequently, the substrate was calcined in a high-purity argon atmosphere at a heating rate of 5°C / min to 550°C for 2 h, followed by natural cooling to room temperature to obtain an in-situ anchored non-platinum AOR catalyst with a metal loading of 2 wt% and a single-atom particle size <0.5 nm. The same process was used to in-situ anchor a Mn / Co single-atom ORR catalyst on the graphene layer of the cathode current collector substrate, with a metal loading of 1.5 wt%.

[0049] (3) An S-1 membrane was prepared on a porous alumina support (pore size 200 nm, thickness 100 μm) using a secondary growth method. Specifically, the support was immersed in a precursor sol with a molar ratio of 1 TEOS: 0.25 TPABr: 0.05 Al2O3: 150 H2O, and hydrothermally crystallized at 175 °C for 24 h. After removal, it was rinsed with deionized water until neutral, dried at 120 °C for 12 h, and calcined at 550 °C for 6 h to remove the template agent, resulting in an S-1 membrane with a thickness of 500 nm. The membrane was modified with trimethylchlorosilane (TMCS) vapor-phase hydrophobic modification at a modification temperature of 120 °C for 6 h. The water contact angle of the modified membrane was ≥120°. The membrane was laser-cut to the designed size, embedded in the anode main-side channel isolation groove, and sealed and fixed with high-temperature resistant ceramic slurry, with no risk of leakage.

[0050] (4) A high-temperature proton exchange membrane with phosphoric acid doped polyimide is used, with a thickness of 25 μm, a phosphoric acid doping amount of 85 wt%, a proton conductivity of ≥0.12 S / cm at 200℃, and a thermal expansion coefficient matching degree of ≥95% with the MAX phase matrix.

[0051] (5) The anode current collector substrate, high-temperature proton exchange membrane, and cathode current collector substrate are stacked in sequence. The four corner positioning pin holes are aligned with an alignment accuracy of ±20μm. The PEEK insulating packaging frame is inserted and hot-pressed at 160℃ and 2MPa for 8 minutes to achieve integrated packaging. The on-chip pulse electric field control unit is integrated on the edge of the substrate using LTCC process. The MEMS passive sensor array (temperature, pressure, voltage, current, and ammonia concentration sensor) is integrally processed on the substrate using magnetron sputtering and photolithography processes. The three-in-one standardized fluid / electric interface is assembled and the edge is sealed with PTFE sealant to complete the chip fabrication. The chip size is 30mm×30mm×4.5mm.

[0052] Performance test results: Peak power density of 862 mW / cm² under the conditions of 200℃, normal pressure, 5V / cm, and 10kHz pulsed electric field enhancement. 2 Rated power density 520mW / cm³ 2 The AOR half-wave potential is 0.58V (vs RHE), a positive shift of 32mV compared to a commercial 20wt% Pt / C catalyst; ammonia utilization rate is 98.6%, power generation efficiency is 55.8%; performance degradation is 2.1% after 1000h continuous operation, catalyst activity retention is 97.2%; performance degradation is 2.8% after 1000 thermal cycles; femtosecond laser processing yield is 96.2%; corrosion current density in ammonia atmosphere at 200℃ is 1.82μA / cm². 2 .

[0053] Based on the aforementioned chip products, the direct ammonia fuel cell chip stacking module in this embodiment consists of several of the aforementioned direct ammonia fuel cell chips tightly stacked together via mechanically mating connectors, and connected in parallel to electrical and fluid inlet / outlet components via electrical and fluid interfaces. The specific design is as follows:

[0054] The stack design employs 100 chips, stacked in series via a standardized stacking interface, and is equipped with an adaptive flow-sharing manifold, redundant flexible electrical busbars, a chip-level signal synchronous acquisition backplane, and an edge AI controller. The flow manifold adopts a symmetrical flow channel design, with a single-chip flow resistance deviation of <2%. The electrical busbars adopt a parallel redundant design, with a single-chip power supply deviation of <0.01V. The signal acquisition backplane is plugged into the chip electrical interface to achieve synchronous acquisition of single-chip parameters.

[0055] Battery stack assembly: 100 chips are sequentially positioned and stacked using locating pin holes. Fluid manifolds, electrical busbars, and signal acquisition backplanes are then assembled. The locking torque is 2 N·m, and the overall helium leak detection rate is <1×10⁻⁶. -6 Pa·m 3 / s, insulation class >1500V.

[0056] Performance test results: Under rated operating conditions at 200℃, the rated output power of the fuel cell stack is 3.52kW, with a deviation of only 0.57% from the theoretical value of the single chip. The power expansion linearity is >99%, and the performance deviation of the single chip is <2.5%. After 720 hours of continuous operation, the performance degradation of the fuel cell stack is <3%, which meets the requirements for industrial applications.

[0057] Example 2:

[0058] In this embodiment, the chip is ultra-thin, and most of the contents are the same as in Embodiment 1. The difference is that the thickness of the Ti3AlC2MAX phase ceramic core layer is 0.2mm; the pulse electric field intensity in the pulse electric field control unit is 1V / cm and the frequency is 1kHz; and the width of the three-level micro-nano channel of the main reaction channel of the anode current collector is 40μm.

[0059] Performance test results: Peak power density 845mW / cm³ under 200℃ and normal pressure conditions. 2 Rated power density 505mW / cm³ 2 With an ammonia utilization rate of 98.2% and a volumetric power density 2.8 times higher than the basic specification, it is suitable for portable, high-density energy storage scenarios.

[0060] Example 3:

[0061] In this embodiment, the chip is an ultra-thick specification for low-temperature applications, and most of its contents are the same as those in Example 1. The differences are as follows: the proton exchange membrane is a quaternized polysulfone anion exchange membrane; the Ti3AlC2MAX phase ceramic core layer has a thickness of 0.8 mm; the pulse electric field strength in the pulse electric field control unit is 8 V / cm and the frequency is 20 kHz; and the width of the three-stage micro-nano channel of the main reaction channel of the anode current collector is 60 μm.

[0062] Performance test results: Peak power density 285mW / cm³ under 80℃ and normal pressure conditions. 2 Rated power density 150mW / cm³ 2 Ammonia utilization rate is 97.8%, start-up time is <5s, and it is suitable for low-temperature scenarios.

[0063] Comparative Example 1:

[0064] This embodiment adopts the technical solution of Chinese invention patent with publication number CN115224295A.

[0065] Comparative Example 2:

[0066] The rest of this comparative example is the same as that in Example 1, except that it does not have a pulse electric field control unit and uses a conventional constant voltage electric field.

[0067] Comparative Example 3:

[0068] The rest of this comparative example is the same as that in Example 1, except that: the anode current collector has only the main reaction channel and no ammonia capture channel; the cathode current collector has only the cathode oxidation gas channel and no trace ammonia recovery channel.

[0069] Comparative Example 4:

[0070] The rest of this comparative example is the same as that in Example 1, except that: a conventional fuel cell reaction module is used, Ti3AlC2MAX phase ceramic is used as the bipolar plate, and it does not have a nanodiamond gradient composite layer and passivation layer, nor is it a microchip structure.

[0071] The parameters of the products from Example 1 and Comparative Examples 1-4 were compared, and the results are shown in Table 1:

[0072]

[0073] Table 1

[0074] The following conclusions can be drawn from Table 1:

[0075] The Ti3AlC2MAX phase composite ceramic material matrix of the present invention has excellent corrosion resistance; by setting a pulsed electric field, the power density is greatly increased; compared with traditional precious metal catalysts, the present invention significantly reduces the catalyst cost; the present invention uses parallel main reaction channels and ammonia-free collection channels as anode flow fields, and parallel cathode oxidation flow channels and trace ammonia recovery channels as cathode flow fields, so as to separate and recover most of the ammonia gas, thereby improving the ammonia utilization rate.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A direct ammonia fuel cell chip, comprising a vertically stacked anode current collector substrate, an anode catalyst layer, a proton exchange membrane, a cathode catalyst layer, and a cathode current collector substrate, characterized in that: The anode current collector and cathode current collector are composite ceramic substrates, including a Ti3AlC2MAX phase ceramic core layer, a nanodiamond gradient composite layer grown in situ on the surface of the core layer, and a passivation layer grown in situ on the surface of the gradient composite layer. The anode current collector and cathode current collector are integrally formed with a flow field on opposite sides, and the inner wall of the flow field is respectively attached with an anode catalyst layer and a cathode catalyst layer. The anode catalyst layer includes an ammonia oxidation catalyst, and the cathode catalyst layer includes an oxygen reduction catalyst; A pulsed electric field control unit is integrated on the anode current collector and the cathode current collector. The pulsed electric field control unit uses the anode current collector and the cathode current collector as electrodes to form an adjustable high-frequency pulsed electric field at both ends of the anode catalyst layer and the cathode catalyst layer. The anode current collector and / or cathode current collector are provided with fluid interfaces, electrical interfaces, and mechanical interfaces on their sides, and an encapsulation frame is integrally formed on the outer edge; so that the anode current collector, proton exchange membrane and cathode current collector are stacked in sequence to form an overall closed structure, thereby constituting a chip; a sensor module is integrated inside the anode current collector and / or cathode current collector.

2. The direct ammonia fuel cell chip as described in claim 1, characterized in that: The thickness of the Ti3AlC2MAX phase ceramic core layer is 0.2-0.8 mm; in the nanodiamond gradient composite layer, the diamond content increases in four steps from near the core layer to the outside, from 0%, 30%, 70% and 100%.

3. The direct ammonia fuel cell chip as described in claim 1, characterized in that: The flow field on the anode current collector includes a main reaction channel and an ammonia capture channel. The main reaction channel and the ammonia capture channel are arranged adjacent to each other and separated by a hydrophobic all-silica molecular sieve membrane, wherein the hydrophobic all-silica molecular sieve membrane is an ammonia selective permeation membrane.

4. The direct ammonia fuel cell chip as described in claim 3, characterized in that: The main reaction channel is a three-level self-similar fractal microchannel, including a primary main channel, a secondary sub-channel, and a tertiary micro-nano channel. The primary main channel has a width of 2 mm, the secondary sub-channel has a width of 0.8 mm, and the tertiary micro-nano channel has a width of 40-60 μm. An anode catalyst layer is grown in situ on the inner wall of the primary main channel, the secondary sub-channel, and the tertiary micro-nano channel.

5. The direct ammonia fuel cell chip as described in claim 1, characterized in that: The anode current collector and cathode current collector have in-situ grown nitrogen-deficient graphene support layers inside their flow fields, and the anode catalyst layer and cathode catalyst layer are anchored on the graphene support layer; the ammonia oxidation catalyst is a Fe / Ni / Mo dual single-atom catalyst, and the oxygen reduction catalyst is a Mn / Co single-atom oxygen reduction catalyst.

6. The direct ammonia fuel cell chip as described in claim 1, characterized in that: The electric field strength applied by the pulse electric field control unit is 0-8V / cm and the frequency is 1-20kHz.

7. The direct ammonia fuel cell chip as described in claim 1, characterized in that: The fluid interface includes an ammonia fuel inlet, an oxidant inlet, a tail gas outlet, and a circulating ammonia return inlet; the electrical interface includes an elastic conductive post; and the mechanical interface includes a positioning pin hole.

8. A method for preparing a direct ammonia fuel cell chip as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. The Ti3AlC2 raw material powder was dry-pressed into a green body, and the Ti3AlC2MAX phase ceramic matrix was prepared by high-temperature sintering in an argon atmosphere. The flow field, encapsulation frame, interface structure and mechanical positioning structure were integrally formed by laser milling. Then, the nanodiamond gradient composite layer was grown in situ by MPCVD process, and a passivation layer was generated on the surface of the gradient composite layer by oxygen plasma treatment. Finally, the in-situ hydrophilic and hydrophobic partitions were generated in the flow field by laser induction. Finally, the anode current collector matrix and the cathode current collector matrix were prepared respectively. S2. Nitrogen-deficient graphene support layers are grown in situ on the inner walls of the flow channels of the anode current collector and the cathode current collector using PECVD process. Then, an equal-volume impregnation process is used to calcine the graphene support layers under an argon atmosphere, thereby anchoring the ammonia oxidation catalyst and the oxygen reduction catalyst on the graphene support layers respectively, forming the anode catalyst layer and the cathode catalyst layer. S3. After positioning and aligning the anode current collector, proton exchange membrane, and cathode current collector through a mechanical interface, they are stacked and then hot-pressed to achieve integrated packaging. S4. The pulse electric field control unit is integrated at the edge of the anode current collector or cathode current collector using LTCC process. Then, the sensor module is fabricated using magnetron sputtering / photolithography process. The electrical interface, fluid interface and mechanical interface are assembled in accordance with the interface structure position to complete the chip fabrication.

9. The direct ammonia fuel cell chip, its fabrication method, and its stacking module as described in claim 1, characterized in that: In step S2, after the catalyst is processed, an all-silicon molecular sieve membrane is prepared on a porous alumina support by a secondary growth method. After being modified by trimethylchlorosilane vapor phase hydrophobicity, it is laser-cut to the design size, installed in the flow field, and the main reaction channel and ammonia collection channel are separated. It is then sealed and fixed with high-temperature resistant ceramic slurry.

10. A direct ammonia fuel cell chip stacking module, characterized in that: The direct ammonia fuel cell chip as described in any one of claims 1-7 is positioned by a mechanical interface and tightly stacked with a connecting component, and is connected in parallel to electrical and fluid inlet and outlet components through an electrical interface and a fluid interface.

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