Composite catalyst, preparation method and application thereof, and anion exchange membrane fuel cell

Abstract

The invention relates to the technical field of fuel cell anode catalysts, in particular to a composite catalyst, a preparation method and application thereof and an anion exchange membrane fuel cell. The invention provides a composite catalyst. The composite catalyst comprises a carrier and Pt loaded in the carrier in situ, the carrier comprises a carbon nanotube and molybdenum oxide in a non-stoichiometric state; the mass percentage of Pt in the composite catalyst is 1-5%. The composite catalyst can reduce the loading amount of Pt, and has excellent catalytic activity and CO poisoning resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell anode catalyst, in particular to a composite catalyst, a preparation method and application thereof, and an anion exchange membrane fuel cell. BACKGROUND

[0002] Hydrogen energy, as a secondary energy, is considered as the most potential clean energy due to its zero carbon emission, high efficiency, and wide source. Hydrogen-oxygen fuel cell generates electricity through hydrogen-oxygen reaction and only emits water, completely getting rid of pollution problems. Hydrogen energy can be produced by electrolysis of water through renewable energy (such as wind power and photovoltaic power), realizing "green hydrogen" production and promoting low-carbon energy structure. Therefore, hydrogen-oxygen fuel cell has been considered as one of the important solutions for effectively utilizing hydrogen energy and solving future energy crisis.

[0003] Hydrogen-oxygen fuel cell is composed of hydrogen oxidation reaction (HOR) at the anode and oxygen reduction reaction (ORR) at the cathode. At present, hydrogen-oxygen fuel cell is divided into proton exchange membrane fuel cell (PEMFC) and anion exchange membrane fuel cell (AEMFC). Since AEMFC uses non-noble metal catalyst (such as iron and nickel-based catalyst) to replace platinum (Pt) in the cathode oxygen reduction reaction (ORR) in the alkaline environment, it can also exhibit similar Pt performance, while PEMFC needs to rely on noble metal (such as Pt). Therefore, current research mainly focuses on anion exchange membrane fuel cell (AEMFC). Alkaline exchange membrane fuel cell (AEMFC) has been recognized as one of the most potential energy supply methods due to its green characteristics and high energy efficiency. However, anion exchange membrane fuel cell still has the challenge of slow anode hydrogen oxidation reaction (HOR) kinetics, and even the commercial 20wt%Pt / C catalyst has 2-4 orders of magnitude lower HOR kinetics in alkaline conditions than in acidic conditions, which makes it reach the performance in acidic environment and needs to increase the loading of noble metal, thereby increasing the cost. At the same time, the crude hydrogen produced by industrial production contains low concentration of CO. Since there is a strong adsorption between CO and platinum group metal (PGM), the active sites of the anode catalyst are extremely easy to be poisoned, resulting in catalyst deactivation. So far, although many existing technologies have reported various non-Pt-based (such as Ni-based and Fe-based) catalysts for HOR in alkaline conditions, there is still a big gap between their HOR intrinsic activity and Pt-based. However, the high cost and limited reserves of platinum seriously limit its wide application, and therefore, a catalyst that can reduce the loading of Pt while improving its activity and CO poisoning resistance is needed. SUMMARY

[0004] Therefore, the present application aims to provide a composite catalyst, a preparation method and application thereof, and an anion exchange membrane fuel cell.

[0005] To achieve the above-mentioned application purposes, the present application provides the following technical solutions.

[0006] The present application provides a composite catalyst, comprising a carrier and Pt in-situ loaded in the carrier.

[0007] The carrier comprises carbon nanotubes and non-stoichiometric molybdenum oxide.

[0008] The mass percentage of Pt in the composite catalyst is 1-5%.

[0009] Preferably, the mass percentage of non-stoichiometric molybdenum oxide in the composite catalyst is 3-10%.

[0010] The mass percentage of non-stoichiometric molybdenum oxide in the composite catalyst is calculated based on the mass percentage of Mo element.

[0011] The present application also provides a preparation method of the composite catalyst as described above, comprising the following steps.

[0012] The soluble molybdenum source, carbon nanotubes and water are first mixed to obtain a mixed solution.

[0013] After the hydrothermal reaction of the mixed solution, the obtained solid substance is calcined to obtain a carrier precursor.

[0014] The carrier precursor, soluble platinum source and water are secondly mixed to load and obtain a catalyst precursor.

[0015] The catalyst precursor is heat-treated in a reducing atmosphere to obtain the composite catalyst.

[0016] Preferably, the soluble molybdenum source comprises one or more of sodium molybdate hexahydrate, ammonium molybdate tetrahydrate, molybdenum pentachloride and molybdenum hexacarbonyl.

[0017] The carbon nanotubes comprise one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, functionalized multi-walled carbon nanotubes and functionalized single-walled carbon nanotubes.

[0018] The mass ratio of the soluble molybdenum source and carbon nanotubes is (0.75-1.5):1.

[0019] Preferably, the pH value of the mixed solution is 1-3.

[0020] The hydrothermal reaction is carried out at a temperature of 80–150°C for a duration of 6–24 hours.

[0021] Preferably, the calcination is carried out in a protective atmosphere;

[0022] The calcination temperature is 200–500℃, and the holding time is 1–4 hours.

[0023] Preferably, the soluble platinum source includes one or more of chloroplatinic acid hexahydrate, potassium chloroplatinate, platinum acetylacetonate, platinum tetrachloride, and platinum nitrate;

[0024] The mass ratio of the carrier precursor to the soluble platinum source is (2-3):(0.2-3);

[0025] The load is carried out under stirring conditions, with the stirring temperature being 25–80°C, the stirring speed being 400–600 rpm, and the stirring time being 2–5 hours.

[0026] Preferably, the reducing atmosphere comprises hydrogen and argon, wherein the volume ratio of hydrogen to argon is (1-2):19;

[0027] The heat treatment temperature is 300–600°C, the heating rate to the heat treatment temperature is 5–10°C / min, and the heat treatment holding time is 1–4 hours.

[0028] The present invention also provides the application of the composite catalyst described in the above technical solution or the composite catalyst prepared by the preparation method described in the above technical solution in anion exchange membrane fuel cells.

[0029] The present invention also provides an anion exchange membrane fuel cell, wherein the anode catalyst in the anion exchange membrane fuel cell is the composite catalyst described in the above technical solution or the composite catalyst prepared by the preparation method described in the above technical solution.

[0030] This invention provides a composite catalyst comprising a support and Pt in situ supported within the support; the support comprises carbon nanotubes and non-stoichiometric molybdenum oxide; the mass percentage of Pt in the composite catalyst is 1-5%. Due to the non-stoichiometric state of molybdenum oxide (MoO₂), 3-x The presence of oxygen vacancies significantly enhances electrocatalytic performance, promoting water molecule adsorption and electron transfer, and lowering the energy barrier of the hydrogen oxidation reaction (HOR). By introducing non-stoichiometric molybdenum oxide to interact with Pt, the electronic structure and surface chemistry of the catalyst can be optimized, enhancing the hydroxyl binding energy (OHBE) of the HOR catalyst, weakening the hydrogen binding energy (HBE), and improving resistance to CO poisoning. Specifically:

[0031] First, MoO in the carrier 3-xThe Pt can form micro-nano structures, so that the d-band center of Pt is lowered, which leads to the decrease of the binding strength of the key reaction intermediate *H, because in the alkaline HOR reaction, the strength of the adsorbed H on the Pt is stronger than that in the acidic HOR reaction, which is not conducive to the reaction, so the decrease of the adsorbed state *H binding energy is beneficial to the adsorption-desorption balance, and the reaction is accelerated; secondly, in the alkaline HOR system, according to the bifunctional theory, in addition to the adsorbed state *H, the adsorbed state *OH is also a key reaction intermediate, but the pure Pt surface is too weak to adsorb the key intermediate, which is not conducive to the rate-determining step, so the introduction of MoO 3-x The introduction of MoO enhances the oxygen affinity of the catalyst surface, enhances the binding energy of the intermediate *OH on the catalyst surface, so that the catalyst in the catalytic hydrogen oxidation process is accelerated, and higher activity is achieved, and the enhancement of the binding energy of the adsorbed state *OH is also one of the main reasons for the enhancement of the CO poisoning resistance of the catalyst, the adsorbed state *OH accelerates the oxidation of the CO adsorbed on the Pt surface, and promotes the regeneration of the catalytic active site; finally, due to the lowering of the d-band center of Pt, the corresponding CO binding energy on the Pt surface is reduced, which is more conducive to the oxidation and separation of CO, and the release of the catalytic active site prevents the poisoning of the catalyst.

[0032] In summary, the composite catalyst described in the application can precisely control the adsorption strength of the key reaction intermediates *H, *OH and CO on the catalyst surface, so as to realize high HOR activity and excellent CO poisoning resistance. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The SEM graph of the composite catalyst described in Example 1;

[0034] Figure 2 The TEM graph and the HRTEM graph of the composite catalyst described in Example 1;

[0035] Figure 3 The XRD graph of the composite catalyst described in Example 1, the carrier precursor described in Example 1 and the composite catalyst described in Comparative Examples 2-3;

[0036] Figure 4 The LSV curve of the electrode prepared by the composite catalyst described in Example 1 and Comparative Examples 1-4 and 20wt% commercial Pt / C catalyst in H2-saturated 0.1M KOH electrolyte;

[0037] Figure 5 The LSV curve of the electrode prepared by the composite catalyst described in Example 1, 5-9 and Comparative Example 1 in H2-saturated 0.1M KOH electrolyte;

[0038] Figure 6LSV curves of electrodes prepared from the composite catalysts described in Examples 1, 10-12 measured in 0.1 M KOH electrolyte saturated with H2;

[0039] Figure 7 LSV curves of electrodes prepared from the composite catalysts described in Examples 1-4 and Comparative Example 1 measured in 0.1 M KOH electrolyte saturated with H2;

[0040] Figure 8 Relative current-time curves of electrodes prepared from the composite catalysts described in Examples 1 and Comparative Example 4 and 20 wt.% Pt / C recorded at overpotential 50 mV in 0.1 M KOH electrolyte saturated with H2;

[0041] Figure 9 Relative current-time curves of electrodes prepared from the composite catalysts described in Examples 1, Comparative Example 4 and 20 wt.% Pt / C recorded at overpotential 50 mV in 0.1 M KOH electrolyte saturated with H2 / 1000 ppm CO;

[0042] Figure 10 Voltage-current density curves and power density-current density curves of a hydrogen-oxygen fuel cell prepared from the composite catalyst described in Example 1 at 80°C. DETAILED DESCRIPTION

[0043] The present application provides a composite catalyst comprising a carrier and Pt in situ supported on the carrier;

[0044] The carrier comprises carbon nanotubes and molybdenum oxide in a non-stoichiometric state;

[0045] The mass percentage of Pt in the composite catalyst is 1-5%.

[0046] In the present application, the mass percentage of Pt in the composite catalyst is preferably 1-5%, more preferably 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%. In the examples of the present application, the mass percentage of Pt in the composite catalyst can be 1.7%

[0047] In the present application, the mass percentage of molybdenum oxide in a non-stoichiometric state in the composite catalyst is preferably 3-10%, more preferably 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%. In the examples of the present application, the mass percentage of molybdenum oxide in a non-stoichiometric state in the composite catalyst can be 5%. In the present application, the mass percentage of molybdenum oxide in a non-stoichiometric state in the composite catalyst is calculated based on the mass percentage of Mo element.

[0048] This invention also provides a method for preparing the composite catalyst described in the above technical solution, comprising the following steps:

[0049] A soluble molybdenum source, carbon nanotubes, and water are first mixed to obtain a mixture.

[0050] After the mixture is subjected to a hydrothermal reaction, the resulting solid material is calcined to obtain a carrier precursor.

[0051] The carrier precursor, soluble platinum source and water are mixed and loaded to obtain the catalyst precursor;

[0052] The catalyst precursor is heat-treated in a reducing atmosphere to obtain the composite catalyst.

[0053] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0054] In this invention, a soluble molybdenum source, carbon nanotubes, and water are first mixed to obtain a mixed solution.

[0055] In this invention, the first mixing is preferably performed by mixing carbon nanotubes and water, followed by the addition of a soluble molybdenum source. In this invention, the mixing of carbon nanotubes and water is preferably carried out under ultrasonic conditions, and the ultrasonication time is preferably 15–60 min, more preferably 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min. In an embodiment of this invention, the ultrasonication time can be 30 min. This invention does not impose any special limitation on the frequency of the ultrasonication, as long as it ensures that the carbon nanotubes are uniformly dispersed in the water within the aforementioned time. This invention does not impose any special limitation on the process of adding the soluble molybdenum source; any process well-known to those skilled in the art can be used. After adding the soluble molybdenum source, stirring is also preferred. This invention does not impose any special limitation on the stirring process; any process well-known to those skilled in the art can be used.

[0056] In this invention, the soluble molybdenum source preferably includes one or more of sodium molybdate hexahydrate, ammonium molybdate tetrahydrate, molybdenum pentachloride, and molybdenum hexacarbonyl, more preferably sodium molybdate hexahydrate.

[0057] In this invention, the carbon nanotube is preferably one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, functionalized multi-walled carbon nanotubes, and functionalized single-walled carbon nanotubes, and more preferably multi-walled carbon nanotubes.

[0058] In this invention, the water is preferably deionized water.

[0059] In the present application, the mass ratio of the soluble molybdenum source and the carbon nanotubes is preferably (0.75-1.5):1, more preferably 0.75:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1. In an embodiment of the present application, the mass ratio of the soluble molybdenum source and the carbon nanotubes can be 1.2:1.

[0060] In the present application, the amount of the soluble molybdenum source and water is preferably (100-150) mg:(30-60) mL, more preferably (110-130) mg:50 mL. In an embodiment of the present application, the amount of the soluble molybdenum source and water can be 120 mg:50 mL.

[0061] After the first mixing is completed, the present application further preferably comprises adjusting the pH value, which is preferably adjusted by using 3% hydrochloric acid by mass concentration. The 3% hydrochloric acid by mass concentration is preferably used to adjust the pH value in a dropwise manner.

[0062] In the present application, the pH value of the mixed solution is preferably 1-3.

[0063] After the mixed solution is obtained, the present application performs hydrothermal reaction on the mixed solution, and then calcines the obtained solid substance to obtain a carrier precursor.

[0064] In the present application, the temperature of the hydrothermal reaction is preferably 80-150°C, more preferably 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C; and the time is preferably 6-24 h, more preferably 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h or 24 h. In an embodiment of the present application, the temperature of the hydrothermal reaction can be 100°C, and the time can be 12 h. In the present application, the hydrothermal reaction is preferably performed in a polytetrafluoroethylene reaction kettle.

[0065] After the hydrothermal reaction is completed, the present application further preferably comprises sequentially performing cooling, washing, suction filtration and drying. The present application does not have any special limitation on the process of the cooling and suction filtration, which can be performed by using the process well known to those skilled in the art. In the present application, the washing is preferably performed by sequentially using deionized water and ethanol; and the number of times of washing is preferably 3-5. In the present application, the temperature of the drying is preferably 40-80°C, more preferably 60°C, and the time is preferably 1-3 h, more preferably 2 h. In an embodiment of the present application, the temperature of the drying can be 60°C, and the time can be 2 h.

[0066] In the present application, the calcination is preferably carried out in a protective atmosphere, which is preferably an argon atmosphere. In the present application, the temperature of the calcination is preferably 200-500℃, more preferably 200℃, 300℃, 400℃ or 500℃; the time is preferably 1-4h, more preferably 1h, 2h, 3h or 4h; and the temperature rising rate to the temperature of the calcination is preferably 5-10℃ / min, more preferably 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min. In the embodiments of the present application, the temperature of the calcination can be 400℃, the holding time can be 2h, and the temperature rising rate can be 10℃ / min.

[0067] After obtaining the carrier precursor, the present application second mixes the carrier precursor, a soluble platinum source and water to load and obtain a catalyst precursor;

[0068] In the present application, the second mixing is preferably mixing the carrier precursor and water and then adding the soluble platinum source. In the present application, the mixing of the carrier precursor and water is preferably carried out under ultrasonic condition, and the time of the ultrasonic is preferably 15-60min, more preferably 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min or 60min. In the embodiments of the present application, the time of the ultrasonic can be 30min; the present application does not have any special limitation on the frequency of the ultrasonic, and a frequency known to those skilled in the art can be used to ensure that the carrier precursor is uniformly dispersed in water within the above time range.

[0069] In the present application, the water is preferably deionized water.

[0070] In the present application, the soluble platinum source preferably includes one or more of chloroplatinic acid hexahydrate, potassium chloroplatinate, platinum acetylacetonate, platinum tetrachloride and platinum nitrate, and more preferably includes chloroplatinic acid hexahydrate.

[0071] In the present application, the mass ratio of the carrier precursor and the soluble platinum source is preferably (2-3):(0.2-3), more preferably (2-3):0.2, (2-3):0.5, (2-3):1, (2-3):1.5, (2-3):2 or (2-3):3.

[0072] In the present application, the dosage ratio of the carrier precursor and water is preferably 25-35mg:40-60mL, more preferably 35mg:40-60mL. In the embodiments of the present application, the dosage ratio of the carrier precursor and water can be 35mg:50mL.

[0073] In the present application, the loading is preferably carried out under stirring, the temperature of the stirring is preferably 25-80℃, more preferably 25℃, 40℃, 60℃ or 80℃; the rotating speed is preferably 400-600rpm, more preferably 500rpm; the time is preferably 2-5h, more preferably 3h. In the present application, the loading mode is preferably metal bath.

[0074] After the loading is completed, the present application further preferably comprises sequentially carrying out washing and suction filtration; the washing is preferably carried out by sequentially using deionized water and ethanol; the present application does not have any special limitation on the process of the suction filtration, which can be carried out by using the process well known to those skilled in the art.

[0075] After the catalyst precursor is obtained, the present application carries out heat treatment on the catalyst precursor in a reducing atmosphere to obtain the composite catalyst.

[0076] In the present application, the reducing atmosphere preferably comprises hydrogen and argon, and the volume ratio of the hydrogen and argon is preferably (1-2):19, more preferably 1:19. In the embodiment of the present application, the volume ratio of the hydrogen and argon is 1:19. In the present application, the temperature of the heat treatment is preferably 300-600℃, more preferably 300℃, 400℃, 500℃ or 600℃; the heating rate for heating to the temperature of the heat treatment is preferably 5-10℃ / min, more preferably 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min, most preferably 10℃ / min; and the holding time of the heat treatment is preferably 1-4h, more preferably 1h, 2h, 3h or 4h, most preferably 2h.

[0077] After the heat treatment is completed, the present application further preferably comprises grinding, and the present application does not have any special limitation on the process of the grinding, which can be carried out by using the process well known to those skilled in the art.

[0078] The present application further provides the application of the composite catalyst in the above technical solution or the composite catalyst prepared by the preparation method in the anion exchange membrane fuel cell.

[0079] The present application further provides an anion exchange membrane fuel cell, wherein the anode catalyst in the anion exchange membrane fuel cell is the composite catalyst in the above technical solution or the composite catalyst prepared by the preparation method in the above technical solution.

[0080] In the present application, the anion exchange membrane of the anion exchange membrane fuel cell is preferably PiperION membrane with a thickness of 20μm.

[0081] In the present application, the electrolyte of the anion exchange membrane fuel cell is preferably an alkaline electrolyte, and the alkaline electrolyte is preferably commercially available KOH with a mass concentration of 95%.

[0082] In the present application, the working temperature of the anion exchange membrane fuel cell is preferably 80-100℃.

[0083] In the present application, the cathode catalyst of the anion exchange membrane fuel cell is preferably a Pt / C catalyst, and the Pt / C catalyst is preferably a conventional commercially available product.

[0084] In the present application, the preparation method of the anion exchange membrane fuel cell preferably comprises the following steps:

[0085] According to a ratio of 250μL:1mL:4mL:5mg, a Piper ION dispersion liquid with a mass concentration of 5wt%, deionized water, isopropyl alcohol and a cathode catalyst are mixed, and ultrasonic treatment is performed under ice bath conditions for 1h to obtain a cathode catalyst slurry;

[0086] According to a ratio of 250μL:1mL:4mL:5mg, a Piper ION dispersion liquid with a mass concentration of 5wt%, deionized water, isopropyl alcohol and an anode catalyst are mixed, and ultrasonic treatment is performed under ice bath conditions for 1h to obtain an anode catalyst slurry;

[0087] Under the condition of heating (≥100℃), the anode and cathode catalyst inks are respectively sprayed onto two sides of a Piper ION membrane with a thickness of 20μm, with an area of 5 square centimeters, to obtain a platinum loading of 0.1mg / cm 2 on the anode and a platinum loading of 0.4mg / cm 2 on the cathode;

[0088] After the anion exchange membrane Piper ION membrane (20μm) electrode coated with anode catalyst slurry and cathode catalyst slurry on the two sides is treated in a KOH solution with a concentration of 1mol / L for 1h (the solution is replaced every twenty minutes), an anode gas diffusion layer and a cathode membrane gas diffusion layer are respectively arranged on the two sides thereof and assembled, and cold pressing is performed to obtain a cold-pressed membrane electrode.

[0089] The cold-pressed membrane electrode and a fuel cell clamp constitute the anion exchange membrane fuel cell.

[0090] In the present application, the role of heating is to evaporate water in the anode catalyst slurry and the cathode catalyst slurry in time.

[0091] In the present application, the area of the Piper ION membrane is preferably slightly larger than the area of the gas diffusion layer.

[0092] In the present application, the cold pressing is preferably cold pressing by using a membrane electrode conversion hot press.

[0093] In the present application, the fuel cell clamp preferably comprises a flow channel, a current collector, an end plate and a sealing and insulating assembly.

[0094] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0095] Embodiment 1

[0096] 0.1 g of multi-walled carbon nanotubes was added into 50 mL of deionized water, and ultrasonic treatment was performed for 30 min to uniformly disperse the multi-walled carbon nanotubes, then 0.12 g of sodium molybdate hexahydrate (the mass ratio of the multi-walled carbon nanotubes to the sodium molybdate hexahydrate was 1:1.2) was added, and magnetic stirring was used to completely dissolve the sodium molybdate hexahydrate, then hydrochloric acid (3% by mass concentration) was added dropwise to adjust the pH value to 1-3, and a mixed solution was obtained;

[0097] The mixed solution was transferred into a polytetrafluoroethylene reaction kettle, and hydrothermal reaction was performed in an oven at 100 ℃ for 12 h, then the reaction kettle was cooled to room temperature, and deionized water and ethanol were used to wash the reaction kettle for 3 times in sequence, then suction filtration was performed, and the reaction kettle was dried in an oven at 60 ℃ for 2 h, and then calcination and dehydration were performed in a tube furnace in an argon atmosphere at 400 ℃ (the temperature rising rate was 10 ℃ / min) for 3 h, and a carrier precursor (MoO3 / CNT) was obtained.

[0098] 30 mg of the carrier precursor was added into 50 mL of deionized water, and ultrasonic treatment was performed for 30 min to uniformly disperse the carrier precursor, then 1.2 mL of a chloroplatinic acid hexahydrate solution with a concentration of 10 mg / mL (the mass ratio of the carrier precursor to the chloroplatinic acid hexahydrate was 2.3:1) was added, and metal bath was performed at 80 ℃ and 500 rpm for 3 h, then deionized water and ethanol were used to wash the reaction kettle in sequence, and suction filtration was performed to obtain a catalyst precursor (a black powder sample).

[0099] The catalyst precursor was transferred into a tube furnace, and reduction was performed by heat treatment at 500 ℃ for 2 h in a mixed gas atmosphere of hydrogen and argon with a volume ratio of 1:19, then the sample was collected and fully ground, and a composite catalyst (denoted as Pt-MoO3 / CNT or Pt-MoO3 / CNT-500 ℃) was obtained. 3-x 3-x The particle size of the composite catalyst was 1-3 nm, the mass percentage of Pt in the composite catalyst was 1.72%, and the mass percentage of Mo in the composite catalyst was 3.53% (measured by ICP-OES element content analysis). ​

[0100] Figure 1 The image shown is a SEM image of the composite catalyst described in Example 1. Figure 1 It can be seen that the particle size of the composite catalyst described in Example 1 is in the nanoscale range, and the Pt is uniformly grown on the surface of the support.

[0101] Figure 2 The images shown are TEM (a) and HRTEM (b) images of the composite catalyst described in Example 1. Figure 2 It can be seen that Pt in the composite catalyst is uniformly distributed on the surface of the support, with a particle size of approximately 1–3 nm. Furthermore, some particles exhibit Pt lattice fringes, which can be attributed to the Pt(111) crystal plane and MoO. 3-x It exists in an amorphous form around Pt clusters.

[0102] Example 2

[0103] Referring to Example 1, the difference is that the heat treatment temperature is 300°C, resulting in a composite catalyst (denoted as Pt-MoO). 3-x / CNT-300℃).

[0104] Example 3

[0105] Referring to Example 1, the difference is that the heat treatment temperature is 400°C, resulting in a composite catalyst (denoted as Pt-MoO). 3-x / CNT-400℃).

[0106] Example 4

[0107] Referring to Example 1, the difference is that the heat treatment temperature is 600°C, resulting in a composite catalyst (denoted as Pt-MoO). 3-x / CNT-600℃).

[0108] Comparative Example 1

[0109] Referring to Example 1, the difference is that no heat treatment is performed to obtain the composite catalyst (denoted as Pt-MoO3 / CNT).

[0110] Comparative Example 2

[0111] 30 g of multi-walled carbon nanotubes were added to 50 mL of deionized water, and ultrasonic dispersion was performed for 30 min to uniformly disperse the multi-walled carbon nanotubes. Then, 1.2 mL of a chloroplatinic acid hexahydrate solution having a concentration of 10 mg / mL (the mass ratio of the multi-walled carbon nanotubes to the chloroplatinic acid hexahydrate was 2.3:1) was added, and a metal bath was performed at 80°C and 500 rpm for 3 h. After the reaction was completed, the black powder sample was separated by sequentially using deionized water, ethanol, and suction filtration. Then, the sample was transferred to a tube furnace (the atmosphere of the tube furnace was a mixed gas atmosphere of hydrogen and argon at a volume ratio of 1:19), and reduction was performed at 500°C for 2 h. The sample was collected and sufficiently ground to obtain a carbon-supported Pt catalyst (denoted as Pt / CNT).

[0112] Example 5

[0113] The preparation method of the support precursor was the same as that of Example 1.

[0114] 30 mg of the support precursor was added to 50 mL of deionized water, and ultrasonic dispersion was performed for 30 min to uniformly disperse the support precursor. Then, 0.48 mL of a chloroplatinic acid hexahydrate solution having a concentration of 10 mg / mL (the mass ratio of the support precursor to the chloroplatinic acid hexahydrate was 2.3:0.4) was added, and a metal bath was performed at 80°C and 500 rpm for 3 h. The catalyst precursor (a black powder sample) was separated by sequentially using deionized water and ethanol and suction filtration.

[0115] The catalyst precursor was transferred to a tube furnace, reduction was performed at 500°C for 2 h in a mixed gas atmosphere of hydrogen and argon at a volume ratio of 1:19, the sample was collected and sufficiently ground, and a composite catalyst (denoted as Pt(0.01)-MoO 3-x / CNT) was obtained.

[0116] Example 6

[0117] The preparation method of the support precursor was the same as that of Example 1.

[0118] 30 mg of the support precursor was added to 50 mL of deionized water, and ultrasonic dispersion was performed for 30 min to uniformly disperse the support precursor. Then, 1.8 mL of a chloroplatinic acid hexahydrate solution having a concentration of 10 mg / mL (the mass ratio of the support precursor to the chloroplatinic acid hexahydrate was 2.3:1.5) was added, and a metal bath was performed at 80°C and 500 rpm for 3 h. The catalyst precursor (a black powder sample) was separated by sequentially using deionized water and ethanol and suction filtration.

[0119] The catalyst precursor was transferred to a tube furnace, reduction was performed at 500°C for 2 h in a mixed gas atmosphere of hydrogen and argon at a volume ratio of 1:19, the sample was collected and sufficiently ground, and a composite catalyst (denoted as Pt(0.01)-MoO 3-x / CNT).

[0120] Example 7

[0121] The preparation method of the carrier precursor is reference example 1;

[0122] 30 mg of the carrier precursor was added to 50 mL of deionized water, and after being uniformly dispersed by ultrasonic for 30 min, 2.4 mL of a chloroplatinic acid hexahydrate solution with a concentration of 10 mg / mL (the mass ratio of the carrier precursor to chloroplatinic acid hexahydrate was 2.3:2) was added, and the metal bath was carried out at 80°C and 500 rpm for 3 h, and then deionized water and ethanol were used for washing in sequence, and the catalyst precursor (a black powder sample) was separated by suction filtration.

[0123] The catalyst precursor was transferred to a tube furnace, and reduction was carried out by heat treatment at 500°C for 2 h in a mixed gas atmosphere of hydrogen and argon with a volume ratio of 1:19, and then the sample was collected and fully ground to obtain a composite catalyst (denoted as Pt(0.075)-MoO 3-x / CNT).

[0124] Example 8

[0125] The preparation method of the carrier precursor is reference example 1;

[0126] 30 mg of the carrier precursor was added to 50 mL of deionized water, and after being uniformly dispersed by ultrasonic for 30 min, 2.4 mL of a chloroplatinic acid hexahydrate solution with a concentration of 10 mg / mL (the mass ratio of the carrier precursor to chloroplatinic acid hexahydrate was 2.3:2) was added, and the metal bath was carried out at 80°C and 500 rpm for 3 h, and then deionized water and ethanol were used for washing in sequence, and the catalyst precursor (a black powder sample) was separated by suction filtration.

[0127] The catalyst precursor was transferred to a tube furnace, and reduction was carried out by heat treatment at 500°C for 2 h in a mixed gas atmosphere of hydrogen and argon with a volume ratio of 1:19, and then the sample was collected and fully ground to obtain a composite catalyst (denoted as Pt(0.075)-MoO 3-x / CNT).

[0128] Example 9

[0129] The preparation method of the carrier precursor is reference example 1;

[0130] The 30 mg of the carrier precursor was added into 50 mL of deionized water, and was dispersed uniformly by ultrasonic for 30 min, then 3.6 mL of chloroplatinic acid hexahydrate solution with a concentration of 10 mg / mL (the mass ratio of the carrier precursor and chloroplatinic acid hexahydrate was 2.3:3) was added, and the mixture was subjected to a metal bath at 80℃ and 500 rpm for 3 h, and was washed with deionized water and ethanol in sequence, and was separated by suction filtration to obtain a catalyst precursor (a sample in the form of black powder);

[0131] The catalyst precursor was transferred into a tube furnace, was reduced by heat treatment at 500℃ for 2 h in a mixed gas atmosphere of hydrogen and argon with a volume ratio of 1:19, the sample was collected and was fully ground to obtain a composite catalyst (denoted as Pt(0.15)-MoO 3-x / CNT).

[0132] Comparative Example 3

[0133] The preparation method of the carrier precursor was according to Reference Example 1.

[0134] The catalyst precursor was transferred into a tube furnace, was reduced by heat treatment at 500℃ for 2 h in a mixed gas atmosphere of hydrogen and argon with a volume ratio of 1:19, the sample was collected and was fully ground to obtain a composite catalyst (denoted as Pt(0.15)-MoO 3-x / CNT).

[0135] Figure 3 The XRD patterns of the composite catalyst of Example 1, the carrier precursor of Example 1, and the composite catalysts of Comparative Examples 2-3 were obtained by Figure 3 It can be known that, after the reduction by high-temperature heat treatment, most of the MoO3 is converted into MoO2; however, after the ion exchange with Pt (metal bath), the crystal form of MoO 3-x is destroyed, and the content of the catalyst Pt is too low, so that the phases of metallic Pt and the oxide of Mo cannot be observed in the XRD spectrum of the sample;

[0136] Example 10

[0137] Reference Example 1, except that the temperature of the metal bath was 25℃, to obtain a composite catalyst (denoted as 25℃-Pt-MoO 3-x / CNT).

[0138] Example 11

[0139] Reference Example 1, except that the temperature of the metal bath was 40℃, to obtain a composite catalyst (denoted as 40℃-Pt-MoO 3-x / CNT).

[0140] Example 12

[0141] Reference Example 1, except that the temperature of the metal bath was 60 °C, to obtain a composite catalyst (denoted as 60 °C-Pt-MoO 3-x / CNT).

[0142] Comparative Example 4

[0143] 1 g of CNTs was dispersed in 60 mL of a mixture of concentrated nitric acid (mass concentration of 68%) and concentrated sulfuric acid (mass concentration of 98%) (V:V = 1:3), and condensation reflux was carried out at 50 °C for 3.5 h to obtain oxidized CNTs;

[0144] 100 mg of the oxidized CNTs was dispersed in 15 mL of a mixture of anhydrous ethanol and 43 μL of tetrabutyl titanate (volume ratio of anhydrous ethanol to tetrabutyl titanate was 349:1), and then a mixture of deionized water, glacial acetic acid and anhydrous ethanol (volume ratio of deionized water to glacial acetic acid to anhydrous ethanol was 55.5:1:111) was added dropwise under magnetic stirring at room temperature to obtain a TiO2-CNTs sol;

[0145] The TiO2-CNTs sol was naturally volatilized and dried at room temperature to obtain an amorphous TiO2 modified carbon carrier (denoted as TiO2-CNTs);

[0146] 100 mg of the TiO2-CNTs was ultrasonically dispersed in 30 mL of a sodium molybdate solution with a concentration of 7.15 mg / mL, and then the pH value was adjusted to 1 using a 3% hydrochloric acid solution, and magnetic stirring was continued for 6 h, followed by washing, filtration, drying, and then 3 times of microwave treatment at 2450 MHZ 100 W for 10 s in a microwave oven to obtain MoO3 / TiO2-CNTs;

[0147] 50 mg of the MoO3 / TiO2-CNTs was ultrasonically dispersed in a mixture of 25 mL of ethylene glycol and 10 mL of deionized water, 0.65 mL of a chloroplatinic acid solution with a concentration of 10 mg / mL was added, the pH value was adjusted to 12 using sodium hydroxide, and condensation reflux was carried out at 130 °C for 3 h to obtain a composite catalyst (Pt-MoO3 / TiO2-CNTs).

[0148] The composite catalysts described in Examples 1-12 and Comparative Examples 1-4 were used to prepare a rotating disc electrode, and the preparation method was as follows: 3 mg of the composite catalysts described in Examples 1-12 and Comparative Examples 1-4 were dispersed in 300 μL of isopropanol, 15 μL of a 5% by mass Nafion solution was added, and the mixture was uniformly ultrasonicated for 30 min to obtain a catalyst dispersion liquid; 10 μL of the catalyst dispersion liquid was uniformly dropped on the surface of a glassy carbon electrode, and after the solution was completely dropped and dried, the electrode was tested. Before testing, the electrode was activated by CV. The test conditions were as follows: the linear sweep voltammetry curve (LSV) was tested in a 0.1 mol / L potassium hydroxide solution under hydrogen saturation at a rotation speed of 1600 rpm and a scan rate of 5 mV / s. A 20 wt% commercial Pt / C catalyst (20 wt.% Pt / C) was used as a control, and the HOR electrochemical test was performed in a conventional three-electrode system connected to a Chenhua 760e electrochemical workstation.

[0149] Figure 4 The LSV curves of the electrodes prepared from the composite catalysts described in Examples 1 and Comparative Examples 1-4 and the 20 wt% commercial Pt / C catalyst were measured in a 0.1M KOH electrolyte saturated with H2, and it can be seen from Figure 4 that the electrode prepared from the composite catalyst described in Example 1 exhibited faster kinetics and a larger limiting current in both the kinetic control region and the mass transfer diffusion region, and the Pt and MoO 3-x The synergistic effect of the components significantly improved the catalytic performance, which was better than that of a single metal component.

[0150] Figure 5 The LSV curves of the electrodes prepared from the composite catalysts described in Examples 1, 5-9 and Comparative Example 1 were measured in a 0.1M KOH electrolyte saturated with H2, and it can be seen from Figure 5 that the composite catalyst described in Example 1 exhibited the fastest kinetics, followed by the composite catalyst described in Comparative Example 1, and the limiting diffusion current of both could reach 3 mA·cm -2 -2. Considering the cost, the HOR performance of the composite catalyst described in Example 1 was also very excellent, and therefore, 0.025 mmol was selected as the final amount of the Pt precursor added.

[0151] Figure 6 The LSV curves of the electrodes prepared from the composite catalysts described in Examples 1, 10-12 were measured in a 0.1M KOH electrolyte saturated with H2, and it can be seen from Figure 6 that the sample prepared by ion exchange at 80°C exhibited the fastest kinetic current, and at an overpotential of 50 mV, the limiting diffusion current reached 3 mA·cm -2 -2, which was the largest among all the samples. Therefore, it was determined that 80°C was the optimal ion exchange reaction temperature.

[0152] Figure 7 The LSV curves of the electrodes prepared from the composite catalysts described in Comparative Example 1, Examples 1-4 were measured in 0.1 M KOH electrolyte saturated with H2, as shown in Table 1. Figure 7 It can be seen from Table 1 that the sample reduced at 500°C has the fastest current rise rate and the largest limiting diffusion current, which is probably because the reduction degree is not enough due to the too low temperature, and the active component is prone to agglomeration and sintering at too high temperature, thereby reducing the exposed active sites. Therefore, it is determined that 500°C is the optimal reduction temperature.

[0153] The composite catalysts described in Example 1, Comparative Example 1 and Comparative Example 4 and 20 wt.% Pt / C were subjected to electrochemical HOR stability tests and CO poisoning resistance tests:

[0154] HOR stability test: 1 mg of each of the composite catalysts described in Example 1, Comparative Example 4 and commercial 20 wt.% Pt / C and 20 wt.% Pt / C was dispersed in 500 μL of isopropanol, 20 μL of a 5% Nadion solution was added, and the mixture was uniformly ultrasonicated for 30 min to obtain a catalyst dispersion; the catalyst dispersion was drop-cast on carbon paper, and the drop-cast area was 1 cm 2 Before the formal test, the electrode was subjected to CV activation in a 0.1 M KOH electrolyte solution saturated with H2, and the current-time curve (I-T) of the catalyst at an overpotential of 50 mV was tested;

[0155] CO poisoning resistance test: the test steps were the same as the stability test steps, except that the gas introduced was H2 / 1000 ppm CO.

[0156] Figure 8 The relative current-time curves of the electrodes prepared from the composite catalysts described in Example 1 and Comparative Example 4 and 20 wt.% Pt / C were recorded at an overpotential of 50 mV in 0.1 M KOH electrolyte saturated with H2, as shown in Table 2. Figure 8 It can be seen from Table 2 that the electrode prepared from the composite catalyst described in Example 1 has a current density attenuation of only about 6% after 20 h of stability test, the electrode prepared from the composite catalyst described in Comparative Example 4 has a current density attenuation of about 65% after only 11 h of stability test, and the electrode prepared from 20 wt.% Pt / C has a current density attenuation of about 50%, and the composite catalyst described in Example 1 has more excellent stability.

[0157] Figure 9 The relative current-time curves of the electrodes prepared from the composite catalysts described in Example 1 and Comparative Example 4 and 20 wt.% Pt / C were recorded at an overpotential of 50 mV in 0.1 M KOH electrolyte saturated with H2 / 1000 ppm CO, as shown in Table 3.Figure 9 It can be seen that the electrode prepared by the composite catalyst described in Example 1 showed a current decay of approximately 10% after 10,000 s of CO poisoning resistance test, while the composite catalyst described in Comparative Example 4 completely lost its activity after 3,600 s of CO poisoning resistance test; and the electrode prepared by 20 wt.% Pt / C showed a current decay of approximately 60% after 3,600 s of CO poisoning resistance test. Therefore, the electrode prepared by the composite catalyst described in Example 1 has excellent CO poisoning resistance.

[0158] Anion exchange fuel cell performance testing: The composite catalyst described in Example 1 or 20 wt.% Pt / C and a 5 wt% PiperION dispersion were mixed with deionized water and isopropanol at a ratio of 5 mg: 250 μL: 1 mL: 4 mL, and ultrasonically treated in an ice bath for 1 hour to obtain a uniform catalyst ink; the catalyst ink was sprayed onto both sides of a 20 μm PiperION membrane with an area of ​​5 square centimeters to obtain 0.1 mg / cm² on the anode. 2 Platinum loading yielded 0.4 mg / cm² on the cathode. 2 The membrane electrode assembly was then loaded with platinum. The assembled membrane electrode was then treated in 1M KOH for 1 hour (refreshed every 20 minutes). The complete AEMFC consists of a catalyst-coated membrane, a gas diffusion layer (Sigracet 39BB), a gas seal, two graphite bipolar plates, two metal current collectors on each side (for the anode and cathode), and two end plates to protect the entire fuel cell. Single-cell fuel cell testing was conducted at the Fuel Cell Technologies test station. The AEMFC operated at 80°C. The relative humidity (RH) at the anode and cathode was 100%, the hydrogen and oxygen flow rates were 600 sccm and 1200 sccm, respectively, and the back pressure was 100 kPa.

[0159] Figure 10 The voltage-current density curves and power-current density curves of the hydrogen-oxygen fuel cell prepared with the composite catalyst described in Example 1 are shown at 80°C. Figure 10 It can be seen that the maximum power density of the hydrogen-oxygen fuel cell reaches 751 mW·cm⁻¹. -2 At this point, the corresponding voltage is 0.41V and the current density is 1796mA·cm. -2 .

[0160] In summary, the composite catalyst described in this invention significantly reduces the Pt loading, exhibits excellent electrochemical HOR performance and stability under alkaline conditions, and also demonstrates excellent CO resistance. As an anode HOR catalyst for Qingyang fuel cells, it can efficiently catalyze the hydrogen oxidation reaction.

[0161] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. It should be noted that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the scope of protection of the present application.

Claims

1. A composite catalyst, characterized in that, Includes a carrier and Pt loaded in situ in the carrier; The carrier includes carbon nanotubes and molybdenum oxide in a non-stoichiometric state; The composite catalyst contains 1-5% Pt by mass.

2. The composite catalyst as described in claim 1, characterized in that, The mass percentage of non-stoichiometric molybdenum oxide in the composite catalyst is 3-10%. The mass percentage of non-stoichiometric molybdenum oxide in the composite catalyst is expressed as the mass percentage of Mo element.

3. The method for preparing the composite catalyst according to claim 1 or 2, characterized in that, Includes the following steps: A soluble molybdenum source, carbon nanotubes, and water are first mixed to obtain a mixture. After the mixture is subjected to a hydrothermal reaction, the resulting solid material is calcined to obtain a carrier precursor. The carrier precursor, soluble platinum source and water are mixed and loaded to obtain the catalyst precursor; The catalyst precursor is heat-treated in a reducing atmosphere to obtain the composite catalyst.

4. The preparation method according to claim 3, characterized in that, The soluble molybdenum source includes one or more of sodium molybdate hexahydrate, ammonium molybdate tetrahydrate, molybdenum pentachloride, and molybdenum hexacarbonyl. The carbon nanotubes include one or more of multi-walled carbon nanotubes, single-walled carbon nanotubes, functionalized multi-walled carbon nanotubes, and functionalized single-walled carbon nanotubes. The mass ratio of the soluble molybdenum source to carbon nanotubes is (0.75–1.5):

1.

5. The preparation method according to claim 3 or 4, characterized in that, The pH value of the mixture is 1 to 3; The hydrothermal reaction is carried out at a temperature of 80–150°C for a duration of 6–24 hours.

6. The preparation method according to claim 5, characterized in that, The calcination is carried out in a protective atmosphere; The calcination temperature is 200–500℃, and the holding time is 1–4 hours.

7. The preparation method according to claim 3, characterized in that, The soluble platinum source includes one or more of chloroplatinic acid hexahydrate, potassium chloroplatinate, platinum acetylacetonate, platinum tetrachloride, and platinum nitrate. The mass ratio of the carrier precursor to the soluble platinum source is (2-3):(0.2-3); The load is carried out under stirring conditions, with the stirring temperature being 25–80°C, the stirring speed being 400–600 rpm, and the stirring time being 2–5 hours.

8. The preparation method according to claim 3, characterized in that, The reducing atmosphere includes hydrogen and argon, and the volume ratio of hydrogen to argon is (1-2):

19. The heat treatment temperature is 300–600°C, the heating rate to the heat treatment temperature is 5–10°C / min, and the heat treatment holding time is 1–4 hours.

9. The application of the composite catalyst according to claim 1 or 2 or the composite catalyst prepared by any one of claims 3 to 8 in anion exchange membrane fuel cells.

10. An anion exchange membrane fuel cell, characterized in that, The anode catalyst in the anion exchange membrane fuel cell is the composite catalyst described in claim 1 or 2, or the composite catalyst prepared by the preparation method described in any one of claims 3 to 8.

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