A catalyst for continuous hydrogen production from methanol and water by photothermal coupling catalysis, preparation method and application thereof

Abstract

The present invention provides a catalyst, preparation method and application for photothermal coupling catalysis of methanol and water to produce hydrogen. The catalyst is formed by a first co-catalyst and a second co-catalyst being co-loaded on a photocatalyst substrate; wherein the first co-catalyst is selected from Group VIII metals and oxides thereof, Group IB metals and oxides thereof or Group IIB metals and oxides thereof; and the second co-catalyst is selected from alkali metals or alkaline earth metals. The present invention loads a precursor containing the first co-catalyst and the second co-catalyst on the surface of a photocatalyst substrate by an equal volume impregnation method and then transfers it to a vacuum oven. By controlling the temperature, heating time, vacuum degree and water vapor concentration of the vacuum oven, the catalyst defects, the size and valence of the co-catalyst, and the interface structure are precisely regulated, which greatly improves the charge separation efficiency while reducing the energy barrier for the activation of the reactants. By using a flow reactor, efficient and high-stability photothermal coupling catalysis of methanol and water for continuous hydrogen production is achieved.

Description

Technical Field

[0001] The present invention relates to the field of energy catalysis technology, and in particular to a catalyst for continuous hydrogen production by photothermal coupling catalysis of methanol and water, a preparation method and application thereof. Background Art

[0002] Hydrogen is considered an ideal clean energy source due to its high efficiency, cleanliness and high energy density. However, the storage of H2 has safety risks and high costs. Methanol has a high hydrogen content (12.6wt%) and is easy to transport and store, so it is considered to be a high-quality liquid H2 storage medium. Among the various methods of producing hydrogen from methanol, methanol and water reforming is the most attractive, which can not only release the hydrogen stored in methanol, but also activate an equimolar amount of water to produce H2.

[0003] However, the reaction temperature of traditional methanol and water (both are gaseous molecules) reforming is 200-350°C, the reaction pressure is 2-6MPa, and the energy cost is high. Taking hydrogen production for hydrogen fuel cells as an example, the reaction temperature of traditional methanol and water reforming is much higher than the operating temperature of fuel cells (50-100°C), and CO byproducts are produced, resulting in poisoning of precious metal catalyst electrodes.

[0004] Therefore, it is necessary to develop a method that can efficiently catalyze the continuous production of hydrogen from methanol and water under milder conditions. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a catalyst and preparation method for continuous hydrogen production from methanol and water by photothermal coupling catalysis. The present invention utilizes the vacuum and water vapor atmosphere unique to the vacuum oven to precisely control the catalyst defects, the size and valence of the co-catalyst, and the interface structure. With the help of the designed continuous fixed-bed photothermal reactor, the catalyst can efficiently catalyze the continuous hydrogen production from methanol and water through the photothermal synergistic effect under relatively mild conditions, and the preparation method is simple, easy to operate, and can be mass-produced.

[0006] The specific content of the invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a catalyst for continuous hydrogen production from methanol and water by photothermal coupling catalysis, wherein the catalyst is formed by a first co-catalyst and a second co-catalyst being jointly supported on a photocatalyst substrate; the first co-catalyst is selected from Group VIII metals and oxides thereof, Group IB metals and oxides thereof, or Group IIB metals and oxides thereof; the second co-catalyst is selected from alkali metals or alkaline earth metals; the photocatalyst substrate is selected from original or defect-modified metal oxides or non-metallic semiconductor photocatalysts; the preparation method comprises the following steps:

[0008] Step 1, preparing a first co-catalyst precursor solution with a metal ion concentration of 0.5 to 2 mg / mL, preparing a second co-catalyst precursor solution with a metal ion concentration of 0.1 to 1 mg / mL, and mixing the two at an atomic ratio of 1:1 to 5:1 to obtain 0.5 to 10 mL of a mixed precursor solution;

[0009] Step 2: using the mixed precursor solution to perform an equal volume impregnation treatment on the photocatalytic substrate to obtain a first catalyst precursor;

[0010] Step 3, placing the first catalyst precursor in a vacuum oven, evacuating the vacuum oven to a vacuum, heating the vacuum oven to 100-300° C., maintaining for 1-5 hours, and then taking it out to obtain a second catalyst precursor;

[0011] Step 4: Grind the second catalyst precursor into powder, wash it by centrifugation with deionized water for 2 to 3 times, and dry it at 60 to 80° C. for 12 to 15 hours to obtain the catalyst.

[0012] Optionally, the first co-catalyst is selected from Pt, Pd, Cu, Fe, Au, Ag, Zn, Co, Ni or Ru; the first co-catalyst precursor solution is a chloride, sulfate, nitrate, carbonate, phosphate or acetate solution containing Pt, Pd, Cu, Fe, Au, Ag, Zn, Co, Ni or Ru;

[0013] The second co-catalyst is selected from Li, Na, K, Ca, Mg, Ba or Cs; the second co-catalyst precursor solution is a chloride, sulfate, nitrate, carbonate, phosphate or acetate solution containing Li, Na, K, Ca, Mg, Ba or Cs.

[0014] Optionally, the photocatalyst substrate is selected from pristine or defect-modified P25, TiO2, g-C3N4, ZnO, CeO2, Bi2WO6, Bi2MoO6, Fe2O3, In2O3 or WO3.

[0015] Optionally, in step 3, evacuating the vacuum oven to a vacuum comprises: stopping evacuating the vacuum oven after the vacuum degree reaches 95-10%;

[0016] The vacuum oven is heated to 100-300° C., and the first catalyst precursor releases water vapor during the heating process, so that the heating process is carried out in an environment containing water vapor.

[0017] Optionally, in step 4, the drying is carried out in a forced air oven.

[0018] In a second aspect, the present invention provides a catalyst for producing hydrogen from methanol and water by photothermal coupling catalysis obtained by the preparation method described in the first aspect, wherein the catalyst is formed by a first co-catalyst and a second co-catalyst being jointly loaded on a photocatalyst substrate; wherein the loading amount of the first co-catalyst is 0.2-1%, the loading amount of the second co-catalyst is 0.1-1%, and the rest is the photocatalyst substrate;

[0019] The first promoter is selected from Pt, Pd, Cu, Fe, Au, Ag, Zn, Co, Ni or Ru;

[0020] The second promoter is selected from Li, Na, K, Ca, Mg, Ba or Cs;

[0021] The photocatalyst substrate is selected from pristine or defect-modified P25, TiO2, g-C3N4, ZnO, CeO2, Bi2WO6, Bi2MoO6, Fe2O3, In2O3 or WO3.

[0022] Optionally, the first promoter is selected from Pt, Co or Ru;

[0023] The second promoter is selected from Li, Na, Ba or Cs;

[0024] The photocatalyst substrate is selected from pristine or defect-modified P25, g-C3N4 or In2O3.

[0025] In a third aspect, the present invention provides an application of a catalyst for producing hydrogen from methanol and water by photothermal coupling catalysis obtained by the preparation method described in the first aspect above, wherein the catalyst is used for producing hydrogen continuously from methanol and water by photothermal coupling catalysis, comprising:

[0026] The catalyst is loaded into a continuous fixed-bed photothermal reactor, and then the reactor is purged with an inert gas for 30 minutes, and the reactor is heated to 80-250° C. and the pressure is set at 0.1-3 MPa;

[0027] Methanol gas and water vapor in a molar ratio of 1:1 to 1:10 are introduced into a continuous fixed-bed photothermal reactor, and a light source is turned on. The catalyst catalyzes methanol and water to continuously produce hydrogen under photothermal conditions.

[0028] Optionally, before the catalyst is loaded into the continuous fixed-bed photothermal reactor, the catalyst is ultrasonically dispersed in a glass dish containing DI water, and then dried. After the catalyst film is formed, it is placed in the photothermal reactor together with the glass dish.

[0029] Optionally, the inert gas is N2 or Ar;

[0030] The light source is a natural light source or an artificial light source.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention provides a method for preparing a catalyst for photothermal coupling catalysis of methanol and water to produce hydrogen. The catalyst is formed by a first co-catalyst and a second co-catalyst being loaded on a photocatalyst substrate; wherein the first co-catalyst is selected from group VIII metals and their oxides, group IB metals and their oxides, or group IIB metals and their oxides; the second co-catalyst is selected from alkali metals or alkaline earth metals; and the photocatalyst substrate is selected from original or defect-modified P25, TiO2, g-C3N4, ZnO, CeO2, Bi2WO6, Bi2MoO6, Fe2O3, In2O3, or WO3. The present invention loads a precursor solution containing the first co-catalyst and the second co-catalyst on the surface of the photocatalyst substrate by an equal volume impregnation method and then transfers it to a vacuum oven, and after the vacuum oven is evacuated to a vacuum, it is heated at 100 to 300° C., so that the metal salt in the precursor solution is thermally decomposed and converted into corresponding metal nanoparticles and / or metal oxides (active phase and alkali metal) loaded on the photocatalyst substrate. The present invention precisely regulates catalyst defects, co-catalyst size and valence, and interface structure by controlling the temperature, heating time, vacuum degree, and water vapor concentration of the vacuum oven. The loaded active metal and alkali metal work together to improve the light absorption capacity, adsorption characteristics, and charge separation efficiency of the catalyst, and realize efficient and high-stability photothermal coupling catalysis of methanol and water to produce hydrogen. In addition, the catalyst raw materials are easily available, the metal loading is extremely low, the preparation steps are simple and easy, the conditions are mild, and it can be prepared in large quantities in a short time.

[0033] In addition, the catalyst provided by the present invention is used for photothermal coupling catalysis of methanol and water to produce hydrogen, with a hydrogen production rate of up to 624.1mmol / g / h. During the reaction, light energy causes the catalyst to generate high-energy electrons and holes, selectively activating adsorbed molecules, while thermal energy enhances the mass transfer of reactants and promotes product desorption. At the same time, thermal excitation can extend the life of photogenerated charges. Compared with simple photocatalysis and thermal catalysis, the catalytic production of hydrogen from methanol and water through the photothermal synergistic effect improves energy utilization, and ultimately achieves the goal of efficient and low-cost hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1A flow chart of a catalyst preparation method for continuous hydrogen production from methanol and water by photothermal coupling catalysis provided in an embodiment of the present invention is shown;

[0036] Figure 2 A flow chart showing the use of a catalyst provided by an embodiment of the present invention for photothermal coupling catalysis of methanol and water to produce hydrogen is shown;

[0037] Figure 3 The TEM image of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown;

[0038] Figure 4 The XRD diagram of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown;

[0039] Figure 5 The UV-Vis graph of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown;

[0040] Figure 6 The PL diagram of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown;

[0041] Figure 7 The XPS diagram of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown;

[0042] Figure 8 The data diagram of the reaction performance of methanol and water by photothermal coupling of the catalyst PtLi-P25 provided in an embodiment of the present invention is shown;

[0043] Fig. 9 A data diagram showing the thermal catalytic reaction performance of methanol and water by the catalyst PtLi-P25 provided in an embodiment of the present invention is shown;

[0044] Fig.10 The performance data diagram of other substrate / co-catalyst photothermal coupling catalysis of methanol and water provided by the embodiments of the present invention is shown;

[0045] Fig.11 The data graph of the photothermal coupled catalytic reaction performance of methanol and water by the PtLi-P25 catalyst provided in the embodiments of the present invention and the comparative examples is shown. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work belong to the scope of protection of the present invention.

[0047] In the embodiment, no specific experimental steps or conditions are indicated, and the operation or conditions of the conventional experimental steps described in the prior art in this field can be carried out. The reagents used and other instruments that do not indicate the manufacturer are conventional reagent products that can be obtained commercially. In addition, the accompanying drawings are only schematic diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0048] Technologies, methods, and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the description of the present invention.

[0049] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0050] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0051] The conversion of solar energy into hydrogen energy is a typical form of solar energy energy storage. Under the excitation of photon energy, the electrons in the valence band of the photocatalyst jump to the conduction band, and the electron-hole pairs that migrate to the catalyst surface undergo redox reactions with methanol and water (both are gaseous molecules), thereby producing hydrogen and carbon-containing oxidation products. Although photocatalytic hydrogen production has the advantages of being green and environmentally friendly, the photocatalytic performance is limited by the high electron-hole recombination rate of the catalyst and the low utilization rate of sunlight, resulting in a low hydrogen production rate, making it difficult to advance to industrialization.

[0052] In the past decade, scholars have done a lot of work in the field of low-temperature catalytic methanol and water hydrogen production. For example, Martin's group published a paper in Nature reporting that atomic-level loaded Pt / α-MoC can achieve efficient thermal catalytic methanol and water reforming hydrogen production. Although its hydrogen production rate is excellent (466.5mmol / g / h), the reaction temperature is reduced to 190℃, but its reaction pressure is 6MPa, which still has a high energy cost, and its hydrogen production reaction is carried out in an intermittent reaction system, which does not meet the needs of long-term continuous hydrogen production. Tang's group published a paper in Nature Materials reporting that single-atom and nanoparticle-coordinated PtCu-TiO2 can efficiently photocatalyze methanol-water solution to produce hydrogen at room temperature, achieving a quantum efficiency of nearly 100% at 365nm, but its hydrogen production rate (241.3mmol / g / h) is still lower than thermal catalysis. Coupling thermal catalysis and photocatalysis, and utilizing the photothermal synergistic effect, is expected to efficiently and selectively catalyze methanol and water to produce hydrogen under milder reaction conditions.

[0053] Patent CN202110103818.6 discloses a method for producing hydrogen from methanol using photothermal catalysis. The catalyst is composed of a metal or metal oxide that can absorb long waves for photothermal conversion and a semiconductor that can be excited to produce photogenerated electron-hole pairs. The preparation method is to stir and age the two metal precursor solutions, centrifugally dry them, heat them at 350°C for 4 hours, and finally grind the catalyst with a ball mill. The temperature of the catalyst can reach 173°C under light irradiation, and the hydrogen production rate is 99.6mmol / g / h. But in fact, the principle of this patent is that after the catalyst absorbs solar energy, it converts it into thermal energy, causing the catalyst temperature to rise to allow the catalytic reaction to proceed. That is, the solar photocatalytic part is converted into solar thermal catalysis rather than photothermal coupling. Therefore, it has high requirements on the wavelength and intensity of the light source, and its catalyst layer is infiltrated by the reaction solution, the contact between the reaction active sites and the methanol molecules is limited, and the light absorption is also affected, so the hydrogen production rate is low.

[0054] In view of this, the present invention hopes to provide a bifunctional catalyst with active metals and alkali metals loaded on a photocatalyst substrate, so as to achieve the purpose of continuous hydrogen production from methanol and water (both are gaseous molecules) by photothermal coupling catalysis. Under the combined action of light and heat, the photocatalyst substrate is photoexcited to produce high-energy electron-hole pairs with reduction and oxidation capabilities. The active metal acts as an active site to adsorb and activate the reactants (methanol and water molecules), while receiving photogenerated electrons or holes, promoting the separation of electron-hole pairs, and causing the adsorbed reactant molecules to undergo redox reactions; alkali metal atoms can regulate the electronic structure of the active metal by accepting / providing electrons to the active metal, thereby affecting its adsorption characteristics for the intermediate product and improving the activity and selectivity of the reaction. The specific implementation content is as follows:

[0055] In the first aspect, the present invention provides a method for preparing a catalyst for continuous hydrogen production from methanol and water by photothermal coupling catalysis, wherein the catalyst is formed by a first co-catalyst and a second co-catalyst being jointly loaded on a photocatalyst substrate; the first co-catalyst is selected from Group VIII metals and their oxides, Group IB metals and their oxides, or Group IIB metals and their oxides; the second co-catalyst is selected from alkali metals or alkaline earth metals; the photocatalyst substrate is selected from original or defect-modified P25, TiO2, g-C3N4, ZnO, CeO2, Bi2WO6, Bi2MoO6, Fe2O3, In2O3 or WO3, and the above-mentioned substrates can generate electron-hole pairs with sufficient redox ability under the excitation of ultraviolet or visible light.

[0056] Specifically, Figure 1 The flow chart of the catalyst preparation method for continuous hydrogen production from methanol and water by photothermal coupling catalysis provided in an embodiment of the present invention is shown as follows: Figure 1 As shown, the preparation method comprises the following steps:

[0057] S1, preparing a first co-catalyst precursor solution with a metal ion concentration of 0.5 to 2 mg / mL, preparing a second co-catalyst precursor solution with a metal ion concentration of 0.1 to 1 mg / mL, and mixing the two uniformly at an atomic ratio of 1:1 to 5:1 to obtain 0.5 to 10 mL of a mixed precursor solution;

[0058] In specific implementation, the first co-catalyst of this step can be selected from Pt, Pd, Cu, Fe, Au, Ag, Zn, Co, Ni or Ru, and the first co-catalyst precursor solution can be selected from a chloride, sulfate, nitrate, carbonate, phosphate or acetate solution with a metal ion (Pt, Pd, Cu, Fe, Au, Ag, Zn, Co, Ni or Ru) concentration of 0.5-2 mg / m; the second co-catalyst can be selected from Li, Na, K, Ca, Mg, Ba or Cs, and the second co-catalyst precursor solution can be selected from a chloride, sulfate, nitrate, carbonate, phosphate or acetate solution with a metal ion (Li, Na, K, Ca, Mg, Ba or Cs) concentration of 0.1-1 mg / mL. The first co-catalyst precursor solution and the second co-catalyst precursor solution are mixed evenly at an atomic ratio of 1:1 to 5:1 to form a mixed precursor solution (the total volume is controlled at 0.5-10 mL).

[0059] S2, using the mixed precursor solution to perform an equal volume impregnation treatment on the photocatalytic substrate to obtain a first catalyst precursor;

[0060] During specific implementation, the catalyst obtained by loading too much mixed precursor solution on the surface of the photocatalytic substrate is not only not conducive to improving the efficiency of catalytic methanol and water hydrogen production, but also causes agglomeration due to the large loading of the first co-catalyst and the second co-catalyst, affecting the catalytic efficiency. The mixed precursor solution loaded with too much load will also bring about the problem of excess water, which will cause excessive water vapor in the vacuum heating environment during subsequent vacuum heating, and it is impossible to accurately control the defects of the substrate catalyst and the size and valence of the co-catalyst. After a large number of experimental studies, the embodiments of the present invention have found that the loading amount of the mixed precursor solution on the surface of the photocatalytic substrate is controlled by adopting an equal volume impregnation method and controlling the impregnation time to not exceed 1 minute, while also reducing the loading amount of water on the surface of the photocatalytic substrate.

[0061] As an example, 250 mg of P25 is used as the photocatalyst substrate; 0.3-0.7 mL of the first co-catalyst precursor solution is 2 mg / mL Pt 4+ Solution; Second co-catalyst precursor solution 0.1~0.6mL 2mg / mL Li + The solutions are mixed and stirred evenly; then, at room temperature, the mixed metal precursor solution is used to impregnate the P25 powder in equal volumes, and theoretically, the loading amounts of Pt and Li are 0.2-0.5% and 0.05-0.3%, respectively.

[0062] S3, placing the first catalyst precursor in a vacuum oven, evacuating the vacuum oven to a vacuum, heating the vacuum oven to 100-300° C., maintaining for 1-5 hours, and then taking it out to obtain a second catalyst precursor;

[0063] In specific implementation, the first catalyst precursor obtained after the impregnation treatment is further placed in a vacuum environment for heating treatment to regulate the defects of the photocatalyst substrate and the size and valence of the co-catalyst (metal nanoparticles and / or metal oxides). The vacuum environment is provided by a vacuum oven. In addition, after the vacuum oven is evacuated to a vacuum degree of 95-100%, the evacuation is stopped; then the vacuum oven is heated to 100-300°C, and the first catalyst precursor releases water vapor during the heating process, so that the heating process is carried out in an environment containing an appropriate amount of water vapor. The presence of an appropriate amount of water vapor allows the co-catalyst (active phase and alkali metal) to have a certain fluidity, the active phase and the alkali metal are more tightly combined, and the distribution on the photocatalyst substrate is more uniform, which increases the service life and stability of the catalyst. The size of the co-catalyst (metal nanoparticles and / or metal oxides) formed is maintained at 2-3nm.

[0064] S4. Grind the second catalyst precursor into powder, wash it by centrifugation with deionized water for 2 to 3 times, and dry it at 60 to 80° C. for 12 to 15 hours to obtain a photothermal coupled catalytic catalyst for continuous hydrogen production from methanol and water.

[0065] During specific implementation, the drying can be carried out in a forced air oven.

[0066] In a second aspect, the present invention provides a catalyst for producing hydrogen from methanol and water by photothermal coupling catalysis obtained by the preparation method of the first aspect, wherein the catalyst is formed by a first co-catalyst and a second co-catalyst being jointly loaded on a photocatalyst substrate; wherein the loading amount of the first co-catalyst is 0.2-1%, the loading amount of the second co-catalyst is 0.1-1%, and the rest is the photocatalyst substrate;

[0067] The first promoter is selected from Pt, Pd, Cu, Fe, Au, Ag, Zn, Co, Ni or Ru;

[0068] The second promoter is selected from Li, Na, K, Ca, Mg, Ba or Cs;

[0069] The photocatalyst substrate is selected from pristine or defect-modified P25, TiO2, g-C3N4, ZnO, CeO2, Bi2WO6, Bi2MoO6, Fe2O3, In2O3 or WO3.

[0070] The photothermal coupled catalyst for hydrogen production from methanol and water provided by the embodiment of the present invention is under the combined action of light and heat. The light energy causes the photocatalyst substrate to be photoexcited to generate high-energy electron-hole pairs with reduction and oxidation capabilities to generate high-energy electron-hole pairs, which promotes the separation of electron-hole pairs between methanol and water molecules. The thermal energy is beneficial to the mass transfer between methanol and water molecules and promotes the timely desorption of products. At the same time, the life of the photogenerated charge is extended by thermal excitation to maintain the high efficiency and stability of the catalyst, so as to achieve the purpose of continuous hydrogen production with high yield and high selectivity. As a preferred result, the first co-catalyst is preferably selected from Pt, Co or Ru; the second co-catalyst is preferably selected from Li, Na, Ba or Cs; the photocatalyst substrate is preferably selected from original or defect-modified P25, g-C3N4 or In2O3.

[0071] In a third aspect, the present invention provides an application of a catalyst for producing hydrogen from methanol and water by photothermal coupling catalysis obtained by the preparation method of the first aspect. Figure 2 The flow chart of the catalyst provided in the embodiment of the present invention for the photothermal coupling catalytic continuous hydrogen production from methanol and water is shown as follows: Figure 2 As shown, including:

[0072] S11, loading the catalyst into a continuous fixed-bed photothermal reactor, then purging the reactor with an inert gas for 30 minutes, and heating the reactor to 80-250° C. and setting the pressure at 0.1-3 MPa;

[0073] S12. Methanol gas and water vapor in a molar ratio of 1:1 to 1:10 are introduced into a continuous fixed-bed photothermal reactor, and the light source is turned on. The catalyst catalyzes methanol and water to continuously produce hydrogen under photothermal conditions.

[0074] In specific implementation, before the catalyst is loaded into the continuous fixed-bed photothermal reactor, the catalyst can be first ultrasonically dispersed in a glass dish filled with deionized (DI) water, and then dried. After the catalyst film is formed, it is placed in the photothermal reactor together with the glass dish to increase the contact (action) area between the catalyst and the reaction gas.

[0075] In some embodiments, methanol gas and water vapor can be provided by vaporizing methanol aqueous solution, and the methanol aqueous solution is fed into the continuous fixed bed photothermal reactor by a liquid inlet pump or a plunger pump, and the surface of the pumping pipeline is accompanied by a heating belt, and the temperature of the heating belt is set to 120-270°C to ensure the gasification of methanol aqueous solution. The pumping amount of methanol gas and water vapor can be specifically achieved by regulating the concentration of methanol in the methanol aqueous solution and the pumping flow rate of the methanol aqueous solution to control the vaporization to obtain a molar ratio of methanol gas and water vapor of 1:1 to 1:10. Specifically, the pumping flow rate of the methanol aqueous solution is controlled at 0.1-10 mL / min.

[0076] In some embodiments, the inert gas is N2 or Ar; the light source is a natural light source or an artificial light source, and the intensity of the light source is 1-2 sunlight intensity.

[0077] In order to enable those skilled in the art to more clearly understand the present invention, the catalyst, preparation method and application of the photothermal coupled catalytic continuous hydrogen production from methanol and water described in the present invention are now described in detail through the following examples.

[0078] Example 1

[0079] Preparation of catalyst for continuous hydrogen production from methanol and water by photothermal coupling catalysis:

[0080] 1) Take 250 mg of P25 as the photocatalyst substrate;

[0081] 2) 0.5 mL of 2.5 mg / mL Pt 4+ solution and 0.2mL 1mg / mL Li + The solution was mixed and stirred evenly;

[0082] 3) At room temperature, the metal precursor solution obtained in step 1) is used to impregnate the P25 powder in equal volume, and the theoretical loading amounts of Pt and Li are 0.2% and 0.1%, respectively;

[0083] 4) placing the mixture obtained in step 3) into a vacuum oven, evacuating the air, closing the vacuum system, and then heating the oven to maintain the temperature at 180° C. for 3 hours;

[0084] 5) The solid obtained in 4) was ground into powder, washed three times by centrifugation with DI water, and dried in a forced air oven at 80° C. for 12 h to obtain a photothermal coupled catalytic methanol and water continuous hydrogen production catalyst (PtLi-P25).

[0085] Figure 3 TEM image of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown, Figure 3 As shown, the loaded Pt species are metal clusters of 2 to 3 nm.

[0086] Figure 4 The XRD diagram of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown. Figure 4 It can be seen that loading Pt and Li does not change the crystal structure of P25.

[0087] Figure 5 The UV-Vis graph of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown. Figure 5 It can be seen that after loading Pt and Li, the light absorption capacity of the catalyst is improved.

[0088] Figure 6 The PL diagram of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown. Figure 6 It can be seen that after the introduction of Pt and Li, the charge distribution efficiency of the catalyst is improved.

[0089] Figure 7 The XPS diagram of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown. Figure 7 It can be seen that the Pt in PtLi-P25 is Pt 0 and Pt 2+ of mixed state.

[0090] Example 2

[0091] Performance test of the catalyst for continuous hydrogen production from methanol and water by photothermal coupling catalysis:

[0092] The present invention continues to select the PtLi-P25 catalyst prepared in Example 1 to verify the performance of catalyzing continuous hydrogen production from methanol and water:

[0093] (1) Hydrogen production rate test of continuous hydrogen production from methanol and water catalyzed by PtLi-P25 catalyst under photothermal coupling:

[0094] 10 mg of the PtLi-P25 catalyst prepared in Example 1 was evenly loaded on a glass dish and placed in a photothermal reactor. The reactor was purged with N2 for 30 minutes, and the reactor was heated to 150°C. After the purging was completed, the light source was turned on, and the gas of methanol aqueous solution was introduced at the same time. The catalyst catalyzed the methanol-water vapor reaction to produce hydrogen under photothermal conditions. The reaction conditions were a methanol:water volume ratio of 1:3.3, an injection rate of 1.5 mL / min, and the gas products at the reactor outlet were collected by the drainage method, and the gas products were injected into a gas chromatograph for detection using a syringe.

[0095] Figure 8 The data diagram of the reaction performance of the catalyst PtLi-P25 provided in the embodiment of the present invention for photothermal coupling catalysis of methanol and water is shown as follows: Figure 8 As shown, compared with pure P25, after loading the PtLi co-catalyst, the hydrogen production rate of the PtLi-P25 photothermal coupling catalytic reaction of methanol and water increased by 26.3 times to 624.1 mmol / g / h, and the CO selectivity was as low as 0.23%. The hydrogen production rate was relatively stable in the 10-h experiment. After turning off the lights, under the condition of thermal catalysis alone, the hydrogen production rate dropped sharply to 0.59 mmol / g / h, and the efficient hydrogen production was restored after turning on the lights, indicating that the PtLi-P25 provided by the present invention has excellent photothermal coupling catalytic activity and reaction stability.

[0096] (2) Hydrogen production performance test of PtLi-P25 catalyzing continuous hydrogen production from methanol and water in the absence of light source:

[0097] A glass dish uniformly loaded with 10 mg of catalyst was placed in a photothermal reactor, and the reactor was purged with N2 for 30 minutes. At the same time, the reactor was heated to 110°C. After the purging was completed, the steam of methanol-water solution was introduced, and the catalyst thermally catalyzed the reaction of methanol and water to produce hydrogen. The reaction conditions were methanol: water volume ratio = 1:3.3, the injection rate was 1.5 mL / min, and the gas products at the reactor outlet were collected by drainage method, and the gas products were injected into the gas chromatograph with a syringe for detection.

[0098] Fig. 9 The thermal catalytic reaction performance data of methanol and water of the catalyst PtLi-P25 provided in the embodiment of the present invention is shown in FIG. Fig. 9 As shown in the figure, under the conditions of pure thermal catalysis, the hydrogen production rate of PtLi-P25 is only 0.59 mmol / g / h. It can be seen that the hydrogen production reaction of methanol and water catalyzed by PtLi-P25 is coupled with photocatalysis and thermal catalysis, rather than a thermal catalytic reaction driven by solar energy.

[0099] Example 3

[0100] Performance test of other substrates / co-catalysts for photothermal coupling catalysis of methanol and water:

[0101] The preparation methods of Fe-P25, Cu-P25, Pd-P25, PtK-P25, PtMg-P25, PtLi-ZnO and PtLi-CeO2 catalysts obtained in this embodiment are the same or similar to those in Example 1 and will not be repeated in this embodiment.

[0102] Fig.10 The performance data of other substrate / co-catalyst photothermal coupling catalysis of methanol and water provided by the embodiments of the present invention are shown, such as Fig.10 As shown, loading Fe, Cu, Pd, PtK, and PtMg can effectively improve the reaction activity of P25. When the substrate is replaced with ZnO or CeO2, loading PtLi can also improve its reaction activity. This proves that the catalyst preparation method provided by this patent is universal and supports the selection range of substrates and co-catalysts protected by this patent.

[0103] The following comparative examples 1-3 provide catalysts PtLi-P25 prepared under different heating atmospheres and their reaction performance tests

[0104] Comparative Example 1

[0105] Take 250mg P25 as the photocatalyst substrate, mix 0.5mL 2.5mg / mL H2PtCl6 solution and 0.2mL 1mg / mL LiCl solution and stir evenly. At room temperature, use the above metal precursor solution to impregnate the P25 powder in equal volumes. Put the obtained mixture into a blast oven, heat it at 180℃ for 3 hours without vacuuming. Grind the obtained solid into powder, wash it by centrifugation with DI water 3 times, and dry it in a blast oven at 80℃ for 12 hours to obtain PtLi-P25-1 prepared in an air atmosphere.

[0106] Comparative Example 2

[0107] Take 250mg P25 as the photocatalyst substrate, mix 0.5mL 2.5mg / mL H2PtCl6 solution and 0.2mL 1mg / mL LiCl solution and stir evenly. At room temperature, use the above metal precursor solution to impregnate the P25 powder in equal volumes. Put the obtained mixture into a tube furnace, purge it with 10% H2-90% Ar for 30 minutes, and then heat it to 180℃ for 3 hours. Grind the obtained solid into powder, wash it with DI water by centrifugation 3 times, and dry it in a blast oven at 80℃ for 12 hours to obtain PtLi-P25-2 prepared under H2 atmosphere.

[0108] Comparative Example 3

[0109] Take 250mg P25 as the photocatalyst substrate, mix 0.5mL 2.5mg / mL H2PtCl6 solution and 0.2mL 1mg / mL LiCl solution and stir evenly. At room temperature, use the above metal precursor solution to impregnate the P25 powder in equal volumes. Put the obtained mixture into a vacuum oven, evacuate it at room temperature, and then heat it to 180℃ for 3 hours. When the temperature reaches 180 degrees, the released water vapor is pumped away to ensure that the catalyst is heated under pure vacuum conditions. Grind the obtained solid into powder, wash it by centrifugation with DI water 3 times, and dry it in a blast oven at 80℃ for 12 hours to obtain PtLi-P25-3 prepared under vacuum atmosphere.

[0110] The photothermal coupling catalytic performance of PtLi-P25 prepared under the above three heating atmospheres to produce hydrogen from methanol and water was tested respectively:

[0111] A glass dish uniformly loaded with 10 mg of catalyst was placed in a photothermal reactor, and the reactor was purged with N2 for 30 minutes. At the same time, the reactor was heated to 110°C. After the purging was completed, the steam of methanol-water solution was introduced, and the catalyst thermally catalyzed the reaction of methanol and water to produce hydrogen. The reaction conditions were methanol: water = 1:3.3, the injection rate was 1.5 mL / min, and the gas products at the reactor outlet were collected by the drainage method, and the gas products were injected into the gas chromatograph for detection using an injection agent.

[0112] The photothermal coupled catalytic performance of PtLi-P25 prepared in Example 1 for hydrogen production from methanol and water was compared with the performance of the catalysts prepared under the above three different heating atmospheres. Fig.11 .

[0113] Fig.11 The data diagram of the reaction performance of methanol and water by photothermal coupling of PtLi-P25 catalyst provided in the embodiments of the present invention and the comparative examples is shown, as Fig.11 As shown, the hydrogen production rates of PtLi-P25 prepared in Comparative Example 1 (air atmosphere), Comparative Example 2 (hydrogen atmosphere) and Comparative Example 3 (pure vacuum) are 331.7, 173.2 and 420.2 mmol / g / h, respectively, while the hydrogen production rate of PtLi-P25 prepared in Example 1 under vacuum and water vapor atmosphere is 624.1 mmol / g / h. This is because under vacuum and water vapor atmosphere, part of the co-catalyst is oxidized or reduced to achieve an optimal mixed valence ratio, and the interface structure of the catalyst is optimized, thereby having excellent hydrogen production efficiency.

[0114] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0115] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0116] The above is a detailed introduction to the catalyst, preparation method and application of the photothermal coupled catalytic continuous hydrogen production of methanol and water provided by the present invention. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for preparing a catalyst for continuous hydrogen production from methanol and water by photothermal coupling catalysis, characterized in that: The catalyst is formed by a first co-catalyst and a second co-catalyst being loaded on a photocatalyst substrate; the preparation method comprises the following steps: Step 1, preparing a first co-catalyst precursor solution with a metal ion concentration of 0.5 to 2 mg / mL, preparing a second co-catalyst precursor solution with a metal ion concentration of 0.1 to 1 mg / mL, and mixing the two at an atomic ratio of 1:1 to 5:1 to obtain 0.5 to 10 mL of a mixed precursor solution; Step 2: using the mixed precursor solution to perform an equal volume impregnation treatment on the photocatalytic substrate to obtain a first catalyst precursor; Step 3, placing the first catalyst precursor in a vacuum oven, evacuating the vacuum oven to a vacuum, heating the vacuum oven to 100-300° C., maintaining the temperature for 1-5 hours, and then taking it out to obtain a second catalyst precursor; Step 4, grinding the second catalyst precursor into powder, washing it by centrifugation with deionized water for 2 to 3 times, and drying it at 60 to 80° C. for 12 to 15 hours to obtain the catalyst; The first co-catalyst is selected from Pt or Pd; The first co-catalyst precursor solution is a chloride, sulfate, nitrate, carbonate, phosphate or acetate solution containing Pt or Pd; The second co-catalyst is selected from Li, Na, K, Ca or Mg; the second co-catalyst precursor solution is a chloride, sulfate, nitrate, phosphate or acetate solution containing Li, Na, K, Ca or Mg; The photocatalyst substrate is selected from pristine or defect-modified P25, g-C3N4, ZnO or CeO2; The step of evacuating the vacuum oven to a vacuum comprises: evacuating the vacuum oven to a vacuum degree of 95-100%, and then stopping evacuating the vacuum oven; The vacuum oven is heated to 100-300° C., and the first catalyst precursor releases water vapor during the heating process, so that the heating process is carried out in an environment containing water vapor.

2. The method for preparing a catalyst according to claim 1, characterized in that: In step 4, the drying is carried out in a forced air oven.

3. A catalyst for producing hydrogen from methanol and water by photothermal coupling catalysis obtained by the catalyst preparation method according to any one of claims 1 to 2, characterized in that: The catalyst is formed by a first co-catalyst and a second co-catalyst being loaded on a photocatalyst substrate; wherein the loading amount of the first co-catalyst is 0.2-1%, the loading amount of the second co-catalyst is 0.1-1%, and the rest is the photocatalyst substrate; The first co-catalyst is selected from Pt or Pd; The second promoter is selected from Li, Na, K, Ca or Mg; The photocatalyst substrate is selected from pristine or defect-modified P25, g-C3N4, ZnO or CeO2.

4. An application of a catalyst for producing hydrogen from methanol and water by photothermal coupling catalysis obtained by the catalyst preparation method according to any one of claims 1 to 2, characterized in that: The catalyst is used for photothermal coupling catalysis of methanol and water to produce hydrogen, and comprises: The catalyst is loaded into a continuous fixed-bed photothermal reactor, and then the reactor is purged with an inert gas for 30 minutes, and the reactor is heated to 80-250° C. and the pressure is set at 0.1-3 MPa; Methanol gas and water vapor in a molar ratio of 1:1 to 1:10 are introduced into a continuous fixed-bed photothermal reactor, and a light source is turned on. The catalyst catalyzes methanol and water to continuously produce hydrogen under photothermal conditions.

5. The use according to claim 4, characterized in that: Before the catalyst is loaded into the continuous fixed-bed photothermal reactor, the catalyst is ultrasonically dispersed in a glass dish filled with deionized water, and then dried. After the catalyst film is formed, it is placed in the photothermal reactor together with the glass dish.

6. The use according to claim 4, characterized in that: The inert gas is N2 or Ar; The light source is a natural light source or an artificial light source.

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