Pt-TiO2 (R)-H catalyst as well as preparation method and application thereof

Abstract

The invention provides a Pt-TiO2 (R)-H catalyst as well as a preparation method and application thereof, and the preparation method comprises the following steps: preparing alkaline TiO2 sol in a lining of a hydrothermal reaction kettle, the TiO2 sol containing TiO2 (R) with the average particle size of 75-100nm; adding a chloroplatinic acid solution into the TiO2 sol to enable the mass fraction of Pt relative to TiO2 to be 1.5-2.5 wt%; placing the hydrothermal reaction kettle lining in a stainless steel jacket, and placing the stainless steel jacket in a constant-temperature oven for hydrothermal reaction; after the hydrothermal reaction is finished, centrifuging and washing in sequence, and carrying out vacuum drying to obtain a catalyst powder precursor; and roasting the obtained catalyst powder precursor in a muffle furnace, and activating in a reducing atmosphere in a tubular furnace to obtain the catalyst. The working temperature of the existing noble metal-oxide type catalyst can be reduced, and the hydrogen production rate in a low-temperature interval can be increased.

Description

Technical Field

[0001] The present invention relates to the field of Pt catalysts or methanol hydrogen production, and in particular to a Pt-TiO2(R)-H catalyst and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) offer clean power generation and are free from the limitations of the traditional Carnot cycle of internal combustion engines, enabling them to meet higher environmental standards while improving energy efficiency. Traditional hydrogen fuel cells rely on high-pressure hydrogen as a hydrogen source, but its practical application is limited by its high storage and transportation costs and significant safety hazards.

[0003] Liquid methanol (CH3OH) is an ideal hydrogen carrier due to its high H / C ratio, convenient storage and transportation conditions and low price. Compared with the two methods of methanol hydrogen production, namely methanol pyrolysis and methanol partial oxidation, the methanol steam reforming reaction takes into account both high hydrogen production efficiency and low CO selectivity, and is an ideal hydrogen source for proton exchange membrane fuel cells; at the same time, due to the poor tolerance of traditional low-temperature PEMFCs to CO (<20ppm), the hydrogen-rich reformed gas produced by methanol steam requires palladium membrane purification, which increases the complexity and energy consumption of the system. High-temperature proton exchange membrane fuel cells (HT-PEMFCs) with an operating temperature of 180-200°C have strong resistance to CO poisoning (≤30000ppm), so the reformed gas can be used without purification. Therefore, constructing a temperature-matched (methanol steam reforming hydrogen production and HT-PEMFCs operating temperature are both between 180 and 200°C) methanol steam reforming-high-temperature proton exchange membrane hydrogen fuel cell system is the best solution to achieve online hydrogen production.

[0004] Currently, common methanol reforming catalysts are divided into Cu-based and precious metal-based (Pd, Pt, Au, etc.). Although Cu-based catalysts have low CO selectivity, their high operating temperature (220-260°C) and the easy sintering of Cu species prevent stable hydrogen production under temperature-matching conditions. Precious metal-based catalysts, especially precious metal-oxide-based catalysts, have operating temperatures above 300°C and high CO selectivity (>20%). Precious metal-carbide-based catalysts, while offering high low-temperature hydrogen production performance and low CO selectivity, their harsh preparation and activation conditions, as well as their weak stability (gradually transforming from carbide to oxide), limit their practical application. Summary of the Invention

[0005] In order to reduce the operating temperature of existing noble metal-oxide catalysts, increase the hydrogen production rate in the low temperature range, and reduce the CO selectivity, the present invention provides a Pt-TiO2(R)-H catalyst and its preparation method and use. By using the similar lattice parameters of β-PtO2 and rutile phase TiO2, a PtO2 with deep embedding is successfully constructed. x The invention discloses a Pt-TiO2(R)-H catalyst having a species-rich Pt single-atom structure, and provides a preparation method of the catalyst and its application in methanol steam reforming reaction.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A method for preparing a Pt-TiO2(R)-H catalyst comprises the following steps:

[0008] An alkaline TiO2 sol is prepared in the lining of a hydrothermal reactor, wherein the TiO2 sol contains TiO2(R) with an average particle size of 75 to 100 nm;

[0009] Adding chloroplatinic acid solution to the TiO2 sol to make the mass fraction of Pt relative to TiO2 be 1.5-2.5wt%;

[0010] The hydrothermal reactor liner is placed in a stainless steel jacket and placed in a constant temperature oven for hydrothermal reaction. After the hydrothermal reaction is completed, the catalyst powder precursor Pt-TiO2(R) is obtained by centrifugation and washing, and then vacuum drying.

[0011] The obtained catalyst powder precursor is placed in a muffle furnace for calcination, and then activated in a reducing atmosphere in a tube furnace to obtain Pt-TiO2(R)-H.

[0012] Furthermore, the alkaline TiO2 sol is prepared in the lining of the hydrothermal reactor as follows:

[0013] Add 70-240 ml of deionized water to the lining of the hydrothermal reactor, corresponding to a filling degree of 70%-80%, and then adjust the pH value of the deionized water to 8-9 with NaOH;

[0014] 0.8-2.4 g of TiO2(R) with an average particle size of 75-100 nm was weighed and added to the lining of a hydrothermal reactor with a volume of 100-300 ml; after stirring at room temperature, a uniformly dispersed TiO2 sol was obtained.

[0015] Furthermore, the temperature of the hydrothermal reaction is 100-150° C., and the reaction time is 12-18 hours.

[0016] Furthermore, the calcination temperature of the muffle furnace is 500 - 600 °C, and the calcination time is 4 - 6 h; the reducing atmosphere is a H2 / Ar mixed gas with a volume percentage of 10 - 20 vol%, the activation temperature is 400 - 600 °C, and the activation time is 2 - 3 h.

[0017] A Pt-TiO2(R)-H catalyst, and the Pt-TiO2(R)-H catalyst is prepared by using the preparation method of the Pt-TiO2(R)-H catalyst.

[0018] Furthermore, Pt species exist in two forms simultaneously, namely PtO clusters (2 < x < 4) deeply embedded in the TiO2(R) lattice and Pt single atoms. x The clusters are embedded in the (110) crystal plane of TiO2(R), and the embedding depth is 8 - 10 atomic layers.

[0019] Furthermore, PtO clusters with a size of 2 - 3 nm are embedded in the (110) crystal plane of TiO2(R), and the embedding depth is 8 - 10 atomic layers. x The clusters are embedded in the (110) crystal plane of TiO2(R), and the embedding depth is 8 - 10 atomic layers.

[0020] Furthermore, in the form of Pt single atoms, the Pt-O coordination number is 5 - 6, and the chemical valence state is Pt(0 < δ < 2). δ+ (0 < δ < 2).

[0021] The use of the Pt-TiO2(R)-H catalyst for hydrogen production by methanol steam reforming.

[0022] Furthermore, in the methanol steam reforming reaction, raw materials and the Pt-TiO2(R)-H catalyst are added. The raw materials are water and methanol, and the molar ratio of water to alcohol is 2 - 3; the reaction pressure is 0.1 - 0.2 Mpa; the mass hourly space velocity of methanol is 3 - 9.5 h -1 .

[0023] The beneficial effects of the present invention are as follows: [[ID=3D]]]

[0024] 1. For the Pt-TiO2(R)-H catalyst and its preparation method of the present invention, the Pt-TiO2(R)-H catalyst provided by the present invention has a structure with deeply embedded PtO nanoclusters and abundant Pt single atoms. The single-atom Pt with high atomic utilization rate shows unsaturated Pt-O coordination, and shows a Pt valence state (0 < δ < 2), which strengthens the adsorption and activation of *CH3OH species; at the same time, the deeply embedded PtO(1 < x < 2) clusters enhance the strong metal-support interaction between Pt species and the TiO2(R) support, forming a Pt-Ti coordination structure. This coordination structure induces the transfer of electrons from Pt to Ti to form electron-rich Ti x nanoclusters and a structure rich in Pt single atoms. Among them, the single-atom Pt with high atomic utilization rate shows unsaturated Pt-O coordination and shows a Pt valence state (0 < δ < 2), which strengthens the adsorption and activation of *CH3OH species; at the same time, the deeply embedded PtO δ+ valence state (0 < δ < 2), strengthening the adsorption and activation of *CH3OH species; at the same time, the deeply embedded PtO x (1 < x < 2) clusters enhance the strong metal-support interaction between Pt species and the TiO2(R) support, forming a Pt-Ti coordination structure. This coordination structure induces the transfer of electrons from Pt to Ti to form electron-rich Ti 3+structure, promoting the adsorption and cracking of H2O. In summary, Pt δ+ -Ti 3+ The dual-functional center synergistically promotes the performance of methanol steam reforming to hydrogen production.

[0025] 2. The Pt-TiO2(R)-H catalyst and its preparation method of the present invention, since the preparation of Pt-TiO2 single-atom catalyst relies on the introduction of low-content Pt species, the mass fraction of Pt species must be less than 0.5wt%. Based on the highly similar lattice structure of β-PtO2 and rutile TiO2, the present invention uses a hydrothermal-calcination-reduction preparation method to make PtO x Species are embedded into the TiO2(R) lattice, and the embedded PtO x The structure can stabilize the Pt-O coordination and form a Pt single-atom structure with a high Pt content (2wt%). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is the X-ray diffraction spectrum of Pt-TiO2(R)-H of the present invention.

[0028] Figure 2 This is a spherical aberration electron microscope image of Pt-TiO2(R)-H of the present invention.

[0029] Figure 3 This is the extended X-ray absorption fine structure spectrum of the Pt-L3 edge of Pt-TiO2(R)-H of the present invention.

[0030] Figure 4 This is the X-ray photoelectron spectrum of Pt-TiO2(R)-H of the present invention.

[0031] Figure 5 This is a graph showing the change in hydrogen yield of Pt-TiO2(R)-H with a mass fraction of 1.5wt% as a function of temperature.

[0032] Figure 6 This is a graph showing the change in CO selectivity of Pt-TiO2(R)-H with a mass fraction of 1.5 wt% as a function of temperature.

[0033] Figure 7This is a graph showing the change in hydrogen yield of Pt-TiO2(R)-H with a mass fraction of 2.0 wt% as a function of temperature.

[0034] Figure 8 This is a graph showing the change in CO selectivity of Pt-TiO2(R)-H with a mass fraction of 2.0 wt% as a function of temperature.

[0035] Figure 9 This is a graph showing the change in hydrogen yield of Pt-TiO2(R)-H with a mass fraction of 2.5 wt% as a function of temperature.

[0036] Figure 10 This is a graph showing the change in CO selectivity of Pt-TiO2(R)-H with a mass fraction of 2.5 wt% as a function of temperature. DETAILED DESCRIPTION

[0037] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "axial", "radial", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0039] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0040] The preparation method of the Pt-TiO2(R)-H catalyst described in the present invention includes the following steps:

[0041] S01: Prepare an alkaline TiO2 sol in the inner lining of a hydrothermal reactor, where the TiO2 sol contains TiO2(R) with an average particle size of 75 - 100 nm. Specifically:

[0042] Add 70 - 240 ml of deionized water to the inner lining of the hydrothermal reactor, with a corresponding filling degree of 70% - 80%. Then adjust the pH value of the deionized water to 8 - 9 with NaOH; weigh 0.8 - 2.4 g of TiO2(R) with an average particle size of 75 - 100 nm and add it to the inner lining of a hydrothermal reactor with a volume of 100 - 300 ml; stir at room temperature to obtain a uniformly dispersed TiO2 sol.

[0043] S02: Add chloroplatinic acid solution to the TiO2 sol so that the mass fraction of Pt relative to TiO2 is 1.5 - 2.5 wt%.

[0044] S03: Place the inner lining of the hydrothermal reactor in a stainless steel outer jacket and place it in a constant temperature oven for hydrothermal reaction; after the hydrothermal reaction is completed, successively carry out centrifugation and washing, and then obtain the catalyst powder precursor Pt-TiO2(R) through vacuum drying.

[0045] S04: Place the obtained catalyst powder precursor in a muffle furnace for roasting, and then activate it in a reducing atmosphere in a tubular furnace to obtain Pt-TiO2(R)-H.

[0046] A Pt-TiO2(R)-H catalyst is prepared by using the preparation method of the Pt-TiO2(R)-H catalyst. The Pt species exist in two forms simultaneously, namely PtO x clusters (2 < x < 4) deeply embedded in the TiO2(R) lattice and Pt single atoms. The PtO x clusters with a size of 2 - 3 nm are embedded in the crystal plane of TiO2(R), and the embedding depth is 8 - 10 atomic layers. In the form of Pt single atoms, the Pt-O coordination number is 5 - 6, and the chemical valence state is Pt δ+ (0 < δ < 2).

[0047] The mechanism of forming the embedded PtO x and Pt single atom structure through continuous hydrothermal-roasting-reduction steps is as follows:

[0048] Hydrothermal: Due to the high-temperature and high-pressure environment (100 - 150 °C, 0.3 - 0.6 MPa) during the hydrothermal reaction process, part of the H2PtCl6 precursor hydrolyzes in the hydrothermal environment. The hydrolyzed ionic PtCl62- species can be anchored in the oxygen vacancies (Ti 3+ -OVs) and the lattice interstitial sites of rutile TiO2. That is, in the lattice of rutile TiO2, an embedded metastable PtCl62- species is formed.

[0049] Calcination: Calcining in air (500 - 600 °C) can convert the metastable PtCl62- anchored in the oxygen vacancies (Ti 3+ -OVs) and lattice interstitial sites of rutile TiO2 into stable PtO2, which bonds with the surface of rutile TiO2 to form a strong interaction and a Pt - O - Ti coordination structure.

[0050] Reduction: Under the condition of a strong reducing atmosphere (10 - 20% H2 / Ar, 400 - 600 °C), the PtO2 that has not been embedded in the rutile TiO2 lattice after calcination is reduced to Pt δ+ species (0 < δ < 2). At the same time, the oxygen vacancies (Ti 3+ -OVs) of rutile, as electron defect sites, can enable the stable existence of the Pt single-atom structure through charge transfer. For the PtO2 embedded in rutile TiO2, due to the stronger Pt - O - Ti coordination structure, the deep reduction of PtO2 is inhibited, forming an embedded PtO x (2 < x < 4) structure.

[0051] Example ①

[0052] The preparation method of the Pt - TiO2(R) - H catalyst of Example ① includes the following steps:

[0053] Weigh 0.8 g of TiO2(R) with an average particle size of 75 nm and add it to the inner lining of a 100 ml hydrothermal reaction kettle, as shown in Figure 2 a. 75 ml of deionized water is pre-added to the inner lining, with a filling degree of 75%. Adjust the pH = 8 - 9 with 0.1 mol / L NaOH. At 25 °C, stir magnetically for 1 h to obtain a uniformly dispersed TiO2 sol.

[0054] Add 0.80 ml of chloroplatinic acid solution with a Pt content of 15 mg / ml to the obtained TiO2 sol, so that the theoretical mass fraction of Pt relative to TiO2 is 1.5 wt%, and continue to stir magnetically for 2 h.

[0055] It should be noted that the "①" in the original text is not a standard numbering format. I translated it as "①" directly. If it has a specific meaning, it may need to be adjusted according to the actual situation.Place the inner lining of the above hydrothermal reactor into the stainless-steel outer jacket, tighten it fully, and place it in a constant-temperature oven for hydrothermal reaction at 120 °C for 12 h. After the hydrothermal reaction is completed, wait for the hydrothermal reactor to cool to room temperature, then centrifuge at a speed of 5000 rpm for solid-liquid separation; then wash the separated solid powder with water twice and ethanol twice in sequence, place it in a vacuum drying oven, and conduct vacuum drying at 70 °C for 12 h to obtain the catalyst precursor Pt-TiO2(R).

[0056] Place the obtained solid powder precursor Pt-TiO2(R) in a muffle furnace for roasting, and roast it at 500 °C for 4 h; immediately transfer the roasted product to a tubular furnace, and under the atmosphere of 10-20% H2 / Ar, reduce it at 450 °C for 2 h. The reduced product is Pt-TiO2(R)-H, that is, the catalyst is obtained.

[0057] As Figure 1 shown, through XRD phase analysis of the above catalyst Pt-TiO2(R)-H, Pt-TiO2(R)-H presents the rutile phase of TiO2, and at the same time, the existence of the Pt phase is not found, proving that the Pt species are highly dispersed on the surface of the TiO2(R) support; as Figure 2 shown in b, through aberration-corrected electron microscopy analysis, it can be seen that this highly dispersed Pt species exists in the form of PtO x species (8 atomic layer thickness) and single-atom Pt (Pt-O coordination number 5-6) embedded deeply into the TiO2(R) lattice.

[0058] As Figure 3 and Figure 4 shown, combining the fitting results of the Pt L3 edge in the EXAFS spectrum and XPS Pt 4f in Pt-TiO2(R)-H, the unsaturated coordination of Pt-O proves the formation of the Pt single-atom structure and shows the valence state of Pt δ+ (0 < δ < 2). This single-atom Pt δ+ enhances the adsorption and activation of CH3OH molecules; the Pt-O-Pt coordination proves the formation of deeply embedded PtO x and shows the valence state of Pt x+ (2 < x < 4). At the same time, this structure induces the formation of the Pt-Ti coordination structure, resulting in more electrons transferring from Pt to Ti, forming an electron-rich Ti 3+ structure. This Ti 3+ enhances the adsorption and activation of H2O molecules; therefore, a bifunctional center promoting methanol cracking of single-atom Pt δ+ and electron-rich Ti 3+ for water cracking is constructed, improving the performance of hydrogen production by methanol steam reforming.

[0059] The Pt-TiO2(R)-H catalyst is used for methanol steam reforming to produce hydrogen. The Pt-TiO2(R)-H catalyst in Example 1 is granulated to 40-60 mesh, 100 mg of the catalyst is placed in a quartz reaction tube, quartz wool is inserted into the upper and lower ends, and the reaction tube is fixed in a fixed bed reactor for methanol reforming to produce hydrogen. In the methanol steam reforming reaction, raw materials are added, the raw materials are water and methanol, and the conditions are: a water-to-methanol molar ratio of 2, argon is the carrier gas, the argon pressure is 0.1 MPa, the nitrogen flow rate is 50 mL / min, and the mass space velocity of methanol is maintained at 9.5 h -1 The vaporization temperature is 150°C, the reaction temperature is 140-240°C, and after stabilization at each temperature for 1 hour, the tail gas is passed through a gas chromatograph to detect the components of H2, CO, CO2, and CH4 in the reformed gas. The mass space velocity of methanol is the mass of methanol passing through a unit mass of catalyst per unit time.

[0060] like Figure 5 As shown in FIG. 1 , the hydrogen generation rate of the catalyst prepared in Example 1 at 240° C. is 2212 mmol H2·g Pt -1 ·h -1 .like Figure 6 As shown, the catalyst prepared in Example 1 has a CO selectivity of 4.66% at 40°C.

[0061] Example 2

[0062] The preparation method of the Pt-TiO2(R)-H catalyst of Example 2 comprises the following steps:

[0063] Weigh 1.6g of TiO2(R) with an average particle size of 75nm and add it to the lining of a hydrothermal reactor with a volume of 200ml. Figure 2 As shown in a, 150 ml of deionized water is pre-added to the inner lining, with a filling degree of 75%, and the pH is adjusted to 8-9 with 0.1 mol / L NaOH; at 25° C., magnetic stirring is performed for 1 hour until the TiO 2 sol is uniformly dispersed.

[0064] 2.13 ml of chloroplatinic acid solution with a Pt content of 15 mg / ml was added to the obtained TiO2 sol to make the theoretical mass fraction of Pt relative to TiO2 2 wt%, and magnetic stirring was continued for 2 h.

[0065] Place the inner lining of the above hydrothermal reactor into the stainless-steel outer jacket, tighten it fully, and place it in a constant-temperature oven for hydrothermal reaction at 120 °C for 12 h. After the hydrothermal reaction is completed, wait for the hydrothermal reactor to cool to room temperature, then centrifuge at a speed of 5000 rpm for solid-liquid separation; then wash the separated solid powder with water twice and ethanol twice in sequence, place it in a vacuum drying oven, and conduct vacuum drying at 70 °C for 12 h to obtain the catalyst precursor Pt-TiO2(R).

[0066] Place the obtained solid powder precursor Pt-TiO2(R) in a muffle furnace for calcination and calcine it at 500 °C for 4 h; immediately transfer the calcined product to a tubular furnace and reduce it at 450 °C for 2 h in an atmosphere of 10-20% H2 / Ar. Take out the reduced product Pt-TiO2(R)-H for standby.

[0067] As Figure 1 shown, analyze the structural characteristics of the above Pt-TiO2(R)-H. Through XRD phase analysis, Pt-TiO2(R)-H presents the rutile phase of TiO2, and at the same time, the presence of the Pt phase is not found, which proves that Pt species are highly dispersed on the surface of the TiO2(R) support; through aberration-corrected electron microscopy analysis, it can be seen that this highly dispersed Pt species exists in the form of PtO x species (9 atomic layer thickness) and single-atom Pt (Pt-O coordination number 5-6).

[0068] As Figure 3 and Figure 4 shown, combining the fitting results of the Pt L3 edge in the EXAFS spectrum and XPS Pt 4f in Pt-TiO2(R)-H, the unsaturated coordination of Pt-O proves the formation of the Pt single-atom structure and shows the valence state of Pt δ+ (0 < δ < 2). This single-atom Pt δ+ enhances the adsorption and activation of CH3OH molecules; the Pt-O-Pt coordination proves the formation of deeply embedded PtO x and shows the valence state of Pt x+ (2 < x < 4). At the same time, this structure induces the formation of the Pt-Ti coordination structure, resulting in more electrons transferring from Pt to Ti, forming an electron-rich Ti 3+ structure. This Ti 3+ enhances the adsorption and activation of H2O molecules; therefore, a bifunctional center that promotes methanol cracking of single-atom Pt δ+ and water cracking of electron-rich Ti 3+ is constructed, improving the performance of hydrogen production by methanol steam reforming.

[0069] The Pt-TiO2(R)-H catalyst is used for methanol steam reforming to produce hydrogen. The Pt-TiO2(R)-H catalyst in Example 2 is granulated to 40-60 mesh, 100 mg of the catalyst is placed in a quartz reaction tube, quartz wool is inserted into the upper and lower ends, and the reaction tube is fixed in a fixed bed reactor for methanol reforming to produce hydrogen. In the methanol steam reforming reaction, raw materials and the Pt-TiO2(R)-H catalyst are added. The raw materials are water and methanol. The conditions are: a water-to-methanol molar ratio of 2, argon as the carrier gas, an argon pressure of 0.1 MPa, a nitrogen flow rate of 50 mL / min, and a methanol mass space velocity of 6 h -1 The vaporization temperature is 150°C, the reaction temperature is 140-240°C, and after stabilizing at each temperature point for 1 hour, the tail gas is passed into a gas chromatograph to detect the components of H2, CO, CO2 and CH4 in the reformed gas.

[0070] like Figure 7 As shown in FIG. 2 , the hydrogen generation rate of the catalyst prepared in Example 2 at 240° C. is 2852 mmol H2·g Pt -1 ·h -1 .like Figure 8 As shown, the catalyst prepared in Example 2 has a CO selectivity of 4.37% at 240°C.

[0071] Example 3

[0072] The preparation method of the Pt-TiO2(R)-H catalyst of Example 3 comprises the following steps:

[0073] 2.4 g of TiO2(R) with an average particle size of 75 nm was weighed and added to the lining of a 300 ml hydrothermal reactor, wherein the lining had been pre-added with 225 ml of deionized water, with a filling degree of 75% (i.e., 75% of the total volume of the reactor lining), and the pH was adjusted to 8-9 with 0.1 mol / L NaOH; at 25°C, magnetic stirring was carried out for 1 h until the TiO2 sol was uniformly dispersed.

[0074] 4.0 ml of chloroplatinic acid solution with a Pt content of 15 mg / ml was added to the obtained TiO2 sol to make the theoretical mass fraction of Pt relative to TiO2 2.5 wt %, and magnetic stirring was continued for 2 h.

[0075] Place the inner lining of the above hydrothermal reactor into the stainless-steel outer jacket, tighten it fully, and place it in a constant-temperature oven for hydrothermal reaction at 120 °C for 12 h. After the hydrothermal reaction is completed, wait for the hydrothermal reactor to cool to room temperature, then centrifuge at a speed of 5000 rpm for solid-liquid separation; then wash the separated solid powder twice with water and twice with ethanol, place it in a vacuum drying oven, and carry out vacuum drying at 70 °C for 12 h to obtain the catalyst precursor Pt-TiO₂(R).

[0076] Place the obtained solid powder precursor Pt-TiO₂(R) in a muffle furnace for roasting and roast it at 500 °C for 4 h; immediately transfer the roasted product to a tubular furnace, and under the atmosphere of 10-20% H₂ / Ar, reduce it at 450 °C for 2 h, and take out the reduced product Pt-TiO₂(R)-H for standby.

[0077] As Figure 1 shown, by XRD phase analysis of the above catalyst Pt-TiO₂(R)-H, Pt-TiO₂(R)-H presents the rutile phase of TiO₂, and at the same time, the existence of the Pt phase is not found, which proves that Pt species are highly dispersed on the surface of the TiO₂(R) support; as Figure 2 shown in b, it can be known from the aberration-corrected electron microscopy analysis that this highly dispersed Pt species exists in the form of PtO x species (10 atomic layer thickness) and single-atom Pt (Pt-O coordination number 5-6) embedded deeply into the TiO₂(R) lattice.

[0078] As Figure 3 and Figure 4 shown, combined with the fitting results of the Pt L₃ edge in the EXAFS spectrum and XPS Pt 4f in Pt-TiO₂(R)-H, the unsaturated coordination of Pt-O proves the formation of the Pt single-atom structure and shows the valence state of Pt δ+ (0 < δ < 2), this single-atom Pt δ+ enhances the adsorption and activation of CH₃OH molecules; the Pt-O-Pt coordination proves the formation of deeply embedded PtO x and shows the valence state of Pt x+ (2 < x < 4), at the same time, this structure induces the formation of the Pt-Ti coordination structure, resulting in more electrons transferred from Pt to Ti, forming an electron-rich Ti 3+ structure, this Ti 3+ enhances the adsorption and activation of H₂O molecules; therefore, a bifunctional center that promotes methanol cracking of single-atom Pt δ+ and electron-rich Ti 3+ for water splitting is constructed, improving the performance of hydrogen production by methanol steam reforming.

[0079] The Pt-TiO2(R)-H catalyst described above was used for methanol steam reforming to produce hydrogen. The Pt-TiO2(R)-H catalyst from Example 3 was granulated to a 40-60 mesh size. 100 mg of the catalyst was placed in a quartz reaction tube, with quartz wool inserted at both ends. The tube was then fixed in a fixed-bed reactor for methanol reforming to produce hydrogen. The test conditions were: a water-to-methanol molar ratio of 2, argon as the carrier gas at an argon pressure of 0.1 MPa, a nitrogen flow rate of 50 mL / min, and a methanol mass space velocity of 3 h. -1 The vaporization temperature is 150°C, the reaction temperature is 140-240°C, and after stabilizing at each temperature point for 1 hour, the tail gas is passed into a gas chromatograph to detect the components of H2, CO, CO2 and CH4 in the reformed gas.

[0080] like Figure 9 As shown in FIG. 3 , the hydrogen generation rate of the catalyst prepared in Example 3 at 240°C is 2852 mmol H2·g Pt -1 ·h -1 .like Figure 10 As shown, the catalyst prepared in Example 3 has a CO selectivity of 5.72% at 240°C.

[0081] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0082] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a Pt-TiO2(R)-H catalyst, characterized in that: The steps include: An alkaline TiO2 sol is prepared in the lining of a hydrothermal reactor, wherein the TiO2 sol contains TiO2(R) with an average particle size of 75 to 100 nm; Adding chloroplatinic acid solution to the TiO2 sol to make the mass fraction of Pt relative to TiO2 be 1.5-2.5wt%; The hydrothermal reactor liner is placed in a stainless steel jacket and placed in a constant temperature oven for hydrothermal reaction. After the hydrothermal reaction is completed, the catalyst powder precursor Pt-TiO2(R) is obtained by centrifugation and washing, and then vacuum drying. The obtained catalyst powder precursor is placed in a muffle furnace for calcination, and then activated in a reducing atmosphere in a tube furnace to obtain Pt-TiO2(R)-H.

2. The method for preparing the Pt-TiO2(R)-H catalyst according to claim 1, wherein The preparation of alkaline TiO2 sol in the lining of the hydrothermal reactor is as follows: Add 70-240 ml of deionized water to the lining of the hydrothermal reactor, corresponding to a filling degree of 70%-80%, and then adjust the pH value of the deionized water to 8-9 with NaOH; 0.8-2.4 g of TiO2(R) with an average particle size of 75-100 nm was weighed and added to the lining of a hydrothermal reactor with a volume of 100-300 ml; after stirring at room temperature, a uniformly dispersed TiO2 sol was obtained.

3. The method for preparing the Pt-TiO2(R)-H catalyst according to claim 1, wherein The temperature of the hydrothermal reaction is 100-150° C., and the reaction time is 12-18 hours.

4. The method for preparing the Pt-TiO2(R)-H catalyst according to claim 1, wherein The muffle furnace calcination temperature is 500-600° C., and the calcination time is 4-6 hours; the reducing atmosphere is a H2 / Ar mixed gas with a volume percentage of 10-20 vol%, the activation temperature is 400-600° C., and the activation time is 2-3 hours.

5. A Pt-TiO2(R)-H catalyst, characterized in that The Pt-TiO2(R)-H catalyst is prepared using the preparation method of the Pt-TiO2(R)-H catalyst described in any one of claims 1 to 4.

6. The Pt-TiO2(R)-H catalyst according to claim 5, characterized in that The Pt species exist in two forms simultaneously, namely, PtO clusters (2 < x < 4) deeply embedded in the TiO₂(R) lattice and Pt single atoms. x Clusters (2 < x < 4) and Pt single atoms.

7. The Pt-TiO2(R)-H catalyst according to claim 6, characterized in that 2-3nm PtO x The clusters are embedded into the crystal plane of TiO2(R) with an embedding depth of 8 to 10 atomic layers.

8. The Pt-TiO2(R)-H catalyst according to claim 6, characterized in that In the form of a single Pt atom, the Pt-O coordination number is 5 to 6, and the chemical valence is Pt δ+ (0<δ<2).

9. Use of the Pt-TiO2(R)-H catalyst according to any one of claims 6 to 8 for producing hydrogen by steam reforming of methanol.

10. The use according to claim 9, characterized in that In the methanol steam reforming reaction, raw materials and the Pt-TiO2(R)-H catalyst are added, wherein the raw materials are water and methanol, and the water-to-methanol molar ratio is 2-3; the reaction pressure is 0.1-0.2 MPa; the mass space velocity of methanol is 3-9.5 h -1 .

Images