CN116230971A - Pt/WN catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a Pt/WN catalyst, a preparation method and application thereof, and relates to the technical field of electrocatalysts, wherein the preparation method comprises the steps of firstly reacting a tungsten source with ethanol to prepare W ₁₈ O ₄₉ Nanowires, then from W ₁₈ O ₄₉ The nanowire and a platinum source are used for preparing a catalyst precursor, and then the catalyst precursor is calcined at a high temperature to obtain the Pt/WN catalyst. The invention synthesizes the atomic scale Pt (Pt/WN) loaded by tungsten nitride by an immersion method for HOR reaction, compared with the atomic scale Pt (Pt/W) loaded by tungsten oxide ₁₈ O ₄₉ ) Higher quality activity is realized, and the exchange current density is improved by 5.7 times; compared with the current commercial 20% Pt/C catalyst, the method greatly reduces the use of Pt and lays a foundation for preparing the low-platinum alkaline HOR electrocatalyst with excellent performance.

Description

Pt/WN catalyst and preparation method and application thereof

Technical field:

the invention relates to the technical field of electrocatalysts, in particular to a Pt/WN catalyst and a preparation method and application thereof.

The background technology is as follows:

the hydrogen fuel cell is a power generation device capable of directly converting chemical energy of hydrogen and oxygen into electric energy, has the remarkable characteristics of no pollution, no noise, high efficiency and the like, and is recognized as an optimal power supply device for clean energy automobiles, distributed power stations and the like. The proton exchange membrane fuel cell (Proton Exchange Membrane Fuel Cell, PEMFC) is used as a high-efficiency utilization technology of the hydrogen energy fuel cell, has the advantages of quick start, low working temperature, high energy density, high energy conversion efficiency, wide application and the like, is concerned by all parties, has continuously increased research, demonstration and commercialization application investment, has great progress, and has a certain application scene at present.

However, it is known that PEMFCs have a significant problem in that a large amount of noble metal platinum (Pt) is required to be used as an electrode catalyst to improve their performance. In addition, pt is extremely poisoned by impurity gases in hydrogen such as carbon monoxide (CO) and the like, resulting in a drastic decrease in performance. Although researchers are continuously trying to replace the non-Pt materials such as transition metals, the problem of durability of the non-Pt catalyst is difficult to solve in the acidic environment of the PEMFC, which makes the PEMFC very expensive, and limits the large-scale application and commercialization development of the PEMFC.

With the exploration and development of alkaline membranes (Alkaline Exchange Membrane, AEM), and the breakthrough progress of a series of key materials and technologies such as non-noble metal catalysts in Oxygen Reduction Reactions (ORR) as cathodes under alkaline conditions, the exploration of anion exchange membrane fuel cells (Anion Exchange Membrane Fuel Cell, AEMFC) has been promoted in recent years. AEMFCs can use non-noble metals that are comparable to Pt in performance to act as cathode ORR catalysts, thereby greatly reducing the cost of manufacturing fuel cells. Meanwhile, compared with an acidic medium, the low-corrosiveness alkaline environment can effectively prolong the service lives of the catalyst, the exchange membrane and the electrode plate, and ensure the long-term working efficiency of the fuel cell. Clearly, AEMFC under alkaline conditions is more commercially competitive in the future, and as a complete fuel cell system, its operating efficiency is not only dependent on cathodic ORR performance, but is also closely related to anodic hydrogen oxidation (Hydrogen Oxidation Reaction, HOR). A number of experimental studies have shown that the anode HOR kinetics are very slow under alkaline conditions, even when the most active is usedPt is used as a catalyst, and HOR performance is still 2-3 orders of magnitude lower than in an acidic environment. Therefore, in order to achieve efficient operation of the hydrogen fuel cell, it is necessary to use a high-loading Pt/C catalyst (-0.4 mg Pt/cm) ² ) To improve anode HOR performance, which results in still higher AEMFC costs.

Obviously, developing the HOR catalyst with low cost, high activity and long service life under alkaline condition is an important foundation and key link for promoting the development of AEMFC, and has very important scientific significance and practical value for further reducing the utilization, manufacturing and use costs of hydrogen energy and promoting the popularization of the hydrogen energy.

Platinum Group Metal (PGM) catalysts have so far been considered as the most advanced alkaline medium HOR catalysts. In order to reduce the amount of these noble metals used to reduce costs and increase their catalytic activity, researchers have developed a range of Pt-based electrocatalysts of different configurations, including alloying, core-shell structures and metal loading. Among them, since the metal supported catalyst has a good dimensional adjustability for PGM, it is considered as a promising approach to ensure maximum utilization of atoms and increase the utilization of atoms. Furthermore, for metal supported catalysts, electron transfer between the support and the supported metal may have profound effects on the electronic structure of the metal active site, such as optimizing the adsorption/desorption behavior of the HOR reaction intermediate, etc. However, electron transfer between the metal active site and the substrate is difficult to regulate, often too weak or too strong, resulting in insufficient or too aggressive regulation of the localized electronic structure of the metal active site, thereby further contributing to the HOR activity. Therefore, it remains a challenge to develop metal supported electrocatalysts with moderate interfacial electron transfer and to obtain higher HOR catalytic activity.

The invention comprises the following steps:

the technical problem to be solved by the invention is to provide a tungsten nitride supported atomically dispersed platinum catalyst, a preparation method thereof and application thereof in HOR reaction, wherein the catalyst shows excellent catalytic activity and stability, has moderate electron transfer regulation and control action, avoids the aggressive regulation and control of electron transfer compared with a tungsten oxide-based platinum catalyst, provides a method for moderate regulation and control of electron transfer in the development process of the supported platinum catalyst, and provides a new thought for the exploration of energy catalysis.

The technical problems to be solved by the invention are realized by adopting the following technical scheme:

one of the purposes of the present invention is to provide a preparation method of Pt/WN catalyst, which comprises the steps of firstly reacting a tungsten source with ethanol to prepare W ₁₈ O ₄₉ Nanowires, then from W ₁₈ O ₄₉ The nanowire and a platinum source are used for preparing a catalyst precursor, and then the catalyst precursor is calcined at a high temperature to obtain the Pt/WN catalyst.

It is a second object of the present invention to provide a Pt/WN catalyst obtained according to the aforementioned preparation method.

It is a further object of the present invention to provide the use of the Pt/WN catalyst described above in HOR reactions.

The beneficial effects of the invention are as follows:

(1) The invention synthesizes the atomic scale Pt (Pt/WN) loaded by tungsten nitride by an immersion method for HOR reaction, compared with the atomic scale Pt (Pt/W) loaded by tungsten oxide ₁₈ O ₄₉ ) Higher mass activity is realized, and the exchange current density is improved by 5.7 times.

(2) The invention reveals different electron transfer of Pt between tungsten nitride and tungsten oxide carrier, thus showing that moderate electron transfer is favorable for HOR catalytic reaction, compared with tungsten oxide as substrate, the excessive electron transfer between Pt and Pt does not promote HOR catalytic activity, and Pt and tungsten nitride have moderate electron transfer regulation, thereby optimizing reaction process and finally improving HOR activity. Meanwhile, compared with the current commercial 20% Pt/C catalyst, the method greatly reduces the use of Pt and lays a foundation for preparing the low-platinum alkaline HOR electrocatalyst with excellent performance.

Description of the drawings:

FIG. 1 shows Pt/WN and Pt/W ₁₈ O ₄₉ The preparation flow diagram (a), the XRD spectrum (b) of Pt/WN-700 ℃ and WN, the Pt/W ₁₈ O ₄₉ 、W ₁₈ O ₄₉ XRD pattern (c) of (a); pt/WN-700 ℃, pt/W ₁₈ O ₄₉ XPS spectrum of Pt/C (d);

FIG. 2 shows XRD patterns (a) and TEM patterns (b, c) of Pt/WN-600deg.C;

FIG. 3 shows XRD patterns (a) and TEM patterns (b, c) of Pt/WN-700 ℃;

FIG. 4 shows XRD patterns (a) and TEM patterns (b, c) of Pt/WN-800 ℃;

FIG. 5 shows XRD patterns (a) and TEM patterns (b, c) of Pt/WN-900 ℃;

FIG. 6 is a Pt/W ₁₈ O ₄₉ HR-TEM image (a), HAADF-STEM image (b); w (W) ₁₈ O ₄₉ A simulated atomic structure diagram (c); HR-TEM image (d), HAADF-STEM image (e) of Pt/WN-700 ℃; a simulated atomic structure diagram of WN (f); an elemental analysis map (g-j) of Pt/WN-700 ℃;

FIG. 7 is W ₁₈ O ₄₉ XRD pattern (a) and TEM pattern (b, c);

FIG. 8 is a Pt/W ₁₈ O ₄₉ Is an elemental analysis map of (a);

FIG. 9 is a graph showing electrochemical analysis results; (a) Pt/WN-700 ℃, pt/W ₁₈ O ₄₉ LSV curve of Pt/C (test conditions: electrolyte 0.1M KOH, sweep speed 1mV s) ^-1 Rotating disk electrode speed 1600 rpm); (b) Pt/WN-700 ℃, pt/W ₁₈ O ₄₉ Mass specific activity of Pt/C and electrochemical surface area normalized specific activity; (c) LSV curves at different speeds of Pt/WN; (d) kinetic analysis of the fit at different rotational speeds; (e) fitting a kinetic current density to the exchange current density; (f) Pt/WN-700 ℃ and Pt/C is coated on carbon paper to carry out long-time HOR stability test;

FIG. 10 shows Pt/WN at 700℃in saturated N ₂ Lower and saturated H ₂ Lower LSV curve;

FIG. 11 is a graph showing HOR performance test results for Pt/WN-600deg.C, pt/WN-700deg.C, pt/WN-800 deg.C, and Pt/WN-900 deg.C;

FIG. 12 shows the HOR performance test results of WN and Pt/WN.

The specific embodiment is as follows:

the invention is further described below with reference to specific embodiments and illustrations in order to make the technical means, the creation features, the achievement of the purpose and the effect of the implementation of the invention easy to understand.

The invention provides a preparation method of a Pt/WN catalyst, which comprises the steps of firstly, reacting a tungsten source with ethanol to prepare W ₁₈ O ₄₉ Nanowires, then from W ₁₈ O ₄₉ The nanowire and a platinum source are used for preparing a catalyst precursor, and then the catalyst precursor is calcined at a high temperature to obtain the Pt/WN catalyst.

Preferably, the tungsten source is tungsten hexachloride.

Preferably, the reaction temperature of the tungsten source and ethanol is 160-180 ℃ and the reaction time is 16-24 h.

Preferably, the platinum source is at least one of chloroplatinic acid, potassium chloroplatinate, tetraammine platinum nitrate and potassium chloroplatinate. Similar platinum-containing compounds may also be employed as the platinum source.

Preferably, the W ₁₈ O ₄₉ The mass ratio of the nanowire to the platinum in the platinum source is 100 (2-5).

Preferably, the high temperature calcination is at NH ₃ In an atmosphere.

Preferably, the high-temperature calcination temperature is 600-900 ℃ and the time is 2-3 h.

The invention provides a Pt/WN catalyst obtained by the preparation method.

The invention also provides application of the Pt/WN catalyst in HOR reaction.

Example 1

1、W ₁₈ O ₄₉ Preparation of nanowires

First, 600mg WCl was used ₆ Dissolving in 120mL of ethanol, and stirring to form uniform golden yellow solution; then transferring the solution into a stainless steel autoclave with polytetrafluoroethylene lining, reacting for 16 hours at the constant temperature of 180 ℃, cooling, washing for several times by ethanol, drying in a baking oven at 60 ℃ to obtain W ₁₈ O ₄₉ A nanowire.

2. Preparation of Pt/WN catalyst

100mg W is taken ₁₈ O ₄₉ Adding the nanowire into 30mL of deionized water, stirring and carrying out ultrasonic treatment for 30min to obtain W ₁₈ O ₄₉ A dispersion; and then to W ₁₈ O ₄₉ 4mL of H at a concentration of 1mg/mL was added to the dispersion ₂ PtCl ₆ Stirring the aqueous solution at a constant temperature of 60 ℃ until the water is evaporated to dryness to obtain a catalyst precursor; the catalyst precursor is then subjected to NH at 700 DEG C ₃ Calcining for 2h in the atmosphere to obtain Pt/WN-700 ℃.

Example 2

The calcination temperature of the catalyst precursor was adjusted to 600℃and the rest of the preparation procedure was the same as in example 1, giving Pt/WN-600 ℃.

Example 3

The calcination temperature of the catalyst precursor was adjusted to 800℃and the rest of the preparation procedure was the same as in example 1, giving Pt/WN-800 ℃.

Example 4

The calcination temperature of the catalyst precursor was adjusted to 900℃and the rest of the preparation steps were the same as in example 1, yielding Pt/WN-900 ℃.

Comparative example 1

Replacement of the calcination atmosphere of the catalyst precursor with 5% H ₂ Ar, calcination temperature was adjusted to 300℃and the other preparation steps were the same as in example 1 to obtain Pt/W ₁₈ O ₄₉ 。

Comparative example 2

Preparation of W according to the procedure of example 1 ₁₈ O ₄₉ I.e. W ₁₈ O ₄₉ A nanowire.

Comparative example 3

Directly W prepared in example 1 ₁₈ O ₄₉ NH of nanowires at 700 DEG C ₃ Calcining for 2h in the atmosphere to obtain WN.

Comparative example 4

Pt/C is commercially available with a Pt content of 20% wt.

The catalysts prepared in the above examples and comparative examples were subjected to structural characterization and performance testing.

Pt/WN and Pt/W ₁₈ O ₄₉ As shown in FIG. 1a, pt is first immobilized on solvothermal W by impregnation ₁₈ O ₄₉ On nanowires, then on NH ₃ Calcining under atmosphere to obtain Pt/WN, and calcining under H ₂ Calcining under Ar atmosphere to obtain Pt/W ₁₈ O ₄₉ . As shown in FIG. 1b, pt/WN diffracts with pure WN (JPCDS No. 75-1012)The peaks are the same, without any peak associated with Pt particles, because the loading of Pt is lower and large particles of Pt are not formed by aggregation. Also Pt/W ₁₈ O ₄₉ No Pt peak was observed in the XRD pattern of (c) (fig. 1). As shown in FIG. 1d, pt/W ₁₈ O ₄₉ Pt 4f XPS spectra of Pt/WN and Pt/C, the Pt/C is a commercial catalyst, and the binding energy of the XPS peak of Pt is relatively fixed (71.5 eV and 74.8eV correspond to Pt respectively ⁰ 4f _7/2 And Pt (Pt) ⁰ 4f _5/2 ) The method comprises the steps of carrying out a first treatment on the surface of the The binding energy in Pt/WN is slightly negative shifted by 0.1eV compared to Pt/C, indicating a certain degree of transfer of electrons from WN to Pt; however Pt/W ₁₈ O ₄₉ Compared with Pt/C, the negative displacement of 0.3eV appears, which indicates that more electrons are transferred, and moderate electron transfer is beneficial to HOR catalytic activity corresponding to the subsequent electrochemical test, while Pt/W ₁₈ O ₄₉ The stronger electron transfer in (3) is instead detrimental to HOR catalytic activity.

As shown in fig. 2 to 5, the prepared Pt/WN material structures all conform to the standard card number of WN at the calcination conditions of 600 ℃, 700 ℃, 800 ℃ and 900 ℃, and no diffraction peak of Pt occurs due to the low Pt characteristic; and the appearance and the structure are basically consistent.

As shown in FIGS. 6a and 6b, pt/W ₁₈ O ₄₉ Has the morphological characteristics of the nano wire. W can be clearly observed in FIG. 6a ₁₈ O ₄₉ The (010) plane of (c) corresponds to a lattice spacing of 0.38nm, and no lattice fringes of Pt Nanoparticles (NPs) were observed. As shown in FIGS. 6b and 6c, pt/W ₁₈ O ₄₉ And W ₁₈ O ₄₉ The theoretical crystal structure of (a) is identical, and Pt clusters (yellow circles in FIG. 6 b) are dispersed in W on an atomic scale ₁₈ O ₄₉ A nanowire surface. As shown in FIGS. 6d and 6e, pt/WN and Pt/W ₁₈ O ₄₉ Is similar in morphology and structure and is a nanowire. The lattice spacing corresponding to the (111) plane of WN was clearly observed to be 0.24nm in fig. 6d, and no Pt lattice was observed. As shown in fig. 6e and 6f, the lattice structure of Pt/WN is consistent with the theoretical crystal structure of WN, no platinum nanoparticles were observed in Pt/WN, but some atomic scales could be observedPlatinum clusters (yellow circles in fig. 6 e). As shown in FIGS. 6g-6j, the Pt, W and N elements are uniformly distributed throughout the Pt/WN nanowires.

As shown in FIG. 7a, the invention successfully synthesizes W ₁₈ O ₄₉ The method comprises the steps of carrying out a first treatment on the surface of the As shown in fig. 7b and 7c, W ₁₈ O ₄₉ The appearance of the nano-wires is ultrafine nano-wires.

As shown in FIG. 8, pt/W ₁₈ O ₄₉ The elemental analysis results of (a) also indicate that Pt is uniformly dispersed in W ₁₈ O ₄₉ The distribution of Pt in the nanowires exhibits the same characteristics as Pt/WN.

As shown in FIG. 9, compared to Pt/W ₁₈ O ₄₉ And Pt/C, pt/WN has excellent HOR catalytic performance, and the catalytic current density of Pt/WN is 5 times of that of Pt/C at 50mV by taking the mass specific activity of Pt as a standard, and the mass ratio of Pt is far lower than 20% Pt of Pt/C; in addition, pt/WN has higher stability, and under the same conditions, the current density of Pt/C is obviously attenuated in a long-time stability test.

As shown in fig. 10, at N ₂ Down, pt/WN has no HOR current density; at H ₂ Under normal HOR test conditions, pt/WN has a distinct polarization curve, indicating that the catalytic activity is derived entirely from H ₂ Not the oxidation of the catalyst itself.

As shown in FIG. 11, pt/WN obtained at the calcination temperature of 600 ℃, 700 ℃, 800 ℃ and 900 ℃ all had excellent HOR properties, with the highest HOR properties of Pt/WN-700 ℃.

As shown in fig. 12, the Pt/WN substrate WN does not have HOR properties, that is, the HOR activity of Pt/WN is derived from Pt.

The exchange current density and transfer coefficient (. Alpha.) were calculated by Micro-polarization and Butler-Volmer (Butler Fu Ermo) fitting, the results of which are shown in Table 1.

TABLE 1

As can be seen from Table 1, compared withPt/W ₁₈ O ₄₉ And Pt/C, pt/WN prepared by the invention has higher exchange current density and transfer coefficient.

The foregoing has shown and described the basic principles and main features of the present invention and the advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (9)

1. A preparation method of a Pt/WN catalyst is characterized by comprising the following steps: the preparation method comprises the steps of firstly, reacting a tungsten source with ethanol to prepare W ₁₈ O ₄₉ Nanowires, then from W ₁₈ O ₄₉ The nanowire and a platinum source are used for preparing a catalyst precursor, and then the catalyst precursor is calcined at a high temperature to obtain the Pt/WN catalyst.

2. The method of manufacturing according to claim 1, wherein: the tungsten source is tungsten hexachloride.

3. The method of manufacturing according to claim 1, wherein: the reaction temperature of the tungsten source and the ethanol is 160-180 ℃ and the reaction time is 16-24 h.

4. The method of manufacturing according to claim 1, wherein: the platinum source is at least one of chloroplatinic acid, potassium chloroplatinate, tetrammine platinum nitrate and potassium chloroplatinic acid.

5. The method of manufacturing according to claim 1, wherein: the W is ₁₈ O ₄₉ The mass ratio of the nanowire to the platinum in the platinum source is 100 (2-5).

6. The method of manufacturing according to claim 1, wherein: the saidHigh temperature calcination at NH ₃ In an atmosphere.

7. The method of manufacturing according to claim 1, wherein: the high-temperature calcination temperature is 600-900 ℃ and the time is 2-3 h.

8. A Pt/WN catalyst obtainable by the production process according to any one of claims 1 to 7.

9. Use of the Pt/WN catalyst of claim 8 in HOR reactions.

Images