Preparation and application of a binary palladium-tin nanoalloy catalyst supported on selenium-doped MXene

Abstract

The present invention belongs to the technical field of electrocatalytic methanol oxidation, and specifically relates to the preparation and application of a binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene. The present invention first prepares selenium-doped MXene sheets by high-temperature calcination of selenium powder and MXene nanosheets, and then uses a progressive one-step electrochemical deposition method to anchor the palladium-tin nano-alloy on the selenium-doped MXene sheet to prepare a binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene. The catalyst has good conductivity and high specific surface area, and the palladium-tin nano-alloy particles are evenly distributed on the MXene, with dense active sites, which is conducive to the reaction of the gas-solid-liquid three-phase interface during the catalytic process, and is conducive to the efficient and stable operation of the catalyst, and is expected to be applied to methanol oxidation and methanol fuel cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic methanol oxidation, and specifically relates to the preparation and application of a binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene. Background Art

[0002] Sustainable development has always been an inevitable trend in the progress of human civilization. In recent years, with the increasing environmental pollution and resource depletion caused by the fossil fuel-based energy system, the demand for clean energy and renewable energy has become more urgent. Electricity has always been an efficient and environmentally friendly form of energy. Since the 1960s and 1970s, electricity has become an indispensable part of human society. From the popularity of electric vehicles to almost everyone's smartphone, the importance of electricity is self-evident. However, as a secondary energy source, the storage and conversion of electricity has always been a hot topic and focus of research. Among various energy storage technologies, electrochemical energy storage is highly valued and widely used because of its long life and high energy density. In the existing electrochemical energy storage system, lithium-ion batteries account for a large proportion. Although lithium-ion batteries are still widely used, due to the scarcity of lithium resources, limited specific energy density and safety hazards, the rechargeable battery devices that replace them are increasingly attracting people's attention.

[0003] Methanol fuel cells (DMFCs) are considered as candidates for energy systems in the electrification of electric vehicles and portable electronic products due to their advantages such as high energy density, high portability and safety. The main factors affecting the efficiency of DMFCs devices are the activity and durability of the methanol oxidation reaction (MOR) catalyst. However, the efficiency of DMFCs is far from satisfactory, mainly due to the problem of carbon monoxide poisoning during MOR. In recent years, it has been widely believed that noble metals (such as palladium and platinum) are catalysts for MOR, mainly due to their large number of active surface electronic states. However, these noble metal-based catalysts are affected by methanol intermediates. To date, studies have reported on optimizing the structure and composition of noble metal methanol oxidation catalysts, including reducing the size of the catalyst to the atomic level, anchoring the active sites on good support materials, or combining with other non-noble metals (such as Cu, Co, Ni). In general, the improvement of the catalytic activity and stability of noble metal-based nanomaterials mainly depends on the synergistic effect between the noble metal center and the additional elements. This synergistic effect can be verified by the interaction between the oxophilic metal or the coordination element and the noble metal, which is measured by the improvement of the electronic state of the active center. For example, due to the shortened Pt-Co distance, the electrocatalytic methanol oxidation activity and stability of the Pt-Co site are significantly improved, which can promote the combination of OH radicals at the Co site with methanol intermediates at the adjacent Pt site. This short-range enhancement effect and synergistic interaction are also reflected in Pt-Au and Pd-Ni bimetallic catalytic systems. However, there is still a lack of technology that can effectively improve the electrocatalytic methanol oxidation reaction activity of precious metal catalysts.

[0004] MXenes, as a class of two-dimensional transition metal carbides, nitrides or carbonitrides, have attracted great attention due to their tunable chemical activity, good electronic conductivity and unique mechanical properties. Some studies have shown that MXenes are expected to be used as support materials for fuel cell catalysts. For example, Ti 3 C 2 It has been used as an effective substrate and support for Pd, Pt nanorods and Pt-Pd bimetallic catalysts. However, there is still little technology to build highly electrocatalytic catalysts on MXene supports. Recent studies have shown that the introduction of foreign atoms into MXene can promote charge transfer, improve reaction kinetics and enhance catalytic activity. Selenium has abundant d-orbital electrons and unique electric polarizability, so it has great potential as a dopant for MXene.

[0005] In summary, it is necessary to prepare a highly electrocatalytic catalyst based on selenium-doped MXene. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a method for preparing a binary palladium-tin nanoalloy catalyst loaded on selenium-doped MXene. The prepared catalyst has good conductivity and high specific surface area. The palladium-tin nanoalloy particles are evenly distributed on the MXene, with dense active sites, excellent methanol-oxygen activity and relatively stable methanol oxidation catalytic performance.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a method for preparing a binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene, namely, firstly, selenium powder and MXene nano-sheets are calcined at high temperature to prepare selenium-doped MXene sheets, and then a progressive one-step electrochemical deposition method is used to anchor the palladium-tin nano-alloy on the selenium-doped MXene sheets, thereby synthesizing a binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene.

[0009] Preferably, the MXene nanosheet is Ti 3 C 2 Nanosheets.

[0010] Preferably, the high temperature calcination temperature is 150-300°C, the time is 5-7h, and the heating rate is 2-4°C / min.

[0011] Preferably, the mass ratio of the selenium powder to the MXene nanosheets is 10:1-3.

[0012] Preferably, the specific method of anchoring the palladium-tin nanoalloy on the selenium-doped MXene sheet by the progressive one-step electrochemical deposition method is as follows: using a standard three-electrode measurement system, the selenium-doped MXene nanosheet is loaded onto a glassy carbon electrode, the electrolyte used contains 0.1M KOH and 200-400μM palladium-tin metal precursor, and a deposition potential of 0.1V to -0.4V is used for 25-45 scan cycles with a scan rate of 4-6mV / s.

[0013] More preferably, the metal precursor comprises Pd(OCOCH 3 ) 2 and M SnCl 2 , the Pd(OCOCH 3 ) 2 and SnCl 2 The molar concentration ratio is 2:1.

[0014] Preferably, the selenium powder and MXene nanosheets are ball-milled at a speed of 300-400 rpm for 2-4 h before high-temperature calcination.

[0015] The present invention also provides a binary palladium-tin nano alloy catalyst supported on selenium-doped MXene prepared by the above preparation method.

[0016] The present invention also provides the use of the above-mentioned binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene in methanol oxidation catalysis.

[0017] The present invention also provides a methanol fuel cell, characterized in that the methanol fuel cell comprises the above-mentioned binary palladium-tin nanoalloy catalyst supported on selenium-doped MXene.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention discloses a method for preparing a binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene, wherein selenium powder and MXene nano-sheets are first calcined at high temperature to prepare selenium-doped MXene sheets, and then the palladium-tin nano-alloy is anchored on the selenium-doped MXene sheets by a progressive one-step electrochemical deposition method. The prepared catalyst has good conductivity and high specific surface area, and the palladium-tin nano-alloy particles are evenly distributed on the MXene, and the active sites are dense, which is conducive to the reaction of the gas-solid-liquid three-phase interface during the catalytic process, and is conducive to the efficient and stable operation of the catalyst. At the same time, through selenium doping, the oxidation of MXene can be effectively inhibited, and the evenly distributed active sites of the palladium-tin metal particles are maintained, thereby showing excellent catalytic methanol oxidation characteristics, which is expected to be applied to methanol oxidation and methanol fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Transmission electron microscopy images of (a) MXene nanosheets and (b) palladium-tin nanoalloy catalysts supported on selenium-doped MXene;

[0021] Figure 2 Energy spectrum of palladium-tin nanoalloy catalyst supported on selenium-doped MXene;

[0022] Figure 3 The cyclic voltammetry curve of the palladium-tin nanoalloy catalyst supported on selenium-doped MXene in 1M sodium hydroxide and 1M methanol electrolyte;

[0023] Figure 4 This is the chronoamperometry diagram of the palladium-tin nanoalloy catalyst supported on selenium-doped MXene at a potential of 0.6 V in 1 M sodium hydroxide and 1 M methanol electrolyte. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0026] The present invention provides a method for preparing a palladium-tin nano alloy catalyst supported on selenium-doped MXene

[0027] The preparation method comprises the following steps:

[0028] (1) Selenium powder and Ti 3 C 2 The nanosheets were mixed in a mass ratio of 10:1-3 and ball-milled at a speed of 300-400 rpm for 2-4 h.

[0029] (2) The obtained mixed powder is sealed in a sealed container, heated to 150-300°C at a rate of 2-4°C / min, maintained at 150-300°C for 5-7 hours, and finally cooled naturally to room temperature to obtain selenium-doped Ti 3 C 2 Nanosheets.

[0030] (3) Using a standard three-electrode measurement system, the selenium-doped Ti 3 C 2 The nanosheets were loaded onto a glassy carbon electrode using an electrolyte containing 0.1 M KOH and 200-400 μM of a palladium tin metal precursor, which included Pd(OCOCH 3 ) 2 and SnCl 2 , using a deposition potential of 0.1 V to -0.4 V for 25-45 scan cycles (scan rate of 4-6 mV / s), and finally obtaining PdSn / Se-Ti from the cathode 3 C 2 Nanosheets, namely, palladium-tin nanoalloy catalyst supported on selenium-doped MXene.

[0031] The above method can be used to uniformly embed binary palladium-tin nanoalloy particles on selenium-doped MXene, and the catalyst particle size is nanometer-scale. Moreover, the binary palladium-tin alloy catalyst embedded on selenium-doped MXene has excellent methanol-oxygen activity and relatively stable methanol oxidation catalytic performance.

[0032] Example 1 Preparation method of palladium-tin nanoalloy catalyst supported on selenium-doped MXene

[0033] (1) Selenium powder and Ti 3 C 2 The nanosheets were mixed at a mass ratio of 10:1 and ball milled at 350 rpm for 3 h.

[0034] (2) The obtained mixed powder is sealed in a sealed container, heated to 200°C at a rate of 3°C / min, maintained at 200°C for 6 hours, and finally cooled naturally to room temperature to obtain selenium-doped Ti 3 C 2 Nanosheets.

[0035] (3) Using a standard three-electrode measurement system, the selenium-doped Ti 3 C 2 The nanosheets were loaded onto a glassy carbon electrode using an electrolyte containing 0.1 M KOH and 300 μM metal precursors including 200 μM Pd(OCOCH 3 ) 2 and 100 μM SnCl 2 , using a deposition potential of 0.1 V to -0.4 V for 30 scan cycles (scan rate of 5 mV / s), and finally obtaining PdSn / Se-Ti from the cathode 3 C 2 After nanosheet deposition, the electrode was washed with deionized water.

[0036] Figure 1 The sample synthesized in this example (PdSn / Se-Ti 3 C 2 ), the two-dimensional structure in the figure is MXene, palladium-tin nanoalloy is evenly embedded in the tin-doped MXene, the catalyst particle size is nanoscale, the particle radius is about 9nm, and the reaction active sites are better and more evenly exposed on the MXene.

[0037] Figure 2 The sample synthesized in this example (PdSn / Se-Ti 3 C 2 ) spectrum, it can be seen that palladium atoms and tin atoms are evenly distributed on Ti 3 C 2 At the same time, the doping of selenium atoms is beneficial to regulating the stability of MXene materials during the catalytic reaction.

[0038] Example 2 Catalytic activity of methanol oxidation of palladium-tin nanoalloy catalyst supported on selenium-doped MXene

[0039] A three-electrode configuration was selected, with the reference electrode being Ag / AgCl, the counter electrode being graphite, and the catalyst (PdSn / Se-Ti 3 C 2 The glassy carbon electrode (Pd / C) was used as the working electrode; the test was carried out in an electrolyte of 1 M sodium hydroxide and 1 M methanol at a scan rate of 20 mV+s -1 .

[0040] Figure 3 For the sample PdSn / Se-Ti 3 C 2 The electrochemical polarization curve of methanol oxidation reaction shows that the turn-on potential and methanol oxidation current are much larger than those of commercial Pd / C electrode. Figure 4 PdSn / Se-Ti 3 C 2 The samples were tested by chronoamperovoltammetry for MOR activity and durability. During the whole measurement process, the PdSn / Se-Ti 3 C 2 The methanol oxidation current of Pd / C is greater than that of Pd / C, and the maximum current density per unit area of ​​methanol oxidation is 95.8 mA / cm 2 , indicating that compared with commercial Pd / C, PdSn / Se-Ti 3 C 2 The above results demonstrate that the enhanced electronic interaction between metal crystals and Se-doped MXene supports and the optimized distribution of Pd-Sn active sites can adjust the d-band center, reduce the adsorption energy of CO active intermediates on Pd sites, and enhance the generation of OH active intermediates on Sn sites, thereby improving the reaction activity of methanol oxidation.

[0041] At the same time, the binary palladium-tin alloy catalyst on the selenium-doped MXene has good stable methanol oxidation catalytic performance. The stability test under the bias voltage of 0.6V (vs.RHE) exceeded 10000s, and the current density decayed by only 12% ( Figure 4 ).

[0042] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A binary palladium-tin nanoalloy catalyst supported on selenium-doped MXene for methanol oxidation catalysis. It is characterized in that The preparation method of the binary palladium-tin nano alloy catalyst is as follows: firstly, selenium powder and MXene nano sheets are calcined at high temperature to prepare selenium-doped MXene sheets, and then the palladium-tin nano alloy is anchored on the selenium-doped MXene sheets by a progressive one-step electrochemical deposition method, thereby synthesizing a binary palladium-tin nano alloy catalyst supported on the selenium-doped MXene; the MXene nano sheet is Ti 3 C 2 Nanosheets.

2. A binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene for methanol oxidation catalysis according to claim 1, It is characterized in that The high temperature calcination temperature is 150-300°C, the time is 5-7 h, and the heating rate is 2-4°C / min.

3. The binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene for methanol oxidation catalysis according to claim 1, It is characterized in that The mass ratio of the selenium powder to the MXene nanosheets is 10:1-3.

4. The binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene for methanol oxidation catalysis according to claim 1, It is characterized in that The specific method of anchoring palladium-tin nanoalloy on selenium-doped MXene sheets using a progressive one-step electrochemical deposition method is as follows: using a standard three-electrode measurement system, the selenium-doped MXene nanosheets are loaded onto a glassy carbon electrode. The electrolyte used contains 0.1 M KOH and 200-400 μM palladium-tin metal precursor. A deposition potential of 0.1 V to -0.4 V is used for 25-45 scan cycles with a scan rate of 4-6 mV / s.

5. The binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene for methanol oxidation catalysis according to claim 4, It is characterized in that The metal precursor includes Pd(OCOCH 3 ) 2 and SnCl 2 , the Pd(OCOCH 3 ) 2 and SnCl 2 The molar concentration ratio is 2:

1.

6. The binary palladium-tin nano-alloy catalyst supported on selenium-doped MXene for methanol oxidation catalysis according to claim 1, It is characterized in that The selenium powder and MXene nanosheets are ball-milled at a speed of 300-400 rpm for 2-4 h before high-temperature calcination.

7. A methanol fuel cell, It is characterized in that The methanol fuel cell comprises the binary palladium-tin nano-alloy catalyst supported on the selenium-doped MXene as described in any one of claims 1-6.

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