A heterojunction PdTe / Bi2Te3 nanosheet electrocatalyst and a preparation method and application thereof

Abstract

The application relates to a heterojunction PdTe / Bi2Te3 nanometer plate electrocatalyst and a preparation method and application thereof, and the preparation method comprises the following steps: uniformly mixing a palladium salt and hydrochloric acid according to a molar ratio of 1:2 to obtain a palladium precursor solution; weighing polyvinylpyrrolidone K-30, bismuth oxide, tellurium dioxide and sodium hydroxide, placing them in ethylene glycol, stirring and dissolving at 50-90 DEG C, transferring into a polytetrafluoroethylene reaction kettle, placing into a constant-temperature air drying oven, reacting at 200-230 DEG C to obtain a product, washing the product, centrifugally separating to obtain a sample, dispersing the sample in deionized water to obtain a bismuth telluride solution; dispersing the bismuth telluride solution in deionized water, adding the palladium precursor solution at room temperature, stirring and reacting, alternately washing with anhydrous ethanol and deionized water, centrifugally separating and vacuum drying to prepare the heterojunction PdTe / Bi2Te3 nanometer plate electrocatalyst. The application has the advantages of simple process, easy operation, good repeatability, easy control of product morphology and size, and great potential in industrial production.

Description

Technical Field

[0001] This invention belongs to the field of ethylene glycol fuel cells, and specifically relates to a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst, its preparation method, and its application. Background Technology

[0002] Direct alcohol fuel cells, which convert chemical energy into electrical energy, are potential energy conversion devices. Among various liquid alcohol fuels, ethylene glycol is widely considered a promising candidate for direct alcohol fuel cells due to its advantages such as low toxicity, low volatility, and higher theoretical energy density. To realize the large-scale commercial application of alkaline direct ethylene glycol fuel cells, the design of highly efficient catalysts is essential.

[0003] Noble metal Pt has been widely studied as an electrocatalyst for EGOR due to its inherently high activity. However, Pt catalysts still suffer from drawbacks such as high cost and poor durability. Therefore, exploring a suitable Pt alternative is crucial for the development of fuel cells. Among other materials, Pd, with its inherent electroactive properties, has been extensively studied and explored as an electrode material for the electrocatalytic oxidation of alcohols, especially in EGOR. However, due to its unfavorable electronic structure, single-metal Pd exhibits relatively low electrocatalytic performance. Therefore, rationally adjusting the electronic structure of Pd is very important for improving its electrocatalytic performance. Due to the synergistic effects between metals (geometric and electronic effects), alloying Pd with transition metals has become the preferred method for enhancing catalyst performance.

[0004] Reports indicate that certain Pd hybridization interactions between Pd and Group O elements can exhibit excellent electrocatalytic properties. The presence of Te in metal tellurides can improve the utilization rate of the noble metal Pd, alter the electronic structure of the electrocatalyst, promote reaction kinetics, and enhance resistance to CO poisoning, thus demonstrating high catalytic performance in EGOR. Inspired by this, constructing Pd-based catalysts with two-dimensional heterostructures can provide a good structural basis for improving catalytic performance, mainly due to structural advantages such as large surface area and the inherent anisotropy of layered structures. Furthermore, Pd hybridization interactions between Pd and O heteroatoms are also a feasible approach to improve the electronic structure of Pd to achieve efficient EGOR electrocatalysis.

[0005] Currently, noble metal particles are mainly synthesized using methods such as template method, electrodeposition method, and chemical reduction method. Template method generally requires template preparation and removal, and the template removal process can easily damage the particle morphology, making the process cumbersome and complex. Electrodeposition method produces relatively large noble metal particles, typically in the micrometer or micro / nanoscale, and the process is difficult to control, resulting in poor reproducibility. In contrast, chemical reduction method is simple, easy to operate, and the product morphology and size are easily controlled, with good reproducibility, especially the one-step synthesis method at lower temperatures, which has significant advantages. Therefore, this study uses a simple chemical reduction method at lower temperatures to prepare platinum-based nanocatalysts with various morphologies, and modulates the product morphology or size by adjusting process parameters. This provides a reference for simplifying the preparation process and controlling the shape and properties of other noble metal nanoparticles.

[0006] However, the current chemical reduction method still has drawbacks such as high cost, low palladium utilization, and lack of environmental friendliness and stability (surfactants are generally required in the preparation process). Summary of the Invention

[0007] In view of this, the purpose of this invention is to overcome the shortcomings of the prior art and provide a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst, its preparation method and application, which can obtain a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst with low cost, high palladium utilization efficiency and environmental stability.

[0008] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: A method for preparing a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst, comprising: S1, Palladium salt and hydrochloric acid are mixed evenly at a molar ratio of 1:2 to obtain a palladium precursor solution; S2, weigh polyvinylpyrrolidone K-30, bismuth oxide, tellurium dioxide and sodium hydroxide and place them in ethylene glycol. Stir and dissolve at 50-90℃, transfer to polytetrafluoroethylene reaction vessel, place in constant temperature forced air drying oven, react at 200-230℃ to obtain product, wash the product and centrifuge to obtain sample, disperse the sample in deionized water to obtain bismuth telluride solution; S3, the bismuth telluride solution was dispersed in deionized water, and a palladium precursor solution was added at room temperature. After stirring and reacting, the mixture was washed alternately with anhydrous ethanol and deionized water, centrifuged, and then vacuum dried to obtain a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst.

[0009] Preferably, the palladium salt is one or more of sodium tetrachloropalladium, palladium chloride, potassium hexachloropalladium, and potassium chloride palladium.

[0010] Preferably, in step S1, the molar concentration of the palladium precursor solution is 10-100 mmol / L.

[0011] Preferably, in step S2, the mass ratio of polyvinylpyrrolidone K-30, bismuth oxide, tellurium dioxide, and sodium hydroxide is 40:23:23.9:80; and the concentration of the bismuth telluride solution is 5-200 mg / mL.

[0012] Preferably, in step S2, the reaction time is 4 hours at 200-230°C; the stirring time is 30 minutes at 50-90°C; and the product is washed with alternating acetone and anhydrous ethanol.

[0013] Preferably, in step S3, the volume ratio of the bismuth telluride solution, deionized water, and palladium precursor solution is 2:50:0.4-1.2.

[0014] Preferably, in step S3, the stirring time is 5-6 min, the room temperature is 20-25℃, and the centrifugation conditions are: 7000-8000 rpm and 10 min.

[0015] This invention also provides a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst, which is prepared by the preparation method described above.

[0016] This invention also provides an application of the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst described above in the ethylene glycol oxidation reaction.

[0017] In this invention, considering that the amount of precursor solution added and the synthesis time are closely related to the structure and distribution of active sites in the catalyst in the Pd-based ethylene glycol oxidation catalytic system, thus significantly affecting its EGOR performance, this invention utilizes partial reduction etching and ion exchange. The rough surface and pores increase the contact frequency with the catalytic active sites, and the catalyst exhibits good dispersion and uniformity of its components. Furthermore, the strong p-hybridization interaction between Pd and Te, and the interaction between PdTe and Bi₂Te₃, can reduce the d-band center, fundamentally alleviating the binding strength of intermediates during the reaction, effectively promoting the oxidation of EGOR intermediates, and thus greatly improving the electrocatalytic performance of the catalyst for ethylene glycol oxidation. This electrocatalyst also exhibits better electrochemical stability and methanol resistance than commercial Pd / C catalysts.

[0018] Furthermore, compared to the traditional tellurization process, which is complex, time-consuming, and involves surfactants, this invention only requires a simple liquid-phase mixing process to synthesize sheet-like PdTe / Bi2Te3 nanoplate electrocatalysts in one step and in a short time. The entire process is simple, easy to operate, has good repeatability, and the morphology and size of the product are easy to control, which has great potential for industrial production.

[0019] Finally, considering green and sustainable chemistry, the entire process of this invention is surfactant-free, making it more energy-efficient and beneficial than traditional processes. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the process for preparing the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst in Example 1; Figure 2 X-ray diffraction patterns of Bi2Te3 nanoplate seeds and PdTe / Bi2Te3 nanoplate electrocatalyst prepared in Example 1; Figure 3 SEM and TEM images of the Bi2Te3 nanoplate seeds prepared in Example 1; Figure 4 The elemental surface scan and thickness distribution of the Bi2Te3 nanoplate seeds prepared in Example 1 are shown in the image. Figure 5 SEM and TEM images of the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst prepared in Example 1; Figure 6 The elemental surface scan and thickness distribution of the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst prepared in Example 1 are shown in the image. Figure 7 Cyclic voltammetry curves of the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst prepared in Example 1 and the commercial Pd / C catalyst in 1 MKOH + 1 MEG solution; Figure 8 The graph shows the multi-cycle cyclic voltammetry durability test of the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst prepared in Example 1 in 1 M KOH + 1 M EG solution. Figure 9The graph shows the multi-cycle cyclic voltammetry durability test of a commercial Pd / C catalyst in a 1 M KOH + 1 M EG solution. Figure 10 Chronoamperometry curves of the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst prepared in Example 1 and the commercial Pd / C catalyst at 0.85 V vs RHE in 1M KOH + 1 MEG solution. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: First, the preparation method of Bi2Te3 nanoplate seeds is described, which is carried out according to the following steps: S101, after mixing palladium salt and hydrochloric acid at a molar ratio of 1:2, a palladium precursor solution is obtained with a molar concentration of 100 mmol / L.

[0024] Sodium tetrachloropalladium can be selected as the palladium salt.

[0025] S102: Weigh 400 mg of polyvinylpyrrolidone K-30, 230 mg of bismuth oxide, 239 mg of tellurium dioxide, and 800 mg of sodium hydroxide into 40 mL of ethylene glycol. Stir and dissolve at 80 °C for 30 min. Transfer to a 50 mL polytetrafluoroethylene reactor and place in a constant temperature drying oven. React at 210 °C for 4 h. Wash the product alternately with acetone and anhydrous ethanol. After centrifugation, disperse the sample in 20 mL of deionized water to obtain a bismuth telluride solution with a concentration of 20 mg / mL, i.e., Bi2Te3 nanoplate seeds.

[0026] Then, a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst for the electrocatalytic oxidation of ethylene glycol was prepared based on Bi2Te3 nanoplate seeds, following the steps below: S103, refer to Figure 1 Take 2 mL of the bismuth telluride solution prepared above and disperse it in 50 mL of deionized water. Add 0.8 mL of the palladium precursor solution under stirring at room temperature. After stirring for 5 min, wash the mixture alternately with anhydrous ethanol and deionized water, centrifuge, and then vacuum dry to obtain the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst.

[0027] The properties of the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst prepared in Example 1 were then tested.

[0028] First, the obtained heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst was loaded onto conductive carbon black, and then onto a rotating disk electrode. Cyclic voltammetry (vs. RHE) was recorded from 0.1 to 1.3 V in N2-saturated 1.0 M KOH solution or 1.0 M KOH + 1.0 M ethylene glycol solution at a rate of 50 mV s⁻¹. Chronoamperometry (CA) testing was performed in 1.0 M KOH + 1.0 MEG solution at a constant potential of 0.91 V (vs. RHE) for 5000 s, and the catalytic activity was recalculated to evaluate the catalyst's stability. To analyze the duration of catalyst stability, continuous CV was performed for 400 cycles in 1.0 M KOH + 1.0 MEG solution at a scan rate of 50 mV·s⁻¹. All catalyst impedance tests in this experiment were conducted in a 1.0 M KOH + 1.0 M EG solution at a test potential of 0.8 V and a test frequency range of 0.1 Hz to 100 kHz. For comparison, a commercially available Pd / C catalyst (20 wt.% Pd) was used as the control catalyst.

[0029] like Figure 2 As shown, XRD results indicate that Bi2Te3 nanoplate seeds and PdTe / Bi2Te3 nanoplate electrocatalysts were successfully prepared in Example 1. Figure 3 and Figure 4 The prepared Bi2Te3 nanoplate seeds are shown to have a hexagonal disk structure with a thickness of about 15 nm.

[0030] Figure 5 and Figure 6 The prepared PdTe / Bi₂Te₃ heterostructure also exhibits a hexagonal disk structure. However, due to the reducing etching effect on the seed, the heterostructure synthesized on the seed surface suffers from discontinuous lattices formed by the significant dissolution of Te and Bi, potentially leading to the formation of Te vacancies. Furthermore, the nanosheets exhibit abundant micropores / mesopores, and the thickness of the nanodisks becomes approximately 10 nm. These porous structures typically increase the ECSA of the catalyst and provide abundant unsaturated coordination atomic sites and good mass transfer, exposing more active centers and thus enhancing catalytic activity.

[0031] Figure 7The CV curves of different catalysts in 1.0 M KOH + 1.0 M EG solution are shown. The catalysts produce two distinct ethylene glycol oxidation peaks, and the PdTe / Bi2Te3 catalysts all exhibit higher peak currents than the commercial Pd / C catalysts, indicating that they have better anodic electro-oxidation activity. Therefore, the heterojunction catalyst is the optimal choice.

[0032] Figure 8 and Figure 9 The CVs (catalyst dynamics) of PdTe / Bi₂Te₃ and commercial Pd / C catalysts in 1.0 M KOH + 1.0 MEG solution were presented from the start of EGOR to 400 cycles. With increasing CV cycle number, the peak current density gradually decreased, but the rate of decrease for PdTe / Bi₂Te₃ / C was significantly lower than that for commercial Pd / C. After 400 cycles, PdTe / Bi₂Te₃ / C retained a high mass activity of 8.23 ​​A mgPd. -1 It is 5.5 times higher than the original commercial Pd / C catalyst, with an activity decay rate of 25.1% (0.9 VRHE), which is far superior to commercial Pd / C (82.5%), showing that PdTe / Bi2Te3 / C has better EGOR durability.

[0033] Figure 10 The it curves for PdTe / Bi2Te3 / C and Pd / C at 0.85 V show that PdTe / Bi2Te3 / C exhibits a higher initial current density than Pd / C, indicating a greater number of active sites on the catalyst surface. The current decay observed in the it curves can be attributed to the accumulation of toxic intermediates; PdTe / Bi2Te3 / C decays more slowly than Pd / C, demonstrating better resistance to poisoning. After 5000 s, PdTe / Bi2Te3 / C retains some activity, while commercial Pd / C is almost completely deactivated, further demonstrating the significant electrochemical stability of this example.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst, characterized in that, include: S1, Palladium salt and hydrochloric acid are mixed evenly at a molar ratio of 1:2 to obtain a palladium precursor solution; S2, weigh polyvinylpyrrolidone K-30, bismuth oxide, tellurium dioxide and sodium hydroxide and place them in ethylene glycol. Stir and dissolve at 50-90℃, transfer to polytetrafluoroethylene reaction vessel, place in constant temperature forced air drying oven, react at 200-230℃ to obtain product, wash the product and centrifuge to obtain sample, disperse the sample in deionized water to obtain bismuth telluride solution; S3, the bismuth telluride solution was dispersed in deionized water, and a palladium precursor solution was added at room temperature. After stirring and reacting, the mixture was washed alternately with anhydrous ethanol and deionized water, centrifuged, and then vacuum dried to obtain a heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst.

2. The preparation method according to claim 1, characterized in that, The palladium salt is one or more of sodium tetrachloropalladium, palladium chloride, potassium hexachloropalladium, and potassium chloride palladium.

3. The preparation method according to claim 1, characterized in that, In step S1, the molar concentration of the palladium precursor solution is 10-100 mmol / L.

4. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of polyvinylpyrrolidone K-30, bismuth oxide, tellurium dioxide, and sodium hydroxide is 40:23:23.9:80; the concentration of the bismuth telluride solution is 5-200 mg / mL.

5. The preparation method according to claim 1, characterized in that, In step S2, the reaction time is 4 hours at 200-230℃; the stirring time is 30 minutes at 50-90℃; and the product is washed with acetone and anhydrous ethanol alternately.

6. The preparation method according to claim 1, characterized in that, In step S3, the volume ratio of the bismuth telluride solution, deionized water, and palladium precursor solution is 2:50:0.4-1.

2.

7. The preparation method according to claim 1, characterized in that, In step S3, the stirring time is 5-6 min, the room temperature is 20-25℃, and the centrifugation conditions are: 7000-8000 rpm for 10 min.

8. A heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the heterojunction PdTe / Bi2Te3 nanoplate electrocatalyst as described in claim 8 in the ethylene glycol oxidation reaction.

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