Bismuth-based electro-catalytic nano material with adjustable crystallinity as well as preparation method and application of bismuth-based electro-catalytic nano material

Abstract

The invention provides a crystallinity-adjustable bismuth-based electro-catalytic nano material and a preparation method and application thereof, and belongs to the technical field of new energy nano materials, the nano material is formed by integrating an amorphous structure and a crystalline structure on bismuth nano particles at the same time, and the expression is a / c-Bi NPs. According to the bismuth nano-particles, oxygen activation is effectively promoted, and the adsorption energy of a key reaction intermediate on the surface of an a / c-Bi NPs catalyst is regulated and controlled, so that the selectivity and the conversion rate of an electrocatalytic reduction oxygen reaction on hydrogen peroxide are improved, and an effective thought is provided for design and application of bismuth-based electrocatalysis with adjustable crystallinity.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy nanomaterials, and in particular to a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity, and a preparation method and application thereof. Background Art

[0002] The transformation of energy structure is a core issue supporting the sustainable development of the economy and society. The development of electrochemical hydrogen peroxide synthesis technology to replace traditional high-carbon processes has become a key breakthrough in building a new energy system. As an important chemical that combines the functions of an oxidant and an energy carrier, hydrogen peroxide has unique advantages in environmental remediation, medical disinfection, green chemical synthesis and other fields. Its hydrogen mass density and unit calorific value are significantly better than those of pure hydrogen systems, and it has important potential in the storage and transportation of renewable energy. Green electricity-driven electrochemical oxygen reduction can generate hydrogen peroxide through direct electrocatalytic conversion of water and oxygen, and is expected to form a closed link of "renewable electricity-clean production-low-carbon application". Therefore, the development of efficient and low-cost hydrogen peroxide electrosynthesis technology is not only an inevitable choice for reconstructing chemical production from the source, but also an important hub for realizing a new energy system.

[0003] However, most catalysts exhibit low selectivity and current density. The performance of electrocatalytic oxygen reduction depends largely on the microelectronic structure of the catalyst, which can be effectively regulated by crystal engineering. Introducing different crystallinity in Bi nanoparticles is an effective method for preparing hydrogen peroxide, because adjusting the crystallinity can obtain amorphous / crystalline interfaces as highly active centers. However, previous studies generally used electrochemical in situ reduction, which is relatively complicated to operate and has no effect on regulating crystallinity, which is not conducive to industrialization. Therefore, the synthesis of new bismuth-based catalysts with high selectivity, multifunctionality, high stability and low cost for electrocatalytic oxygen reduction to produce hydrogen peroxide remains a challenging and important topic. Summary of the invention

[0004] The purpose of the present invention is to provide a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity, and a preparation method and application thereof, so as to solve the technical problem that most current reduction-to-hydrogen peroxide electrocatalysts exhibit low selectivity and current density.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A bismuth-based electrocatalytic nanomaterial with adjustable crystallinity, wherein the nanomaterial is a bismuth nanoparticle in which an amorphous structure and a crystalline structure are simultaneously integrated. The expression is a / c-Bi NPs.

[0007] A method for preparing a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity comprises the following steps: preparing a bismuth oxycarbonate precursor, reducing the precursor with sodium borohydride, and inducing synthesis of bismuth nanoparticles with different crystallinities under different concentrations of a dispersant, polyvinyl pyrrolidone.

[0008] Furthermore, in the preparation of the bismuth oxycarbonate precursor, bismuth citrate is used as a bismuth source, sodium carbonate is used as a precipitant, and the bismuth oxycarbonate precursor is synthesized by a hydrothermal method.

[0009] Furthermore, the synthesized bismuth oxycarbonate is used as a precursor and sodium borohydride is used as a reducing agent, and the concentration of the dispersant polyvinyl pyrrolidone is controlled to induce the synthesis of bismuth nanoparticles with different crystallinity.

[0010] Furthermore, bismuth citrate and sodium carbonate are dissolved in deionized water and magnetically stirred until completely dissolved, and then the mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel autoclave, which is sealed for high-temperature reaction. After the autoclave is cooled to room temperature, the precipitate is collected by filtration, washed with deionized water and anhydrous ethanol respectively, and then vacuum dried to obtain the product.

[0011] Furthermore, the magnetic stirring temperature was room temperature, the rotation speed was 600RPM, the stirring time was 60min, the polytetrafluoroethylene lining was 100mL, the sealed high temperature reaction condition temperature was 180°C, the time was 24h, it was washed 4 times respectively, and the vacuum drying condition temperature was 70°C, the time was 12h.

[0012] Furthermore, polypyrrolidone and bismuth oxycarbonate precursor are dispersed in deionized water to form solution A, sodium borohydride is added to deionized water to prepare solution B, and then solution B is added dropwise to solution A to obtain solution C, and magnetic stirring is performed until solution C turns black. Solution A of different concentrations is used, and the collected solid product is vacuum dried to obtain.

[0013] Furthermore, the magnetic stirring temperature was room temperature, the rotation speed was 600 RPM, the stirring time was 4 h, the vacuum drying conditions were temperature 40° C. and time was 1 h, and the different concentrations of solution A were 0 mol / L, 0.04 mol / L, and 0.1 mol / L, respectively.

[0014] An application of a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity, wherein the nanomaterial is used as an electrocatalyst for electrocatalytic reduction of oxygen.

[0015] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0016] (1) The present invention belongs to a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity, which has a uniformly dispersed nanoparticle structure. The bismuth-based electrocatalyst with adjustable crystallinity can be used for electrocatalytic reduction of oxygen, and it exhibits high selectivity and high current density for hydrogen peroxide under a wide potential window. It is an electrocatalytic material that meets the needs of "carbon neutrality" sustainable development and new energy, and has great research value in the context of "carbon neutrality".

[0017] (2) The preparation method of the present invention uses bismuth citrate as a bismuth source and sodium carbonate as a precipitant, and adopts a hydrothermal method to synthesize a bismuth oxycarbonate precursor. The synthesized bismuth oxycarbonate is used as a precursor, sodium borohydride is used as a reducing agent, and the concentration of the dispersant polyvinyl pyrrolidone is controlled to induce the synthesis of bismuth nanoparticles with different crystallinities. Bismuth nanoparticles with different crystallinities produce abundant amorphous / crystalline interfaces as highly active sites for the reaction, which effectively enhances the electrochemical performance of the catalyst.

[0018] (3) The bismuth nanoparticles of the present invention effectively promote oxygen activation and regulate the adsorption energy of key reaction intermediates on the surface of a / c-Bi NPs catalyst, thereby improving the selectivity and conversion rate of hydrogen peroxide in the electrocatalytic reduction of oxygen reaction, which provides an effective idea for the design and application of bismuth-based electrocatalysis with adjustable crystallinity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is an X-ray powder diffraction spectrum of Bi NPs electrocatalytic nanomaterials with different crystallinity prepared in embodiment 1 of the present invention.

[0020] Figure 2 It is a scanning electron microscope image of a / c-Bi NPs electrocatalytic nanomaterial with amorphous / crystalline interface prepared in embodiment 1 of the present invention.

[0021] Figure 3 It is a transmission electron microscope image of a / c-Bi NPs electrocatalytic nanomaterial with amorphous / crystalline interface prepared in embodiment 1 of the present invention.

[0022] Figure 4 This is an X-ray electron spectrum of a / c-Bi NPs electrocatalytic nanomaterials having an amorphous / crystalline interface prepared in Example 1 of the present invention.

[0023] Figure 5 This is a diagram of oxygen temperature-programmed desorption of a / c-Bi NPs electrocatalytic nanomaterials having an amorphous / crystalline interface prepared in Example 1 of the present invention.

[0024] Figure 6 This is an electron paramagnetic resonance image of a / c-Bi NPs electrocatalytic nanomaterial with amorphous / crystalline interface prepared in Example 1 of the present invention.

[0025] Figure 7 The ORR performance of the a / c-Bi NPs electrocatalytic nanomaterial with amorphous / crystalline interface prepared in Example 1 of the present invention and the simultaneous H 2 O 2 Comparison graph of detection current density.

[0026] Figure 8The H in the electrochemical test results of the a / c-Bi NPs electrocatalytic nanomaterial with amorphous / crystalline interface prepared in Example 1 of the present invention 2 O 2 Selective graph.

[0027] Fig. 9 This is a diagram of the number of transferred electrons in the electrochemical test results of a / c-Bi NPs electrocatalytic nanomaterials with an amorphous / crystalline interface prepared in Example 1 of the present invention.

[0028] Fig.10 The a / c-Bi NPs electrocatalytic nanomaterial with amorphous / crystalline interface prepared in embodiment 1 of the present invention has ORR stability and H at the ring electrode. 2 O 2 Comparison graph of detection current density. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are only for the purpose of enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0030] Embodiment 1:

[0031] A method for preparing bismuth-based electrocatalytic nanomaterial with amorphous / crystalline interface

[0032] (1) The bismuth oxycarbonate precursor was synthesized by a hydrothermal method. In a typical procedure, 0.8 g of bismuth citrate and 0.23 g of sodium carbonate were dissolved in 50 mL of deionized water and magnetically stirred at 600 RPM for 1 h. The mixed solution was then sealed in a 100 mL hydrothermal reactor and heated to 180 °C for 24 h. After the product was cooled to room temperature, it was rinsed 4 times with ethanol and deionized water and then dried under vacuum at 70 °C for 12 h.

[0033] (2) 400 mg of polyvinyl pyrrolidone and 50 mg of bismuth oxycarbonate precursor were dispersed in 80 mL of deionized water to form solution A. 120 mg of sodium borohydride and 20 mL of deionized water were prepared into solution B, which was then added dropwise into solution A and stirred at 600 RPM for 4 h. Finally, the collected solid product was vacuum dried at 40 ° C for 1 h.

[0034] Embodiment 2:

[0035] A method for preparing pure crystalline bismuth-based electrocatalytic nanomaterial

[0036] (1) The bismuth oxycarbonate precursor was synthesized by a hydrothermal method. In a typical procedure, 0.8 g of bismuth citrate and 0.23 g of sodium carbonate were dissolved in 50 mL of deionized water and magnetically stirred at 600 RPM for 1 h. The mixed solution was then sealed in a 100 mL hydrothermal reactor and heated to 180 °C for 24 h. After the product was cooled to room temperature, it was rinsed 4 times with ethanol and deionized water and then dried under vacuum at 70 °C for 12 h.

[0037] (2) 50 mg of bismuth oxycarbonate precursor was dispersed in 80 mL of deionized water to form solution A. 120 mg of sodium borohydride and 20 mL of deionized water were prepared into solution B, and then solution B was added dropwise into solution A and stirred at 600 RPM for 4 h. Finally, the collected solid product was vacuum dried at 40 ° C for 1 h.

[0038] Embodiment 3:

[0039] A method for preparing pure amorphous bismuth-based electrocatalytic nanomaterial

[0040] (1) The bismuth oxycarbonate precursor was synthesized by a hydrothermal method. In a typical procedure, 0.8 g of bismuth citrate and 0.23 g of sodium carbonate were dissolved in 50 mL of deionized water and magnetically stirred at 600 RPM for 1 h. The mixed solution was then sealed in a 100 mL hydrothermal reactor and heated to 180 °C for 24 h. After the product was cooled to room temperature, it was rinsed 4 times with ethanol and deionized water and then dried under vacuum at 70 °C for 12 h.

[0041] (2) 1 g of polyvinyl pyrrolidone and 50 mg of bismuth oxycarbonate precursor were dispersed in 80 mL of deionized water to form solution A. 120 mg of sodium borohydride and 20 mL of deionized water were prepared into solution B, which was then added dropwise into solution A and stirred at 600 RPM for 4 h. Finally, the collected solid product was vacuum dried at 40 ° C for 1 h.

[0042] The bismuth-based electrocatalyst with adjustable crystallinity obtained in the embodiment was weighed and prepared by weighing 5 mg, mixing with 970uL anhydrous ethanol and 30uL Nafion solution (5wt%) to prepare catalyst ink. Then, the mixture was treated with ultrasound for 4 hours to make it evenly dispersed. Subsequently, 10uL of the catalyst was evenly dropped on the glassy carbon electrode and connected to the rotating ring disk electrode device. The three-electrode system consists of a working electrode (rotating ring disk electrode), a reference electrode (mercury / mercury oxide electrode) and a counter electrode (graphite rod). A five-necked bottle was injected with 0.1mol / L potassium hydroxide solution, and the reaction system O2 (purity of 99.999%, 20sccm) was sent into the five-necked bottle through an F glass tube. The potential was converted to the reversible hydrogen electrode (RHE) scale by calibration using the following equation: E(vs.RHE)=E(vs.Hg / HgO)+0.059×pH+0.098V (all potentials in the present invention are based on the RHE scale), and the current density was converted to a geometric surface area. To accurately measure the H2O2 selectivity, the RRDE was thoroughly cleaned before each experiment. The RRDE was polished with 1 μM alumina aqueous suspension for 10 min and sonicated in deionized water for 20 s. The catalyst-coated RRDE (disc area: 0.2475 cm2, ring area: 0.1866 cm2) was prepared by spin coating (100 rpm), and 5 μL of catalyst ink was dropped on the GC disk and used after drying at room temperature. Cyclic voltammetry (CV) was performed for 20 cycles at 100 mV·s-1 between 0 and 1.2 V in 0.1 mol / L KOH to obtain a stable CV response. Then, the Pt ring was electrochemically scanned at 100 mV·s-1 between 0 and 1.2 V for 20 cycles. The H2O2 selectivity was measured by linear sweep voltammetry (LSV) at a rotation speed of 1600 rpm and a scan rate of 20 mV·s-1 from 0 to 1.0 V in O2-saturated 0.1 mol / L KOH. During the LSV process, the Pt ring potential was kept at 1.2 V.

[0043] The materials obtained in the examples were tested and investigated, and the results of Example 1 (the results of other examples are similar to those of Example 1 and will not be repeated here) are as follows Figures 1 to 10 As shown, specifically:

[0044] Figure 1 In the X-ray powder diffraction spectrum, bismuth nanoparticles with different crystallinity were synthesized by controlling the concentration of dispersant polyvinyl pyrrolidone. It was observed that bismuth nanoparticles with different crystallinity showed a gradient peak intensity, among which the (012) and (104) characteristic peaks of Bi in a / c-Bi NPs electrocatalytic nanomaterials. Figure 2 In the SEM images, uniformly dispersed bismuth nanoparticles of bismuth-based electrocatalytic nanomaterials with amorphous / crystalline interfaces were observed. Figure 3In the transmission electron microscopy images, the coexistence of amorphous parts and clear lattice fringes of bismuth-based electrocatalytic nanomaterials with amorphous / crystalline interfaces was observed. Figure 4 In X-ray photoelectron spectroscopy, it was observed that bismuth-based electrocatalytic nanomaterials with amorphous / crystalline interfaces behave as zero-valent metallic bismuth after reduction. 3+ This is because the bismuth surface is oxidized by air. Figure 5 The results show that the bismuth-based electrocatalytic nanomaterials with amorphous / crystalline interfaces have obvious peaks in the range of 300-500 °C, indicating that the catalyst has strong chemical adsorption of oxygen. Figure 6 The electron paramagnetic resonance images confirmed the existence of structural defects in a / c-Bi NPs nanomaterials. Figure 7 The comparison of ORR performance (bottom) and H2O2 detection current density at the ring electrode (top) confirms that the bismuth-based electrocatalytic nanomaterial with amorphous / crystalline interface has a relatively high starting potential of 0.65V and an ORR current density of 2.3mA / cm2, indicating that the catalyst has excellent ORR performance. The ring current density of 0.8mA / cm2 indicates that there is a large amount of H 2 O 2 generate. Figure 8 H 2 O 2 The selectivity plots show that the catalyst is able to maintain an average of 95% H 2 O 2 Selective. Fig. 9 The transfer electron number diagram in the electrochemical test results shows that the transfer electron number of the catalyst is close to 2, and the ORR pathway is a two-electron pathway to generate H 2 O 2 . Fig.10 ORR stability (top) and simultaneous H 2 O 2 Comparison of detection current density (bottom), a / c-Bi NPs electrocatalytic nanomaterials in the stability test of nearly 8 hours, H 2 O 2 The selectivity remained basically unchanged, all stable at above 94%.

[0045] The present invention obtains bismuth-based electrocatalytic nanomaterials with adjustable crystallinity by controlling the concentration of the dispersant. Different crystallinity can change the electronic structure of the central metal bismuth, thereby affecting the selectivity of the material in the field of electrocatalytic reduction of oxygen.

[0046] The material has both amorphous and crystalline structures, expressed as a / c-Bi NPs. The bismuth-based electrocatalytic nanomaterial with adjustable crystallinity can be used for the electrocatalytic reduction of oxygen to prepare hydrogen peroxide, showing high selectivity for hydrogen peroxide in a rotating ring disk electrode and high activity for hydrogen peroxide in a flow cell. Accordingly, the inventors have also established a corresponding preparation method, namely, using bismuth citrate as a bismuth source and sodium carbonate as a precipitant, and synthesizing a bismuth oxycarbonate precursor by a hydrothermal method. The synthesized bismuth oxycarbonate is used as a precursor and sodium borohydride as a reducing agent, and bismuth nanoparticles of different crystallinities are induced to be synthesized by controlling the concentration of the dispersant polyvinyl pyrrolidone. In short, the present invention has pioneered a simple and controllable means to prepare bismuth-based electrocatalysts with different crystallinities, and revealed the high selectivity and structure-activity relationship of bismuth-based catalysts for preparing hydrogen peroxide.

[0047] Matters not covered by the present invention are known technologies.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A bismuth-based electrocatalytic nanomaterial with adjustable crystallinity, characterized in that: The nanomaterial integrates amorphous structure and crystalline structure simultaneously on bismuth nanoparticles, expressed as a / c-BiNPs.

2. The method for preparing a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 1, characterized in that: Preparation of bismuth oxycarbonate precursor, reduction of the precursor with sodium borohydride, and induction of synthesis of bismuth nanoparticles with different crystallinity at different dispersant polyvinyl pyrrolidone concentrations.

3. The method for preparing a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 2, characterized in that: In the preparation of the bismuth oxycarbonate precursor, bismuth citrate is used as a bismuth source, sodium carbonate is used as a precipitant, and the bismuth oxycarbonate precursor is synthesized by a hydrothermal method.

4. The method for preparing a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 2, characterized in that: The synthesized bismuth oxycarbonate is used as a precursor and sodium borohydride as a reducing agent, and the concentration of the dispersant polyvinyl pyrrolidone is controlled to induce the synthesis of bismuth nanoparticles with different crystallinity.

5. The method for preparing a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 3, characterized in that: Dissolve bismuth citrate and sodium carbonate in deionized water and stir them magnetically until they are completely dissolved. Then transfer the mixed solution to a polytetrafluoroethylene-lined stainless steel autoclave and seal it for high-temperature reaction. After the autoclave is cooled to room temperature, collect the precipitate by suction filtration, wash it with deionized water and anhydrous ethanol respectively, and then dry it in vacuum to obtain the product.

6. The method for preparing a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 5, characterized in that: The magnetic stirring temperature was room temperature, the rotation speed was 600RPM, the stirring time was 60min, the polytetrafluoroethylene lining was 100mL, the sealed high temperature reaction conditions were 180°C and the time was 24h, washed 4 times respectively, and the vacuum drying conditions were 70°C and the time was 12h.

7. The method for preparing a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 4, characterized in that: Polypyrrolidone and bismuth oxycarbonate precursor are dispersed in deionized water to form solution A, sodium borohydride is added to deionized water to prepare solution B, and then solution B is added dropwise to solution A to obtain solution C, and magnetic stirring is performed until solution C turns black. Solution A of different concentrations is used, and the collected solid product is vacuum dried to obtain the product.

8. The method for preparing a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 7, characterized in that: The magnetic stirring temperature was room temperature, the rotation speed was 600RPM, the stirring time was 4h, the vacuum drying conditions were temperature 40°C and time was 1h, and the different concentrations of solution A were 0mol / L, 0.04mol / L, and 0.1mol / L, respectively.

9. The use of a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 1, characterized in that: Nanomaterials as electrocatalysts.

10. The use of a bismuth-based electrocatalytic nanomaterial with adjustable crystallinity according to claim 9, characterized in that: The electrocatalyst is used for the electrocatalytic reduction of oxygen.

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