Preparation of transition metal nitrides and their application in electrocatalytic oxidation of hydrazine hydrate

Abstract

The application discloses a kind of preparation of transition metal nitride and its application in electrocatalytic oxidation hydrazine hydrate, it is related to electrocatalysis technical field, compared with prior art, the application provides a kind of quick preparation method of transition metal nitride, simple operation, easy to control, short preparation period;And the transition metal nitride obtained has relatively broad application prospect, can be applied to the electrocatalytic hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction and hydrogen oxidation reaction in alkaline medium, shows excellent catalytic activity, stability and conductivity, to provide feasible guidance for the development of efficient transition metal nitride-based electrochemical catalyst.

Description

Technical fields:

[0001] This invention relates to the field of electrocatalysis technology, specifically to the preparation of transition metal nitrides and their application in the electrocatalytic oxidation of hydrazine hydrate. Background technology:

[0002] Transition metal nitrides possess the properties of covalent compounds, ionic crystals, and transition metals, exhibiting structural stability and excellent conductivity, and have gradually become a research hotspot in the energy storage field in recent years. Compared with carbon electrode materials, transition metal nitrides have higher specific capacity and greater volumetric energy density (high vibrational density). Compared with transition metal oxide electrode materials, transition metal nitride electrode materials have higher amplification factor and excellent cycle stability. Furthermore, transition metal nitrides also possess a low and flat charge / discharge potential plateau and good reversibility, making them widely used in electrocatalytic anode materials.

[0003] In recent years, several thermodynamically favorable or economically attractive reactants have been proposed for electrochemical oxidation to replace slow-acting oxidation processes (OERs) in water splitting, such as urea, methanol, ethanol, tetrahydroisoquinoline, primary amines, nitrogen, and hydrazine. This holds great potential for achieving lower battery voltages for hydrogen production or the production of value-added products. Among these, hydrazine oxidation is particularly promising due to its low theoretical oxidation potential (HzOR, N₂H₄ + 4OH⁻). - →N2 + 4H2O + 4e - The HzOR (-0.33V vs RHE) has attracted much attention, and because only N2 is a byproduct, it is well-suited for separatorless electrolyzers. Therefore, energy-saving hydrogen production using HzOR to replace OER has broad prospects, and some pioneering work has already made encouraging progress.

[0004] CN116081582A discloses a method for preparing transition metal nitride nanocrystals, using copper nitrate trihydrate as the nitrogen source, synthesizing Cu3N in the liquid phase under mild conditions as a template, and then generating novel nitride crystals through cation exchange. CN115726041A discloses a method for preparing ultrathin two-dimensional transition metal nitride single crystal structures, including the following steps: preparing transition metal salt solutions of different concentrations; pretreating the surface of a sapphire substrate to make its surface hydrophilic; spin-coating the transition metal salt solution onto the surface of the sapphire substrate using a spin coater; and preparing ultrathin two-dimensional transition metal nitride single crystals through chemical vapor deposition in a temperature-programmed tube furnace. By modulating and controlling the growth temperature and precursor concentration, ultrathin two-dimensional transition metal nitride single crystals with different phases can be prepared. CN110586151A discloses a method for preparing ordered mesoporous transition metal nitrides, comprising the following steps: filling a silicon dioxide SBA-15 mesoporous template with transition metal ions, oxidizing it at high temperature, removing the template with an alkali to generate an oxide with a mesoporous structure, and then nitriding the mesoporous oxide at high temperature to synthesize ordered mesoporous transition metal nitrides. Summary of the Invention:

[0005] The technical problem to be solved by the present invention is to provide a transition metal nitride and a rapid preparation method thereof, which has excellent catalytic activity, stability and conductivity, and is suitable for the electrocatalytic oxidation of hydrazine hydrate.

[0006] The technical problem to be solved by this invention is achieved by the following technical solution:

[0007] One objective of this invention is to provide a rapid preparation method for transition metal nitrides, comprising the following steps:

[0008] (1) Dissolve the transition metal salt in a solvent, then add urea and carbon cloth, and heat to react to obtain the transition metal oxide / hydroxide precursor.

[0009] (2) The precursor prepared above was subjected to Joule thermal shock in an ammonia atmosphere to obtain transition metal nitrides.

[0010] Preferably, the transition metal salt is one or more of the following: iron halide salts and their hydrates, cobalt halide salts and their hydrates, nickel halide salts and their hydrates, iron nitrates and their hydrates, cobalt nitrates and their hydrates, nickel nitrates and their hydrates, iron acetates and their hydrates, cobalt acetates and their hydrates, nickel acetates and their hydrates, ammonium molybdate and its hydrate, and sodium molybdate and its hydrate.

[0011] Preferably, the solvent is deionized water.

[0012] Preferably, the molar ratio of urea to transition metal salt is (1-10):1.

[0013] Preferably, the carbon cloth has a size of (1-5cm) × (1-5cm).

[0014] Preferably, the heating reaction is carried out at a temperature of 95–160°C for 2–18 hours.

[0015] Preferably, the Joule thermal shock voltage is 5–20V and the duration is 0.5–5s.

[0016] In step (1), the transition metal salt cations are rapidly adsorbed by carbon cloth and reduced by urea at high temperature to transition metal oxide / hydroxide precursors; in step (2), based on the precursor morphology, Joule thermal shock is performed in an ammonia atmosphere to obtain transition metal nitrides.

[0017] A second objective of this invention is to provide a transition metal nitride prepared according to the aforementioned rapid preparation method.

[0018] A third objective of this invention is to provide the application of the aforementioned transition metal nitrides in electrocatalytic hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and hydrogen hydroxide reaction.

[0019] Preferably, the electrocatalysis is carried out in an alkaline medium.

[0020] The beneficial effects of this invention are as follows: Compared with the prior art, this invention provides a rapid preparation method for transition metal nitrides, which is simple to operate, easy to control, and has a short preparation cycle; and the obtained transition metal nitrides have broad application prospects and can be applied to electrocatalytic hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction and hydrogen oxidation reaction in alkaline media, exhibiting excellent catalytic activity, stability and conductivity, thus providing practical guidance for the development of efficient transition metal nitride-based electrochemical catalysts. Attached image description:

[0021] Figure 1 Co4N / Mo prepared in Example 1 of this invention 16 Structural characterization results of N7 sample: (a) X-ray diffraction pattern; (b) scanning electron microscope image; (c) high-resolution transmission electron microscope image;

[0022] Figure 2 The Ni3N / Ni prepared in Example 2 of this invention 0.2 Mo 0.8 Structural characterization results of sample N: (a) X-ray diffraction pattern; (b) Scanning electron microscope image; (c) High-resolution transmission electron microscope image;

[0023] Figure 3The structural characterization results of the Ni3N / Co4N sample prepared in Example 3 of the present invention are as follows: (a) X-ray diffraction pattern; (b) scanning electron microscope image; (c) high-resolution transmission electron microscope image;

[0024] Figure 4 The structural characterization results of the Fe2N sample prepared in Example 4 of this invention are as follows: (a) X-ray diffraction pattern; (b) scanning electron microscope image; (c) high-resolution transmission electron microscope image;

[0025] Figure 5 The structural characterization results of the Co4N sample prepared in Example 5 of the present invention are as follows: (a) X-ray diffraction pattern; (b) scanning electron microscope image; (c) high-resolution transmission electron microscope image;

[0026] Figure 6 The structural characterization results of the Ni3N sample prepared in Example 6 of the present invention are as follows: (a) X-ray diffraction pattern; (b) scanning electron microscope image; (c) high-resolution transmission electron microscope image;

[0027] Figure 7 The performance test results of the nitride samples prepared in Examples 1-6 of this invention in the electrocatalytic oxidation of hydrazine hydrate are as follows: (a) polarization curve; (b) Tafel plot; (c) Nyquist plot; (d) 24h stability curve. Detailed implementation method:

[0028] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments and illustrations.

[0029] Example 1

[0030] (1) The carbon cloth (1cm × 4cm) was ultrasonically cleaned in deionized water and ethanol for 15 minutes to remove impurities. 0.72g CoCl2·6H2O and 0.52g (NH4)6Mo7O were then added. 24 1.00 g of urea was dissolved in 40 mL of deionized water, and the resulting solution was transferred to a 100 mL high-pressure reactor. Pretreated carbon cloth was then added, the reactor was sealed, and the mixture was hydrothermally reacted at 160 °C for 12 h. After cooling to room temperature, the sample was collected, washed several times with water and ethanol, and dried at 60 °C to obtain the CoMoO4 precursor.

[0031] (2) The CoMoO4 precursor prepared above was placed in an ammonia atmosphere and subjected to Joule thermal shock at 17V for 0.5s to obtain a cobalt nitride / molybdenum nitride heterojunction, denoted as Co4N / Mo 16 N7.

[0032] Co4N / Mo prepared in Example 1 16 The N7 sample was structurally characterized, and the results are shown in [the table below]. Figure 1 .

[0033] Figure 1 (a) All the diffraction peaks appearing in the diagram correspond one-to-one with pure Co4N / Mo. 16 N7 diffraction peak; Figure 1 (b) Displaying Co4N / Mo 16 The structural form of N7; Figure 1 (c) Displaying Co4N / Mo 16 The crystal lattice morphology of N7.

[0034] Example 2

[0035] (1) The carbon cloth (1cm×4cm) was ultrasonically cleaned in deionized water and ethanol for 15 min to remove impurities. The pretreated carbon cloth was immersed in a mixed solution containing 0.73g Ni(NO3)2·6H2O, 0.83g Na2MoO4·7H2O, 1.56g urea and 40mL deionized water, and then transferred to a 50mL high-pressure reactor. The reactor was sealed and hydrothermally reacted at 150℃ for 6h. After cooling to room temperature, the sample was collected, washed several times with water and ethanol, and dried at 60℃ to obtain the NiMoO4 precursor.

[0036] (2) The NiMoO4 precursor prepared above was placed in an ammonia atmosphere and subjected to Joule thermal shock at 12.5V for 0.5s to obtain a nickel nitride / nickel molybdenum nitride heterojunction, denoted as Ni3N / Ni 0.2 Mo 0.8 N.

[0037] Ni3N / Ni prepared in Example 2 0.2 Mo 0.8 Structural characterization of sample N was performed, and the results are shown in [the table below]. Figure 2 .

[0038] Figure 2 All the diffraction peaks appearing in (a) correspond one-to-one with pure Ni3N / Ni 0.2 Mo 0.8 N diffraction peak; Figure 2 (b) Displaying Ni3N / Ni 0.2 Mo 0.8 The structural form of N; Figure 2 (c) Displaying Ni3N / Ni 0.2 Mo 0.8 The crystal lattice morphology of N.

[0039] Example 3

[0040] (1) The carbon cloth (1cm×4cm) was ultrasonically cleaned in deionized water and ethanol for 15min to remove impurities. The pretreated carbon cloth was immersed in a mixed solution containing 0.45g Ni(NO3)2 6H2O, 0.90mg Co(NO3)2 6H2O, 1.08g urea and 40mL deionized water, and then transferred to a 50mL high-pressure reactor. The reactor was sealed and hydrothermally reacted at 150℃ for 6h. After cooling to room temperature, the sample was collected, washed several times with water and ethanol, and dried at 60℃ to obtain the NiCo2O4 precursor.

[0041] (2) The NiCo2O4 precursor prepared above was placed in an ammonia atmosphere and subjected to Joule thermal shock at 11.3V for 0.5s to obtain a nickel nitride / cobalt nitride heterojunction, denoted as Ni3N / Co4N.

[0042] The structure of the Ni3N / Co4N sample prepared in Example 3 was characterized, and the results are shown in the figure. Figure 3 .

[0043] Figure 3 All the diffraction peaks that appear in (a) correspond one-to-one with the pure Ni3N / Co4N diffraction peaks; Figure 3 (b) Showing the structural morphology of Ni3N / Co4N; Figure 3 (c) Showing the crystal morphology of Ni3N / Co4N.

[0044] Example 4

[0045] (1) The carbon cloth (1cm×4cm) was ultrasonically cleaned in deionized water and ethanol for 15min to remove impurities. The pretreated carbon cloth was immersed in a mixed solution containing 0.15M Fe(NO3)3 and 0.35M urea, and then transferred to a 50mL high-pressure reactor. The reactor was sealed and hydrothermally reacted at 95℃ for 4h. After cooling to room temperature, the sample was collected, washed several times with water and ethanol, and dried at 60℃ to obtain the FeOOH precursor.

[0046] (2) The FeOOH precursor prepared above was placed in an ammonia atmosphere and subjected to Joule thermal shock at a voltage of 9.7V for 0.5s to obtain iron nitride, denoted as Fe2N.

[0047] The Fe2N sample prepared in Example 4 was structurally characterized, and the results are shown in the figure. Figure 4 .

[0048] Figure 4 (a) All the diffraction peaks that appear in the diagram correspond one-to-one with the pure Fe2N diffraction peaks; Figure 4 (b) Showing the structural morphology of Fe2N; Figure 4 (c) Showing the crystal morphology of Fe2N.

[0049] Example 5

[0050] (1) The carbon cloth (1cm×4cm) was ultrasonically cleaned in deionized water and ethanol for 15min to remove impurities. The pretreated carbon cloth was immersed in a mixed solution containing 0.47g Co(NO3)2 6H2O, 0.60g urea and 40mL deionized water, and then transferred to a 50mL high-pressure reactor. The reactor was sealed and hydrothermally reacted at 120℃ for 6h. After cooling to room temperature, the sample was collected, washed several times with water and ethanol, and dried at 60℃ to obtain the Co2(OH)2CO3 precursor.

[0051] (2) The Co2(OH)2CO3 precursor prepared above was placed in an ammonia atmosphere and subjected to Joule thermal shock at 14V for 0.5s to obtain cobalt nitride, denoted as Co4N.

[0052] The Co4N sample prepared in Example 5 was structurally characterized, and the results are shown in the figure. Figure 5 .

[0053] Figure 5 All the diffraction peaks that appear in (a) correspond one-to-one with the pure Co4N diffraction peaks; Figure 5 (b) Showing the structural morphology of Co4N; Figure 5 (c) Showing the crystal morphology of Co4N.

[0054] Example 6

[0055] (1) The carbon cloth (1cm×4cm) was ultrasonically cleaned in deionized water and ethanol for 15min to remove impurities. 0.58g Ni(NO3)2 6H2O and 0.6g urea were dissolved in 40mL of deionized water, and the resulting solution was transferred to a 100mL high-pressure reactor. The pretreated carbon cloth was then added, the reactor was sealed, and the reaction was carried out hydrothermally at 120℃ for 6h. After cooling to room temperature, the sample was collected, washed several times with water and ethanol, and dried at 60℃ to obtain the Ni(OH)2 precursor.

[0056] (2) The Ni(OH)2 precursor prepared above was placed in an ammonia atmosphere and subjected to Joule thermal shock at a voltage of 10.5V for 0.5s to obtain nickel nitride, denoted as Ni3N.

[0057] The structure of the Ni3N sample prepared in Example 6 was characterized, and the results are shown in the figure. Figure 6 .

[0058] Figure 6 All the diffraction peaks that appear in (a) correspond one-to-one with the pure Ni3N diffraction peaks; Figure 6 (b) Showing the structural morphology of Ni3N; Figure 6 (c) Showing the crystal morphology of Ni3N.

[0059] Example 7

[0060] Application of the nitride samples prepared in Examples 1-6 as catalysts in the electrocatalytic oxidation of hydrazine hydrate:

[0061] Electrocatalytic oxidation of hydrazine hydrate was tested using a standard three-electrode system on an electrochemical workstation. 1 M KOH solution was used as the electrolyte, 0.5 M hydrazine hydrate as the reactant, and carbon cloth (1 cm × 1 cm) of the nitride samples prepared in Examples 1–6 was used as the working electrode, platinum wire as the counter electrode, and an Hg / HgO electrode as the reference electrode.

[0062] from Figure 7 As can be seen from (a), (b), and (c), Co4N / Mo 16 N7 exhibits the best catalytic activity.

[0063] from Figure 7 (d) It can be seen that Co4N / Mo 16 The catalytic activity of N7 remains unchanged over 24 hours.

[0064] In summary, the transition metal nitrides prepared by this invention exhibit excellent HzOR catalytic activity and good stability in alkaline media.

[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A rapid preparation method for transition metal nitrides, characterized in that: Includes the following steps: (1) Dissolve the transition metal salt in a solvent, then add urea and carbon cloth, and heat to react to obtain the transition metal oxide / hydroxide precursor; (2) The precursor prepared above was subjected to Joule thermal shock in an ammonia atmosphere to obtain a transition metal nitride; The Joule thermal shock voltage is 5~20 V, and the duration is 0.5~5 s.

2. The rapid preparation method as described in claim 1, characterized in that: The transition metal salt is one or more of the following: iron halide and its hydrate, cobalt halide and its hydrate, nickel halide and its hydrate, iron nitrate and its hydrate, cobalt nitrate and its hydrate, nickel nitrate and its hydrate, iron acetate and its hydrate, cobalt acetate and its hydrate, nickel acetate and its hydrate, ammonium molybdate and its hydrate, and sodium molybdate and its hydrate.

3. The rapid preparation method as described in claim 1, characterized in that: The solvent is deionized water.

4. The rapid preparation method as described in claim 1, characterized in that: The molar ratio of urea to transition metal salt is (1~10):

1.

5. The rapid preparation method according to claim 1, characterized in that: The carbon cloth has a size of (1~5 cm) × (1~5 cm).

6. The rapid preparation method according to claim 1, characterized in that: The heating reaction is carried out at a temperature of 95~160℃ for a time of 2~18 h.

7. The transition metal nitride prepared by the rapid preparation method according to any one of claims 1-6.

8. The application of the transition metal nitride according to claim 7 in electrocatalytic hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and hydrogen oxidation reaction.

9. The application as described in claim 8, characterized in that: The electrocatalysis is carried out in an alkaline medium.

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