Porous carbon loaded with single-atom nickel, preparation method thereof and application thereof in iodine batteries

Abstract

The present invention discloses a porous carbon loaded with single-atom nickel, a preparation method thereof, and an application thereof in an iodine battery. The method first immerses the acid-treated porous carbon in a nickel nitrate solution, then performs annealing in an argon tube furnace, and finally immerses it in concentrated hydrochloric acid to obtain the porous carbon loaded with single-atom nickel. When the porous carbon loaded with single-atom nickel of the present invention is used as a positive electrode in an iodine battery, the single-atom nickel loaded on the porous carbon can catalytically accelerate the adsorption of intermediate products I3 ‑ and I2, inhibit their shuttle effect, reduce the loss of active substances, improve the utilization rate of active substances, and thus improve its capacity and cycle stability.

Description

Technical Field

[0001] The invention relates to porous carbon loaded with single-atom nickel, a preparation method and application of the porous carbon in an iodine battery, and belongs to the technical field of electrochemical energy storage. Background Art

[0002] At present, metal ion batteries such as lithium ion batteries have been widely used in the fields of electric vehicles and portable electronic devices, but there are few reports on the research of non-metallic ions. The breakthrough of fluoride ion batteries has pointed out the direction for non-metallic ion batteries, but due to its harsh application conditions and expensive electrode materials, it is difficult to achieve large-scale promotion and application in a short period of time. As an element in the same main group as fluorine and sulfur, iodine has abundant reserves in the ocean and high specific capacity, and has been widely used in batteries in recent years.

[0003] When the electrolyte is a redox active substance, the redox reaction occurs immediately on the electrode surface. Traditional redox active substances exist in solid electrode materials, but the kinetic process in the liquid phase is more efficient than that in the solid phase. Potassium iodide, as a redox electrolyte, is non-toxic and environmentally friendly compared to potassium ferrocyanide and hydroquinone. Since KI, a redox substance, exists in aqueous electrolytes, it is easy to produce a shuttle effect, and the iodine element generated during the circulation process is easy to precipitate and precipitate from the electrolyte, resulting in the loss of active substances, reducing the utilization rate of the electrolyte, and affecting the capacity and cycle stability of the system.

[0004] Reference 1 (Nano Lett, 2015, 15(9): 5982-5987) uses a dissolution-adsorption method to fix iodine in the micropores of activated carbon cloth as the positive electrode material of a lithium battery. The charge and discharge test was carried out at a rate of 0.5C, and the initial discharge capacity was 299 mAhg -1 Reference 2 (Materials Chemistry & Physics, 2016, 169: 192-197) uses a self-supporting iodine quantum dot-modified graphene oxide film as the positive electrode with a current density of 100 mAg -1 When the capacity is 170mAhg -1 .

[0005] Meanwhile, single-atom catalysis has received increasing attention in the field of catalysis. Single-atom catalysts show obvious advantages in maximizing atomic efficiency, enhancing the selectivity of target products, improving intrinsic activity, and enhancing cycling performance. In the field of energy storage, single-atom catalysis is mostly used in lithium-sulfur batteries. Literature 3 (Journal of Energy Chemistry, 2021, 54: 452-466) reported that single-atom catalysis can actively promote the redox reaction of sulfur, and by forming a strong interaction between polysulfides / sulfides and single metal atoms, as well as forming a local coordination structure that is easy for reactants to decompose, greatly reducing the energy barrier of the conversion reaction. Summary of the Invention

[0006] The object of the present invention is to provide a porous carbon loaded with single-atom nickel, a preparation method thereof, and its application in iodine batteries. By loading single-atom nickel on porous carbon, it catalyzes and enhances the adsorption of I3 - , I2 in the electrolyte by porous carbon during charge and discharge and cycling processes, reduces the shuttle reaction, improves the utilization rate of active substances, and improves the capacity and cycling stability of iodine batteries.

[0007] The technical solution for achieving the object of the present invention is as follows:

[0008] A preparation method of porous carbon loaded with single-atom nickel, comprising the following steps:

[0009] Soak the acid-treated porous carbon in nickel nitrate solution, place it in a tube furnace under an argon atmosphere, anneal at 700-900 °C, after the annealing is completed, cool to room temperature, and soak in concentrated hydrochloric acid for 4-8 h to obtain porous carbon loaded with single-atom nickel.

[0010] Preferably, the acid treatment is to soak the porous carbon in concentrated nitric acid at 60 °C for 8 h to remove surface impurities and increase hydrophilicity.

[0011] Preferably, the concentration of the nickel nitrate solution is 0.035-0.075 mol / L, the soaking time is 12 h, and the soaking temperature is 40 °C.

[0012] Preferably, the annealing time is 1 h.

[0013] Preferably, the annealing temperature is 800 °C.

[0014] The present invention also provides the porous carbon loaded with single-atom nickel prepared by the above preparation method.

[0015] Furthermore, the present invention provides the application of the above porous carbon loaded with single-atom nickel in iodine batteries.

[0016] Specifically, in the above application, the porous carbon loaded with single-atom nickel is used as the positive electrode material, and potassium iodide is used as the electrolyte.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The present invention prepares porous carbon loaded with single-atom nickel by a simple thermal decomposition method. The prepared porous carbon loaded with single-atom nickel contains Ni-N sites. Potassium iodide is used as an aqueous redox electrolyte to react with I2 and I3 in the potassium iodide electrolyte. - Forming bonds, forming chemical bonds, plays a role of chemical adsorption. The iodine element generated in the reaction process is adsorbed onto the porous carbon and continues to undergo a reversible redox reaction, instead of being precipitated at the bottom of the electrolyte and becoming an inactive substance, thereby improving the utilization rate of active substances and reducing the shuttle effect. The capacity and cycle stability of the system are greatly improved, and after 20,000 cycles, there is still a 100% cycle retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a spherical aberration corrected high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image of the porous carbon loaded with single-atom nickel prepared in Example 1;

[0020] Figure 2 The porous carbon loaded with single-atom nickel was immersed in concentrated hydrochloric acid for 4 h and 8 h in KI electrolyte at a current density of 7 mA / cm 2 The charge and discharge curve diagram of

[0021] Figure 3 This is a cycle retention rate curve of the porous carbon loaded with single-atom nickel obtained in Example 1;

[0022] Figure 4 The porous carbon loaded with single-atom nickel prepared by soaking in concentrated hydrochloric acid for different time periods was charged in KI electrolyte at a current density of 7 mA / cm 2 The charge and discharge curve diagram of

[0023] Figure 5 The porous carbon loaded with different single-atom metals was subjected to a current density of 7 mA / cm in KI electrolyte. 2 The charge and discharge curve diagram of

[0024] Figure 6 The porous carbon loaded with single-atom nickel prepared from nickel nitrate solutions of different concentrations was subjected to a current density of 7 mA / cm in KI electrolyte. 2 The charge and discharge curve diagram of

[0025] Figure 7 The charge and discharge curves of porous carbon loaded with single-atom nickel in H2SO4, H2SO4 and KI electrolytes. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0027] In the following examples and comparative examples, the acidification treatment method of the porous carbon is as follows: commercial porous carbon is soaked in concentrated nitric acid and soaked at 60 °C for 8 h to remove surface impurities and increase hydrophilicity, forming ordinary porous carbon.

[0028] Example 1

[0029] (1) The acidified porous carbon is soaked in a 0.05 mol / L nickel nitrate solution for 12 h, dried, placed in a tube furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce nickel nitrate to nickel metal. Finally, it is soaked in concentrated hydrochloric acid (12 mol / L) for 8 h to remove excess nickel metal and clusters, obtaining porous carbon loaded with single-atom nickel.

[0030] (2) The porous carbon loaded with single-atom nickel soaked in concentrated hydrochloric acid for 8 h is subjected to electrochemical testing in a three-electrode system, where the electrolyte is an acidic potassium iodide aqueous solution, the counter electrode is a platinum sheet, the reference electrode is Ag / AgCl, and the potential range is 0 - 0.8 V.

[0031] Figure 1 Figure of the aberration-corrected high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) of the porous carbon loaded with single-atom nickel prepared in Example 1. In the HAADF mode, the brightness of an atom is proportional to the 1.8th power of the atomic number, so the metal will be particularly eye-catching on the carbon-nitrogen support. Each small bright spot in the figure is a single nickel atom.

[0032] Example 2

[0033] (1) The acidified porous carbon is soaked in a 0.05 mol / L nickel nitrate solution for 12 h, dried, placed in a tube furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce nickel nitrate to nickel metal. Finally, it is soaked in concentrated hydrochloric acid (12 mol / L) for 4 h to remove excess nickel metal and clusters, obtaining porous carbon loaded with single-atom nickel.

[0034] (2) The porous carbon loaded with single-atom nickel soaked in concentrated hydrochloric acid for 4 h is subjected to electrochemical testing in a three-electrode system, where the electrolyte is an acidic potassium iodide aqueous solution, the counter electrode is a platinum sheet, the reference electrode is Ag / AgCl, and the potential range is 0 - 0.8 V.

[0035] Figure 2 Charge-discharge curves of the porous carbon loaded with single-atom nickel soaked in concentrated hydrochloric acid for 4 h and 8 h respectively in a KI electrolyte, indicating that the catalytic effect of the porous carbon loaded with single-atom nickel soaked for 8 h is the best. 2 at a current density of 7 mA / cm

[0036] After electrochemical testing, Figure 3 Figure Figure 3 is the cyclic voltammetry curve of the porous carbon loaded with single-atom nickel. After 20,000 cycles, the cycling retention rate remains at about 100%, indicating that the porous carbon loaded with single-atom nickel can enhance the adsorption of iodine substances, reduce the shuttle effect, and has excellent cycling retention rate.

[0037] Comparative Example 1

[0038] The acid-treated porous carbon was directly placed in a three-electrode system for electrochemical testing. The electrolyte was acidic potassium iodide, the counter electrode was a platinum sheet, the reference electrode was Ag / AgCl, and the potential range was 0 - 0.8V.

[0039] Comparative Example 2

[0040] (1) The acid-treated porous carbon was immersed in 0.05 mol / L nickel nitrate solution for 12 h, dried, placed in a tubular furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce nickel nitrate to nickel metal. Without immersion in concentrated hydrochloric acid, the porous carbon loaded with single-atom nickel was prepared.

[0041] (2) The porous carbon loaded with single-atom nickel without immersion in concentrated hydrochloric acid was subjected to electrochemical testing in a three-electrode system. The electrolyte was aqueous acidic potassium iodide, the counter electrode was a platinum sheet, the reference electrode was Ag / AgCl, and the potential range was 0 - 0.8V.

[0042] Comparative Example 3

[0043] (1) The acid-treated porous carbon was immersed in 0.05 mol / L nickel nitrate solution for 12 h, dried, placed in a tubular furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce nickel nitrate to nickel metal. Finally, it was immersed in concentrated hydrochloric acid (12 mol / L) for 12 h to remove excess nickel metal and clusters, and the porous carbon loaded with single-atom nickel was prepared.

[0044] (2) The porous carbon loaded with single-atom nickel immersed in concentrated hydrochloric acid for 12 h was subjected to electrochemical testing in a three-electrode system. The electrolyte was aqueous acidic potassium iodide, the counter electrode was a platinum sheet, the reference electrode was Ag / AgCl, and the potential range was 0 - 0.8V.

[0045] Figure 4 Figure 2 shows the charge-discharge curves of the porous carbon loaded with single-atom nickel prepared by immersing in concentrated hydrochloric acid for different times in a KI electrolyte with a current density of 7 mA / cm 2 . It can be seen from the figure that the porous carbon loaded with single-atom nickel immersed in concentrated hydrochloric acid for 8 h has the best catalytic effect.

[0046] Comparative Example 4

[0047] (1) The acid-treated porous carbon was immersed in a 0.05 mol / L iron nitrate solution for 12 h, dried, placed in a tube furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce iron nitrate to elemental iron. Finally, it was immersed in concentrated hydrochloric acid (12 mol / L) for 8 h to remove excess elemental iron and clusters, and porous carbon loaded with single-atom iron was prepared.

[0048] (2) The porous carbon loaded with single-atom iron was subjected to electrochemical testing in a three-electrode system. The electrolyte was an acidic potassium iodide aqueous solution, the counter electrode was a platinum sheet, the reference electrode was Ag / AgCl, and the potential range was 0 - 0.8 V.

[0049] Comparative Example 5

[0050] (1) The acid-treated porous carbon was immersed in a 0.05 mol / L cobalt nitrate solution for 12 h, dried, placed in a tube furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce cobalt nitrate to elemental cobalt. Finally, it was immersed in concentrated hydrochloric acid (12 mol / L) for 8 h to remove excess elemental cobalt and clusters, and porous carbon loaded with single-atom cobalt was prepared.

[0051] (2) The porous carbon loaded with single-atom cobalt was subjected to electrochemical testing in a three-electrode system. The electrolyte was an acidic potassium iodide aqueous solution, the counter electrode was a platinum sheet, the reference electrode was Ag / AgCl, and the potential range was 0 - 0.8 V.

[0052] Figure 5 For porous carbons loaded with different single-atom metals in an acidic KI electrolyte, the galvanostatic charge-discharge curve at a current density of 7 mA / cm -2 It can be seen from the figure that the porous carbon loaded with single-atom nickel has the best catalytic effect on iodine batteries.

[0053] Comparative Example 5

[0054] (1) The acid-treated porous carbon was immersed in a 0.035 mol / L nickel nitrate solution for 12 h, dried, placed in a tube furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce nickel nitrate to elemental nickel. Finally, it was immersed in concentrated hydrochloric acid (12 mol / L) for 8 h to remove excess elemental nickel and clusters, and porous carbon loaded with single-atom nickel was prepared.

[0055] (2) The porous carbon loaded with single-atom nickel was subjected to electrochemical testing in a three-electrode system. The electrolyte was an acidic potassium iodide aqueous solution, the counter electrode was a platinum sheet, the reference electrode was Ag / AgCl, and the potential range was 0 - 0.8 V.

[0056] Comparative Example 6

[0057] (1) The acid-treated porous carbon was immersed in a 0.075 mol / L nickel nitrate solution for 12 h, dried, placed in a tube furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce nickel nitrate to nickel metal. Finally, it was immersed in concentrated hydrochloric acid (12 mol / L) for 8 h to remove excess nickel metal and clusters, and porous carbon loaded with single-atom nickel was prepared.

[0058] (2) The porous carbon loaded with single-atom nickel was electrochemically tested in a three-electrode system. The electrolyte was an acidic potassium iodide aqueous solution, the counter electrode was a platinum sheet, the reference electrode was Ag / AgCl, and the potential range was 0 - 0.8 V.

[0059] Figure 6 Figure showing the galvanostatic charge-discharge curves of porous carbon loaded with single-atom nickel prepared from nickel nitrate solutions of different concentrations in an acidic KI electrolyte. It can be seen from the figure that when the concentration of the nickel nitrate solution is 0.05 mol / L, the catalytic effect of the porous carbon loaded with single-atom nickel is the best. -2

[0060] Comparative Example 7

[0061] (1) The acid-treated porous carbon was immersed in a 0.05 mol / L nickel nitrate solution for 12 h, dried, placed in a tube furnace, and annealed at 800 °C for 1 h under an argon atmosphere to reduce nickel nitrate to nickel metal. Finally, it was immersed in concentrated hydrochloric acid (12 mol / L) for 8 h to remove excess nickel metal and clusters, and porous carbon loaded with single-atom nickel was prepared.

[0062] (2) The porous carbon immersed in concentrated hydrochloric acid for 8 h was electrochemically tested in a three-electrode system. The electrolyte was 1 mol / L sulfuric acid solution without adding 0.1 mol / L potassium iodide redox electrolyte, the counter electrode was a platinum sheet, the reference electrode was Ag / AgCl, and the potential range was 0 - 0.8 V.

[0063] Figure 7 Figure showing the GCD curves of porous carbon loaded with single-atom nickel in different electrolytes. It can be seen from the figure that the increase in battery capacity is contributed by the redox reaction of potassium iodide in the electrolyte.

Claims

1. Application of porous carbon loaded with single-atom nickel in iodine batteries, characterized in that, Porous carbon loaded with single-atom nickel is used as the positive electrode material, and potassium iodide is used as the electrolyte. The preparation method of the porous carbon loaded with single-atom nickel is as follows: The acid-treated porous carbon is immersed in a nickel nitrate solution, placed in a tube furnace under an argon atmosphere, annealed at 700-900 °C, cooled to room temperature after annealing, and immersed in concentrated hydrochloric acid for 4-8 h to obtain porous carbon loaded with single-atom nickel; the porous carbon loaded with single-atom nickel contains Ni-N sites.

2. The application according to claim 1, characterized in that, The acid treatment is to immerse the porous carbon in concentrated nitric acid and soak it at 60 °C for 8 h to remove surface impurities and increase hydrophilicity.

3. The application according to claim 1, wherein The concentration of the nickel nitrate solution is 0.035-0.075 mol / L, the soaking time is 12 h, and the soaking temperature is 40 °C.

4. The application according to claim 1, wherein The annealing time is 1 h.

5. The application according to claim 1, characterized in that The annealing temperature is 800 °C.

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