A transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and a neutral zinc-air battery

Abstract

The present application relates to a kind of transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and neutral zinc-air battery.The neutral zinc-air battery uses transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst as air catalytic electrode, uses aqueous solution containing large size hydrophobic anion zinc salt as electrolyte, and uses zinc material as negative electrode.Transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst includes transition metal element, inorganic doped element and porous carbon base.Compared with prior art, the present application has excellent electronic conductivity and ionic conductivity, can further reduce the activation energy of ORR / OER reaction, and then improve the energy density and energy efficiency of neutral zinc-air battery with the material as air electrode catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and a neutral zinc-air battery. BACKGROUND

[0002] Zinc-air battery has been widely studied and concerned due to its high theoretical specific capacity (820 mAh g Zn -1 ), safety and non-toxicity, and abundant reserves of zinc. The studied rechargeable zinc-air batteries are mostly alkaline zinc-air batteries, and the used electrolyte is generally a high-concentration potassium hydroxide or sodium hydroxide solution, which is highly corrosive. In the battery reaction process, a large amount of carbon dioxide in the air inevitably diffuses into the battery together with oxygen, and reacts with the electrolyte to generate insoluble carbonates, which accumulate on the surface of the air electrode, inhibit the diffusion of oxygen, and cause the catalyst to be inactivated. On the other hand, the discharge product of the alkaline zinc-air battery is an insulating ZnO deposited on the surface of the negative electrode, and the generation of the ZnO insulating layer reduces the utilization rate of zinc. The deposition and decomposition of ZnO in the charging and discharging process also causes serious zinc dendrite growth problems. In addition, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the alkaline zinc-air battery are 4e - mechanism, and the reaction kinetics is slow. Therefore, in order to further improve the battery performance of the zinc-air battery, a new zinc-air battery system needs to be developed.

[0003] Recently, in view of the problems in the alkaline zinc-air battery, researchers have proposed a neutral zinc-air battery with a large-size hydrophobic anion zinc salt aqueous solution as the electrolyte. The large-size hydrophobic anion can form a Helmholtz double layer on the surface of the air electrode, the formation of the double layer inhibits the enrichment of H2O on the electrode surface, and allows the free migration of zinc ions, so that the zinc-air battery charges and discharges with a 2e - mechanism with more optimal reaction kinetics. The discharge product is ZnO2 generated on the air electrode side, which improves the utilization rate of zinc and to some extent inhibits the formation of zinc dendrites in the negative electrode during charging and discharging. In addition, since the electrolyte used in the zinc-air battery system is a near-neutral electrolyte, the side reaction involving CO2 is inhibited. The neutral zinc-air battery has solved the problems in the alkaline zinc-air battery to a great extent, but due to the lack of a suitable bifunctional electrocatalyst material for the 2e - transfer of the zinc-air battery, the discharge voltage plateau of the battery is low, resulting in a low energy density of the neutral zinc-air battery. In addition, the large charging and discharging voltage polarization leads to a poor energy efficiency of the battery. SUMMARY

[0004] The present application aims to overcome the defects of the prior art and provides a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and a neutral zinc-air battery, which has excellent electronic conductivity and ionic conductivity, can further reduce the activation energy of ORR / OER reaction, and thus improves the energy density and energy efficiency.

[0005] The present application aims to overcome the defects of the prior art and provides a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and a neutral zinc-air battery, which has excellent electronic conductivity and ionic conductivity, can further reduce the activation energy of ORR / OER reaction, and thus improves the energy density and energy efficiency. - The present application aims to overcome the defects of the prior art and provides a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and a neutral zinc-air battery, which has excellent electronic conductivity and ionic conductivity, can further reduce the activation energy of ORR / OER reaction, and thus improves the energy density and energy efficiency. x / Se x / Se x The present application aims to overcome the defects of the prior art and provides a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and a neutral zinc-air battery, which has excellent electronic conductivity and ionic conductivity, can further reduce the activation energy of ORR / OER reaction, and thus improves the energy density and energy efficiency.

[0006] The present application aims to overcome the defects of the prior art and provides a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and a neutral zinc-air battery, which has excellent electronic conductivity and ionic conductivity, can further reduce the activation energy of ORR / OER reaction, and thus improves the energy density and energy efficiency.

[0007] The present application aims to overcome the defects of the prior art and provides a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst and a neutral zinc-air battery, which has excellent electronic conductivity and ionic conductivity, can further reduce the activation energy of ORR / OER reaction, and thus improves the energy density and energy efficiency.

[0008] Further, the transition metal element includes one or two of Co, Fe, Mn or Ni; and the inorganic doping element includes nitrogen, sulfur or selenium.

[0009] Further, the porous carbon substrate includes single-walled carbon nanotubes, multi-walled carbon nanotubes or porous carbon formed by high-temperature pyrolysis of metal-organic framework compounds (MOFs).

[0010] Further, the porous carbon catalyst is prepared by the following method: first, a precursor is synthesized by a template method or a hydrothermal / solvothermal method, and then a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst is prepared by high-temperature pyrolysis.

[0011] For example, a suitable transition metal nitrate, transition metal acetate or transition metal hydrochloride (such as Co(NO3)2, Co(Ac)2, NiCl2) is selected as a metal salt, a nitrogen-containing or sulfur-containing organic ligand is selected as an organic carbon source, or a single-armed carbon nanotube is selected as an inorganic carbon source to synthesize a corresponding precursor by a hydrothermal / solvothermal method, a template method or the like, and the target catalyst material is prepared by high-temperature pyrolysis or the like.

[0012] Further, the pyrolysis temperature is 600-800℃, and the atmosphere is inert atmosphere.

[0013] A neutral zinc-air battery, which uses the transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst as the air catalytic electrode, uses the aqueous solution containing large-size hydrophobic anion zinc salt as the electrolyte, and uses the zinc material as the negative electrode.

[0014] In other words, the neutral zinc-air battery is composed of the air catalytic electrode, the large-size hydrophobic anion zinc salt electrolyte, the zinc negative electrode, and the separator, etc. The air catalytic electrode is prepared by coating the transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst, the conductive agent, and the binder on the current collector in a certain proportion.

[0015] Further, the electrolyte is the aqueous solution of the large-size hydrophobic anion zinc salt with the concentration of 0.5-3 mol kg -1 , preferably 1-2 mol kg -1 , wherein the large-size hydrophobic anion includes trifluoromethanesulfonate ion (OTf - ), bis(trifluoromethylsulfonyl)imide ion (TFSI - ), or trifluoroacetate.

[0016] Further, the zinc material includes pure metal zinc, specifically including zinc foil, zinc plate, or foamed zinc; zinc alloy, specifically including zinc-aluminum alloy; and zinc composite material.

[0017] Further, the air catalytic electrode is composed of the transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst, the conductive agent, the binder, and the current collector; the mass ratio of the transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst, the conductive agent, and the binder is x:(9-x):1, wherein the range of x:(9-x) is 2:7-6:3.

[0018] Further, the conductive agent includes carbon black, acetylene black, or ketjen black; the binder includes polytetrafluoroethylene (PTFE) dispersion liquid or Nafion solution; and the current collector includes carbon paper, titanium mesh, or nickel mesh.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] (1) The present application selects the transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst as the catalyst of the neutral zinc-air battery, and compared with the carbon black used in the report, the porous carbon has a larger specific surface area and pore volume, which is beneficial to the adsorption and diffusion of O2 and other reactants and discharge products on the surface of the catalyst.

[0021] (2) The M-Nx / S x / Se x The C-doped sites are conducive to reducing the activation energy of the ORR / OER reaction process, improving the reaction kinetics, and thus reducing the voltage polarization in the battery charging and discharging process, and improving the energy density and energy efficiency of the battery.

[0022] (3) The transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst prepared in the application has M-N x / S x / Se x The C-doped sites are uniformly loaded in the porous carbon substrate, so that the discharge products are uniformly distributed on the surface of the catalyst, effectively inhibiting the problem of poor battery reversibility caused by the aggregation of the discharge products. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The charging and discharging curves of Example 1 and Comparative Example 1 are compared;

[0024] Figure 2 The charging and discharging curves of Example 2 and Comparative Example 1 are compared;

[0025] Figure 3 The charging and discharging curves of Example 3 and Comparative Example 2 are compared;

[0026] Figure 4 The scanning electron microscope and element distribution map of the ZIF derivative in the application. DETAILED DESCRIPTION

[0027] The application will be described in detail below in combination with the drawings and specific examples. The present embodiment is implemented on the premise of the technical solution of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following examples.

[0028] A neutral zinc-air battery, which uses a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst as an air catalytic electrode, uses an aqueous solution containing a large-size hydrophobic anion zinc salt as an electrolyte, and uses zinc as a negative electrode. The electrolyte can be an aqueous solution of a large-size hydrophobic anion zinc salt with a concentration of 1 m or 2 m ("m" refers to mol kg -1 ), etc. The large-size hydrophobic anion can be trifluoromethanesulfonate ion (OTf - ), bis(trifluoromethylsulfonyl)imide ion (TFSI - ), trifluoroacetate, etc. The zinc negative electrode can be pure metal zinc (including zinc foil, zinc plate, foamed zinc, etc.), zinc alloy (such as zinc-aluminum alloy), and zinc composite material, etc. The air catalytic electrode is composed of a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst, a conductive agent, a binder, and a current collector.

[0029] The conductive agent can be carbon black, acetylene black, ketjen black, etc., the binder can be polytetrafluoroethylene (PTFE) dispersion liquid, Nafion solution, etc., and the current collector can be carbon paper, titanium mesh, nickel mesh, etc. The use ratio of the transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst, the conductive agent and the binder is x:(9-x):1, wherein the range of x:(9-x) can be 2:7-6:3.

[0030] The transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst is mainly composed of one or two of transition metal elements Co, Fe, Mn and Ni, nitrogen or sulfur or selenium and carbon elements. First, a precursor is synthesized by a template method, a hydrothermal / solvothermal method, etc., and the target catalyst is prepared by high-temperature pyrolysis. The porous carbon base in the catalyst can be single-walled carbon nanotubes, multi-walled carbon nanotubes, porous carbon formed by high-temperature pyrolysis of metal-organic framework compounds (MOFs), etc. The pyrolysis temperature of the precursor can be 600, 700 or 800°C, etc., and the pyrolysis atmosphere can be an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere.

[0031] Example 1

[0032] Preparation of a uniformly loaded Co-N x The porous carbon material with uniformly loaded Co-N-C sites: first, an aqueous solution dissolving 2 mmol of Co(NO3)2·6H2O and 12 mmol of dimethylimidazole is left standing for 6 h, and a ZIF-67 precursor is obtained by water washing and centrifugation. The precursor is immersed in a 1 mol / L NaCl solution and stirred overnight, then evaporated to dryness, and then calcined at 800°C for 2 h under an argon atmosphere, and then washed with water to obtain a porous carbon material with uniformly loaded Co-N-C sites. x The porous carbon material with uniformly loaded Co-N-C sites: first, an aqueous solution dissolving 2 mmol of Co(NO3)2·6H2O and 12 mmol of dimethylimidazole is left standing for 6 h, and a ZIF-67 precursor is obtained by water washing and centrifugation. The precursor is immersed in a 1 mol / L NaCl solution and stirred overnight, then evaporated to dryness, and then calcined at 800°C for 2 h under an argon atmosphere, and then washed with water to obtain a porous carbon material with uniformly loaded Co-N-C sites.

[0033] Example 2

[0034] Preparation of a uniformly loaded CoMn-N x The porous carbon material with uniformly loaded Co-N-C sites: first, an aqueous solution dissolving 2 mmol of Co(NO3)2·6H2O and 12 mmol of dimethylimidazole is left standing for 6 h, and a ZIF-67 precursor is obtained by water washing and centrifugation. The precursor is immersed in a 1 mol / L NaCl solution and stirred overnight, then evaporated to dryness, and then calcined at 800°C for 2 h under an argon atmosphere, and then washed with water to obtain a porous carbon material with uniformly loaded Co-N-C sites. x The porous carbon material with uniformly loaded Co-N-C sites: first, an aqueous solution dissolving 2 mmol of Co(NO3)2·6H2O and 12 mmol of dimethylimidazole is left standing for 6 h, and a ZIF-67 precursor is obtained by water washing and centrifugation. The precursor is immersed in a 1 mol / L NaCl solution and stirred overnight, then evaporated to dryness, and then calcined at 800°C for 2 h under an argon atmosphere, and then washed with water to obtain a porous carbon material with uniformly loaded Co-N-C sites.

[0035] Example 3

[0036] Preparation of a uniformly loaded Co-Se x -C site porous carbon catalyst: 0.25 g Co(Ac)₂ and 0.18 g Na₂SeO₃ were dissolved in 40 mL of a mixed solution of diethyl phthalate and deionized water (2:1 volume ratio), and 0.5 g single-walled carbon nanotubes were added. After stirring evenly, the mixture was transferred to a reactor and reacted at 180 °C for 20 h. The precipitate was washed three times with water and dried. 200 mg of the precipitate was weighed and dispersed in a mixed solution containing 10 mL 1 mL H₂SO₄ and 30 mL ethanol, and heated under reflux at 100 °C for 12 h to obtain the target catalyst. A zinc-air battery was assembled and tested using a 1 mL Zn(CF₃SO₃)₂ solution as the electrolyte, the target catalyst as the air electrode, and zinc foil as the negative electrode.

[0037] Example 4

[0038] Preparation of a uniformly loaded Ni-N x &S x -C site porous carbon catalyst: The target catalyst was prepared by template method. First, 0.1g Ni(NO3)2 was weighed and placed in a mortar and dissolved in 200μL ethanol. Then, 0.8g glucose, 1.6g SiO2 nanospheres and 1.6g thiourea were added. After grinding for 30min and mixing, the powder was calcined at 700℃ for 5h under nitrogen atmosphere to obtain the target catalyst. A zinc-air battery was assembled and tested using 1m Zn(CF3SO3)2 solution as electrolyte, the target catalyst as air electrode and zinc foil as negative electrode.

[0039] Comparative Example 1

[0040] A porous carbon-based catalyst was prepared in this comparative example. The preparation method was basically the same as in Example 1, except that Co(NO3)2·6H2O was replaced with an equimolar amount of Zn(NO3)2·6H2O to prepare the ZIF-8 precursor. The precursor was then directly calcined at 800°C for 2 hours under an argon atmosphere to obtain the porous carbon material. A zinc-air battery was assembled and tested using a 1 mL Zn(CF3SO3)2 solution as the electrolyte, the porous carbon material as the air electrode catalyst, and zinc foil as the negative electrode.

[0041] Comparative Example 2

[0042] A zinc-air battery was assembled and tested using commercial carbon black as the air electrode catalyst, 1m Zn(CF3SO3)2 solution as the electrolyte, and zinc foil as the negative electrode.

[0043] The performance test results of the catalysts provided in the above embodiments and comparative examples are shown in Table 1 below:

[0044] Table 1

[0045] Example Discharge specific capacity (mAh g Zn -1 )]]> Energy efficiency (%) Example 1 688.3 73.93 Example 2 687.8 76.92 Example 3 683.5 72.63 Example 4 686.9 75.30 Comparative Example 1 680.1 56.98 Comparative Example 2 683.5 53.79

[0046] As shown in Table 1, the prepared transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst as an air electrode catalyst has a discharge capacity comparable to that of ordinary catalysts, but the energy efficiency is greatly improved, which is mainly due to the rich catalytic sites and pore structure, which promotes the ORR / OER reaction kinetics, speeds up the electron and ion transmission in the battery reaction process, and increases the battery discharge voltage while reducing the charging voltage, such as Figures 1-3 , which is intuitively shown by the accompanying drawings, thereby improving the energy efficiency of the battery.

[0047] In addition, the applicant uses zinc as the coordination center of ZIF-8. In the high-temperature calcination process, zinc is more easily volatilized, and the high-temperature sintered product is a nitrogen-doped porous carbon material, while the high-temperature sintered product of ZIF-67 with cobalt as the coordination center is a cobalt-nitrogen doped porous carbon material, as shown in the elemental distribution map of Figure 4 . Figure 4 (a-c) Scanning electron microscope and elemental distribution map of ZIF-8 derivative, (d-g) Scanning electron microscope and elemental distribution map of ZIF-67 derivative.

[0048] In this application, it is proved that the Co-Nx-C site porous carbon-based catalyst can also exhibit good catalytic performance in a neutral zinc-air battery with a large size hydrophobic anion zinc salt aqueous solution as the electrolyte, which increases the battery discharge voltage while reducing the charging voltage polarization, such as Figure 1 . The energy efficiency refers to the ratio of battery discharge energy to charging energy, and the energy is proportional to the battery voltage, so the battery assembled with the Co-Nx-C site porous carbon-based catalyst has higher discharge energy and lower charging energy, which makes it have higher energy efficiency.

[0049] The above is only the preferred embodiment of the present application, and is not intended to limit the other forms of the present application. Any skilled person in the art can use the disclosed technical content to make changes or modifications to equivalent embodiments. However, any simple modification, equivalent change and modification of the above embodiments made according to the technical essence of the present application without departing from the technical solution content of the present application still belongs to the protection scope of the present application.

Claims

1. A neutral zinc-air battery, characterized by, The battery takes a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst as an air catalytic electrode, takes an aqueous solution containing a large-size hydrophobic anion zinc salt as an electrolyte, and takes a zinc material as a negative electrode. The transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst comprises a transition metal element, an inorganic doping element and a porous carbon substrate. The transition metal element comprises one or two of Co, Fe, Mn or Ni; and the inorganic doping element comprises nitrogen, sulfur or selenium. The porous carbon substrate comprises single-walled carbon nanotubes, multi-walled carbon nanotubes or porous carbon formed by high-temperature pyrolysis of metal-organic framework compounds (MOFs). The porous carbon catalyst is prepared by the following method: first, a precursor is synthesized by a template method or a solvothermal method, and then a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst is prepared by high-temperature pyrolysis. The transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst is 2e - Bifunctional electrocatalyst materials with catalytic performance.

2. A neutral zinc-air battery according to claim 1, characterized in that, The temperature of the pyrolysis is 600-800℃, and the atmosphere is an inert atmosphere.

3. A neutral zinc-air battery according to claim 1, wherein The electrolyte is an aqueous solution of a large size hydrophobic anion zinc salt having a concentration of 0.5-3 mol kg -1 -1, comprising triflate ions (OTf - ), bis(trifluoromethylsulfonyl)imide ions (TFSI - ) or trifluoroacetate.

4. A non-aqueous zinc-air cell according to claim 1, wherein The zinc material comprises pure metal zinc.

5. A non-aqueous zinc-air cell according to claim 4, wherein the zinc-air cell is a primary cell. The pure metal zinc comprises zinc foil, zinc plate or foamed zinc.

6. A non-aqueous zinc-air cell according to claim 1, wherein The zinc material comprises a zinc alloy.

7. A non-aqueous zinc-air cell according to claim 6 wherein, The zinc alloy comprises, for example, a zinc-aluminum alloy.

8. A non-aqueous zinc-air cell according to claim 1, wherein, The air catalytic electrode is composed of a transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst, a conductive agent, a binder and a current collector; and the mass ratio of the transition metal-nitrogen / sulfur / selenium doped porous carbon catalyst, the conductive agent and the binder is x:(9-x):1, wherein the range of x:(9-x) is 2:7-6:

3.

9. A neutral zinc-air battery according to claim 8, characterized in that, The conductive agent comprises carbon black, acetylene black or ketjen black, the binder comprises polytetrafluoroethylene (PTFE) dispersion or Nafion solution, and the current collector comprises carbon paper, titanium mesh or nickel mesh.

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