Preparation method and application of nitrogen-doped reduced graphene oxide nanomaterial loaded with nickel-doped trimanganese tetraoxide with photothermal effect

Abstract

This invention provides a method for preparing a nickel-doped manganese tetroxide nitrogen-doped reduced graphene oxide nanomaterial with photothermal effect and its application in a zinc-air battery. The preparation method is as follows: graphene oxide is dispersed in H2O, and then n-pentanol, manganese salt, nickel salt and ammonia are added and mixed to obtain a mixture; the mixture is then reacted in a high-pressure reactor using a hydrothermal method, and the suspension is washed with organic solvent and water, and finally freeze-dried to obtain Ni-Mn3O4 / N-rGO material, wherein the doping amount of nickel salt is less than 10% of the molar amount of manganese salt. The nanomaterial prepared by this invention has a photothermal effect and can be used as a bifunctional photothermal catalyst with excellent OER / ORR performance, and also has excellent stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical fields of nanofunctional materials and electrocatalytic energy technology, and particularly to a preparation method and application of a nitrogen-doped reduced graphene oxide nanomaterial loaded with nickel-doped trimanganese tetraoxide and having a photothermal effect. BACKGROUND

[0002] With the gradual depletion of fossil fuels and the continuous deterioration of the environment, the global demand for energy is increasing, prompting people to urgently seek renewable energy, such as wind and solar energy. However, these sustainable energy sources are usually intermittent, and there is a time gap between supply and demand. Therefore, in order to realize the sustainable energy prospect, there is a great need for energy conversion and storage technologies, such as water electrolysis technology for converting solar and wind generated electricity into hydrogen fuel, rechargeable metal-air batteries, which have extremely high energy density and show low cost, environmental friendliness and safety, and also reversible fuel cells that can produce hydrogen fuel through electrochemical processes. Controlled by electrochemical reactions, the development of these energy conversion and storage systems is significantly hindered by the slow kinetics of the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), which have attracted a lot of research attention in the past few decades.

[0003] For air electrode, the performance of rechargeable zinc-air batteries (ZABs) depends largely on the bifunctional electrocatalyst of the air electrode, which can effectively carry out oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during discharge and charge processes, respectively. Therefore, it is essential to develop high-activity bifunctional electrocatalysts. ZABs mainly use noble metals such as Pt, Pd, Au, etc. as anode ORR catalysts; RuO2 and IrO2 as cathode OER catalysts. However, these noble metal catalysts have problems such as resource scarcity, slow reaction kinetics, poor stability, etc., which seriously hinder the development of ZABs. Therefore, developing new types of low-cost, high-catalytic-performance bifunctional catalysts is of great significance to promote the kinetics of cathode ORR and OER and improve the performance of rechargeable zinc-air batteries. Transition metal oxides are abundant in resources and have electrocatalytic performance, and are considered as alternative materials for ORR and OER catalysts. However, transition metal catalysts generally have low catalytic performance and poor stability, so it is necessary to improve their ORR and OER catalytic performance and stability through modification before they can be directly applied to rechargeable zinc-air batteries. It is well known that Mn has excellent ORR performance, but its OER active sites are insufficient, so we doped it with metal Ni to improve its OER performance, making it a bifunctional catalyst, and applied it to liquid zinc-air batteries and flexible zinc-air batteries. However, transition metal oxides have poor conductivity, limited exposed active sites, poor stability, and other factors, which result in unsatisfactory bifunctional catalytic activity. This patent proposes a new strategy to improve the catalytic performance of transition metal oxides. By collecting the thermal energy of near-infrared light, the surface of the catalyst can be reconstructed into a high-activity substance, accelerating the electrocatalytic kinetics, while the enhanced reaction kinetics, more active sites, accelerated electron transfer, and easier bubble release provide excellent bifunctional ORR-OER performance. The photo-thermal electrocatalyst (referred to as photo-thermal electrocatalyst) with photo-thermal effect can convert light into heat under the illumination of visible light or near-infrared (NIR) light, thereby achieving in-situ heating without the need for additional equipment to provide thermal energy. The challenge of using photo-thermal effect in electrocatalysis is to develop materials with photo-response and electrocatalytic activity that can effectively convert light energy into heat energy, thereby improving efficiency. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, and to provide a preparation method and application of a nickel-doped manganese oxide-loaded nitrogen-doped reduced graphene oxide nanomaterial with photo-thermal effect. The technical solutions adopted by the present application are as follows: a preparation method of a nickel-doped manganese oxide-loaded nitrogen-doped reduced graphene oxide nanomaterial with photo-thermal effect, comprising the following steps:

[0005] The graphene oxide (GO) is dispersed in H2O, and then n-pentanol, manganese salt, nickel salt and ammonia water are added to mix to obtain a mixture; the mixture is placed in a reaction autoclave by using a hydrothermal method to react, the suspension liquid is washed with an organic solvent and water, and finally freeze-drying is performed to obtain a Ni-Mn3O4 / N-rGO material; wherein the doping amount of the nickel salt is less than 10% of the manganese salt. As the most preferred, the doping amount of the nickel salt is 3% of the molar amount of the manganese salt.

[0006] As preferred, the graphene oxide is a single-layer structure; the reaction temperature of the hydrothermal method is 100-300 ℃, and the reaction time is 1-20 h; the manganese salt uses manganese acetate tetrahydrate Mn(Ac)2·4H2O, and the nickel salt uses nickel acetate tetrahydrate Ni(Ac)2·4H2O as the nickel source.

[0007] The application of the Ni-doped Mn3O4-loaded N-doped reduced graphene oxide nanomaterial (Ni-Mn3O4 / N-rGO) with a photo-thermal effect prepared by the above preparation method is also provided: a zinc-air battery with a chargeable liquid phase is assembled by using a current collector (such as carbon cloth or nickel foam) loaded with the Ni-Mn3O4 / N-rGO electrocatalyst as an air cathode, using zinc as an anode, and using a KOH solution as an electrolyte to ensure the reversible oxidation-reduction reaction of the zinc anode; or a zinc-air battery with a chargeable flexibility is assembled by using a current collector (such as carbon fiber paper or nickel foam) loaded with the Ni-Mn3O4 / N-rGO electrocatalyst as an air cathode, using zinc as an anode, and using a water gel containing KOH as a solid-state electrolyte.

[0008] The Ni-doped Mn3O4-loaded N-doped reduced graphene oxide nanomaterial with a photo-thermal effect prepared by the above method as a bifunctional electrocatalyst, and the application of the bifunctional electrocatalyst in the preparation of a liquid phase or flexible zinc-air battery anode all fall within the protection scope of the present application.

[0009] The beneficial effects of the present application are as follows:

[0010] (1) The transition metal oxide nanomaterial is one of the most effective materials for obtaining the catalytic activity of the air electrode of a liquid phase and flexible zinc-air battery. However, there are still great challenges in increasing the effective collision of the reaction, reducing the energy barrier of the reaction, increasing the active sites of the catalyst and increasing the conductivity. The present application synthesizes a Ni-doped Mn3O4-loaded N-doped reduced graphene oxide nanomaterial with a photo-thermal effect by using a hydrothermal method, which is used as a bifunctional photo-thermal catalyst with excellent OER / ORR performance and excellent stability. The Ni doping can not only effectively adjust the adsorption energy of the active substance and reduce the kinetic potential barrier of ORR, but also can effectively increase the conductivity of the material and the active sites of the catalyst. adThe interaction strength is optimal, the Sabatier principle of catalyst design is met, and better OER activity than Co, Fe or Mn-based catalysts is shown. Therefore, compared with conventional materials, excellent hydrophilicity is provided, the formation barrier of intermediate products is reduced, and the mass transfer of products in the catalytic process is promoted.

[0011] (2) The application proposes a new strategy of photothermal effect to improve catalytic activity, provides a nano-composite material with light response performance and electrocatalytic activity of converting light energy into heat energy by loading Ni-doped Mn3O4 N-doped reduced graphene oxide nanomaterial with photothermal effect, improves the effective collision between reactant molecules by converting near-infrared light into heat, reduces the energy barrier of the reaction, and improves the electron transport, so that the obtained bifunctional electrocatalyst shows very high OER / ORR catalytic performance. -2 In an embodiment of the application, the OER has an overpotential of 286 mV at a current density of 10 mA cm -2 , and the ORR has a half-wave potential of 0.831 V vs RHE. When applied to liquid and flexible zinc-air batteries, it shows high power density of 168.15 mW cm -2 and 100.53 mW cm -2 , respectively, and long cycle stability. Therefore, the nano-composite material provided by the application has excellent electrochemical performance, especially in the field of electrocatalysis and shows excellent liquid and flexible zinc-air battery performance, and has good industrialization potential. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings obtained according to these drawings without creative labor are still within the scope of the application.

[0013] Figure 1 TEM of Ni 3% -Mn3O4 / N-rGO in Example 1, a and b are the results at different magnifications, respectively;

[0014] Figure 2 XRD of Ni 3% -Mn3O4 / N-rGO in Example 1;

[0015] Figure 3 EDS element map of Ni 3% -Mn3O4 / N-rGO in Example 1;

[0016] Figure 4 Ni in Example 1 3% Photothermal effect diagram of -Mn3O4 / N-rGO;

[0017] Figure 5 Ni in Example 1 3% -Mn3O4 / N-rGO and comparative sample LSV oxygen evolution performance (OER) diagram, where Ni 3% -Mn3O4 / N-rGO-Light indicates light-assisted operation;

[0018] Figure 6 Ni in Example 1 3% -Mn3O4 / N-rGO and the LSV oxygen reduction performance (OER) of the control sample, where Ni 3% -Mn3O4 / N-rGO-Light indicates light-assisted operation;

[0019] Figure 7 For example Ni in application 1 3% -Mn3O4 / N-rGO as the specific capacity density diagram of the positive electrode of liquid zinc-air battery, where Ni 3% -Mn3O4 / N-rGO-Light indicates light-assisted operation;

[0020] Figure 8 For example Ni in application 1 3% Mn3O4 / N-rGO was used as the positive electrode in a liquid zinc-air battery at a current density of 10 mAcm⁻¹. -2 The cyclic stability plot, where Ni 3% -Mn3O4 / N-rGO-Light indicates light-assisted operation;

[0021] Figure 9 For example Ni in application 2 3% -Mn3O4 / N-rGO is used as the discharge rate diagram for flexible zinc-air batteries, where Ni 3% -Mn3O4 / N-rGO-Light indicates light-assisted operation;

[0022] Figure 10 For example Ni in application 2 3% Cycling curves of Mn3O4 / N-rGO as a flexible zinc-air battery under various mechanical deformations;

[0023] Figure 11 For example Ni in application 2 3% -Mn3O4 / N-rGO as a practical application of flexible zinc-air batteries. Detailed Implementation

[0024] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings.

[0025] Example 1:

[0026] S1, take graphite, NaNO3, concentrated sulfuric acid, mechanical stirring in ice bath for 2 h, then slowly add KMnO4, the whole process temperature needs to be kept less than 10 ℃, continue to stir for 2 h; ice bath is replaced with normal temperature water, heat at 35 ℃ for 1 h; slowly drop pure water with a needle tube, present green yellow thick liquid; in oil bath 98 ℃, stir for 30 min; add water, stir at room temperature for 1 h; add H2O2, the solution changes from brown yellow to golden yellow, gas bubbles are generated, stand and settle down, pour off the supernatant; repeatedly add water and stand; centrifugal to get colloidal yellow brown material, transfer to 8000-10000 dialysis capacity of dialysis bag, dialysis in water to neutral, synthesize GO;

[0027] S2, ultrasonic dispersion of the above synthesized GO in H2O, take 2 mL of GO aqueous solution with a concentration of 5 mg mL -1 , add 20 mL of n-pentanol, 2 mL of NH4OH, 98 mg of Mn(Ac)2·4H2O, 2.94 mg of Ni(Ac)2·4H2O; the mixture is kept at 80 ℃ for 10 h (stir all the time), the mixture is put into a reaction autoclave by hydrothermal method, and heated to 200 ℃ at high temperature for 5 h; washed with ethanol and water respectively for two times, and finally freeze-dried for 24 h. As shown in Figure 1 , the size of the obtained Ni 3% -Mn3O4 / N-rGO is below 100 nm, and has obvious lattice fringes, which proves that it has good crystallinity.

[0028] Comparative Example 1:

[0029] Without adding Ni precursor, other conditions are the same as those of Example 1, Mn3O4 / N-rGO is prepared.

[0030] The Ni 3% -Mn3O4 / N-rGO prepared in Example 1 is subjected to X-ray diffraction test analysis with the Mn3O4 / N-rGO prepared in Comparative Example 1, as shown in Figure 2 , the peak value of the Ni 3% -Mn3O4 / N-rGO is consistent with that of the Mn3O4 / N-rGO (JCPDS card No. 80-0382), and there is no obvious peak value due to less Ni doping, but through Figure 3 energy dispersive X-ray spectroscopy (EDS) element map, it can be seen that the Ni element is successfully doped into the Mn3O4 / N-rGO.

[0031] Comparative Example 2:

[0032] The content of the Ni precursor in Example 1 was reduced to 0.98 mg, and Ni was synthesized using the same hydrothermal method to obtain Ni. 1% -Mn3O4 / N-rGO.

[0033] Comparative Example 3:

[0034] The content of the Ni precursor in Example 1 was increased to 4.90 mg, and Ni was synthesized using the same hydrothermal method to obtain Ni. 5% -Mn3O4 / N-rGO.

[0035] Electrocatalytic application: The composite material prepared above was used as the working electrode. In a three-electrode system (carbon rod as counter electrode, Hg / HgO or Ag / AgCl electrode as reference electrode), the performance of the catalyst was tested for ORR with 0.1 M KOH solution as electrolyte; the performance of the catalyst was tested for OER with 1.0 M KOH solution as electrolyte.

[0036] Through experimental testing and screening, the inventors found that Ni-Mn3O4 / N-rGO prepared with a nickel salt doping amount of 0-10% (relative to the mass of manganese salt) exhibited superior performance compared to Ni-Mn3O4 / N-rGO prepared with a nickel salt doping amount greater than 10%. Further screening of products prepared with a nickel salt doping amount of 0-10% revealed that the bifunctional catalytic activity was best when the Ni doping amount was 3%. Some data are shown in Example 1 and Comparative Examples 1-3. Compared to Comparative Examples 1, 2, and 3 with no Ni doping and when the Ni doping ratio was 1% or 5%, the Ni doping amount in Example 1 was significantly higher. 3% The Mn3O4 / N-rGO configuration exhibits the best bifunctional catalytic activity, with the highest half-wave potential E during the ORR process. 1 / 2 = 0.806 V vs RHE; During the OER process, at a current density of 10 mA / cm² 2 At that time, the overpotential was 378 mV. This sample exhibited the best electrocatalytic performance.

[0037] The material prepared in Example 1 was used as a photothermal material, and its photothermal properties were measured by irradiation with an 808 nm near-infrared laser. Figure 4 It can be seen from the data that Ni was irradiated with near-infrared light in 1.0 M KOH solution. 3% The temperature of the -Mn3O4 / N-rGO electrode can rise rapidly to 88℃ in a very short time, while the temperature of the electrolyte remains almost unchanged, indicating that the electrode only experiences localized temperature rise.

[0038] ORR was tested using 0.1 M KOH solution as the electrolyte to assess its performance after photothermal treatment; OER was tested using 1.0 M KOH solution as the electrolyte to assess its catalyst performance. During the ORR process, its half-wave potential E... 1 / 2 = 0.831 V vs RHE; During the OER process, the catalytic performance is at 10 mAcm -1 At current density, it is 1.516 V vs RHE, and the overpotential is 286 mV.

[0039] from Figure 5 As can be seen from Example 1, the composite material prepared in Example 1 exhibits superior OER performance under near-infrared light irradiation.

[0040] from Figure 6 As can be seen from Example 1, the composite material prepared in Example 1 exhibits superior ORR performance under near-infrared light irradiation.

[0041] Furthermore, the inventors also prepared Ni using this method. 3% -Mn3O4 / N-rGO was applied to zinc-air batteries, and performance tests were conducted according to use cases 1-2.

[0042] Application Example 1:

[0043] Sample preparation: The catalyst slurry consisted of 6 mg of the material obtained in Example 1, 3 mg of Ketjen black, 50 μL of 5 wt% Nafion, and 1000 μL of ethanol solution. A homogeneous solution was formed by ultrasonic treatment. 80 μL of catalyst ink was uniformly dropped onto hydrophobic carbon paper (loading was 1 mg cm⁻¹). -2 The zinc-air battery was used as the air cathode in a liquid-phase zinc-air cell. Under the same conditions, a commercially available 20% wt Pt / C and RuO2 electrocatalyst at a mass ratio of 1:1 was used as a control to prepare a liquid-phase zinc-air battery. The electrolyte consisted of 0.2 M Zn(Ac)2 + 6 M KOH. All zinc-air batteries were tested at room temperature (25 °C). The LSV was measured using a scan rate of 5 mV / s. -1 Polarization curves were measured. Current density and power density were calculated based on the effective surface area of ​​the electrocatalyst coating. Charge-discharge cycle performance was measured at a constant current density of 10 mA / cm². -2 It is carried out under the following conditions.

[0044] Application: at 10 mA / cm 2 At current density, Figure 7 The material Ni can be seen from 3% The specific capacity of -Mn3O4 / N-rGO is 766 mAh / g. zn, its specific capacity increased to 787 mAh / g zn , which is close to the theoretical value. Based on the strong coupling between metal ions between nickel and manganese promoted by the composite on the conductive N-doped rGO, a coupling reaction is provided, thereby improving the performance. In addition, the strong coupling also reduces the interface resistance, improves the electron transport; enhances the stability of the material. Figure 8 At a current density of 10 mA / cm 2 , the optimal material exhibits excellent stability and can be relatively stably cycled for more than 350 h, fully demonstrating that the material has excellent cycle stability.

[0045] Application Example 2:

[0046] Sample preparation: 6 mg of the material synthesized in Example 1, 3 mg of Ketjen black, 50 μL of 5 wt% Nafion, and 1000 μL of ethanol solution were composed and formed into a homogeneous solution by ultrasonic treatment, and 80 μL of catalyst ink was uniformly dropped on the current collector composed of hydrophobic carbon cloth and foam nickel (loading amount was 1 mg cm -2 ), as the air cathode of the flexible zinc-air battery. Under the same conditions, we used commercial 20% wt Pt / C and RuO2 as the electrocatalyst according to the mass ratio of 1:1 to prepare a flexible zinc-air battery as a comparison. All the flexible zinc-air batteries were tested in an atmosphere at room temperature 25 ℃, respectively. Among them, LSV is measured by polarization curve measurement with a scan rate of 50 mV s -1 . The current density and power density are calculated based on the effective surface area coated with the electrocatalyst, and the charge-discharge cycle performance is carried out under the condition of constant current density of 2 mA cm -2 .

[0047] Application: When irradiated by 808 nm near-infrared laser, the discharge platform of Ni 3% -Mn3O4 / N-rGO at different current densities is higher than that of the sample without near-infrared light (about 1.2 V) Figure 9 . Due to the needs of practical application, such as Figure 10 The flexible zinc-air battery was subjected to various mechanical performance bending tests, and the flexible zinc-air battery could still work normally, at the same time, the flexible zinc-air battery could still make a small bulb light up in an environment lower than room temperature, in addition, a flexible zinc-air battery could make a timer work normally and smoothly (such as under the conditions of bending, cutting, low temperature, etc.), showing good practicability and environmental adaptability (such as Figure 11 ).

[0048] The above merely provides the preferred embodiment of the application, and cannot allude the protection scope of the application, therefore any equivalent changes made according to the claims of the application shall be within the scope of the application.

Claims

1. A method for preparing nitrogen-doped reduced graphene oxide nanomaterials loaded with nickel-doped manganese tetroxide and exhibiting photothermal effect, characterized in that... Includes the following steps: Graphene oxide was dispersed in H2O, and then n-pentanol, manganese salt, nickel salt and ammonia were added and mixed to obtain a mixture. The mixture was then placed in a high-pressure reactor for reaction using a hydrothermal method. The resulting suspension was washed with organic solvent and water, and finally freeze-dried to obtain Ni-Mn3O4 / N-rGO material, which is a nitrogen-doped reduced graphene oxide nanomaterial loaded with nickel doped manganese tetroxide with photothermal effect. The nickel salt doping amount is 3% of the molar amount of the manganese salt; Manganese salt is Mn(Ac)2·4H2O, and nickel salt is Ni(Ac)2·4H2O. Among them, graphene oxide has a single-layer structure; The hydrothermal reaction temperature is 100-300 ℃, and the time is 1-20 h.

2. The application of the nitrogen-doped reduced graphene oxide nanomaterial with photothermal effect supported on nickel-doped manganese tetroxide prepared as claimed in claim 1, characterized in that: A rechargeable liquid-phase zinc-air battery was assembled using a current collector supported on a Ni-Mn3O4 / N-rGO electrocatalyst as the air cathode, zinc as the anode, and KOH solution as the electrolyte.

3. The application of the nitrogen-doped reduced graphene oxide nanomaterial with photothermal effect supported on nickel-doped manganese tetroxide prepared as claimed in claim 1, characterized in that: A rechargeable flexible zinc-air battery was assembled using a current collector supported on a Ni-Mn3O4 / N-rGO electrocatalyst as the air cathode, zinc as the anode, and a KOH-containing hydrogel as the solid electrolyte.

4. The nitrogen-doped reduced graphene oxide nanomaterial with photothermal effect supported on nickel-doped manganese tetroxide prepared according to claim 1 as a bifunctional electrocatalyst.

5. The application of the bifunctional electrocatalyst according to claim 4 in the preparation of positive electrodes for liquid-phase or flexible zinc-air batteries.

6. A liquid-phase or flexible zinc-air battery, characterized in that: It includes a positive electrode prepared from the bifunctional electrocatalyst as described in claim 4.

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