Carbon-supported metal cluster hydrogen evolution electrode, preparation method and application

Abstract

The invention belongs to the technical field of electrochemistry, and provides a carbon-supported metal cluster hydrogen evolution electrode, a preparation method and application, and the method comprises the following steps: manufacturing a carbon conductive substrate; preparing deposition liquid containing soluble metal salt and carbon quantum dots; the carbon conductive substrate is placed in a deposition solution containing soluble metal salt and carbon quantum dots, and the carbon-supported metal cluster hydrogen evolution electrode is prepared through a one-step electrodeposition method. The electrode prepared by the method can be used for chlor-alkali industry, hydrogen preparation by electrolyzing water or hydrogen isotope separation and fuel cells, is low in preparation raw material cost and mild in preparation condition, has ultralow hydrogen evolution overpotential and excellent stability, and shows good industrial prospect and economic value.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of electrochemistry, and particularly relates to a carbon-supported metal cluster hydrogen evolution electrode, a preparation method and an application thereof. Background Art

[0002] During the process of electrolytic water for hydrogen production, the hydrogen evolution electrode is a core component, and its performance directly affects the electrolysis efficiency, stability and hydrogen production purity. An ideal hydrogen evolution electrode needs to have high catalytic activity to reduce the overpotential of the electrolysis reaction and improve the energy conversion efficiency; it also needs to have good catalytic stability and durability to resist side reactions such as corrosion and oxidation during long-term electrolysis; at the same time, it should have excellent electrical conductivity to reduce the resistance loss.

[0003] Macroscopically, under alkaline conditions, the concentration of protons is very low, so it is considered that H2O directly participates in the reaction and obtains electrons on the surface of the cathode catalyst to generate hydrogen. Microscopically, the HER (Hydrogen Evolution Reaction) includes the adsorption of reaction species on the electrode surface, the transfer of electrons, and the desorption process of reaction species.

[0004] Currently, the following main problems exist in the preparation process of alkaline hydrogen evolution electrodes:

[0005] 1) Currently, the main active material of the cathode electrode in commercial alkaline electrolyzers is Raney nickel, which has the problem of low current density, resulting in a large volume and large floor area of the electrolyzer;

[0006] 2) When operating under long-term high current density conditions, the method of loading the catalyst based on the binder onto the carrier is prone to large-scale shedding due to the relatively weak interaction between the catalyst and the carrier;

[0007] 3) The electrode is in an oxidation / reduction potential and a high-temperature, high-concentration alkaline corrosion environment, which is likely to cause the reconstruction of the active phase and the dissolution of the active substance in the electrode.

[0008] Therefore, it is of great practical significance to research and develop high-efficiency electrocatalysts with low cost, high reserves and environmental friendliness to improve energy conversion. Summary of the Invention

[0009] To solve the above problems, the present invention discloses a one-step electrodeposition method, which uses a soluble metal salt and an aqueous solution of nitrogen-doped carbon quantum dots as the deposition solution, and can provide an active cathode with good catalytic activity and stable structure, as well as a preparation method and an application thereof.

[0010] The technical key points of the present disclosure can be embodied by the following solutions:

[0011] In a first aspect, an embodiment of the present disclosure provides a method for preparing a carbon-supported metal cluster hydrogen evolution electrode, the method comprising the following steps: fabricating a carbon conductive substrate; preparing a deposition solution containing a soluble metal salt and carbon quantum dots; placing the carbon conductive substrate in the deposition solution containing the soluble metal salt and carbon quantum dots, and preparing the carbon-supported metal cluster hydrogen evolution electrode by a one-step electrodeposition method.

[0012] Further,

[0013] The deposition solution containing the soluble metal salt and carbon quantum dots is prepared from an aqueous solution of carbon quantum dots and a soluble metal salt.

[0014] Further,

[0015] The soluble metal salt is one or more of inorganic salts of transition metals.

[0016] Further,

[0017] The carbon quantum dots are nitrogen-doped carbon quantum dots.

[0018] Further,

[0019] The one-step electrodeposition method includes:

[0020] Using the carbon conductive substrate as the working electrode, a platinum sheet electrode as the counter electrode, and a saturated calomel electrode as the reference electrode to form a three-electrode system;

[0021] Using one of the potentiostatic method, potentiostatic method, and cyclic voltammetry method to perform electrodeposition in the three-electrode system.

[0022] Further,

[0023] Preparing the aqueous solution of carbon quantum dots includes the following steps:

[0024] Using at least one of microwave hydrothermal method, hydrothermal method, solvothermal method, microwave-assisted method, acid oxidation method, and electrochemical method to prepare a nitrogen-doped carbon quantum dot solution;

[0025] Centrifuging and filtering the obtained nitrogen-doped carbon quantum dot solution to remove the agglomerated carbon;

[0026] Using a dialysis bag to remove the unreacted small molecules from the centrifuged and filtered nitrogen-doped carbon quantum dot solution to obtain the aqueous solution of carbon quantum dots.

[0027] In a second aspect, another embodiment of the present disclosure provides a carbon-supported metal cluster hydrogen evolution electrode, the electrode comprising a carbon conductive substrate, and a uniform carbon-supported metal cluster coating is covered on the surface of the carbon conductive substrate.

[0028] Further,

[0029] The coating is prepared by a one-step electrodeposition method by placing a carbon conductive substrate in a deposition solution containing a soluble metal salt and carbon quantum dots.

[0030] Furthermore,

[0031] The carbon-supported metal cluster is a carbon-supported nickel metal cluster.

[0032] In a third aspect, the present disclosure also provides the use of any of the aforementioned carbon-supported metal cluster hydrogen evolution electrodes or the electrodes prepared by any of the aforementioned methods in the chlor-alkali industry, electrolytic water for hydrogen production or hydrogen isotope separation, and fuel cells.

[0033] Compared with the prior art, the present disclosure has the following advantages:

[0034] 1) The present disclosure uses carbon paper as the substrate material, which can provide more active sites for the hydrogen evolution reaction. This means that more hydrogen evolution catalysts can be loaded, increasing the contact area between the catalyst and the reaction solution, enabling the catalyst to fully play its role, and thus improving the rate and hydrogen production of the hydrogen evolution reaction.

[0035] 2) The present disclosure uses the electrodeposition method to make the electrolyte evenly distributed on the substrate surface, so that metal ions and carbon quantum dots are evenly deposited on the electrode surface, thereby obtaining a coating with uniform thickness and dense structure, and further improving the alkaline hydrogen evolution performance of the electrode.

[0036] Other features and advantages of the present disclosure will be described in the subsequent description, and part of them will be obvious from the description, or understood by implementing the present disclosure. The objectives and other advantages of the present disclosure can be achieved and obtained through the structures pointed out in the description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 Scanning electron microscope photograph of the hydrogen evolution electrode prepared in Example 1 of the present invention.

[0039] Figure 2 LSV curve of the carbon-supported nickel metal cluster electrode prepared in Example 1 of the present invention.

[0040] Figure 3 For the carbon-supported nickel metal cluster electrode prepared in Example 1 of the present invention at 10 mA cm -2Chronopotentiometry curves under the current density condition of

[0041] Figure 4 The I-V curve of the carbon-supported metal nickel cluster electrode prepared in Example 1 of the present invention.

[0042] Figure 5 The carbon-supported metal nickel cluster electrode group prepared in Example 1 of the present invention was assembled as a cathode electrode into an electrolytic cell. Under the operating conditions of 80 °C and 30% KOH, at 500 mA cm -2 Stability diagram at a current density of

[0043] Figure 6 The carbon-supported metal nickel cluster electrode prepared in Example 1 of the present invention at 500 mA cm -2 Current efficiency diagram under the current density condition of Detailed implementation manners

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0045] The carbon quantum dots (CQDs) involved in the embodiments of the present disclosure, also known as carbon dots or carbon nanodots, are a class of zero-dimensional carbon nanomaterials with remarkable fluorescence properties. They are composed of ultra-fine, dispersed, quasi-spherical carbon nanoparticles with a size below 10 nm.

[0046] Example 1

[0047] A preparation method of a carbon-supported metal cluster hydrogen evolution electrode of the present disclosure includes the following steps:

[0048] 1) Fabricate a carbon conductive substrate.

[0049] a) Cut a carbon paper with a size of 10×30 mm; b) Pretreatment: Place the cut carbon paper in ethanol and acetone respectively and ultrasonically treat for 15 min to remove the oil stains on the surface; c) Rinse the carbon paper with ultra-pure water after removing the oil stains on the surface; d) Dry the rinsed carbon paper. Set aside.

[0050] Preferably, the conductive substrate can also be one of carbon cloth, graphite sheet, etc.

[0051] Using carbon paper as the substrate material can provide more active sites for the hydrogen evolution reaction, which means that more hydrogen evolution catalysts can be loaded, increasing the contact area between the catalyst and the reaction solution, allowing the catalyst to fully function, thereby increasing the rate of the hydrogen evolution reaction and the amount of hydrogen produced.

[0052] 2) Prepare carbon quantum dot aqueous solution.

[0053] a) A nitrogen-doped carbon quantum dot solution was prepared by microwave hydrothermal method, and the reaction solution preparation process was as follows:

[0054] First, accurately weigh 25 g of citric acid and dissolve it in deionized water to prepare a citric acid aqueous solution with a concentration of 25 g / L. Then, use a 50 mL graduated cylinder to accurately measure 25 mL of ethylenediamine and mix it evenly with the citric acid aqueous solution.

[0055] Reaction conditions: microwave digestion power 100-1000W, heating rate 2-10℃ / min, insulation temperature 120-280℃, insulation time 1-60min;

[0056] b) centrifuging the obtained nitrogen-doped carbon quantum dot solution at 10,000 rpm for 10 min to filter out agglomerated carbon;

[0057] c) Then, the solution was purified by dialysis bag (molecular cutoff: 500 Da) and dialyzed for 24 hours to remove unreacted small molecules, thereby obtaining a carbon quantum dot aqueous solution for later use.

[0058] In other preferred embodiments, methods for preparing the carbon quantum dot aqueous solution include hydrothermal method, solvothermal method, microwave-assisted method, acid oxidation method and electrochemical method.

[0059] 3) Preparing a deposition solution containing soluble metal salts and nitrogen-doped carbon quantum dots, the preparation process is as follows:

[0060] Weigh 1.45 g of nickel nitrate hexahydrate, transfer it to a 500 mL volumetric flask, and dilute to the mark with deionized water to prepare a nickel nitrate hexahydrate standard solution with a concentration of 0.01 mol / L. Subsequently, use a pipette to accurately measure 10 mL of the pre-prepared carbon quantum dot aqueous solution and mix it evenly with the above nickel nitrate hexahydrate solution.

[0061] In other preferred embodiments, the metal salt in the deposition solution is one or more of hydrochloride, nitrate, and sulfate of a transition metal (the molar ratio of Ni is controlled to be 1:1 or 1:1:1, and the final concentration of the mixed nickel salt is 0.01 mol / L), and the concentration of the nickel salt is 0.01 mol / L. The volume of the carbon quantum dot aqueous solution is 10 mL.

[0062] 4) A carbon-supported metal cluster hydrogen evolution electrode is prepared by a one-step electrodeposition method by placing a carbon conductive substrate in a deposition solution containing a soluble metal salt and nitrogen-doped carbon quantum dots.

[0063] a) Take 100 mL of the prepared deposition solution containing a soluble metal salt and nitrogen-doped carbon quantum dots and place it in a beaker. Electrochemical deposition is carried out in a three-electrode system by the potentiostatic method (E = -1V vs. SCE) for 20 - 90 min. The above carbon conductive substrate serves as the working electrode, a platinum sheet serves as the counter electrode, and a saturated calomel electrode serves as the reference electrode to form the three-electrode system.

[0064] In other preferred embodiments, the electrodeposition process uses one of the constant current method, potentiostatic method, and cyclic voltammetry, and the deposition time is 10 s - 10 h. The preferred deposition time is 20 - 120 min.

[0065] b) Subsequently, it is washed with a large amount of ultrapure water and dried to obtain a carbon-supported nickel metal cluster hydrogen evolution electrode.

[0066] The electrodeposition method is used to make the electrolyte evenly distributed on the substrate surface, so that metal ions and carbon quantum dots are evenly deposited on the electrode surface, thereby obtaining a coating with uniform thickness and dense structure, and further improving the alkaline hydrogen evolution performance of the electrode.

[0067] The scanning electron microscope photograph of the carbon-supported nickel metal cluster hydrogen evolution electrode obtained in Example 1 is as Figure 1 shown, and it can be seen that the electrode surface coating is uniform and dense.

[0068] The carbon-supported metal cluster hydrogen evolution electrode is subjected to electrochemical testing, and the LSV (linear sweep voltammetry) curve is as Figure 2 shown (where the reaction temperature is 25 °C, the electrolyte is 1 M KOH, and the scanning rate is 10 mV / s). Compared with the commercial 20% Pt / C catalyst, the potential of the carbon-supported metal cluster prepared in this example is lower at 10 mA cm -2 .

[0069] The prepared NiO x / C electrode's chronopotentiometry curve under the current density condition of 10 mA cm 2 is as Figure 3 shown (where the reaction temperature is 25 °C and the electrolyte is 1 M KOH). The NiO x / C electrode prepared in this example has a lower potential, and the electrode performance is relatively stable during the test without obvious fluctuations.

[0070] Using the carbon-supported metal cluster electrode as the hydrogen evolution cathode and the Raney nickel electrode as the oxygen evolution anode, an electrolytic cell was assembled. At a temperature of 80 °C and in an electrolyte of 30% KOH, an I-V curve was obtained from the alkaline water test as Figure 4 shown. At a current density of 1 A cm -2 , the corresponding cell voltage was relatively low.

[0071] The alkaline water electrolysis stability test was as Figure 5 shown. A stability test was carried out for 8 hours at a current density of 500 mA cm -2 . The cell voltage hardly changed, further indicating that the hydrogen evolution electrode obtained in this example has relatively stable and excellent performance. The alkaline water electrolysis current efficiency test was as Figure 6 shown. The current efficiency was above 98% in the same time interval, proving that the hydrogen evolution electrode prepared in this example has a wide range of applications.

[0072] In another embodiment of the present disclosure, a carbon-supported metal cluster hydrogen evolution electrode prepared by the foregoing method is provided, including a carbon conductive substrate, and the surface of the carbon conductive substrate has a uniform carbon-supported metal cluster coating. The coating is prepared by a one-step electrodeposition method by placing the carbon conductive substrate in a deposition solution containing a soluble metal salt and nitrogen-doped carbon quantum dots.

[0073] On the other hand, the carbon-supported metal cluster hydrogen evolution electrode in the embodiments of the present disclosure can be applied to the chlor-alkali industry, electrolytic water for hydrogen production or separation of hydrogen isotopes, and fuel cells.

[0074] The electrode provided by the embodiments of the present disclosure has low raw material costs for preparation, mild preparation conditions, an ultra-low hydrogen evolution overpotential, and excellent stability, showing good industrial prospects and economic value.

[0075] Although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A method for preparing a carbon-supported metal cluster hydrogen evolution electrode, characterized in that: The method comprises the following steps: preparing a carbon conductive substrate; preparing a deposition solution containing a soluble metal salt and carbon quantum dots; The carbon conductive substrate is placed in a deposition solution containing soluble metal salts and carbon quantum dots, and a carbon-supported metal cluster hydrogen evolution electrode is prepared by a one-step electrodeposition method.

2. The preparation method according to claim 1, characterized in that: The deposition liquid containing soluble metal salt and carbon quantum dots is prepared from carbon quantum dot aqueous solution and soluble metal salt.

3. The preparation method according to claim 1 or 2, characterized in that: The soluble metal salt is one or more inorganic salts of transition metals.

4. The preparation method according to claim 3, characterized in that: The carbon quantum dots are nitrogen-doped carbon quantum dots.

5. The preparation method according to claim 1, characterized in that: The one-step electrodeposition process includes: A three-electrode system is formed by a carbon conductive substrate as a working electrode, a platinum electrode as a counter electrode, and a saturated calomel electrode as a reference electrode. Electrodeposition is performed in the three-electrode system by using one of constant potential method, constant potential method and cyclic voltammetry method.

6. The preparation method according to claim 1, 4 or 5, characterized in that: The preparation of a carbon quantum dot aqueous solution comprises the following steps: The nitrogen-doped carbon quantum dot solution is prepared by at least one of microwave hydrothermal method, hydrothermal method, solvothermal method, microwave-assisted method, acid oxidation method and electrochemical method; The obtained nitrogen-doped carbon quantum dot solution is centrifuged and filtered to remove agglomerated carbon; The nitrogen-doped carbon quantum dot solution after centrifugal filtration is used to remove unreacted small molecules using a dialysis bag to obtain a carbon quantum dot aqueous solution.

7. A carbon-supported metal cluster hydrogen evolution electrode, characterized in that: The electrode comprises a carbon conductive substrate, and a uniform carbon-supported metal cluster coating is covered on the surface of the carbon conductive substrate.

8. The carbon-supported metal cluster hydrogen evolution electrode according to claim 7, characterized in that: The coating is prepared by placing a carbon conductive substrate in a deposition solution containing soluble metal salts and carbon quantum dots through a one-step electrodeposition method.

9. The carbon-supported metal cluster hydrogen evolution electrode according to claim 7 or 8, characterized in that: The carbon-supported metal clusters are carbon-supported metal nickel clusters.

10. Use of the carbon-supported metal cluster hydrogen evolution electrode according to claims 7-9 or the electrode prepared by the method according to claims 1-6 in the chlor-alkali industry, electrolysis of water to produce hydrogen or separation of hydrogen isotopes, and fuel cells.

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