阅读说明：本技术 一种碳基复合电催化剂及其制备方法与应用 (Carbon-based composite electrocatalyst and preparation method and application thereof ) 是由 陈敏 高梦涵 姜德立 李娣 孟素慈 徐菁 于 2019-10-25 设计创作，主要内容包括：本发明属于电催化剂领域,具体涉及一种高性能电化学分解水产氢的碳基复合催化剂的制备方法与应用。通过络合、煅烧、酸洗过程合成的氮掺杂碳(NC),以其为基底材料,乙二醇为还原剂,在回流条件下得到Ru/NC电催化剂。该电催化剂材料具有较低的电荷转移电阻和析氢反应的反应势垒,在电催化析氢反应中具有优越的性能。同时,Ru在Pt系贵金属材料中价格最为低廉该催化剂成本低廉,实验操作简便,工艺简单,催化性能优越,为该类材料在电催化领域提供了基础应用研究。(The invention belongs to the field of electrocatalysts, and particularly relates to a preparation method and application of a high-performance carbon-based composite catalyst for electrochemically decomposing water to produce hydrogen. The Ru/NC electrocatalyst is prepared by using nitrogen-doped carbon (NC) synthesized through the processes of complexation, calcination and acid washing as a substrate material and ethylene glycol as a reducing agent under the reflux condition. The electro-catalyst material has lower charge transfer resistance and reaction barrier of hydrogen evolution reaction, and has excellent performance in the electro-catalytic hydrogen evolution reaction. Meanwhile, the catalyst has the advantages of low cost, simple and convenient experimental operation, simple process and excellent catalytic performance due to the lowest price of Ru in the Pt-series noble metal material, and provides basic application research for the material in the field of electrocatalysis.)

1. A preparation method of a carbon-based composite electrocatalyst is characterized by comprising the following steps:

(1) preparation of nitrogen-doped carbon (NC):

a: weighing dopamine hydrochloride and FeCl₃·6H₂Grinding O in a mortar, transferring the reactant into a magnetic boat after the reactant is fully complexed, transferring the magnetic boat into an automatic program temperature control heating tube furnace, heating to 600-900 ℃ at a heating rate of 3-5 ℃/min, and calcining for 1-3 h; naturally cooling to room temperature, and taking out;

b: grinding the sample obtained in the step a, then placing the sample in an HCl solution for stirring, centrifuging after the simple substance iron in the sample is cleaned, washing with water and alcohol, and drying to obtain NC;

(2) preparing a Ru/NC water electrolysis hydrogen production catalyst with NC as a substrate:

a: weighing RuCl₃To prepare RuCl₃The ethylene glycol solution is reserved;

b: weighing the dried NC obtained in the step (1), adding ethylene glycol for ultrasonic dispersion, and then adding the RuCl prepared in the step a₃The ethylene glycol solution is uniformly dispersed, the solution is transferred into a round-bottom flask and is refluxed for 1 to 2 hours at the temperature of between 180 and 200 ℃; and naturally cooling to room temperature, transferring to a centrifuge tube, washing with water and alcohol for several times, and drying to obtain the carbon-based composite electrocatalyst.

2. The method of preparing a carbon-based composite electrocatalyst according to claim 1, wherein: in the step a of the step (1), dopamine hydrochloride and FeCl₃·6H₂The molar ratio of O is 1: x, wherein x is 1-14.

3. The method of claim 1, wherein the carbon-based composite catalyst comprises: in the step b of the step (1), the concentration of HCl is 1 mol/L.

4. The method of preparing a carbon-based composite electrocatalyst according to claim 1, wherein: in the step a of the step (2), RuCl₃The concentration of the ethylene glycol solution of (2) was 5 mg/mL.

5. The method of preparing a carbon-based composite electrocatalyst according to claim 1, wherein: in the step b of the step (2), the concentration of NC in the glycol solution is 1-1.5 mg/mL, and NC nano-sheets and RuCl are added₃The mass ratio of (a) to (b) is 1: x, wherein x is 0.1-0.5.

6. The method of preparing a carbon-based composite electrocatalyst according to claim 5, wherein: in the step b of the step (2), NC nanosheet and RuCl₃In the mass ratio of (a) to (b) of 1: x, wherein x is 0.5.

7. The method of preparing a carbon-based composite electrocatalyst according to claim 1, wherein: in the steps (1) and (2), the drying temperature is 60 ℃, and the drying time is 12 hours.

8. Use of the carbon-based composite electrocatalyst prepared by the preparation method according to any one of claims 1 to 7, characterized in that the carbon-based composite electrocatalyst is used for hydrogen production by electrocatalytic decomposition of water under alkaline conditions.

Technical Field

The invention belongs to the field of electrocatalysis, and particularly relates to a high-performance carbon-based composite electrocatalyst for electrochemically decomposing water to produce hydrogen, and a preparation method and application thereof.

Technical Field

With the continuous consumption of fossil fuels, various new energy production plans are receiving wide attention in order to meet the huge energy demand of the current. Hydrogen energy is a clean energy without any pollution and is expected to become the most effective substitute of fossil fuel. Hydrogen production (HER) by electrochemically decomposing water has the advantages of high efficiency, environmental friendliness, high hydrogen production purity, strong energy fluctuation adaptability and the like, and has great application prospect in the development of chemical energy storage technology.

Pt-based catalysts are still the most efficient HER catalysts at present, but their scarcity and high cost make them not widely applicable in industrial production applications. Thus, various non-platinum metal catalysts have been reported, mainly including transition metal oxides, carbides, nitrides, sulfides, selenides, phosphides, and hydroxides. However, these catalysts suffer from the disadvantages of poor stability and easy deactivation, and are not suitable for industrial application. Therefore, there is an urgent need to develop an electrocatalyst with high efficiency, long life and low cost. Among Pt noble metals, ruthenium (Ru) is the least expensive, and the composite of Ru and carbon is used as the catalyst for hydrogen production by water electrolysis, so that the catalyst has the advantages of moderate price, high hydrogen production efficiency, good circulation stability and the like. The nitrogen is doped into the carbon-based material, so that the electron donating performance of the carbon-based material can be improved, the dispersion of ruthenium particles is facilitated, and more active sites are easily exposed.

Scholars both at home and abroad have worked well in this regard. For example, Su et al, successfully synthesized a RuCo @ NC HER catalyst at a current density of 10mA cm^-2And 100mA cm^-2The overpotential is 28mV and 218mV respectively, and after 10000 CV stability tests, the overpotential is only increased by 4mV (Su J, Yang Y, Xia G, equivalent, Ruthenium-cobalt-aluminium encapsulated in nitro-gene-amplified graphene active electrolytes for producing hydrogen in alkalline media [ J ]]Naturecommunications,2017,8: 14969.). Successful synthesis of Ru @ C by Sun et al₄N catalyst having excellent acidic and basic HER electrocatalytic activity. Under acidic conditions, the current density was 10mA cm^-2The time overpotential is only 6mV, and the current density under alkaline condition is 10mA cm^-2Time overpotential is only 7mV(Sun S W,Wang G F,Zhou Y,et al.High-Performance [email protected] Electrocatalyst for Hydrogen Evolution Reaction in BothAcidic and Alkaline Solutions[J].ACS applied materials&interfaces,2019.)。

Disclosure of Invention

The invention aims to provide a high-performance Ru/NC electrocatalyst for electrochemically decomposing water to produce hydrogen. The catalyst prepared by the method can greatly reduce the overpotential and the Tafel slope, has good conductivity, and can greatly improve the catalytic hydrogen production efficiency of the Ru-based catalyst for decomposing water. In addition, the Ru/NC synthesized in situ by taking NC as a substrate can reduce the internal resistance of the electrode, improve the conductivity of the electrode and obviously improve the catalytic activity of the material. Meanwhile, the catalyst cost can be greatly reduced by using cheap and easily-obtained nitrogen-doped carbon (NC) as a substrate material of the catalyst. Therefore, the Ru/NC electrocatalyst synthesized in situ by taking NC as a substrate material is applied to the field of hydrogen production by water electrolysis, and has better application prospect.

The technical scheme of the invention is as follows:

(1) preparation of nitrogen-doped carbon (NC):

a: weighing dopamine hydrochloride and FeCl₃·6H₂Grinding O in a mortar, transferring the reactant into a magnetic boat after the reactant is fully complexed, transferring the magnetic boat into an automatic program temperature control heating tube furnace, heating to 600-800 ℃ at a heating rate of 3-5 ℃/min, and calcining for 1-3 h; naturally cooling to room temperature, and taking out;

b: grinding the sample obtained in the step a, then placing the sample into an HCl solution, stirring, washing simple substance iron in the sample, then centrifuging, washing with water and alcohol, and drying to obtain an NC nanosheet;

(2) preparing an Ru/NC water electrolysis hydrogen production electrocatalyst with NC as a substrate:

a: weighing RuCl₃To prepare RuCl₃The ethylene glycol solution is reserved;

b: weighing the dried NC nanosheets obtained in the step (1), adding ethylene glycol for ultrasonic dispersion, and then adding the RuCl prepared in the step a₃The ethylene glycol solution is uniformly dispersed, the solution is transferred into a round-bottom flask and is refluxed for 1 to 2 hours at the temperature of between 180 and 200 ℃; naturally cooling to room temperatureAnd then transferring the product to a centrifuge tube, washing with water and alcohol for several times, and drying to obtain the Ru/NC catalyst.

In the step a of the step (1), dopamine hydrochloride and FeCl₃·6H₂The molar ratio of O is 1: x, wherein x is 1-14.

In the step b of the step (1), the concentration of HCl is 1 mol/L.

In the step a of the step (2), RuCl₃The concentration of the ethylene glycol solution is 5 mg/mL;

in the step b of the step (2), the concentration of NC in the glycol solution is 1-1.5 mg/mL, and NC nano-sheets and RuCl are added₃The mass ratio of (1) to (x) is 1: x, wherein x is 0.1-0.5; preferably, x is 0.5.

In the steps (1) and (2), the drying temperature is 60 ℃, and the drying time is 12 hours.

The Ru/NC catalyst provided by the invention is applied to the aspect of electrocatalytic hydrogen production.

And (3) analyzing the composition morphology of the product by using an X-ray diffractometer (XRD) and a Transmission Electron Microscope (TEM). A three-electrode reaction device is adopted, a platinum wire is used as a counter electrode, a silver-silver chloride (Ag/AgCI) electrode is used as a reference electrode, and the electrochemical performance of the product is tested in 1MKOH electrolyte;

the invention has the beneficial effects that:

(1) the preparation method provided by the invention is composed of simple calcination reaction and reflux reaction, and has the advantages of simple steps, short reaction time, convenience in operation, environmental friendliness and strong repeatability.

(1) The Pt/C catalyst is still the most efficient electrocatalyst for hydrogen production by water electrolysis at present, but Ru used in the invention is used as the cheapest metal in Pt-series noble metals, the cost is less than 1/20 of Pt, but the electrocatalytic activity of Pt/C can be achieved, and the preparation cost of the catalyst is greatly reduced.

(3) The NC nanosheets provide an ultra-large specific surface area for the growth of the Ru simple substance, so that the particle size is effectively limited, and more active sites are exposed; and the good conductivity of the NC nanosheet is beneficial to electron transfer, and the factors synergistically enhance the electrocatalytic capacity of the material in a water decomposition reaction.

Drawings

FIG. 1 is an XRD diffraction spectrum of the prepared 20% Ru/NC nanosheet electrocatalyst and NC nanosheets.

FIGS. 2a, b, c are transmission photographs of the prepared pure NC nanosheet, 20% Ru/NC nanosheet, and 20% Ru/bulk NC electrocatalyst, respectively.

FIGS. 3a and b are a comparison graph of polarization curves and a comparison graph of overpotential values of hydrogen evolution reaction of the prepared electrocatalyst under the condition of 1M KOH, respectively.

FIG. 4 is a graph showing the comparison of the gradient of the Phillips curve of the prepared electrocatalyst in a hydrogen evolution reaction tower under the condition of 1M KOH.

FIG. 5 is a graph comparing the cycle stability of the prepared electrocatalyst CV after 3000 cycles.

Detailed Description

The invention will be further described with reference to the following figures and specific examples, but the scope of the invention is not limited thereto.