阅读说明：本技术 一种室温制备硫掺杂多孔NiFe-LDH电催化剂的方法 (Method for preparing sulfur-doped porous NiFe-LDH electrocatalyst at room temperature ) 是由 王孝广 万子豪 马自在 李晋平 于 2021-09-29 设计创作，主要内容包括：本发明提出一种室温制备硫掺杂多孔NiFe-LDH纳米片析氧电催化剂的方法。所述方法包括水热法制备NiFe-LDH纳米片,并在室温条件下用一定摩尔浓度的Na-(2)S·9H-(2)O溶液浸润蚀刻NiFe-LDH纳米片,真空干燥后得到硫掺杂多孔NiFe-LDH纳米片。本发明无需传统硫掺杂所需要的高温、高压条件,可避免高温条件下材料加工中的硫化物强烈团聚,减少有害副产物的生成。金属阳离子通常作为析氧反应(OER)的实际活性位点,而室温条件下掺杂的硫阴离子可作为电子供体来调节金属阳离子活性位点极化程度,产生有利于电催化剂的电子结构。同时,NiFe-LDH纳米片上会因蚀刻产生独特的三维多孔纳米片结构,这使得该电催化剂暴露大量的活性位点和电荷转移通道,作为电化学OER催化剂时表现出优异的催化性能。(The invention provides a method for preparing a sulfur-doped porous NiFe-LDH nanosheet oxygen evolution electrocatalyst at room temperature. The method comprises the steps of preparing NiFe-LDH nano-sheets by a hydrothermal method and using Na with a certain molar concentration at room temperature 2 S·9H 2 And infiltrating and etching the NiFe-LDH nanosheets by using the O solution, and drying in vacuum to obtain the sulfur-doped porous NiFe-LDH nanosheets. The method does not need high temperature and high pressure conditions required by the traditional sulfur doping, can avoid the strong agglomeration of sulfides in the material processing under the high temperature condition, and reduces the generation of harmful byproducts. The metal cation usually acts as the actual active site for Oxygen Evolution Reaction (OER), while the doped sulfur anion at room temperature can act as an electron donor to modulate the metal cationThe degree of polarization of the sub-active sites creates an electronic structure that is favorable for the electrocatalyst. Meanwhile, a unique three-dimensional porous nanosheet structure can be generated on the NiFe-LDH nanosheet due to etching, so that the electrocatalyst exposes a large number of active sites and charge transfer channels, and has excellent catalytic performance when used as an electrochemical OER catalyst.)

1. A method for preparing a sulfur-doped porous NiFe-LDH nanosheet electrocatalyst at room temperature is characterized by comprising the following steps of: the method comprises the following steps:

(1) a certain mass of Ni (NO)₃)₂·6H₂O、Fe(NO₃)₃·9H₂O and CO (NH)₂)₂Dissolving in deionized water, stirring, pouring the solution into a polytetrafluoroethylene bottle, putting the polytetrafluoroethylene bottle and the substrate into a hydrothermal reaction kettle, and putting the hydrothermal reaction kettle and the substrate into a forced air drying oven to react at a certain temperature;

(2) washing the reacted sample with deionized water and ethanol respectively, and vacuum drying at 40-80 ℃ for 8-12h to obtain NiFe-LDH;

(3) preparing 0.2M-1M Na₂S·9H₂O solution, placing NiFe-LDH in Na at room temperature₂S 9H₂Soaking in O solution for a certain time, washing the soaked sample with deionized water and ethanol respectively, and drying in vacuum at 40-80 ℃ for 4-6h to obtain the sulfur-doped porous NiFe-LDH nanosheet electrocatalyst.

2. The method for preparing the sulfur-doped porous NiFe-LDH nanosheet electrocatalyst according to claim 1, wherein the method comprises the following steps: in step (1), Ni (NO)₃)₂·6H₂O、Fe(NO₃)₃·9H₂O and CO (NH)₂)₂The amount of the nickel-based catalyst is 2-4mM, 0.8-1.2mM and 0.2-0.4mM respectively, the hydrothermal reaction condition is 100-: respectively placing foamed nickel in 0.5-2M hydrochloric acid, acetone, ethanol and deionized water for ultrasonic treatment for 5-20min, and then placing in a vacuum drying oven at 40-80 ℃ for drying for 10-30min, wherein in the step (3), the room temperature is 20-30 ℃ under normal pressure; na (Na)₂S·9H₂The molar concentration of the O solution is 0.2-1M, and the soaking time is 0.5-24 h.

3. The method for preparing the sulfur-doped porous NiFe-LDH nanosheet electrocatalyst at room temperature recited in claim 1, wherein the method is used for electrocatalytic oxygen evolution reaction.

Technical Field

The invention relates to a preparation method of an electrocatalyst for an anodic oxygen evolution reaction in an alkaline solution, belonging to the technical field of material science and the field of oxygen production by electrolyzing water.

Background

The traditional fossil fuel has low energy utilization efficiency, is not friendly to the environment, and causes problems such as energy crisis and the like, which seriously restrict the sustainable development of the human society. Therefore, there is an urgent need to find clean renewable energy sources, such as solar energy, wind energy, tidal energy, etc., to replace the conventional fossil energy sources. However, the characteristics of discontinuous supply and high rejection rate of these energy sources limit further scale development of clean renewable energy sources. As an important secondary energy source, hydrogen has the characteristics of high energy density, various sources, easiness in storage, various application industries and the like. Compared with the traditional hydrogen production by cracking fossil energy, the hydrogen production by biomass and the hydrogen production by photocatalytic water, the hydrogen production by water electrolysis is one of the key technologies which most probably realize the recycling of hydrogen energy. However, the hydrogen gas produced by electrolyzing water accounts for only about 3% of the total hydrogen consumption, because the electric energy consumption is excessive in the actual water electrolysis process, the overpotential caused by the activation energy barrier of the cathode and the anode needs to be overcome in the reaction process, and more energy (i.e., higher overpotential) needs to be consumed in the actual water electrolysis process to promote the water electrolysis reaction. Therefore, a high efficiency electrocatalyst needs to be designed to reduce the activation energy of the reaction process. The electrolyzed water is formed by two half reactions of cathodic Hydrogen Evolution (HER) and anodic Oxygen Evolution (OER), four electrons are needed to participate in the reaction in the oxygen evolution process, and the multi-step and multi-electron reaction causes high overpotential and slow reaction kinetics. Therefore, the oxygen evolution reaction is more difficult than the hydrogen evolution reaction. Therefore, in the process of water electrolysis, in order to improve the energy conversion efficiency of hydrogen production by water electrolysis, the development of an OER electrocatalyst becomes one of the key technologies of hydrogen production by water electrolysis. Currently, Ru/Ir-based compounds are considered to be highly active OER electrocatalysts, but their high cost and scarcity prevent their large-scale utilization. Therefore, the design of an electrocatalyst with high efficiency, abundant reserves and low price is imperative. Among them, Fe and Ni are abundant in the earth, and have great potential to replace noble metal elements.

The Layered Double Hydroxide (LDH) is a two-dimensional layered material assembled by a main body laminate with positive charges and interlayer anions through the interaction of non-covalent bonds, and the types and the compositions of metal ions of the main body laminate and the interlayer anions have the advantage of being adjustable. And the special electronic structure and the layered structure can endow the catalyst with enough large specific surface area and good electrochemical water cracking catalytic activity. However, the inherent poor activity of the catalytic sites of layered double hydroxides remains a drawback to be overcome.

Disclosure of Invention

The invention aims to provide a method for preparing a sulfur-doped porous NiFe-LDH nanosheet electrocatalyst at room temperature, wherein Na is used at a certain molar concentration₂S·9H₂And (3) etching the NiFe-LDH nanosheets at room temperature by using the O solution as an etching solution to prepare the sulfur-doped porous NiFe-LDH nanosheet electrocatalyst with excellent oxygen evolution performance.

The invention is realized by adopting the following technical scheme:

a method for preparing a sulfur-doped porous NiFe-LDH nanosheet electrocatalyst at room temperature comprises the following steps:

(1) a certain mass of Ni (NO)₃)₂·6H₂O、Fe(NO₃)₃·9H₂O、CO(NH₂)₂Dissolving the nickel foam in a certain amount of deionized water, uniformly stirring, putting the mixture and the nickel foam into a hydrothermal reaction kettle, and then putting the reaction kettle into a forced air drying oven for hydrothermal reaction;

(2) washing the sample with deionized water and ethanol for several times, and vacuum drying at 40-80 ℃ to obtain NiFe-LDH;

(3) configuring Na with 0.2M-1M₂S·9H₂O solution, NiFe-LDH is placed in Na at room temperature of 15-30 DEG C₂S·9H₂Soaking in O for 0.5-24h, washing the soaked sample with deionized water and ethanol for several times, and vacuum drying at 40-80 ℃ to obtain the sulfur-doped porous NiFe-LDH nanosheet electro-catalytic material.

The catalyst prepared by the invention has the following advantages:

(1) through Na₂S·9H₂The O solution etches on the NiFe-LDH nano-sheets to generate a plurality of micron-sized holes which are beneficial to the diffusion of the electrolyte solution, thereby greatly increasing the capacity of the electrolyte solutionMore active sites are exposed, and oxygen bubbles are promoted to be released from the surface of the catalyst, so that the oxygen evolution performance is improved.

(2) The sulfur atom doping can adjust local chemical combination environment and electronic structure around Ni and Fe, and improve electronic conductivity and ion mobility.

(3) The preparation method has low requirement on preparation conditions, is simple and feasible in process, and is easy to realize large-scale preparation.

Drawings

FIG. 1 shows an X-ray diffraction (XRD) pattern of example 1.

FIG. 2 shows a Scanning Electron Microscope (SEM) image of example 1.

Fig. 3 shows a Transmission Electron Microscope (TEM) image of example 1.

FIG. 4 shows a High Resolution Transmission Electron Microscope (HRTEM) image of example 1.

FIG. 5 shows the oxygen evolution polarization curve of the electrocatalyst of example 1 in 1M KOH.

FIG. 6 shows the oxygen evolution polarization curve of the electrocatalyst for example 2 in 1M KOH.

FIG. 7 shows the oxygen evolution polarization curve of the electrocatalyst for example 3 in 1M KOH.

FIG. 8 shows the oxygen evolution polarization curve of the electrocatalyst for example 4 in 1M KOH.

Detailed Description

The first embodiment is as follows: in the embodiment, foam nickel is used as a substrate, and a three-dimensional NiFe-LDH nanosheet is grown on the foam nickel in situ by a hydrothermal method. Subsequently soaking NiFe-LDH to a certain molar concentration of Na under the condition of room temperature₂S 9H₂Preparing a sulfur-doped porous NiFe-LDH nanosheet electrocatalyst in an O solution.

The method for preparing the sulfur-doped porous NiFe-LDH nanosheet electrocatalyst at room temperature comprises the following steps:

(1) cutting the foamed nickel into a rectangle of 2cm multiplied by 4cm, respectively carrying out ultrasonic treatment for 10min by using 1M hydrochloric acid, acetone, alcohol and ultrapure water to remove an oxide layer and dirt on the surface, and then carrying out vacuum drying for 10min at 60 ℃;

(2) 35mL of 0.5mM Fe (NO)₃)₃·9H₂O、1.5mM Ni(NO₃)·6H₂O and 2.5mM CO (NH)₂)₂The mixed solution is uniformly stirred and is put into a hydrothermal reaction kettle together with foamed nickel, and then the hydrothermal reaction kettle is put into an air-blowing drying oven for hydrothermal reaction, wherein the reaction time is 10 hours and the reaction temperature is 120 ℃;

(3) washing a sample with ethanol and deionized water for 3 times respectively, and then carrying out vacuum drying at 60 ℃ for 6h to obtain NiFe-LDH;

(4) soaking NiFe-LDH into 0.5M Na at room temperature of 25 DEG C₂S·9H₂And standing the mixture in the O solution for 3 hours. Then taking out the sample, washing with ethanol and deionized water for 3 times respectively, and then drying in vacuum at 60 ℃ for 6 h;

(5) the electrochemical test of the embodiment is performed in a three-electrode electrolytic cell at 25 ℃ and normal pressure, the counter electrode is Pt (10 × 10 × 0.1mm), the reference electrode is an Hg/HgO electrode, and the working electrode is the sulfur-doped porous NiFe-LDH nanosheet prepared in the embodiment; the electrochemical workstation is Costett CS2350H, and the electrolyte is 1M KOH. As can be seen from the oxygen evolution polarization curve chart, the electrode is at 50mA/cm²Only a 247mV overpotential is required for the oxygen evolution current density.

Taking the sulfur-doped porous NiFe-LDH nanosheet electrocatalyst obtained in the embodiment as an example, the powder of the sulfur-doped porous NiFe-LDH nanosheet electrocatalyst is scraped from foamed nickel and subjected to XRD analysis, as shown in FIG. 1, the diffraction peak of the sparsely-doped porous NiFe-LDH nanosheet electrocatalyst prepared in the embodiment is consistent with the PDF card (PDF #00-051-0463) of standard NiFe-LDH, and no related sulfide peak exists, which indicates that sulfur atoms are successfully doped into the NiFe-LDH crystal lattice. It can be observed from the SEM image of NiFe-LDH (FIG. 2) that sulfur-doped porous NiFe-LDH nanosheets grow vertically on the foamed nickel substrate. From the TEM image (FIG. 3), it can be observed that a large number of micron-sized pores are distributed on the NiFe-LDH nanosheets; HRTEM (FIG. 4) is the fine structure of sulfur-doped porous NiFe-LDH nanosheets, with the 0.259nm and 0.153nm interplanar spacings matching the (012) and (110) crystal planes of NiFe-LDH, respectively.

The second embodiment is as follows: according to the embodiment, foam nickel is used as a substrate, and the three-dimensional NiFe-LDH nanosheet grows on the foam nickel in situ through a hydrothermal method. Followed by strip at room temperatureUnder the condition, NiFe-LDH is infiltrated to Na with a certain molar concentration₂S·9H₂Preparing a sulfur-doped porous NiFe-LDH nanosheet electrocatalyst in an O solution.

(1) The pretreatment of the foamed nickel matrix and the preparation of the NiFe-LDH are the same as the step (1), the step (2) and the step (3) of the first example;

(2) soaking NiFe-LDH into 0.2M Na at room temperature of 25 DEG C₂S·9H₂And standing the mixture in the O solution for 3 hours. Then taking out the sample, washing with ethanol and deionized water for 3 times respectively, and then drying in vacuum at 60 ℃ for 6 h;

(3) the electrochemical test of the embodiment is performed in a three-electrode electrolytic cell at 25 ℃ and normal pressure, the counter electrode is Pt (10 × 10 × 0.1mm), the reference electrode is an Hg/HgO electrode, and the working electrode is the sulfur-doped porous NiFe-LDH nanosheet prepared in the embodiment; the electrochemical workstation is Costett CS2350H, and the electrolyte is 1M KOH. As can be seen from the oxygen evolution polarization curve chart, the electrode is at 50mA/cm²Only 256mV of overpotential is needed for the oxygen evolution current density.

The third concrete embodiment: according to the embodiment, foam nickel is used as a substrate, and the three-dimensional NiFe-LDH nanosheet grows on the foam nickel in situ through a hydrothermal method. Subsequently soaking NiFe-LDH to a certain molar concentration of Na under the condition of room temperature₂S·9H₂Preparing a sulfur-doped porous NiFe-LDH nanosheet electrocatalyst in an O solution.

(1) The pretreatment of the foamed nickel matrix and the preparation of the NiFe-LDH are the same as the step (1), the step (2) and the step (3) of the first example;

(2) soaking NiFe-LDH into 1M Na at room temperature of 25 DEG C₂S·9H₂And standing the mixture in the O solution for 3 hours. Then taking out the sample, washing with ethanol and deionized water for 3 times respectively, and then drying in vacuum at 60 ℃ for 6 h;

(3) the electrochemical test of the embodiment is performed in a three-electrode electrolytic cell at 25 ℃ and normal pressure, the counter electrode is Pt (10 × 10 × 0.1mm), the reference electrode is an Hg/HgO electrode, and the working electrode is the sulfur-doped porous NiFe-LDH nanosheet prepared in the embodiment; the electrochemical workstation is Costett CS2350H, and the electrolyte is 1M KOH. The oxygen evolution polarization curve graph shows thatThe electrode is at 50mA/cm²Only 263mV overpotential is needed for the oxygen evolution current density.

The fourth concrete embodiment: according to the embodiment, foam nickel is used as a substrate, and the three-dimensional NiFe-LDH nanosheet grows on the foam nickel in situ through a hydrothermal method. Subsequently soaking NiFe-LDH to a certain molar concentration of Na under the condition of room temperature₂S·9H₂Preparing a sulfur-doped porous NiFe-LDH nanosheet electrocatalyst in an O solution.

(1) The pretreatment of the foamed nickel matrix and the preparation of the NiFe-LDH are the same as the step (1), the step (2) and the step (3) of the first example;

(2) soaking NiFe-LDH into 1M Na at room temperature of 25 DEG C₂S·9H₂And standing the mixture in the O solution for 24 hours. Then taking out the sample, washing with ethanol and deionized water for 3 times respectively, and then drying in vacuum at 60 ℃ for 6 h;

(3) the electrochemical test of the embodiment is performed in a three-electrode electrolytic cell at 25 ℃ and normal pressure, the counter electrode is Pt (10 × 10 × 0.1mm), the reference electrode is an Hg/HgO electrode, and the working electrode is the sulfur-doped porous NiFe-LDH nanosheet prepared in the embodiment; the electrochemical workstation is Costett CS2350H, and the electrolyte is 1M KOH. As can be seen from the oxygen evolution polarization curve chart, the electrode is at 50mA/cm²Only 268mV overpotential is required for the oxygen evolution current density of (1).