Caterpillar nickel-cobalt sulfide nano array and its synthesis and application
阅读说明：本技术 一种毛虫状镍钴硫化物纳米阵列及其合成与应用 (Caterpillar nickel-cobalt sulfide nano array and its synthesis and application ) 是由 陈作锋 宋文娇 于 2020-05-11 设计创作，主要内容包括：本发明涉及一种毛虫状镍钴硫化物纳米阵列及其合成与应用,该毛虫状镍钴硫化物纳米阵列的制备包括以下步骤：首先,以水热法在碳布基底上原位生长毛虫状的NiCo层状双金属氢氧化物(LDH)前驱体,分别以Co(NO<Sub>3</Sub>)<Sub>2</Sub>·6H<Sub>2</Sub>O、Ni(NO<Sub>3</Sub>)<Sub>2</Sub>·6H<Sub>2</Sub>O、CH<Sub>4</Sub>N<Sub>2</Sub>O作为反应物,NH<Sub>4</Sub>F作为表面控制剂；随后,利用Na<Sub>2</Sub>S为硫化剂与前驱体发生阴离子交换反应进一步获得多孔NiCo<Sub>2</Sub>S<Sub>4</Sub>阵列。与现有技术相比,本发明通过引入过渡金属硫化物的组成、形貌、三维多孔导电结构以及Ni/Co的协同效应,使得该电极材料在电解水以及尿素电解方面表现出优异性能。(The invention relates to a caterpillar nickel cobalt sulfide nano array and synthesis and application thereof, wherein the preparation of the caterpillar nickel cobalt sulfide nano array comprises the following steps: firstly, a hydrothermal method is adopted to grow caterpillar NiCo layered double-layer on a carbon cloth substrate in situMetal hydroxide (LDH) precursors, each with Co (NO) 3 ) 2 ·6H 2 O、Ni(NO 3 ) 2 ·6H 2 O、CH 4 N 2 O as a reactant, NH 4 F is used as a surface control agent; subsequently, using Na 2 S is a vulcanizing agent and undergoes anion exchange reaction with the precursor to further obtain the porous NiCo 2 S 4 And (4) array. Compared with the prior art, the electrode material has excellent performance in the aspects of electrolysis of water and urea by introducing the composition, the appearance, the three-dimensional porous conductive structure and the synergistic effect of Ni/Co of the transition metal sulfide.)
1. A synthetic method of a caterpillar nickel cobalt sulfide nano array is characterized by comprising the following steps:
(1) cleaning carbon cloth and using the cleaned carbon cloth as a substrate for later use;
(2) taking Ni (NO)3)2·6H2O、Co(NO3)2·6H2O、CH4N2Adding O and a surface control agent into deionized water, dissolving to obtain a uniform and clear pink solution, transferring the pink solution into a reaction kettle, vertically putting the substrate obtained in the step (1), heating for reaction, taking out the substrate after the reaction is finished, washing and drying to obtain an intermediate product;
(3) adding a vulcanizing agent into deionized water, dissolving to obtain a clear colorless solution, transferring the clear colorless solution into a reaction kettle, vertically putting the intermediate product prepared in the step (2), heating for reaction, washing and drying the obtained product to obtain the target product, namely the black load NiCo2S4CC caterpillar-shaped porous nano array material.
2. The method for synthesizing the caterpillar-shaped nickel-cobalt sulfide nano array as claimed in claim 1, wherein in the step (1), the carbon cloth cleaning process specifically comprises: and (3) carrying out ultrasonic treatment on the carbon cloth in absolute ethyl alcohol, 10% nitric acid solution and ultrapure water for 20min in sequence to finish the process.
3. The method for synthesizing the caterpillar-shaped nickel-cobalt sulfide nano array as claimed in claim 1, wherein in the step (2), Ni (NO) is added3)2·6H2O、Co(NO3)2·6H2O, surface control agent and CH4N2The molar ratio of O is (1-2): (1-2): (5-7): (12-18).
4. The method for synthesizing the caterpillar-shaped nickel-cobalt sulfide nano array as claimed in claim 1, wherein in the step (2), the surface control agent is NH4F。
5. The method for synthesizing the caterpillar-shaped nickel-cobalt sulfide nano array as claimed in claim 1, wherein in the step (2), the heating reaction is carried out under the following specific conditions: keeping at 90-120 deg.C for 6-10 h.
6. The method for synthesizing the caterpillar-shaped nickel-cobalt sulfide nano array as claimed in claim 1, wherein in the step (2), the washing and drying processes are as follows: rinsing with ultrapure water and ethanol for multiple times, and drying in an oven at 60 deg.C.
7. The method for synthesizing the caterpillar-shaped nickel-cobalt sulfide nano array as claimed in claim 1, wherein in the step (3), the vulcanizing agent is added in an amount such that the concentration of the obtained clear colorless solution is 80-120 mM.
8. The method for synthesizing the caterpillar-shaped nickel-cobalt sulfide nano array as claimed in claim 1, wherein in the step (3), the heating reaction process conditions are as follows: keeping at 140-180 ℃ for 6-10 h.
9. A caterpillar-like nickel cobalt sulfide nanoarray prepared by the synthetic method of any one of claims 1 to 8.
10. The use of a caterpillar-like nickel cobalt sulfide nanoarray according to claim 9 for electrolysis of water or urea.
Technical Field
The invention belongs to the technical field of preparation of electrocatalytic materials, and relates to a caterpillar-shaped nickel-cobalt sulfide nano array and synthesis and application thereof.
Background
Currently, human demand for renewable energy is increasing due to the decrease in fossil fuels, as well as various environmental problems that accompany their use. In order to be able to effectively utilize renewable energy, it is important to develop a high-performance, low-cost and environmentally friendly energy conversion and storage system.
Electrochemical water decomposition is attracting attention as a method for mass production of hydrogen, which is a sustainable clean energy, due to its environmental protection, low cost of equipment, and the like. However, the slow kinetics of the oxygen-generating half-reaction at the anode is considered to be a bottleneck for water splitting. Therefore, on the one hand, the search for inexpensive, durable and efficient catalysts for electrolysis of water is a necessary requirement for the development of technology, and on the other hand, the use of other molecules such as urea and the like in anodic oxidation instead of oxygen production reactions to reduce the reaction thermodynamics or to improve the reaction kinetics is also a promising approach.
Fundamentally, the performance of these energy conversion systems is directly related to the electrode material properties. Therefore, the design and development of electrode materials play a significant role in the development of electrochemical energy conversion. Besides, the bifunctional/multifunctional properties of the material are fields which are urgently needed to be researched at present, are beneficial to the commercial production of the material, and also provide space for further development.
In order to improve the catalytic performance, another doped metal can be introduced into the single metal compound, and the electronic structure or the surface performance is adjusted through the bimetallic synergistic effect to enhance the catalytic activity. Therefore, the selection of proper elements for doping is the key to preparing excellent electrocatalysts, and the invention is also based on the problems.
Disclosure of Invention
The invention aims to provide a caterpillar nickel cobalt sulfide nano array and synthesis and application thereof. First, by hydrothermal methodIn-situ growth of caterpillar-shaped NiCo Layered Double Hydroxide (LDH) precursor on carbon cloth substrate with Co (NO) respectively3)2·6H2O、Ni(NO3)2·6H2O、CH4N2O as a reactant, NH4F is used as a surface control agent. Subsequently, using Na2S is a vulcanizing agent and undergoes anion exchange reaction with the precursor to further obtain the porous NiCo2S4And (4) array. The composition, the morphology, the three-dimensional porous conductive structure and the synergistic effect of Ni/Co of the transition metal sulfide enable the electrode material to show excellent performance in the aspects of water electrolysis and urea electrolysis.
The purpose of the invention can be realized by the following technical scheme:
one of the technical schemes of the invention provides a synthesis method of a caterpillar nickel cobalt sulfide nano array, which comprises the following steps:
(1) cleaning carbon cloth and using the cleaned carbon cloth as a substrate for later use;
(2) taking Ni (NO)3)2·6H2O、Co(NO3)2·6H2O、CH4N2Adding O (namely urea) and a surface control agent into deionized water, dissolving to obtain a uniform and clear pink solution, transferring the pink solution into a reaction kettle, vertically placing the substrate obtained in the step (1), heating for reaction, taking out the substrate after the reaction is finished, washing and drying to obtain an intermediate product;
(3) adding a vulcanizing agent into deionized water, dissolving to obtain a clear colorless solution, transferring the clear colorless solution into a reaction kettle, vertically putting the intermediate product prepared in the step (2), heating for reaction, washing and drying the obtained product to obtain the target product, namely the black load NiCo2S4CC caterpillar-shaped porous nano array material.
Further, in the step (1), the carbon cloth cleaning process specifically comprises: and (3) carrying out ultrasonic treatment on the carbon cloth in absolute ethyl alcohol, 10% nitric acid solution and ultrapure water for 20min in sequence to finish the process.
Further, in the step (2), Ni (NO)3)2·6H2O、Co(NO3)2·6H2O, surface control agent and CH4N2The molar ratio of O is (1-2): (1-2): (5-7): (12-18).
Further, in the step (2), the surface control agent is NH4F。
Further, in the step (2), the specific conditions of the heating reaction are as follows: keeping at 90-120 deg.C for 6-10 h.
Further, in the step (2), the washing and drying processes are specifically as follows: rinsing with ultrapure water and ethanol for multiple times, and drying in an oven at 60 deg.C.
Further, in the step (3), the addition amount of the vulcanizing agent satisfies the following condition: the concentration of the resulting clear colorless solution was 80-120 mM.
Further, in the step (3), the process conditions of the heating reaction are as follows: keeping at 140-180 ℃ for 6-10 h.
In the present invention, Ni is provided by nickel and cobalt salts respectively2+、Co2+Hydrolysis of urea to provide an alkaline environment, NH4F can act as a surface control agent to coordinate with the nanostructured surface and prevent its anisotropic growth. At a set temperature, the components react to form nickel cobalt hydroxide bicarbonate (NiCo LDH), NH on the carbon cloth4F plays a role in controlling the appearance in the reaction process, so that the final product has a caterpillar-shaped appearance of long lines on the sheet, and the appearance has a larger specific surface area compared with the rest conventional appearance.
The specific reaction formula can be shown as follows:
OC(NH2)2+2H2O→2NH3+CO2
2NH3+CO2+H2O→NH4HCO3+NH4OH
[M(H2O)6]2++xF-→[M(H2O)6-xFx](x-2)-+xH2O(MII-Co, Ni or Co and Ni)
2NH4HCO3+2NH4OH+2[M(H2O)6-xFx](x-2)-→2M(CO3)0.5(OH)+2xF-+4NH4 ++(13-2x)H2O(x＝2-5)
As mentioned above, the proper ratio of the three raw materials is an important factor for preparing the product with caterpillar-shaped appearance, and the change of the feeding amount can change the appearance of the final product. In the hydrothermal method preparation process, the reaction speed is accelerated due to overhigh reaction temperature, the agglomeration is easy to occur, the target morphology cannot be formed, and the specific surface area is reduced; if the reaction temperature is too low, the reaction speed is reduced, the yield is low, the loading capacity is small, and the carbon cloth cannot be completely and uniformly covered.
Too low a temperature in the hydrothermal sulfidation step may result in failure of the sulfidation reaction to occur or complete sulfidation to be achieved, and too high a temperature may result in morphology damage that reduces its specific surface area. In addition, sodium sulfide needs to be present in sufficient quantity during the sulfidation process to adequately sulfide the precursor to NiCo2S4However, excessive sodium sulfide can cause waste, and can also damage the appearance, cause collapse, generate agglomeration and reduce the specific surface area. The sodium sulphide concentration is therefore preferably 100 mM.
The second technical scheme of the invention provides a caterpillar nickel cobalt sulfide nano array which is prepared by adopting any one of the synthesis methods. The caterpillar special shape and the porous structure of the long wires on the chip expose more active sites and accelerate the diffusion rate of electrolyte ions and bubbles, the transition metal sulfide active catalytic material has stronger metal property and improved conductivity, meanwhile, the synergistic effect of the bimetallic Ni/Co enhances the catalytic activity, and the material has excellent performance in the aspects of electrolyzing water and urea.
The third technical scheme of the invention provides application of the caterpillar-shaped nickel-cobalt sulfide nano array for electrolyzing water or urea, and particularly shows excellent catalytic performance on electrolysis of water and urea in an alkaline medium. In particular, NiCo is obtained2S4The CC caterpillar-shaped porous nano array material reaches 10mA cm in full water decomposition-2The required voltage is only 1.66V. When assembled into a urea electrolytic cell, the concentration reaches 10mA cm-2The required voltage is 1.45V, which is lower than the voltage required for full water splitting at the same current density.
Compared with the prior art, the electrode material has excellent performance in the aspects of electrolysis of water and urea by introducing the composition, the appearance, the three-dimensional porous conductive structure and the synergistic effect of Ni/Co of the transition metal sulfide.
Drawings
In FIG. 1, (A) and (B) are SEM pictures of NiCo-LDH/CC, (C) is its XRD pattern, and (D) is its EDX data.
In FIG. 2, (A, B, C) are each NiCo2S4SEM image of/CC, (D, E) are TEM image and HRTEM image (inset: corresponding selected area electron diffraction pattern), respectively, and (F) is element distribution image.
In FIG. 3, (A) is NiCo2S4XRD spectrum of/CC, and (B, C, D) are high-resolution XPS spectrum.
In FIG. 4, (A) is NiCo2S4XPS survey scan of/CC and (B) EDX data.
In FIG. 5, (A, B) are SEM images of NiS/CC, (C) is its XRD spectrum, and (D) is its EDX spectrum.
In FIG. 6, (A, B) is Co9S8SEM image of/CC, (C) is its XRD spectrum, and (D) is its EDX spectrum.
In FIG. 7, (A) is NiCo2S4/CC、Co9S8OER performance of/CC, NiS/CC and blank carbon cloth in 1M KOH solution, (B) polarization curve for comparison of HER performance, scan rate of 2mV s-1(C) Tafel curves corresponding to OER and HER for each electrode, and (D) NiCo2S4Stability test curves for/CC OER and HER.
In FIG. 8, (A) is NiCo2S4PerCC Scan Rate 2mV s in 1.0M KOH with and without 0.33M Urea-1Polarization curve of time; (B) is NiCo2S4/CC，Co9S8the/CC and NiS/CC scanning speeds were 2mV s in 1.0M KOH with 0.33M urea-1Comparing the polarization curves of (1); (C) corresponding Tafel curves are obtained; (D) is NiCo2S4Stability test curve at overpotential of 0.3V (vs. SCE)/CC.
In FIG. 9, (A) is a two-electrode system NiCo2S4/CC∥NiCo2S4Polarization curve of/CC in 1.0M KOH with and without 0.33M urea; (B) NiCo2S4/CC∥NiCo2S4Chronoamperometric curve at a constant potential of 1.51V for/CC.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
In the following examples, unless otherwise specified, the starting materials or the treatment techniques are all conventional and commercially available materials or conventional treatment techniques in the art.