Preparation method of needle-shaped cobalt phosphide with phosphorus vacancies and application of needle-shaped cobalt phosphide in seawater electrolysis hydrogen production
阅读说明：本技术 一种具有磷空位的针状磷化钴的制备方法及其在电解海水产氢中的应用 (Preparation method of needle-shaped cobalt phosphide with phosphorus vacancies and application of needle-shaped cobalt phosphide in seawater electrolysis hydrogen production ) 是由 应杰 王欢 肖宇轩 于 2021-09-22 设计创作，主要内容包括：本发明属于海水电解制氢技术领域,具体涉及一种具有磷空位的针状磷化钴的制备方法及其在电解海水产氢中的应用,本发明通过水热法以及煅烧法等简易的方法制备得到一种具有磷空位的针状磷化钴催化剂,即将清洗后的泡沫镍先进行水热反应,取出清洗干燥后经煅烧后得到Co-(3)O-(4),而v-CoP-(x)经两次煅烧得到制备得到。本发明制备的具有磷空位的针状磷化钴催化剂不仅能在海水电解液下进行析氢反应,解决海水析氢的部分难题,还可以达到取代贵金属的要求,经济环保,更具备操作简单,高活性,高稳定性和自支撑等优势。(The invention belongs to the technical field of seawater electrolytic hydrogen production, and particularly relates to a preparation method of needle-shaped cobalt phosphide with phosphorus vacancies and application thereof in seawater electrolytic hydrogen production 3 O 4 And v-CoP x The catalyst is prepared by twice calcination. The needle-shaped cobalt phosphide catalyst with phosphorus vacancy prepared by the inventionThe agent can not only carry out hydrogen evolution reaction under seawater electrolyte, solve partial difficult problem of seawater hydrogen evolution, but also meet the requirement of replacing noble metal, is economic and environment-friendly, and has the advantages of simple operation, high activity, high stability, self-support and the like.)
1. A preparation method of needle-shaped cobalt phosphide with phosphorus vacancies is characterized by comprising the following steps:
s1, placing foamed nickel in Co (NO)3)2·6H2O, Urea and NH4In the aqueous solution of F, a precursor product Co (CO) is prepared by washing and drying after hydrothermal reaction3)0.5(OH)·0.11H2O；
S2, p-Co (CO)3)0.5(OH)·0.11H2Calcining O in inert atmosphere to obtain Co3O4；
S3, mixing Co3O4Transferred to a porcelain boat downstream of the tube furnace and upstreamAdding NaH into the porcelain boat2PO2·H2And O, calcining under Ar, and finally washing and drying to obtain the needle-shaped cobalt phosphide with phosphorus vacancies.
2. The method of claim 1, wherein the two calcinations of step S3 are performed under Ar atmosphere at 2 ℃. min-1The temperature rise rate is increased to 250-350 ℃ for calcining for 1.5-2.5 h.
3. The method for preparing acicular cobalt phosphide with phosphorus vacancy as claimed in claim 1, wherein the calcination of step S2 is in N2At 3 ℃ min under atmosphere-1The temperature rise rate is increased to 300-400 ℃ for calcination for 1.5-2.5 h.
4. The method for preparing the acicular cobalt phosphide with phosphorus vacancies according to claim 1, wherein the temperature of the hydrothermal reaction is 100-140 ℃ and the time is 10-14 h.
5. The method for preparing acicular cobalt phosphide having phosphorus vacancy as claimed in claim 1, wherein Co (NO) is used as the catalyst3)2·6H2The molar concentration of O is 0.02M-0.06M, the molar concentration of urea is 0.1M-0.3M, NH4The molar concentration of F is 0.14M-0.18M.
6. The method for preparing needle-shaped cobalt phosphide with phosphorus vacancies as claimed in claim 1, wherein the foamed nickel is cleaned by ultrasonic cleaning with hydrochloric acid, acetone, ethanol and water respectively before use.
7. The method for preparing acicular cobalt phosphide with phosphorus vacancies as claimed in claim 6, wherein the power of the ultrasonic cleaning is 300-400W, and the time is 20-40 min.
8. The acicular cobalt phosphide with phosphorus vacancies prepared by the method for preparing acicular cobalt phosphide with phosphorus vacancies as described in any one of claims 1 to 7.
9. Use of the acicular cobalt phosphide having phosphorus vacancies as a catalyst in the electrolysis of seawater to produce hydrogen as claimed in claim 8.
Technical Field
The invention belongs to the technical field of seawater electrolytic hydrogen production, and particularly relates to a preparation method of needle-shaped cobalt phosphide with phosphorus vacancies and application of the needle-shaped cobalt phosphide in seawater electrolytic hydrogen production.
Background
In response to environmental problems such as climate change and ecological badness caused by overuse of global fossil energy, sustainable, clean and efficient energy development is an effective response mode. The electrochemical water cracking is a promising technology for converting electric energy into hydrogen fuel, has the characteristics of high energy density, high output energy, zero carbon emission and the like, and is simple, environment-friendly, high in yield and high in product purity. Electrochemical water splitting therefore has great potential in developing and utilizing renewable energy sources to address the growing energy needs and significant problems of fossil fuel (e.g., petroleum, coal, and natural gas) depletion. On the other hand, abundant seawater resources on the earth are used as the electrolyte for hydrogen production by electrochemical water splitting, so that the consumption rate of global fresh water resources can be effectively reduced, and the method is particularly important for high-requirement fresh water areas such as arid areas, coastal countries, islands and the like.
The noble metal Pt is commonly used as a commercial catalytic water-splitting hydrogen production, but it is expensive, scarce in quantity and poor in durability, resulting in a limitation in its large-scale application. Therefore, it is necessary to develop a Hydrogen Evolution Reaction (HER) catalyst with abundant earth resources, high cost performance and strong performance to realize efficient seawater cracking. The transition metal has unique electronic structure and chemical characteristics, and has the advantages of high activity, low overpotential, long-term stability, rich content, easy acquisition and the like. Therefore, it is necessary to regulate the structure of the transition metal catalytic material to improve HER performance, so that it can be applied to hydrogen evolution reaction. However, most of these electrocatalytic systems operate in pure water electrolytes including acids, bases or buffers, and there are few reports of electrocatalytic water splitting using seawater, and about 97% of the water resources available on earth are seawater. Since natural seawater contains hundreds of different impurities, it may cause catalyst poisoning and the generation of unknown side reactions. Therefore, the electro-catalysis of seawater hydrogen evolution has become a hotspot and difficulty in recent research.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a preparation method of needle-shaped cobalt phosphide with phosphorus vacancies, and the prepared cobalt phosphide has the potential of being used as a catalyst for electrolyzing seawater to prepare hydrogen.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a preparation method of needle-shaped cobalt phosphide with phosphorus vacancies, which comprises the following steps:
s1, placing foamed nickel in Co (NO)3)2·6H2O, Urea and NH4In the aqueous solution of F, a precursor product Co (CO) is prepared by washing and drying after hydrothermal reaction3)0.5(OH)·0.11H2O；
S2, p-Co (CO)3)0.5(OH)·0.11H2Calcining O in inert atmosphere to obtain Co3O4；
S3, mixing Co3O4Transferring to porcelain boat at downstream of tube furnace, and adding NaH into porcelain boat at upstream2PO2·H2And O, calcining under Ar, and finally washing and drying to obtain the needle-shaped cobalt phosphide with phosphorus vacancies.
The needle-shaped cobalt phosphide catalyst with the phosphorus vacancies is prepared by a simple and easy-to-operate method, and can effectively overcome the defect of taking nano particles as an electrode material when being used as a self-supporting electrode for simulating seawater electrolysis hydrogen evolution, compared with the needle-shaped cobalt phosphide without the phosphorus vacancies, the needle-shaped cobalt phosphide with the phosphorus vacancies has the advantages of obviously improved performance, higher stability and no obvious reduction of current density after 25h test. The needle structure has many advantages of enlarging electrochemical surface area, facilitating air bubble migration from the surface of the catalyst, and the like, thereby further improving the performance of the electrocatalyst. In addition, phosphorus vacancy can effectively improve electronic conversion, and researches show that the needle-shaped cobalt phosphide catalyst with phosphorus vacancy has good hydrogen evolution performance in simulated seawater, and is expected to be applied to the seawater electrolysis hydrogen production industry.
Preferably, both the calcinations of step S3 are performed at 2 ℃. min under Ar atmosphere-1The temperature rise rate is increased to 250-350 ℃ for calcining for 1.5-2.5 h. In particular toThe two times of calcination are performed at 2 ℃ and min in Ar atmosphere-1The temperature rising rate of (2) is increased to 300 ℃ for calcining for 2.0 h.
Preferably, the calcination of step S2 is at N2At 3 ℃ min under atmosphere-1The temperature rise rate is increased to 300-400 ℃ for calcination for 1.5-2.5 h. In particular, the calcination is in N2At 3 ℃ min under atmosphere-1The temperature rising rate of (2) is increased to 350 ℃ and the calcination is carried out for 2.0 h.
Preferably, the temperature of the hydrothermal reaction is 100-140 ℃ and the time is 10-14 h. Specifically, the temperature of the hydrothermal reaction is 120 ℃, and the time is 12 h.
Preferably, said Co (NO)3)2·6H2The molar concentration of O is 0.02M-0.06M, the molar concentration of urea is 0.1M-0.3M, NH4The molar concentration of F is 0.14M-0.18M. In particular, the Co (NO)3)2·6H2The molar concentration of O is 0.04M, the molar concentration of urea is 0.2M, NH4The molar concentration of F was 0.16M.
Preferably, the foamed nickel is ultrasonically cleaned with hydrochloric acid, acetone, ethanol and water respectively before use.
Further, the power of the ultrasonic cleaning is 300-400W, and the time is 20-40 min. Specifically, the power of the ultrasonic cleaning is 360W, and the time is 30 min.
The invention also provides the acicular cobalt phosphide with phosphorus vacancies prepared by the preparation method of the acicular cobalt phosphide with phosphorus vacancies.
The invention also provides the application of the needle-shaped cobalt phosphide with phosphorus vacancy as a catalyst in the preparation of hydrogen by electrolyzing seawater.
Compared with the needle-shaped cobalt phosphide catalyst without phosphorus vacancies, the needle-shaped cobalt phosphide catalyst with phosphorus vacancies has the advantages that the hydrogen evolution activity of the cobalt phosphide with phosphorus vacancies in simulated seawater is obviously improved, the stability is higher, and the current density is not obviously reduced after a constant-voltage stability test for 25 hours. The needle-shaped cobalt phosphide catalyst with phosphorus vacancies can not only overcome the problem of chloride ion corrosion in seawater electrolyte and solve the important problem of seawater hydrogen evolution, but also meet the requirement of replacing noble metals, is economical and environment-friendly, and has the advantages of simple preparation, high porosity (namely, the substrate is foamed nickel, so the porosity is high), high stability and the like.
Compared with the prior art, the invention has the beneficial effects that:
the needle-shaped cobalt phosphide catalyst with phosphorus vacancies is prepared by simple methods such as a hydrothermal method, a calcination method and the like, namely, the cleaned nickel foam is firstly subjected to hydrothermal reaction, taken out, cleaned, dried and calcined to obtain Co3O4，Co3O4And calcining again to obtain the catalyst. The needle-shaped cobalt phosphide catalyst with phosphorus vacancies prepared by the invention can not only carry out hydrogen evolution reaction under seawater electrolyte, solve part of the problems of seawater hydrogen evolution, but also meet the requirement of replacing noble metals, is economical and environment-friendly, and has the advantages of simple operation, high catalytic activity, high stability, self-support (namely prepared by taking foamed nickel as a substrate) and the like.
Drawings
FIG. 1 shows NF (Ni foam), Co (CO)3)0.5(OH)·0.11H2O and Co3O4X-ray electron diffraction images of the catalyst;
FIG. 2 is a scanning electron microscope image of various catalysts (A picture is Co (CO)3)0.5(OH)·0.11H2O precursor; b is Co3O4An intermediate; graph C is g-CoPx(ii) a Graph D is v-CoPx)；
FIG. 3 is g-CoPxAnd v-CoPxAn X-ray electron diffraction image (A); g-CoPxAnd v-CoPxAn X-ray photoelectron spectrum (B, C); g-CoPxAnd v-CoPxElectron paramagnetic resonance spectrum (D);
FIG. 4 shows the HER performance of various catalysts in simulated seawater 1M KOH +0.5M NaCl electrolyte (graph A is the polarization curve; graph B is the durability test).
In fig. 4, the abscissa is the potential: E/V, ordinate is current density: j/mAcm-2。
Detailed Description
The following further describes the embodiments of the present invention. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The experimental procedures in the following examples were carried out by conventional methods unless otherwise specified, and the test materials used in the following examples were commercially available by conventional methods unless otherwise specified.
EXAMPLE 1 preparation of acicular cobalt phosphide catalyst having phosphorus vacancies
(1) Ultrasonically cleaning foamed nickel (Ni foam, NF) with the size of 1cm multiplied by 2mm with 6M hydrochloric acid, acetone, absolute ethyl alcohol and water respectively for 30min under the power of 360W, and drying at the temperature of 60 ℃ in vacuum;
(2) 50mL of H was placed in a 100mL stainless steel autoclave2O, then adding Co (NO) with the concentration of 0.04M3)2·6H2O, urea at a concentration of 0.2M, NH at a concentration of 0.16M4And F, adding the treated foam nickel into the high-pressure autoclave, carrying out hydrothermal reaction at 120 ℃ for 12 hours, and naturally cooling the high-pressure autoclave to room temperature after the reaction is finished. Then repeatedly and alternately washing the foamed nickel for three times by using absolute ethyl alcohol and water, and finally drying in vacuum at 60 ℃ to obtain a precursor product Co (CO)3)0.5(OH)·0.11H2O。
(3) Mixing the Co (CO) prepared in the step (2)3)0.5(OH)·0.11H2O is transferred to a tube furnace at 3 ℃ min-1At a rate of N2Heating to 350 ℃ in the atmosphere, calcining for 2 hours, cooling to room temperature, taking out, washing with ultrapure water, and vacuum drying at 60 ℃ to obtain Co3O4；
(4) Mixing Co3O4(in foamed nickel unit, two pieces of the mixture are added) is transferred to a porcelain boat at the downstream of the tube furnace, and 1g of NaH is added to the porcelain boat at the upstream2PO2·H2O, under Ar atmosphere at 2 ℃ min-1Rate ofHeating to 300 ℃, calcining for 2h, washing and vacuum drying to obtain cobalt phosphide (marked as v-CoP) containing vacancyx)。
Comparative example 1 cobalt phosphide free of vacancies (noted as g-CoP)x) Preparation of
The steps (1) and (2) are the same as the steps (1) and (2) of the embodiment 1, and the step (3) is specifically as follows:
mixing Co (CO)3)0.5(OH)·0.11H2O (two pieces in total, in terms of nickel foam) was transferred to a porcelain boat downstream of the tube furnace, and 1g of NaH was added to the porcelain boat upstream2PO2·H2O, under Ar atmosphere at 2 ℃ min-1The temperature is increased to 300 ℃ and calcined for 2h, and the cobalt phosphide (marked as g-CoP) without vacancy is obtained after washing and vacuum dryingx)。
v-CoP prepared in example 1xAnd g-CoP prepared in comparative example 1xAn X-ray diffraction scan was performed using the instrument model Ultima IV. The X-ray diffraction analysis chart shown in FIG. 1 was obtained by comparing the standard cards [ Ni (ICCD No:04-0850), Co (CO)3)0.5(OH)·0.11H2O(ICCD No:48-0083),Co3O4(ICCD No:42-1467), it is apparent that Co has been successfully prepared by the above-mentioned method3O4Intermediate and Co (CO)3)0.5(OH)·0.11H2And (4) O precursor. At the same time, for v-CoPxScanning electron microscope observation was carried out using an instrument model JEOL JSM-IT 200A. As shown in FIG. 2, Co (CO) was observed separately3)0.5(OH)·0.11H2O catalyst, Co3O4Catalyst, g-CoPxCatalyst and v-CoPxThe catalyst is in a needle structure.
In addition, for g-CoP respectivelyxCatalyst and v-CoPxThe catalyst is subjected to X-ray diffraction analysis, X-ray photoelectron spectroscopy analysis and electron paramagnetic resonance spectroscopy analysis. g-CoP as shown in FIG. 3AxCatalyst and v-CoPxX-ray diffraction pattern of the catalyst, showing g-CoPxAnd v-CoPxAre similar in peak position and are all composed of CoP and Co2P composition at 31.6 °, 36.3 ° and 48.1 °The peak values of (A) and (B) are (011), (111) and (211) crystal planes of the CoP crystal respectively, and the peak at 40.7 DEG is Co2The (121) plane of P; FIGS. 3B and C are g-CoPxAnd v-CoPxAccording to high resolution Co 2p3/2(B) And P2P (C) spectrum, calculating v-CoP by integration methodxThe percentage of P in (in the form of Co-P bonds) is 15.76%, much lower than g-CoPx17.52% in (1), and therefore, v-CoP was confirmedxIn the presence of PvAnd the content thereof was 1.76%. FIG. 3D is g-CoPxAnd v-CoPxFurther confirmed the v-CoPxThe existence of phosphorus vacancies.
EXAMPLE 2 preparation of acicular cobalt phosphide catalyst having phosphorus vacancies
(1) Ultrasonically cleaning foamed nickel (Ni foam, NF) with size of 1cm × 2cm × 2mm with 6M hydrochloric acid, acetone, anhydrous ethanol and water under 300W power for 40min, and vacuum drying at 60 deg.C;
(2) 50mL of H was placed in a 100mL stainless steel autoclave2O, then adding Co (NO) with a concentration of 0.02M3)2·6H2O, urea at a concentration of 0.1M, NH at a concentration of 0.14M4And F, adding the treated foam nickel into the high-pressure autoclave, carrying out hydrothermal reaction at 100 ℃ for 14h, and naturally cooling the high-pressure autoclave to room temperature after the reaction is finished. Then repeatedly and alternately washing the foamed nickel for three times by using absolute ethyl alcohol and water, and finally drying in vacuum at 60 ℃ to obtain a precursor product Co (CO)3)0.5(OH)·0.11H2O。
(3) Mixing the Co (CO) prepared in the step (2)3)0.5(OH)·0.11H2O is transferred to a tube furnace at 3 ℃ min-1Heating to 300 ℃ in Ar atmosphere, calcining for 2.5 hours, cooling to room temperature, taking out, washing with ultrapure water, and vacuum drying at 60 ℃ to obtain Co3O4；
(4) Mixing Co3O4(in foamed nickel unit, two pieces of the mixture are added) is transferred to a porcelain boat at the downstream of the tube furnace, and 1g of NaH is added to the porcelain boat at the upstream2PO2·H2O, in N2At 2 ℃ min under an atmosphere-1The temperature is increased to 250 ℃ at the speed, the mixture is calcined for 2.5h, and cobalt phosphide (marked as v-CoP) containing vacancy is obtained after washing and vacuum dryingx)。
EXAMPLE 3 preparation of acicular cobalt phosphide catalyst having phosphorus vacancies
(1) Ultrasonically cleaning foamed nickel (Ni foam, NF) with size of 1cm × 2cm × 2mm with 6M hydrochloric acid, acetone, anhydrous ethanol and water under 300W power for 40min, and vacuum drying at 60 deg.C;
(2) 50mL of H was placed in a 100mL stainless steel autoclave2O, then adding Co (NO) with concentration of 0.06M3)2·6H2O, urea at a concentration of 0.3M, NH at a concentration of 0.18M4And F, adding the treated foam nickel into the high-pressure autoclave, carrying out hydrothermal reaction at 140 ℃ for 10 hours, and naturally cooling the high-pressure autoclave to room temperature after the reaction is finished. Then repeatedly and alternately washing the foamed nickel for three times by using absolute ethyl alcohol and water, and finally drying in vacuum at 60 ℃ to obtain a precursor product Co (CO)3)0.5(OH)·0.11H2O；
(3) Mixing the Co (CO) prepared in the step (2)3)0.5(OH)·0.11H2O is transferred to a tube furnace at 3 ℃ min-1Heating to 400 ℃ in Ar atmosphere, calcining for 3.5 hours, cooling to room temperature, taking out, washing with ultrapure water, and vacuum drying at 60 ℃ to obtain Co3O4；
(4) Mixing Co3O4(in foamed nickel unit, two pieces of the mixture are added) is transferred to a porcelain boat at the downstream of the tube furnace, and 1g of NaH is added to the porcelain boat at the upstream2PO2·H2O, in N2At 2 ℃ min under an atmosphere-1The temperature is increased to 350 ℃ at the speed of (1) and the mixture is calcined for 1.5h, and cobalt phosphide (marked as v-CoP) containing vacancy is obtained after washing and vacuum dryingx)。
Experimental example 1 electrochemical test
The electrochemical test was carried out using a three-electrode system, the test instrument was AUTOLAB (model AUT88171), the electrolyte was simulated seawater (1M KOH +0.5M NaCl), the reference electrode was Hg/HgO, the counter electrode was a graphite rod electrode, and the working electrode was the v-CoP prepared in example 1xCircuit connection check is error-freeAnd setting a program, selecting a Linear sweep voltage measurement potential program to perform a hydrogen evolution test, wherein the scanning speed is 1mV/s, and drawing a Linear Sweep Voltammetry (LSV) curve chart.
As shown in the HER diagram of FIG. 4, as can be seen from FIG. 4A, v-CoPxOnly 75mV (vs RHE) overpotential is required in 1M KOH +0.5M NaCl electrolyte to reach 10mAcm-2The current density of (1) is 93mV, Co are required for g-CoPx at the same current density3O4Catalyst v-CoP requiring 137mV and NF requiring 200mV, so P vacancies are presentxThe performance is obviously improved, and the catalytic activity is high. As can be seen from FIG. 4B, at constant voltage, v-CoPxThe current density of the alloy can be kept stable within 25h, and the HER current density after 25h is from 10mAcm-2Only reduced by 0.7mAcm-2. Visible, v-CoPxHas good hydrogen evolution performance and stability in simulated seawater.
Furthermore, the v-CoP prepared in examples 2 and 3xThe electrochemical test results of (a) are the same as or similar to those of example 1.
The embodiments of the present invention have been described in detail, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, and the scope of protection is still within the scope of the invention.