CN114763620B

CN114763620B - Preparation method of transition metal phosphorus sulfide electrolytic water hydrogen evolution catalyst

Info

Publication number: CN114763620B
Application number: CN202210394626.XA
Authority: CN
Inventors: 李翔; 孟利红; 胡洋; 盛强
Original assignee: Tianjin University of Science and Technology
Current assignee: Tianjin University of Science and Technology
Priority date: 2022-04-15
Filing date: 2022-04-15
Publication date: 2023-12-05
Anticipated expiration: 2042-04-15
Also published as: CN114763620A

Abstract

The invention relates to a preparation method of a transition metal phosphorus sulfide electrolytic water hydrogen-separating catalyst, which adopts a mixture of a transition metal phosphate of a VIII group or a VIB group and thiourea as a precursor, and prepares the transition metal phosphorus sulfide catalyst by a temperature programming reduction method under the condition of hydrogen. In the mixture precursor, the mass ratio of the transition metal phosphate to the thiourea is 1-3. In the temperature-programmed reduction method, the reaction pressure is between normal pressure and 10MPa. With direct or indirect use of H ₂ S or organic sulfur-containing compound is used as vulcanizing agent to vulcanize transition metal phosphide, and compared with the preparation method of temperature programming reduction transition metal sulfur-containing precursor, the method has the characteristics of simplicity, convenience, practicability, safety, low cost and the like. In the electrolytic water hydrogen evolution reaction under the acidic condition, the prepared catalyst has better performance than the corresponding transition metal phosphide catalyst.

Description

Preparation method of transition metal phosphorus sulfide electrolytic water hydrogen evolution catalyst

Technical Field

The invention belongs to the technical field of heterogeneous catalysis, and particularly relates to a preparation method of a transition metal phosphide solid electrochemical catalyst.

Background

With Ni ₂ P、Co ₂ The transition metal phosphide represented by P, moP and WP and the like is a covalent compound and has metallic properties. They are conductors with high hardness and thermal and chemical stability and can be used for many reactions catalyzed by metals. In 1996, robinson et al reported Ni in the Hydrodenitrogenation (HDN) reaction of quinoline ₂ The activity of the P catalyst is higher than that of the traditional Ni-Mo/Al ₂ O ₃ Sulfide catalysts (w.r.a.m. robinson, et al,catal, 1996, 161:539-550). Li was equal to 1998, moP was prepared using the transition metal phosphate precursor Temperature Programmed Reduction (TPR) method under a hydrogen atmosphere and was found to have good Hydrodesulfurization (HDS) performance and stability (W.Li, et al, chem. Lett.,1998, 27:207-208). With the breakthrough of the preparation method, intensive researches on industrial catalysts of transition metal phosphide are started.

Early studies conducted mainly around these transition metal phosphide HDS and HDN properties and found that their intrinsic reactivity was higher than that of commercial sulfide catalysts, forming an important family of hydrofinishing catalysts. The transition metal phosphides also exhibit unique catalytic properties during HDS, i.e., their activity increases with the reaction time in the initial stages of the reaction (S.J.Sawhill, et al, J.Catal.,2003, 215:208-219). Further studies have shown that sulfur intercalates into transition metal phosphides during the HDS reaction, forming a new active phase containing sulfur, the so-called "phosphosulfide" phase. The active phase of the transition metal phosphorus sulfide remains the corresponding transition metal phosphide, and the sulfur species are present as partially negatively charged or nearly elemental sulfur. Transition metal phosphides and phosphorus sulfides have also been used in hydrogenation, hydrodeoxygenation, electrolyzed water hydrogen evolution, oxygen reduction, and CO in recent years ₂ The catalyst has excellent catalytic performance in a series of important reactions such as hydrogenation of CO mixed gas, and the catalyst has become a novel high-efficiency multifunctional catalytic material of a large class which is widely focused in the fields of clean fossil fuel production, renewable energy, hydrogen energy and energy storage.

Among various new energy sources, hydrogen has the advantages of rich resources, no pollution, renewable energy, high energy density and the like, is a clean energy carrier with the most development potential in the 21 st century, and hydrogen energy is also widely paid attention to all countries in the world. The main approaches of hydrogen production at present comprise fossil resource hydrogen production, water decomposition hydrogen production, biotechnology hydrogen production, solar hydrogen production and the like. Fossil resources such as petroleum, coal and natural gas are the main raw materials for hydrogen production. However, this hydrogen production method consumes non-renewable fossil resources, and generates a large amount of greenhouse gases and causes environmental pollution. The clean green hydrogen is produced by electrolysis of water by utilizing clean renewable energy sources such as wind energy, hydroelectric energy and the like and electric energy generated by three processes (water disposal, wind disposal and light disposal), and the development direction of the hydrogen production technology in the future. The water electrolysis hydrogen production comprises two reactions of cathodic hydrogen evolution and anodic oxygen evolution. The hydrogen evolution reaction is slower, and particularly, the serious cathode polarization phenomenon exists under the condition of high current density meeting the industrial production requirement, so that the energy conversion efficiency from electric energy to chemical energy can be greatly reduced, the higher hydrogen production cost is caused, and the industrial application of the hydrogen production is limited. The electrocatalytic Hydrogen Evolution (HER) can greatly reduce hydrogen evolution overpotential under the action of a catalyst, has the advantages of low energy consumption, high efficiency, environmental friendliness and the like, and is a green hydrogen production technology with wide application prospect. The hydrogen evolution reaction can be carried out under either acidic or basic conditions. HER reaction kinetics are very slow under alkaline conditions, with activity 2-3 orders of magnitude lower than under acidic conditions. However, equipment and metal catalysts are severely corroded under acidic conditions, and good stability of the catalyst is required. The noble metal Pt catalyst has low initial overpotential, excellent activity and stability under acidic condition, and is the HER catalyst with the best performance at present. However, noble metals are expensive, low in reserves and difficult to apply on a large scale, and development of high-performance non-noble metal HER catalysts are urgently needed. Among the non-noble metal HER catalysts, transition metal phosphide and phosphorus sulfide have high activity and stability under acidic conditions, and form a high-performance acid-resistant HER catalyst.

Currently transition metal phosphorus sulfides are produced mainly by direct or indirect use of H ₂ S or organic sulfur-containing compound, etc. H ₂ S is a highly toxic gas, directly using H ₂ S is difficult to be applied to the preparation of industrial catalysts as a vulcanizing agent. In the preparation method disclosed in the Chinese patent No. CN112877712A, sodium hydrosulfide arranged above the ventilation of the reactor can decompose and release hydrogen sulfide when reaching the melting point under the protective atmosphere, and phosphide is arranged below the reactor to finally generate phosphorus sulfide, thereby indirectly utilizing H ₂ One example of S vulcanization. It can be seen that the indirect sulfiding process is carried out in a pressure reactor or a reactor designed specifically to stage the solid sulfiding agent and precursor salt, with an increaseCatalyst preparation cost. Among precursors of transition metal phosphides, the phosphate has the highest valence state and is the most stable and inexpensive precursor. The development of a simple, easy, safe and low-cost preparation method using transition metal phosphate as a precursor has important significance for preparing the HER catalyst in the transition metal phosphosulfide industry.

Disclosure of Invention

The invention aims to provide a method for preparing a transition metal phosphosulfide catalyst by using transition metal phosphate as a precursor, which is simple, convenient, easy, safe and low in cost, namely, only thiourea and phosphide precursor are mixed, ground and reduced, a complex device is not required to be built, and extremely toxic gas H is avoided ₂ Use of S. The HER performance of the catalyst under acidic conditions is superior to that of transition metal phosphorus sulfide prepared by using vulcanizing agents such as organic sulfur compounds and the like.

The invention provides a preparation method of a transition metal phosphorus sulfide HER catalyst, which comprises the steps of mixing transition metal phosphate and thiourea (C ₂ H ₄ N ₂ S) using the mechanical mixture as a precursor, and preparing the transition metal phosphorus sulfide by temperature programming reduction under normal pressure.

The invention is not particularly limited to the method of preparing the precursor of the mechanical mixture of transition metal phosphate and thiourea. As a preferred embodiment, the present invention is preferably prepared in a simple manner by mixing the transition metal phosphate powder with the thiourea powder at room temperature.

In the precursor of the mechanical mixture of the transition metal phosphate and the thiourea, the mass ratio of the transition metal phosphate to the thiourea is 1-3, preferably 2. Too little or too much thiourea can lead to incomplete or excessive vulcanization, even generation of metal sulfides, and the like, respectively, which affects the performance of the catalyst.

In the precursor of the mechanical mixture of the transition metal phosphate and the thiourea, the metal component can be the transition metals of Fe, co, ni, pd, pt, ru, ir, rh and the like of the VIII family, and can also be the transition metals of Mo and W of the VIB family. Fe, co, ni, pd, pt, ru, mo and W are preferred, and Ni, co, mo and W are further preferred.

In the precursor of the mechanical mixture of the transition metal phosphate and the thiourea, the transition metal phosphate is prepared by adopting a coprecipitation method. Not only can the nano powder material with small granularity and even distribution be directly obtained through the chemical reaction among substances in the solution, but also the ratio of metal to phosphorus can be adjusted.

In a specific embodiment, in the preparation method of the transition metal phosphorus sulfide, the temperature programming reduction is performed, wherein the reducing gas is hydrogen, the reducing pressure is between normal pressure and 10MPa, the reducing temperature is between 300 and 800 ℃, and the reducing time is not more than 12 hours.

Further, the temperature programming conditions of the phosphorus sulfide catalyst of group VIB MoP or WP are: the temperature was raised from room temperature to 400℃at a rate of 2℃per minute in a hydrogen atmosphere of 150 ml/min, then to 650℃at a rate of 1℃per minute, and maintained at the final reduction temperature for 2 hours.

Further, ni of group VIII ₂ P or Co ₂ The temperature programming conditions of the P phosphorus sulfide catalyst are: the temperature was raised from room temperature to 120℃at a rate of 4℃per minute in a hydrogen atmosphere of 150 ml/min and maintained at 120℃for 1 hour, then to 400℃at a rate of 10℃per minute, and then to a final reduction temperature of 500℃at a rate of 1℃per minute and maintained at the final reduction temperature for 2 hours.

The HER reaction according to the present invention means a HER reaction under acidic conditions.

The invention has the advantages and beneficial effects that:

1. the invention takes the mixture of transition metal phosphate and thiourea as the precursor, and has the characteristics of safety and low cost. In particular, the thiourea is a white solid, has no pungent smell, does not contain impurity atoms, has low price, and has no residue in the catalyst after reduction.

2. HER activity of the transition metal phosphosulfide catalyst prepared by the invention is superior to that of C under the acidic condition ₂ H ₆ S ₂ And (3) a phosphorus sulfide catalyst prepared by vulcanizing transition metal phosphide with an organic sulfur-containing compound. The former is to vulcanize phosphide by decomposing thiourea in the process of reducing phosphate, and the latter is to vulcanize phosphide after preparing phosphide. The degree of vulcanization of the formerThe sulfur profile is superior to the latter.

Drawings

FIG. 1 is an XRD spectrum of WP and tungsten phosphosulfide (WP-S) prepared by reducing a phosphate precursor of group VIB tungsten and a mechanical mixture of tungsten phosphate and thiourea using temperature programming.

FIG. 2 is an XRD spectrum of MoP and molybdenum phosphosulfide (MoP-S) prepared using a temperature programmed reduction of a phosphate precursor of group VIB molybdenum and a mechanical mixture of molybdenum phosphate and thiourea.

FIG. 3 is Ni prepared by reducing a phosphate precursor of group VIII nickel with temperature programming and a mechanical mixture of nickel phosphate and thiourea ₂ P and phosphorus sulfide of nickel (Ni ₂ P-S).

FIG. 4 is Co prepared by reducing a phosphate precursor of group VIII cobalt with temperature programming and a mechanical mixture of cobalt phosphate and thiourea ₂ P and cobalt phosphorus sulfides (Co ₂ P-S).

FIG. 5 shows the preparation of Co from a phosphate precursor using temperature programmed reduction of cobalt ₂ P followed by C under hydrogen atmosphere ₂ H ₆ S ₂ The obtained cobalt phosphosulfide (Co ₂ P-C ₂ H ₆ S ₂ ) Is a XRD spectrum of (C).

Figure 6 is a Linear Sweep Voltammetric (LSV) curve of HER reactions under WP and WP-S catalyzed acidic conditions.

Figure 7 is a HER response LSV curve under acidic conditions catalyzed by MoP and MoP-S.

FIG. 8 is Ni ₂ P and Ni ₂ HER response LSV curve under P-S catalyzed acidic conditions.

FIG. 9 is Co ₂ P、Co ₂ P-S and Co ₂ P-C ₂ H ₆ S ₂ HER reaction LSV curve under catalytic acidic conditions.

Detailed Description

The invention will now be described in further detail by way of specific examples, which are given by way of illustration only and not by way of limitation, with reference to the accompanying drawings.

Example 1

The WP catalyst is prepared by adopting a phosphate precursor through temperature programming reduction.

5.60 g of ammonium metatungstate ((NH) are weighed out ₄ ) ₆ W ₁₂ O ₃₉ ·xH ₂ O) and 3.00 g of diammonium hydrogen phosphate (NH) ₄ ) ₂ HPO ₄ Dissolved in 15 ml and 10 ml deionized water, respectively. Then (NH) was slowly added under stirring ₄ ) ₂ HPO ₄ The solution was added dropwise to (NH) ₄ ) ₆ W ₁₂ O ₃₉ ·xH ₂ And O solution. After the dropwise addition was completed, stirring was continued for 30 minutes, and then the water in the solution was evaporated to dryness, followed by drying in an oven at 120 ℃. Finally, roasting for 3 hours at 500 ℃ in a muffle furnace to obtain the phosphate precursor of the WP catalyst.

The phosphate precursor of the catalyst is pressed and crushed to 20-40 meshes, 0.20 g of the catalyst precursor is weighed and filled into a U-shaped quartz tube reactor, the temperature is increased to 400 ℃ from room temperature at a speed of 2 ℃/min under the conditions of normal pressure and a hydrogen flow of 150 ml/min, then the temperature is increased to 650 ℃ at a speed of 1 ℃/min, and the catalyst is kept at the reduction final temperature for 2 hours. As can be seen from the XRD pattern of fig. 1, the active phase of the catalyst is WP.

Example 2

Preparing the WP-S catalyst.

0.20 g of the WP phosphate precursor prepared in example 1 and 0.1 g of thiourea powder were weighed, mixed and ground for 15 minutes, pressed and crushed to 20 to 40 mesh, and filled into a U-shaped quartz glass tube, and a catalyst was prepared under the same conditions as in example 1. As can be seen from the XRD pattern of fig. 1, the active phase of the catalyst is WP.

Example 3

And preparing the MoP catalyst by adopting a phosphate precursor through temperature programming reduction.

2.37 g of ammonium molybdate ((NH) are weighed out ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O) and 1.77 g of (NH) ₄ ) ₂ HPO ₄ Dissolved in 15 ml and 10 ml deionized water, respectively. Then (NH) was slowly added under stirring ₄ ) ₂ HPO ₄ Drop by drop of solutionAdded to (NH) ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ And O solution. After the dropwise addition was completed, stirring was continued for 30 minutes, and then the water in the solution was evaporated to dryness, followed by drying in an oven at 120 ℃. Finally, roasting for 3 hours at 500 ℃ in a muffle furnace to obtain the MoP catalyst phosphate precursor.

The phosphate precursor of the catalyst is pressed and crushed to 20-40 meshes, 0.20 g of the catalyst precursor is weighed and filled into a U-shaped quartz tube reactor, the temperature is increased to 400 ℃ from room temperature at a speed of 2 ℃/min under the conditions of normal pressure and a hydrogen flow of 150 ml/min, then the temperature is increased to 650 ℃ at a speed of 1 ℃/min, and the catalyst is kept at the reduction final temperature for 2 hours. As can be seen from the XRD pattern of fig. 2, the active phase of the catalyst is MoP.

Example 4

MoP-S catalyst was prepared.

0.20 g of the MoP phosphate precursor prepared in example 3 and 0.1 g of thiourea powder were weighed, mixed and ground for 15 minutes, pressed and crushed to 20 to 40 mesh, and filled into a U-shaped quartz glass tube, and a catalyst was prepared under the same conditions as in example 3. As can be seen from the XRD pattern of fig. 2, the active phase of the catalyst is MoP.

Example 5

Preparation of Ni by programmed temperature reduction using phosphate precursors ₂ And (3) a P catalyst.

3.90 g of nickel nitrate hexahydrate (Ni (NO) ₃ ) ₂ ·6H ₂ O) and 1.77 g of (NH) ₄ ) ₂ HPO ₄ Dissolved in 15 ml and 10 ml deionized water, respectively. Then (NH) was slowly added under stirring ₄ ) ₂ HPO ₄ Dropwise adding the solution to Ni (NO) ₃ ) ₂ ·6H ₂ And O solution. After the dropwise addition was completed, stirring was continued for 30 minutes, and then the water in the solution was evaporated to dryness, followed by drying in an oven at 120 ℃. Finally, roasting in a muffle furnace at 500 ℃ for 3 hours to obtain Ni ₂ Phosphate precursor of P catalyst.

Crushing the phosphate precursor of the catalyst into 20-40 meshes, weighing 0.20 g of the catalyst precursor, filling the catalyst precursor into a U-shaped quartz tube reactor, and under normal pressure,the hydrogen flow rate was 150 ml/min, and the temperature was raised from room temperature to 120℃at a rate of 4℃per minute and maintained at 120℃for 1 hour, then raised to 400℃at a rate of 10℃per minute, further raised to 500℃at a rate of 1℃per minute and maintained at the final reduction temperature for 2 hours. As can be seen from the XRD pattern of FIG. 3, the active phase of the catalyst is Ni ₂ P。

Example 6

Preparation of Ni ₂ P-S catalyst.

0.20 g of Ni prepared in example 5 was weighed out ₂ The P phosphate precursor and 0.1 g of thiourea powder were mixed and ground for 15 minutes, pressed and crushed to 20 to 40 mesh, and filled into a U-shaped quartz glass tube, and a catalyst was prepared under the same conditions as in example 5. As can be seen from the XRD pattern of FIG. 3, the active phase of the catalyst is Ni ₂ P。

Example 7

Preparation of Co by programmed temperature reduction using phosphate precursors ₂ And (3) a P catalyst.

2.70 g of cobalt nitrate hexahydrate (Co (NO) ₃ ) ₂ ·6H ₂ O) and 0.53 g of (NH) ₄ ) ₂ HPO ₄ Dissolved in 15 ml and 10 ml deionized water, respectively. Then (NH) was slowly added under stirring ₄ ) ₂ HPO ₄ Dropwise adding the solution to Co (NO) ₃ ) ₂ ·6H ₂ And O solution. After the dropwise addition was completed, stirring was continued for 30 minutes, and then the water in the solution was evaporated to dryness, followed by drying in an oven at 120 ℃. Finally, roasting in a muffle furnace at 500 ℃ for 3 hours to obtain Co ₂ Phosphate precursor of P catalyst.

The phosphate precursor of the catalyst is pressed and crushed to 20-40 meshes, 0.20 g of the catalyst precursor is weighed and filled into a U-shaped quartz tube reactor, the temperature is raised to 120 ℃ from room temperature at a speed of 4 ℃/min under the condition of normal pressure and a hydrogen flow of 150 ml/min, the temperature is kept at 120 ℃ for 1 hour, then the temperature is raised to 400 ℃ at a speed of 10 ℃/min, the temperature is raised to 500 ℃ at a speed of 1 ℃/min, and the temperature is kept at the final reduction temperature for 2 hours. As can be seen from the XRD pattern of FIG. 4, the active phase of the catalyst is Co ₂ P。

Example 8

Preparation of Co ₂ P-S catalyst.

0.20 g of Co prepared in example 7 was weighed out ₂ The P-phosphate precursor and 0.1 g of thiourea powder were mixed and ground for 15 minutes, pressed and crushed to 20 to 40 mesh, and filled into a U-shaped quartz glass tube, and a catalyst was prepared under the same conditions as in example 7. As can be seen from the XRD pattern of FIG. 4, the active phase of the catalyst is Co ₂ P。

Comparative example 1

Preparation of Co ₂ P-C ₂ H ₆ S ₂ A catalyst.

Co was prepared as in example 7 ₂ After P, the temperature was reduced to 400℃and the pressure was reduced, and dimethyl disulfide (C) was entrained by a bubbler using hydrogen gas ₂ H ₆ S ₂ ) Blowing into the catalyst and continuously vulcanizing for 2 hours at 400 ℃ to prepare Co ₂ P-C ₂ H ₆ S ₂ . As can be seen from the XRD pattern of FIG. 5, the active phase of the catalyst is Co ₂ P。

The HER performance of the catalysts was tested under acidic conditions using three electrodes. Polishing glassy carbon electrode with diameter of 6 mm is used as working electrode, silver/silver chloride (Ag/AgCl) is used as reference electrode, platinum wire (Pt) is used as contrast electrode, and 0.5. 0.5M H ₂ SO ₄ Is an electrolyte. The glassy carbon working electrode was prepared as follows: the prepared 10.0 mg catalyst and 10. Mu.l Nafion solution (5 wt%) were dispersed in 1 ml isopropanol solution and sonicated for 20 minutes to prepare a homogeneous ink. The prepared catalyst ink was dropped onto a glassy carbon electrode and dried at room temperature. Wherein the mass loading of the catalyst on the electrode was constant at 0.56 mg/cm.

Electrochemical testing was performed using Linear Sweep Voltammetry (LSV). The scan rate was 5 mv/sec to test for HER polarization curve. The electrode potential obtained from the test was then converted to a standard Reversible Hydrogen Electrode (RHE) as shown in fig. 9. The Nernst equation for the conversion is: e (vs. rhe) =e (vs. Ag/AgCl) +0.2+0.059·ph, where 0.2 represents the standard electrode potential of the Ag/AgCl reference electrode at 25 ℃, the solution pH referred to herein=0.3.

As can be seen from FIGS. 5 to 8, WP-S, moP-S, ni at the same overpotential ₂ P-S and Co ₂ The current densities of P-S are correspondingly greater than WP, moP, ni ₂ P and Co ₂ P. As shown in FIG. 9, co ₂ HER performance of P-S is superior to Co ₂ P-C ₂ H ₆ S ₂ 。

The present invention has been described above with the understanding that the catalyst composition and the preparation conditions of the present invention are clearly disclosed. However, it will be apparent to those skilled in the art that certain modifications and improvements may be made to the present invention. Therefore, any modification and improvement of the present invention should be within the scope of the present invention as long as it does not depart from the spirit of the present invention. The scope of the invention is set forth in the appended claims.

Claims

1. A preparation method of a transition metal phosphorus sulfide electrolytic water hydrogen-separating catalyst is characterized in that: preparing transition metal phosphosulfide by adopting a mixture of transition metal phosphate and thiourea as a precursor and adopting a temperature programming reduction method under a hydrogen atmosphere;

the transition metal in the transition metal phosphorus sulfide is W or Mo or Ni or Co;

the active phase of the transition metal phosphorus sulfide is sulfur-containing WP or MoP or Ni ₂ P or Co ₂ P；

The transition metal phosphate is prepared by adopting a coprecipitation method;

the mixture of the transition metal phosphate and the thiourea is a mechanical mixture of the transition metal phosphate and the thiourea, wherein the mass ratio of the transition metal phosphate to the thiourea is 1-3;

the reducing gas for temperature programming reduction is hydrogen, the pressure is normal pressure to 10MPa, the reducing temperature is 300-800 ℃, and the reducing time is 6-12 hours.

2. The method of manufacturing according to claim 1, characterized in that: the temperature programming is to raise the temperature from room temperature to 400 ℃ at a speed of 2 ℃/min in a hydrogen atmosphere of 150 ml/min, then raise the temperature to 650 ℃ at a speed of 1 ℃/min, and keep the temperature at the final reduction temperature for 2 hours, so as to prepare the phosphorus sulfide catalyst of MoP or WP.

3. The method of manufacturing according to claim 1, characterized in that: the temperature programming is to firstly heat up to 120 ℃ from room temperature at the speed of 4 ℃/min in 150 ml/min hydrogen atmosphere, keep at 120 ℃ for 1 hour, then heat up to 400 ℃ at the speed of 10 ℃/min, heat up to 500 ℃ of final reduction temperature at the speed of 1 ℃/min, and keep at the final reduction temperature for 2 hours, thus obtaining Ni ₂ P or Co ₂ P phosphorus sulfide catalyst.

4. Use of the electrolyzed water hydrogen evolution catalyst prepared by the preparation method of claim 2 or 3 in an electrolyzed water hydrogen evolution reaction under an acidic condition.