Transition metal selenide catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of nano material preparation and application, in particular to a transition metal selenide catalyst and a preparation method and application thereof.The preparation method comprises the steps that firstly, metal nickel salt, ferric salt, urea and ammonium fluoride are dissolved in deionized water, and a nickel-iron layered hydroxide nanosheet precursor is synthesized through a hydrothermal method; secondly, preparing an iron-doped nickel selenide catalyst by adopting a selenylation reaction; the electronic structure of nickel selenide is regulated and controlled by utilizing an iron doping strategy, and the catalytic performance is improved. The prepared iron-doped nickel selenide catalyst has good catalytic activity when being used for hydrogen evolution reaction and sulfur ion oxidation reaction. In a two-electrode sulfur ion oxidation coupling hydrogen production electrolytic tank, the current density of 10mAcm <-2 > can be output only by the voltage of 0.439 V, and the targets of efficient and energy-saving hydrogen production and sulfur ion oxidation upgrading into a high-added-value elemental sulfur product are achieved. The method has the advantages of simple and controllable preparation process, low raw material price, easiness in batch production and the like, and can be used as a catalyst for efficient water electrolysis hydrogen production and sulfur ion oxidation reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation and application of nanomaterials, and particularly relates to a transition metal selenide catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous consumption of fossil fuels and the increasingly deteriorating environment, the human demand for sustainable clean energy is increasing day by day. As a highly potential clean energy, hydrogen has significant advantages of high energy density and environmental friendliness, and plays a key role in the future energy transformation. Traditional hydrogen production methods have many disadvantages such as complex production equipment processes, high investment and operation costs. In comparison, the electrocatalytic water splitting technology driven by renewable energy has become a highly promising high-purity hydrogen production technology due to mild operating conditions and simple processes. However, this technology faces the problem of a relatively high required voltage caused by the slow anodic oxygen evolution reaction rate, resulting in a large increase in energy consumption. Currently, noble metal-based materials represented by Pt / C, RuO 2 and IrO 2 are the best choices to achieve low energy consumption, but their low reserves and high costs seriously hinder commercial applications. Therefore, it is very crucial to develop efficient electrocatalytic systems and inexpensive catalysts.

[0003] At present, researchers have optimized the catalytic system and reduced energy consumption by using the oxidation reactions of thermodynamically favorable molecules such as methanol, glycerol, urea, 5-hydroxymethylfurfural, and hydrazine hydrate to replace the oxygen evolution reaction. Among these alternative reactions, the sulfur ion oxidation reaction has received extensive attention due to its low thermodynamic potential. During the sulfur ion oxidation reaction, the formation and transformation of polysulfide intermediates involve the transfer of sixteen electrons, which makes the catalytic kinetics slow. At the same time, sulfur species are prone to poisoning metal catalysts, reducing the activity and stability of the catalysts. To address these challenges, researchers have adopted various strategies, such as doping heteroatoms and constructing heterostructures, to regulate the electronic structure and reduce the reaction energy barrier, achieving good catalytic performance. However, most of the currently developed catalysts only exhibit single-functional catalytic reaction performance, and the related research on bifunctional catalysts with hydrogen evolution reaction and sulfur ion oxidation reaction is still relatively limited. Based on this, the present invention provides a transition metal selenide catalyst (Fe-Ni 0.85 Se), which has excellent activity and stability in both the hydrogen evolution reaction and the sulfur ion oxidation reaction. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies existing in the prior art, and to propose a transition metal selenide catalyst, a preparation method thereof, and an application thereof. The prepared catalyst exhibits high catalytic performance, and realizes efficient energy-saving hydrogen production and sulfur ion upgrading and recovery in a two-electrode sulfur ion oxidation coupled hydrogen production system.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A preparation method of a transition metal selenide catalyst, comprising the following steps:

[0007] Step 1: Dissolve 10 parts of metal nickel salt, 0 - 5 parts of metal iron salt, 30 - 100 parts of urea, and 10 - 100 parts of ammonium fluoride in water according to the molar ratio to obtain a homogeneous solution;

[0008] Step 2: Transfer the above solution to a polytetrafluoroethylene-lined reaction kettle, add a conductive substrate, seal the reaction kettle, and place it in a blast drying oven to prepare a nickel-iron hydroxide nanosheet precursor by the first hydrothermal reaction;

[0009] Step 3: Add the above nickel-iron hydroxide nanosheet precursor to an aqueous solution of sodium borohydride containing 1 - 3 parts of selenium powder, and carry out the second hydrothermal reaction to obtain an iron-doped nickel selenide nanosheet catalyst.

[0010] Preferably, in the step 1, the metal nickel salt is nickel nitrate or nickel chloride, and the metal iron salt is iron nitrate or iron chloride.

[0011] Preferably, in the step 2, the temperature and reaction time of the first hydrothermal reaction are 100 - 160 °C and 4 - 12 hours respectively.

[0012] Preferably, in the step 2, the conductive substrate is one or more of nickel foam, cobalt foam, copper foam, titanium foam, titanium mesh, carbon paper, and carbon cloth.

[0013] Preferably, in the step 3, the temperature and reaction time of the second hydrothermal reaction are 120 - 160 °C and 8 - 16 hours respectively.

[0014] A transition metal selenide catalyst prepared by the above preparation method, wherein the catalyst uses a conductive substrate as a carrier, and uniformly shaped selenide nanosheets grow on the surface of the carrier

[0015] The present invention also provides an application of a transition metal selenide catalyst prepared by the above preparation method in electrocatalytic hydrogen evolution reaction, sulfide ion oxidation reaction, and two-electrode sulfide ion oxidation-coupled hydrogen production. The selenide catalyst is used as a catalyst for electrocatalytic hydrogen evolution reaction and sulfide ion oxidation reaction, and the anode and cathode of a two-electrode sulfide ion oxidation-coupled hydrogen production system.

[0016] Preferably, after adding sulfuric acid to the electrolyte solution after the sulfide ion oxidation-coupled hydrogen production system, the generated precipitate is separated and dried to obtain a sulfur product.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The transition metal selenide catalyst prepared by the present invention can regulate the electronic structure of the catalyst and expose a large number of catalytic active sites by using metal iron doping and a uniform nanosheet morphology, improving the catalytic performance and the mass transfer rate in the electrocatalytic process.

[0019] 2. The transition metal selenide catalyst prepared by the present invention has good electrocatalytic hydrogen evolution reaction, sulfide oxidation reaction and hydrogen production performance by coupling sulfide oxidation, solving the problems of slow catalytic kinetics and high required voltage in the process of electrolytic water hydrogen production.

[0020] 3. When the transition metal selenide catalyst prepared by the present invention is applied to a two-electrode hydrogen production system by coupling sulfide oxidation, a small electrolysis voltage of 0.439 and 0.811 V is required to output current densities of 10 and 200 mA cm -2 , achieving the goal of efficient and energy-saving hydrogen production and upgrading sulfide oxidation to high-value elemental sulfur.

[0021] 4. The preparation method of the present invention has the advantages of low raw material price, simple and controllable operation, etc., and can replace noble metal catalysts and promote the industrial application of electrolytic water hydrogen production. Brief Description of the Drawings

[0022] Figure 1 X-ray diffraction patterns of Ni 0.85 Se and Fe-Ni 0.85 Se prepared in Example 1 of the present invention;

[0023] Figure 2 Scanning electron microscope and transmission electron microscope photos of Fe-Ni 0.85 Se prepared in Example 1 of the present invention; where a is the scanning electron microscope photo of Fe-Ni 0.85 Se, and b is the transmission electron microscope photo of Fe-Ni 0.85 Se;

[0024] Figure 3 Hydrogen evolution reaction performance diagrams of Ni 0.85 Se and Fe-Ni 0.85 Se in alkaline electrolyte; where a is the polarization curve diagram of the hydrogen evolution reaction, and b is the Tafel slope diagram of the hydrogen evolution reaction;

[0025] Figure 4 Sulfide oxidation reaction performance diagrams of Ni 0.85 Se and Fe-Ni 0.85 Se; where a is the polarization curve diagram of the sulfide oxidation reaction, and b is the Tafel slope diagram of the sulfide oxidation reaction;

[0026] Figure 5 Ni prepared in Example 1 of the present invention 0.85 Se and Fe-Ni 0.85 Performance graphs of Se in a conventional water electrolysis and hydrogen production electrolytic cell coupled with sulfide ion oxidation, and the anodic products obtained after adding sulfuric acid to the electrolytic cell; where a is the polarization curve of Fe-Ni 0.85 Se in a conventional water electrolysis and hydrogen production electrolytic cell coupled with sulfide ion oxidation, and b is the X-ray diffraction pattern and optical photograph of the anodic products obtained after adding sulfuric acid to the sulfide ion oxidation coupled hydrogen production electrolytic cell. Detailed implementation manners

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, and thus make a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Example 1

[0029] A preparation method of a transition metal selenide catalyst specifically includes the following steps:

[0030] First step: Dissolve 1.6 mmol of nickel nitrate, 0.4 mmol of iron nitrate, 10 mmol of urea and 6 mmol of ammonium fluoride in 35 mL of water to obtain a homogeneous solution;

[0031] Second step: Transfer the above solution to a 50 mL polytetrafluoroethylene liner, add a piece of nickel foam carrier, seal the polytetrafluoroethylene liner and put it into a stainless steel autoclave. After sealing, place it in a forced air drying oven, heat it to 120 °C, and keep it warm for 6 hours to obtain a NiFe-LDH precursor;

[0032] Third step: Add 0.118 g of selenium powder to a sodium borohydride solution, add water and a piece of the above NiFe-LDH precursor, and use hydrothermal reaction to obtain a Fe-Ni 0.85 Se catalyst, and the temperature and time of the hydrothermal reaction are 140 °C and 12 hours respectively.

[0033] Test the electrocatalytic hydrogen evolution reaction, sulfide ion oxidation reaction, overall water electrolysis reaction and hydrogen production process coupled with sulfide ion oxidation of the above-prepared Fe-Ni 0.85 Se catalyst in an alkaline solution; the working electrode in the electrolytic cell is the product of the present invention, and an electrochemical workstation is used to test the electrocatalytic reaction performance. All electrode potentials in the test results have been converted to reversible hydrogen electrode potential (RHE).

[0034] The as-prepared Fe-Ni 0.85 Se catalyst was studied for its phase, microscopic morphology, and electrocatalytic reaction performance. As Figure 1 shown, the X-ray diffraction pattern of Fe-Ni 0.85 Se is presented, Figure 1 indicating the synthesis of the Fe-Ni 0.85 Se catalyst.

[0035] As Figure 2 shown, a and b are the scanning electron microscopy and transmission electron microscopy images of Fe-Ni 0.85 Se respectively, Figure 2 indicating that the synthesized Fe-Ni 0.85 Se has a uniform nanosheet morphology.

[0036] As Figure 3 shown, a is the polarization curve of the hydrogen evolution reaction of Fe-Ni 0.85 Se, and b is the Tafel slope plot of the hydrogen evolution reaction of Fe-Ni 0.85 Se, Figure 3 indicating that the synthesized Fe-Ni 0.85 Se has good hydrogen evolution reaction activity. The overpotential required for an output current density of 10 mA cm -2 is 114 mV, and the Tafel slope is 71 mV dec -1 .

[0037] As Figure 4 shown, a is the polarization curve of the sulfide ion oxidation reaction of Fe-Ni 0.85 Se, and b is the Tafel slope plot of the sulfide ion oxidation reaction of Fe-Ni 0.85 Se, Figure 4 indicating that the synthesized Fe-Ni 0.85 Se has good sulfide ion oxidation reaction activity. The potential required for an output current density of 10 mA cm -2 is 0.34 V, and the Tafel slope is 81 mV dec -1 .

[0038] As Figure 5 shown, a is the polarization curve of Fe-Ni 0.85 Se in a conventional water electrolysis and hydrogen production electrolyzer coupled with sulfide ion oxidation, and b is the anodic product obtained after adding sulfuric acid to the hydrogen production electrolyzer coupled with sulfide ion oxidation, Figure 5 indicating that the synthesized Fe-Ni 0.85 Se has good catalytic activity in the hydrogen production electrolyzer coupled with sulfide ion oxidation. The voltage required for an output current density of 10 mA cm -2 is 0.439 V, and the anodic product is elemental sulfur.

[0039] Example 2

[0040] Same as Example 1, except that iron nitrate was not added, to obtain Ni 0.85 Se. As Figure 3 and Figure 4 shown, when this catalyst is used for the hydrogen evolution reaction and the sulfide ion oxidation reaction, the required potentials for an output current density of 10 mA cm -2 are -0.138 and 0.372 V respectively.

[0041] Example 3

[0042] Same as Example 1, except that the amount of iron nitrate added was changed to 0.2 mmol. The required potentials for the hydrogen evolution reaction and the sulfide ion oxidation reaction for an output current density of 10 mA cm -2 are -0.126 and 0.359 V respectively.

[0043] Example 4

[0044] Same as Example 1, except that the amount of iron nitrate added was changed to 0.6 mmol. The required potentials for the hydrogen evolution reaction and the sulfide ion oxidation reaction for an output current density of 10 mA cm -2 are -0.137 and 0.368 V respectively.

[0045] In summary, the iron-doped nickel selenide catalyst prepared by the present invention has good catalytic activity for the hydrogen evolution reaction and the sulfide ion oxidation reaction. In a two-electrode electrolytic cell for hydrogen production by coupling sulfide ion oxidation, a voltage of only 0.439 V is required to output a current density of 10 mA cm -2 , achieving the goal of highly efficient and energy-saving hydrogen production and upgrading sulfide ion oxidation to high-value-added elemental sulfur products. The present invention has the advantages of simple and controllable preparation process, low raw material price, and easy mass production, and can be used as an efficient catalyst for electrolytic water hydrogen production and sulfide ion oxidation reaction.

[0046] The descriptions and practices disclosed in the present invention are easy to think about and understand for those of ordinary skill in the art. Without departing from the principles of the present invention, several improvements and refinements can also be made. Therefore, modifications or improvements made without departing from the spirit of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing a transition metal selenide catalyst, characterized in that: The steps include: Step 1: dissolving 10 parts of metal nickel salt, 0-5 parts of metal iron salt, 30-100 parts of urea and 10-100 parts of ammonium fluoride in water according to molar ratio to prepare a uniform solution; Step 2: transferring the above solution to a polytetrafluoroethylene-lined reactor, adding a conductive substrate, sealing the reactor and placing it in a forced air drying oven, and preparing a nickel iron hydroxide nanosheet precursor by a first hydrothermal reaction; Step 3: Add the nickel iron hydroxide nanosheet precursor to a sodium borohydride aqueous solution containing 1-3 parts of selenium powder, and perform a second hydrothermal reaction to obtain an iron-doped nickel selenide nanosheet catalyst.

2. The method for preparing a transition metal selenide catalyst according to claim 1, characterized in that: In the step 1, the metal nickel salt is nickel nitrate or nickel chloride, and the metal iron salt is ferric nitrate or ferric chloride.

3. The method for preparing a transition metal selenide catalyst according to claim 1, characterized in that: In the step 2, the temperature and reaction time of the first hydrothermal reaction are 100-160° C. and 4-12 hours, respectively.

4. The method for preparing a transition metal selenide catalyst according to claim 1, characterized in that: In the step 2, the conductive substrate is one or more of nickel foam, cobalt foam, copper foam, titanium foam, titanium mesh, carbon paper, and carbon cloth.

5. The method for preparing a transition metal selenide catalyst according to claim 1, characterized in that: In step 3, the temperature and reaction time of the second hydrothermal reaction are 120-160° C. and 8-16 hours, respectively.

6. A transition metal selenide catalyst prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The catalyst uses a conductive substrate as a carrier, and selenide nanosheets with uniform morphology grow on the surface of the carrier.

7. An application of a transition metal selenide catalyst prepared by the preparation method according to any one of claims 1 to 5 in electrocatalytic hydrogen evolution reaction, sulfide ion oxidation reaction and two-electrode sulfide ion oxidation coupled hydrogen production, characterized in that: The selenide catalyst is used as a catalyst for electrocatalytic hydrogen evolution reaction, sulfur ion oxidation reaction and as an anode and cathode of a two-electrode sulfur ion oxidation coupled hydrogen production system.

8. The use according to claim 7, characterized in that: After sulfuric acid is added to the electrolyte after the sulfide ion oxidation coupling hydrogen production system, the generated precipitate is separated and dried to obtain an elemental sulfur product.

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