Phosphide-based heterostructure 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 phosphide-based heterostructure catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, dissolving metal nickel salt, molybdenum salt, cerium salt, urea and ammonium fluoride in deionized water, and synthesizing a layered hydroxide nanosheet precursor through a hydrothermal method; then, the precursor is subjected to phosphating treatment, and the phosphide-based heterostructure catalyst is prepared. According to the invention, the electron configuration of phosphide is optimized by utilizing a heterostructure regulation strategy, so that the catalytic activity of the phosphide is remarkably improved. The catalyst shows excellent catalytic performance in both hydrogen evolution reaction and biomass oxidation reaction; when the device is applied to a two-electrode biomass oxidative coupling hydrogen production electrolytic tank, the current density of 10 mA cm <-2 > can be output only by applying 1.58 V voltage, and the purposes of efficient energy-saving hydrogen production and biomass directional conversion are achieved. In addition, the preparation method also has the advantages of simple and controllable preparation process, low raw material cost, easiness in large-scale mass production and the like.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation and application technology, and in particular to a phosphide-based heterostructure catalyst, its preparation method and application. Background Technology

[0002] With the exacerbation of the ecological crisis caused by the overconsumption of traditional fossil fuels, hydrogen energy, as a clean and pollution-free secondary energy source, has become a research hotspot in the energy field. Electrolysis of water to produce hydrogen is a core technology for achieving large-scale green hydrogen production. This process consists of the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. HER is the process by which protons gain electrons to generate hydrogen gas; the reaction mechanism is clear, but a highly efficient catalyst is needed to lower the reaction energy barrier. OER, however, involves multiple electron transfer steps, resulting in slow kinetics and high overpotentials, becoming a key bottleneck restricting the energy conversion efficiency of hydrogen production through water electrolysis. Although researchers have developed a series of noble metal and non-noble metal-based OER catalysts that effectively reduce the reaction overpotential, the overall energy consumption of the water electrolysis system remains high, and the commercial value of the anode product, oxygen, is low, making it difficult to improve the overall economic benefits of the technology.

[0003] To overcome the aforementioned limitations, researchers have proposed a strategy of replacing OER with biomass small molecule oxidation reactions, with 5-hydroxymethylfurfural electro-oxidation (HMFOR) being one of the most promising alternatives. HMF, as a widely available biomass-based platform compound, produces 2,5-furandicarboxylic acid (FDCA), a key raw material for the synthesis of biodegradable plastics, possessing significant market value. Compared to OER, HMFOR exhibits superior thermodynamic and kinetic properties, can react at lower potentials, and, when coupled with HER, can significantly reduce the overall operating voltage of the electrolysis system. However, in practical applications, HMFOR faces the challenge of competing with OER. As the anode potential increases, OER readily occurs, leading to a decrease in the catalytic selectivity and efficiency of HMFOR; simultaneously, insufficient activity of the cathode HER catalyst further restricts the performance of the entire electrolysis system. Based on this, this application provides a phosphide-based heterostructure catalyst (Ni-Mo-P / Ce7O). 12 This catalyst exhibits excellent activity and stability in both HER and HMFOR. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a phosphide-based heterostructure catalyst, its preparation method, and its application. The catalyst prepared by this invention exhibits high catalytic performance and can achieve the dual goals of efficient and energy-saving hydrogen production and high-value conversion of biomass in a two-electrode biomass oxidation coupled hydrogen production system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a phosphide-based heterostructure catalyst includes the following steps:

[0007] Step 1: Dissolve 10 parts of nickel salt, 10 parts of molybdenum salt, 0-5 parts of cerium salt, 30-100 parts of urea and 10-100 parts of ammonium fluoride in water to prepare a homogeneous solution.

[0008] Step 2: Transfer the above solution to a polytetrafluoroethylene-lined reactor, add a conductive substrate, seal the reactor and place it in a forced-air drying oven to prepare a bilayer hydroxide nanosheet precursor using a hydrothermal reaction;

[0009] Step 3: The above-mentioned layered hydroxide nanosheet precursor is subjected to a phosphating reaction in a nitrogen atmosphere containing 0.2-1 g of phosphorus source to obtain a phosphide-based heterostructure catalyst.

[0010] Preferably, in step 1, the nickel salt is nickel nitrate or nickel nitrate, the molybdenum salt is molybdenum pentachloride or molybdenum acetylacetonate, and the cerium salt is cerium nitrate or cerium acetate.

[0011] Preferably, in step 2, the temperature and reaction time of the hydrothermal reaction are 100-160 ℃ and 4-10 hours, respectively.

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

[0013] Preferably, in step 3, the phosphorus source is sodium hypophosphite or red phosphorus.

[0014] Preferably, in step 3, the temperature and reaction time of the phosphating reaction are 280-400 °C and 1-3 hours, respectively.

[0015] A phosphide-based heterostructure catalyst prepared by the above-described method, wherein the catalyst uses a conductive substrate as a support, and phosphide nanosheets with uniform morphology are grown on the surface of the support.

[0016] The present invention also provides the application of the phosphide-based heterostructure catalyst prepared by the above preparation method in electrocatalytic hydrogen evolution reaction, biomass oxidation reaction and two-electrode biomass oxidation coupled hydrogen production, wherein the phosphide-based heterostructure catalyst serves as the catalyst for electrocatalytic hydrogen evolution reaction and biomass oxidation reaction and as the anode and cathode of the two-electrode biomass oxidation coupled hydrogen production system.

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

[0018] 1. The phosphide-based heterostructure catalyst prepared by this invention utilizes cerium oxide coupling and uniform nanosheet morphology to regulate the electronic structure of the catalyst and expose a large number of catalytic active sites, thereby improving catalytic performance and reaction rate in electrocatalytic processes.

[0019] 2. The phosphide-based heterostructure catalyst prepared by this invention has good electrocatalytic performance in HER, HMFOR and biomass oxidation coupled hydrogen production, and solves the problems of slow catalytic kinetics and high voltage required in the water electrolysis hydrogen production process.

[0020] 3. When the phosphide-based heterostructure catalyst prepared in this invention is applied to a two-electrode biomass oxidation coupled hydrogen production system, it can output current densities of 10 and 100 mA cm⁻¹ at electrolysis voltages of 1.58 and 1.79 V, respectively. -2 This achieves the goals of efficient and energy-saving hydrogen production and high-value conversion of biomass.

[0021] 4. The preparation method of the present invention has the advantages of low raw material price and simple and controllable operation, and can replace precious metal catalysts and promote the industrial application of hydrogen production by water electrolysis. Attached Figure Description

[0022] Figure 1 The Ni-Mo-P / Ce7O prepared in Example 1 of this invention 12 X-ray diffraction pattern;

[0023] Figure 2 The Ni-Mo-P / Ce7O prepared in Example 1 of this invention 12 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images; where a is Ni-Mo-P / Ce7O 12 Scanning electron microscope image, b is Ni-Mo-P / Ce7O 12 Transmission electron microscope images;

[0024] Figure 3 The Ni-Mo-P and Ni-Mo-P / Ce7O prepared in Example 1 of this invention 12 HER performance diagram in alkaline electrolyte; where a is the polarization curve of HER and b is the Tafel slope diagram of HER;

[0025] Figure 4 The Ni-Mo-P / Ce7O prepared in Example 1 of this invention 12 OER performance diagram and Ni-Mo-P / Ce7O in alkaline electrolyte 12 The HMFOR performance diagrams are shown; where a is the polarization curve of OER and b is the polarization curve of HMFOR.

[0026] Figure 5The Ni-Mo-P / Ce7O prepared in Example 1 of this invention 12 Polarization curves in a conventional water electrolysis and biomass oxidation coupled hydrogen production electrolyzer. Detailed Implementation

[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, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing a phosphide-based heterostructure catalyst specifically includes the following steps:

[0030] Step 1: Dissolve 1.7 mmol nickel nitrate, 0.3 mmol molybdenum pentachloride, 0.4 mmol cerium nitrate, 10 mmol urea and 6 mmol ammonium fluoride in 35 mL of water to prepare a homogeneous solution;

[0031] Step 2: Transfer the above solution to a 50 mL polytetrafluoroethylene (PTFE) liner, add a piece of carbon cloth support, seal the PTFE liner, and place it in a stainless steel reactor. After sealing, place it in a forced-air drying oven, heat to 120 °C, and maintain the temperature for 6 hours to obtain Ni-Mo / Ce7O. 12 -LDH precursor;

[0032] Step 3: Mix 0.6 g of sodium hypophosphite with one piece of the above-mentioned Ni-Mo / Ce7O 12 -LDH precursors were placed in a tube furnace and subjected to heat treatment to prepare Ni-Mo-P / Ce7O 12 The catalyst, phosphating temperature, and time were 300 °C and 2 hours, respectively.

[0033] The Ni-Mo-P / Ce7O prepared above 12 The catalyst was tested in an alkaline solution for its performance in electrocatalytic hydrogen evolution reaction, biomass oxidation reaction, full water electrolysis reaction, and biomass oxidation coupled to hydrogen production process. The working electrode in the electrolytic cell was the product of this invention. The electrocatalytic reaction performance was tested using an electrochemical workstation. In the test results, all electrode potentials were converted to reversible hydrogen electrode potentials (RHE).

[0034] The Ni-Mo-P / Ce7O prepared above 12 The catalyst is studied for its phase composition, microstructure, and electrocatalytic reaction performance. For example... Figure 1 As shown, it is Ni-Mo-P / Ce7O 12 X-ray diffraction pattern of the catalyst, Figure 1 This indicates that Ni-Mo-P / Ce7O was synthesized. 12 catalyst.

[0035] like Figure 2 As shown, a and b are Ni-Mo-P / Ce7O 12 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the catalyst. Figure 2 This indicates that the synthesized Ni-Mo-P / Ce7O 12 The catalyst has a uniform nanosheet morphology.

[0036] like Figure 3 As shown, a is Ni-Mo-P / Ce7O 12 HER polarization curves of the catalyst, b represents Ni-Mo-P / Ce7O 12 Tafel slope plot of HER for catalysts, Figure 3 This indicates that the synthesized Ni-Mo-P / Ce7O 12 The catalyst exhibits good HER activity, with an output current density of 10 mA cm⁻¹. -2 The required overpotential is 225 mV, and the Tafel slope is 126.4 mV dec. -1 .

[0037] like Figure 4 As shown, a is the polarization curve of the oxygen evolution reaction, and b is the polarization curve of HMFOR. Figure 4 This indicates that the synthesized Ni-Mo-P / Ce7O 12 The catalyst exhibits good HMFOR activity, with an output current density of 10 mA cm⁻¹. -2 The required potential is 1.36 V.

[0038] like Figure 5 As shown, it is Ni-Mo-P / Ce7O 12 Polarization curves of the catalyst in a conventional water electrolysis and biomass oxidation coupled hydrogen production electrolyzer. Figure 5 This indicates that the synthesized Ni-Mo-P / Ce7O 12 The catalyst exhibits good catalytic activity in a biomass oxidation-coupled hydrogen production electrolyzer, with an output current density of 10 mA cm⁻¹. -2 The required voltage is 1.58 V.

[0039] Example 2

[0040] Same as Example 1, except that cerium nitrate was not added, resulting in Ni-Mo-P. Figure 3 and Figure 4As shown, the catalyst produces an output current density of 10 mA cm⁻¹ when used in HER and HMFOR. -2 The required potentials are -0.422 V and 1.88 V, respectively.

[0041] Example 3

[0042] Same as Example 1, except that the amount of cerium nitrate added was changed to 0.2 mmol, and the output current density of HER and HMFOR was 10 mA cm⁻¹. -2 The required potentials are -0.210 V and 1.66 V, respectively.

[0043] Example 4

[0044] Same as Example 1, except that the amount of cerium nitrate added was changed to 0.6 mmol, and the output current density of HER and HMFOR was 10 mA cm⁻¹. -2 The required potentials are -0.337 V and 1.78 V, respectively.

[0045] In summary, the phosphide-based heterostructure catalyst prepared in this invention exhibits excellent catalytic activity in hydrogen evolution reaction and biomass oxidation reaction. In a two-electrode biomass oxidation coupled hydrogen production electrolyzer, only a voltage of 1.58 V is required to output a current density of 10 mA cm⁻¹. -2 This invention achieves the dual goals of efficient and energy-saving hydrogen production and targeted biomass conversion. It also boasts advantages such as a simple and controllable preparation process, low raw material costs, and ease of large-scale production, providing a high-performance catalyst option for hydrogen production via water electrolysis and biomass oxidation reactions, with broad prospects for industrial application.

[0046] The descriptions and practices disclosed in this invention are readily apparent and understandable to those skilled in the art, and various modifications and refinements can be made without departing from the principles of this invention. Therefore, any modifications or improvements made without departing from the spirit of this invention should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a phosphide-based heterostructure catalyst, characterized in that, Includes the following steps: Step 1: Dissolve 10 parts of nickel salt, 10 parts of molybdenum salt, 0-5 parts of cerium salt, 30-100 parts of urea and 10-100 parts of ammonium fluoride in water to prepare a homogeneous solution. Step 2: Transfer the above solution to a polytetrafluoroethylene-lined reactor, add a conductive substrate, seal the reactor and place it in a forced-air drying oven to prepare layered hydroxide nanosheet precursors using hydrothermal reaction; Step 3: The above-mentioned layered hydroxide nanosheet precursor is subjected to a phosphating reaction in a nitrogen atmosphere containing 0.2-1 g of phosphorus source to obtain a phosphide-based heterostructure catalyst.

2. The method for preparing a phosphide-based heterostructure catalyst according to claim 1, characterized in that, In step 1, the nickel salt is nickel nitrate or nickel chloride, the molybdenum salt is molybdenum pentachloride or molybdenum acetylacetonate, and the cerium salt is cerium nitrate or cerium acetate.

3. The method for preparing a phosphide-based heterostructure catalyst according to claim 1, characterized in that, In step 2, the temperature and reaction time of the hydrothermal reaction are 100-160 ℃ and 4-10 hours, respectively.

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

5. The method for preparing a phosphide-based heterostructure catalyst according to claim 1, characterized in that, In step 3, the phosphorus source is sodium hypophosphite or red phosphorus.

6. The method for preparing a phosphide-based heterostructure catalyst according to claim 1, characterized in that, In step 3, the temperature and reaction time of the phosphating reaction are 280-400 ℃ and 1-3 hours, respectively.

7. A phosphide-based heterostructure catalyst prepared by the preparation method according to any one of claims 1-6, characterized in that: The catalyst uses a conductive substrate as a support, and phosphide nanosheets with uniform morphology are grown on the surface of the support.

8. The application of a phosphide-based heterostructure catalyst prepared by the preparation method according to any one of claims 1-6 in electrocatalytic hydrogen evolution reaction, biomass oxidation reaction, and two-electrode biomass oxidation coupled hydrogen production, characterized in that: The phosphide-based heterostructure catalyst serves as a catalyst for electrocatalytic hydrogen evolution reaction and biomass oxidation reaction, and as the anode and cathode of a two-electrode biomass oxidation coupled hydrogen production system.

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