Doped neodymium-based composite electrocatalyst for alkaline hydrogen precipitation reaction as well as preparation and application of doped neodymium-based composite electrocatalyst

Abstract

The invention relates to a doped neodymium-based composite electrocatalyst for an alkaline hydrogen precipitation reaction as well as a preparation method and application of the doped neodymium-based composite electrocatalyst. According to the catalyst, neodymium oxide (Nd2O3) serves as a base material, phosphorus (P) and ruthenium (Ru) are doped, the electronic structure of the catalyst is optimized, and the catalytic activity and stability of the catalyst are remarkably improved. The catalyst is prepared by adopting a simple hydrothermal method and low-temperature phosphating treatment, has a uniform, continuous and flat nano-layer structure, and is beneficial to electron transmission and exposure of reaction active sites. In a 1.0 M KOH electrolyte, the catalyst shows extremely low overpotential (11.8 mV) and excellent stability, and is obviously superior to a commercial Pt / C catalyst and an undoped neodymium oxide catalyst. The composite electrocatalyst provided by the invention not only realizes efficient and stable alkaline hydrogen precipitation reaction, but also provides a new thought for designing a high-performance non-noble metal catalyst.

Description

Technical Field

[0001] The present invention relates to an electrocatalyst for alkaline hydrogen evolution reaction (HER) and its preparation method and application; in particular, a composite electrocatalyst based on neodymium oxide, which is suitable for highly efficient and low-cost electrocatalytic water splitting for hydrogen production. Background Art

[0002] As an energy carrier with high energy density, cleanliness and no pollution, hydrogen energy is considered to be an important part of the future energy structure. With the global pursuit of carbon neutrality goals, water electrolysis for hydrogen production technology has received extensive attention due to its cleanliness and sustainability. Currently, water electrolysis for hydrogen production is mainly divided into two technologies: alkaline water electrolysis (ALK) and proton exchange membrane water electrolysis (PEM). Among them, alkaline water electrolysis technology occupies a large market share due to its low cost and mature industrialization.

[0003] In the process of water electrolysis for hydrogen production, electrocatalysts are the key factors to reduce the overpotential of water splitting and improve the energy conversion efficiency. Currently, noble metal catalysts (such as Pt, RuO 2 ) although show excellent catalytic performance, their high cost and limited reserves limit large-scale applications. Therefore, the development of highly efficient, stable and low-cost non-noble metal catalysts has become a research hotspot.

[0004] In recent years, significant progress has been made in the research of non-noble metal catalysts. For example, transition metal-based catalysts (such as Ni, Co, Cu, etc.) have received attention due to their rich reserves and low cost. However, the activity and stability of these catalysts under alkaline conditions still need to be further improved.

[0005] Although studies have been conducted to improve the performance of catalysts by doping transition metals or non-metallic elements, the catalytic activity and durability of most non-noble metal catalysts under alkaline conditions are still not as good as those of noble metal catalysts. For example, some transition metal oxides show high overpotential and poor stability at high current density. Therefore, the development of a non-noble metal catalyst with both high activity and high stability is of great significance for promoting the development of water electrolysis for hydrogen production technology. Summary of the Invention

[0006] Based on the above research status and technical challenges, the present invention aims to develop a composite electrocatalyst based on neodymium oxide (Nd 2 O 3 ) by doping phosphorus (P) and ruthenium (Ru) to optimize the electronic structure of the catalyst and significantly improve its catalytic activity and stability under alkaline conditions. Through simple hydrothermal method and low-temperature phosphidation treatment, the catalyst of the present invention not only exhibits extremely low overpotential and excellent electrochemical performance, but also solves the problem that the catalyst in the prior art is easily dissolved in alkaline electrolyte.

[0007] The present invention provides a composite electrocatalyst based on neodymium oxide (Nd 2 O 3 ), and by doping phosphorus (P) and ruthenium (Ru), its catalytic activity and stability are significantly improved.

[0008] The catalyst is prepared by a simple hydrothermal method and low-temperature phosphidation treatment, and has a uniform nanostructure, which is beneficial to electron transport and the exposure of reactive sites.

[0009] A doped neodymium-based composite electrocatalyst for the alkaline hydrogen evolution reaction, and the chemical formula of the composite electrocatalyst is Ru / P-Nd 2 O 3 / CC, where P is phosphorus, Ru is ruthenium, Nd 2 O 3 is neodymium oxide, and CC is a carbon cloth support.

[0010] Furthermore, the composite electrocatalyst is prepared by a hydrothermal method and low-temperature phosphidation treatment, and Ru / P-Nd 2 O 3 has a continuous and flat nanolayer structure, uniformly wrapped outside the carbon cloth fibers, to obtain Ru / P-Nd 2 O 3 / CC.

[0011] The preparation method of the catalyst includes the following steps: 1) Dissolve RuCl 3 ·3H 2 O and NdCl 3 ·6H 2 O in distilled water, add urea, and prepare a solution.

[0012] 2) Immerse the carbon cloth in the above solution, carry out a hydrothermal reaction, and obtain a Ru / Nd 2 O 3 / CC precursor.

[0013] 3) Place the precursor and a phosphorus source (NaH 2 PO 2 ·H 2 O) together in a tubular furnace, and carry out a heating phosphidation treatment under a nitrogen atmosphere to obtain a Ru / P-Nd 2 O 3 / CC catalyst.

[0014] Furthermore, the temperature of the hydrothermal reaction is 90 °C and the time is 4 hours; the temperature of the phosphidation treatment is 300 °C and the time is 2 hours.

[0015] Furthermore, during the phosphidation treatment, the phosphorus source and the precursor are respectively placed in the left and right temperature zones of the tubular furnace, and the heating rate is 2 °C·min-1 。

[0016] The nanostructure of the catalyst is uniformly coated outside the carbon cloth fibers, which is beneficial to improving the conductivity and stability of the electrode.

[0017] The doping ratio of neodymium and ruthenium in the catalyst is Nd:Ru = 4:2 (molar ratio), and this ratio optimizes the electronic structure of the catalyst.

[0018] The introduction of phosphorus causes the lattice expansion of the catalyst, further optimizing its catalytic performance.

[0019] Application: Application of the doped neodymium-based composite electrocatalyst in the alkaline hydrogen evolution reaction.

[0020] The composite electrocatalyst of the present invention exhibits an extremely low overpotential (11.8 mV) in 1.0 M KOH electrolyte, far lower than that of commercial Pt / C catalyst (52.78 mV) and undoped neodymium oxide catalyst (498.3 mV).

[0021] The catalyst in 1.0 M KOH electrolyte, 10 mA·cm -2 The overpotential required at the current density is only 11.8 mV, indicating its high catalytic activity under alkaline conditions.

[0022] The Tafel slope of the catalyst in 1.0 M KOH electrolyte is 61.95 mV·decade -1 , indicating its fast electron transfer speed and excellent catalytic reaction kinetics performance.

[0023] The electrochemically active surface area (ECSA) of the catalyst is 21.11 mF·cm -2 , superior to commercial Pt / C catalyst and undoped neodymium oxide catalyst in the prior art.

[0024] In the 300-hour stability test, the catalyst shows good durability, and the overpotential only increases by 7 mV, solving the problem that the catalyst is easily dissolved in alkaline solution in the prior art.

[0025] Through the electrochemical impedance spectroscopy (EIS) test, Ru / P-Nd 2 O 3 / CC catalyst shows a smaller charge transfer resistance, further proving its excellent catalytic performance.

[0026] The electrochemical performance of the catalyst in 1.0 M KOH electrolyte is superior to that of other non-noble metal catalysts reported in the literature.

[0027] The advantages of the present invention are: The preparation method of the catalyst is simple and low-cost, making it suitable for large-scale industrial production.

[0028] The high catalytic performance and good stability of the catalyst endow it with broad application prospects in the alkaline hydrogen evolution reaction.

[0029] Nd has unfilled 4f orbitals and 5d electrons, which can effectively promote electron transfer, thereby improving the catalytic performance. The catalyst of the present invention significantly enhances the catalytic activity and durability of neodymium oxide by optimizing the electronic structure.

[0030] The low overpotential and high stability of the catalyst confer significant economic advantages in practical electrolytic water hydrogen production systems.

[0031] The present invention not only provides a high-performance electrocatalyst for the alkaline hydrogen evolution reaction but also offers new ideas for designing other efficient non-noble metal catalysts. Description of the Drawings

[0032] Figure 1 TEM image of the Ru / P-Nd 2 O 3 / CC catalyst prepared in Example 1; Figure 2 SEM image of the Ru / Nd 2 O 3 / CC catalyst prepared in Comparative Example 1; Figure 3 SEM image of the Ru / P-Nd 2 O 3 / CC catalyst prepared in Example 1; Figure 4 EDS image of the Ru / P-Nd 2 O 3 / CC catalyst prepared in Example 1; Figure 5 XRD images of Ru / P-Nd 2 O 3 / CC, Ru / Nd 2 O 3 / CC, Nd 2 O 3 / CC, CC; Figure 6 a) in is Nd 2 O 3 XPS image of the Nd 4d orbital of / CC; b) is the Nd 4d orbital of Ru / Nd 2 O 3 XPS image of / CC; c) is the Nd 4d orbital of Ru / P-Nd 2 O 3XPS images of the Nd 4d orbitals of Nd / CC; d) Ru / Nd 2 O 3 XPS images of the Ru 3d orbitals of Ru / CC; e) Ru / P-Nd 2 O 3 XPS images of the Ru 3d orbitals of Ru / P-Nd 2 O 3 XPS images of the P 2p orbitals of Ru / P-Nd Figure 7 for Ru / P-Nd 2 O 3 / CC, Ru / Nd 2 O 3 / CC, Nd 2 O 3 LSV images of Ru / P-Nd Figure 8 for Ru / P-Nd 2 O 3 / CC, Ru / Nd 2 O 3 / CC, Nd 2 O 3 Tafel images of Ru / P-Nd Figure 9 for Ru / P-Nd 2 O 3 / CC, Ru / Nd 2 O 3 / CC, Nd 2 O 3 EIS images of Ru / P-Nd Figure 10 for Ru / P-Nd 2 O 3 / CC, Ru / Nd 2 O 3 / CC, Nd 2 O 3 ECSA images of Ru / P-Nd Figure 11 for Ru / P-Nd 2 O 3 Stability test images of Figure 12 for Ru / P-Nd 2 O 3 LSV test images of Detailed implementation manners

[0033] To better understand the present invention, the following provides specific embodiments for the preparation of the ruthenium-doped rare earth-based catalyst of the present invention and its HER application.

[0034] Comparative Example 1 A doped neodymium-based composite electrocatalyst for green hydrogen production, its preparation and application, comprising the following steps: Add 4 mmol of RuCl 3 ·3H 2 O, 12 mmol of NdCl 3 ·6H 2 O, 20 mmol of urea and 50 mL of deionized water into a 100 mL sample bottle. After ultrasonic homogenization, it becomes a reddish-brown liquid. Place 0.8 * 3 cm 2 carbon cloth in the solution and react at 90 °C for 4 h. After cooling to room temperature, rinse three times with deionized water and then vacuum dry to obtain Ru / Nd 2 O 3 / CC.

[0035] Comparative Example 2 A doped neodymium-based composite electrocatalyst for green hydrogen production, its preparation and application, comprising the following steps: Add 4 mmol of RuCl 3 ·3H 2 O, 20 mmol of urea and 50 mL of deionized water into a 100 mL sample bottle. After ultrasonic homogenization, it becomes a reddish-brown liquid. Place 0.8 * 3 cm 2 carbon cloth in the solution and react at 90 °C for 4 h. After cooling to room temperature, rinse three times with deionized water and then vacuum dry to obtain Ru / CC.

[0036] Comparative Example 3 A doped neodymium-based composite electrocatalyst for green hydrogen production, its preparation and application, comprising the following steps: Add 12 mmol of NdCl 3 ·6H 2 O, 20 mmol of urea and 50 mL of deionized water into a 100 mL sample bottle. After ultrasonic homogenization, it becomes a reddish-brown liquid. Place 0.8 * 3 cm 2 carbon cloth in the solution and react at 90 °C for 4 h. After cooling to room temperature, rinse three times with deionized water and then vacuum dry to obtain Nd 2 O 3 / CC.

[0037] Example 1 A doped neodymium-based composite electrocatalyst for green hydrogen production, its preparation and application, including the following steps: Add 4 mmol RuCl 3 ·3H 2 O, 12 mmol NdCl 3 ·6H 2 O, 20 mmol urea and 50 mL deionized water into a 100 mL sample bottle. After ultrasonic homogenization, it becomes a reddish-brown liquid. Place a 0.8*3 cm 2 carbon cloth in the solution and react at 90 °C for 4 h. After cooling to room temperature, rinse it three times with deionized water and then dry it under vacuum to obtain Ru / Nd 2 O 3 / CC. Then, place a piece of carbon cloth loaded with Ru / Nd 2 O 3 / CC and 3 g of NaH 2 PO 2 ·H 2 O in a nitrogen atmosphere in a tube furnace and calcine it at 300 °C for 2 h at a heating rate of 2 °C·min -1 . After cooling to room temperature, Ru / P-Nd 2 O 3 / CC is obtained.

[0038] Comparative Example 4 A doped neodymium-based composite electrocatalyst for green hydrogen production, its preparation and application, including the following steps: Disperse 20 μL of Nafion, 980 μL of isopropanol, and 2 mg of commercial 20% platinum-carbon catalyst evenly by ultrasonic treatment, and drop-coat it on a 0.8 cm*1 cm carbon cloth, and dry it in an oven at 80 °C to obtain PtC.

[0039] Application Example An application of a doped neodymium-based composite electrocatalyst for green hydrogen production, including the following steps: All electrochemical tests were carried out on a Chenhua electrochemical workstation (model 660e) using chi660e software. Electrochemical studies were carried out using a three-electrode system. A platinum plate electrode (1×1 cm 2 ), a platinum plate electrode clip, and a Hg / HgO electrode were used as the counter electrode, working electrode, and reference electrode respectively. The working area of the catalyst carbon cloth material was 1×0.8 cm 2 . Place the carbon cloth material on the platinum plate electrode clip for reaction. All reactions were carried out in a 1M KOH solution with pH = 14 for HER performance testing. The conversion formula between the mercury oxide (SCE) electrode and the reversible hydrogen electrode (RHE) is as follows.

[0040] ERHE = E 0 Hg / HgO + 0.059 × pH + E Hg / HgO (1) Among them, E 0 Hg / HgO has a potential of 0.159 V, and E RHE and E Hg / HgO are the potential relative to the reversible hydrogen electrode and the experimental potential, respectively.

[0041] As Figure 1 shown, the HRTEM image of Ru / P-Nd 2 O 3 / CC clearly shows the characteristic lattice fringes of the Nd 2 O 3 (111) crystal plane (0.312 nm) and the metal Ru (101) crystal plane (0.214 nm). It is worth noting that after phosphating treatment, the lattice fringe boundaries show a significant blurring phenomenon ( Figure 1 ), combined with Figure 2 and Figure 3 SEM comparative analysis shows that the rough nanoflower morphology of the original Ru / Nd 2 O 3 / CC is transformed into a continuous and flat nanolayer structure after phosphating treatment. The EDS surface scan spectrum ( Figure 4 ) confirms the uniform distribution of Ru, Nd, and P elements in the material, while the XRD refinement results ( Figure 5 ) show that the characteristic peak positions are in good agreement with the Nd 2 O 3 standard card (PDF#01-072-0685). The above evidence together indicates that the non-metallic phosphorus element has been successfully incorporated into the neodymium-based oxide lattice, realizing the precise construction of the Ru, P double-doped composite catalyst.

[0042] XPS depth analysis reveals a significant electron redistribution effect caused by phosphorus doping: as a strong electron donor, the introduction of P injects an electron-rich environment to the catalyst surface, resulting in a positive shift of the binding energies of Ru 3d 3 / 2 , Ru 3d 5 / 2 by 1.73 eV and 1.36 eV respectively (d and e in Figure 6 ), indicating an electron deficiency phenomenon at the Ru active center. This electronic state regulation optimizes the adsorption-desorption equilibrium of the Ru sites for key reaction intermediates (H 2 O, H*), making it close to the optimal value of the Sabatier theory. At the same time, the binding energy of Nd 3d 3 / 2 shifts negatively by 1.42 eV ( Figure 6a and b), Nd 3d 3 / 2 The binding energy shifts negatively by 0.12 eV ( Figure 6 In b and c), it is confirmed that electrons transfer from Ru and P to Nd 2 O 3 substrate, and this interfacial charge rearrangement significantly enhances the intrinsic conductivity of the material.

[0043] The electrochemical performance of this material was further studied. In a three-electrode system, the HER performance of the catalyst was measured in 1 M KOH solution. And the HER performance of commercial PtC catalyst was studied as a reference. As Figure 7 shown, the overpotential required for the P-Ru / Nd 2 O 3 / CC electrode to achieve a current density of 10 mA·cm -2 is only 11.8 mV, which is 55.15 mV and 41.02 mV smaller than that of commercial PtC / CC and Ru / Nd 2 O 3 / CC, respectively. As Figure 8 shown, Ru / P-Nd 2 O 3 / CC shows a minimum Tafel slope of 61.95 mV dec -1 , indicating that the electron transfer rate of HER on Ru / P-Nd 2 O 3 / CC is the fastest. In addition, the influence of the electrochemically active surface area (ECSA) on the HER performance was further analyzed and studied. By measuring the cyclic voltammetry (CV) of different catalysts at different scan rates, and then calculating the double-layer capacitance (Cdl) according to the relationship between the current density and different scan rates. As Figure 10 shown, the Cdl of Ru / P-Nd 2 O 3 / CC is 21.11 mF·cm -2 , which is greater than that of Ru / Nd 2 O 3 / CC (18.83 mF·cm -2 ) and commercial PtC / CC (11.13 mF·cm -2 ). This is due to the highly dispersed characteristics of Ru / -Nd 2 O 3 / CC, which also reveals that Ru / P-Nd 2 O 3 / CC has higher intrinsic activity than commercial platinum-carbon electrodes. For Ru / P-Nd 2 O 3 / CC and Ru / Nd 2 O3 The / CC also performed electrochemical impedance spectroscopy (EIS) tests to explore the electrode kinetics at the corresponding potential of 100 mV. As Figure 9 shown, compared with Ru / Nd 2 O 3 / CC, Ru / P-Nd 2 O 3 / CC exhibited significantly smaller charge transfer resistance (Rct), indicating that the catalytic process of P-Ru / Nd 2 O 3 / CC was faster.

[0044] In 1 M KOH electrolyte, at a constant temperature of 30 °C, the stability of the Ru / P-Nd -2 O 2 O 3 / CC catalyst was evaluated by chronopotentiometry (CP) at 100 mA·cm Figure 11 As shown, Ru / P-Nd 2 O 3 / CC showed good stability. After 300 hours of continuous durability measurement, through polarization curve testing, the overpotential corresponding to a current density of 10 mA·cm -2 increased by 7 mV ( Figure 12 ), indicating that Ru / P-Nd 2 O 3 / CC could work for a long time at a relatively stable overpotential, and also solved the problem that the commercial platinum-carbon electrode was prone to dissolution during the hydrogen evolution reaction in alkaline solution for a long time.

[0045] The above shows and describes the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights. In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A doped neodymium-based composite electrocatalyst for alkaline hydrogen evolution reaction, characterized in that: The chemical formula of the composite electrocatalyst is Ru / P-Nd2O3 / CC, wherein P is phosphorus, Ru is ruthenium, Nd2O3 is neodymium oxide, and CC is a carbon cloth carrier.

2. The doped neodymium-based composite electrocatalyst according to claim 1, characterized in that: The composite electrocatalyst is prepared by a hydrothermal method and a low-temperature phosphating treatment, has a continuous and smooth nano-layer structure, and is uniformly wrapped around the carbon cloth fiber.

3. The doped neodymium-based composite electrocatalyst according to claim 1 or 2, characterized in that: The molar ratio of neodymium to ruthenium in the composite electrocatalyst is Nd:Ru=4:

2.

4. The method for preparing the doped neodymium-based composite electrocatalyst according to claim 1, characterized in that: The following steps are involved: 1) Dissolve RuCl3·3H2O and NdCl3·6H2O in distilled water, add urea to prepare a solution; 2) immersing the carbon cloth in the solution obtained in step 1) to perform a hydrothermal reaction to obtain a Ru / Nd2O3 / CC precursor; 3) placing the precursor and the phosphorus source together in a tube furnace, and performing heating phosphating treatment under a nitrogen atmosphere to obtain a Ru / P-Nd2O3 / CC catalyst.

5. The preparation method according to claim 4, characterized in that: Step 2) The temperature of the hydrothermal reaction is 90° C. and the time is 4 hours.

6. The preparation method according to claim 4, characterized in that: Step 3) The phosphating treatment is carried out at a temperature of 300°C and for a period of 2 hours.

7. The preparation method according to claim 4, characterized in that: Step 3) The phosphorus source is NaH2PO2·H2O.

8. The preparation method according to claim 4, characterized in that: During phosphating treatment, the phosphorus source and precursor were placed in the left and right temperature zones of the tube furnace, and the heating rate was 2 °C min -1 .

9. Use of the doped neodymium-based composite electrocatalyst according to claim 1 in an alkaline hydrogen evolution reaction.

10. The use according to claim 9, characterized in that: The composite electrocatalyst has a high conductivity at 10 mA·cm in 1.0 M KOH electrolyte. -2 The overpotential required at the current density is only 11.8 mV, and in the 300-hour stability test, the overpotential only increases by 7 mV; the Tafel slope is 61.95 mV·decade -1 ; The electrochemical active surface area is 21.11 mF·cm -2 .

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