High-entropy perovskite oxide, preparation method thereof and application of high-entropy perovskite oxide as electrocatalyst

Abstract

The invention discloses a high-entropy perovskite oxide, a preparation method thereof and application of the high-entropy perovskite oxide as an electrocatalyst, and belongs to the technical field of high-entropy transition metal oxides. A sol-gel method is adopted, various metal nitrates and lanthanum nitrate are dissolved in water and ethylene glycol in an equimolar mode, and an ammonium citrate complexing agent is added. And then heating at 120 DEG C for 10 hours. And heating the obtained gel precursor to 600 DEG C in a muffle furnace at a heating rate of 10 DEG C / min, maintaining the temperature for 2 hours, and cooling to obtain the high-entropy perovskite oxide LaBxO3. The high-entropy perovskite oxide electrocatalyst which is simple in synthesis method, stable in structure and easy in raw material obtaining is obtained, and the electrocatalyst can be applied to electrocatalytic nitrate radical reduction and sulfur ion oxidation; and a foundation is laid for developing other high-entropy transition metal oxides as electrocatalysts for synthesizing value-added chemicals by electrocatalyzing nitrate radicals and sulfur-containing wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-entropy transition metal oxides, and in particular relates to a high-entropy perovskite oxide, a preparation method thereof, and an application thereof as an electrocatalyst. Background Art

[0002] With the rapid development of industrialization and the intensification of agricultural activities, water pollution has become a major global problem threatening ecosystems and human health. The most prevalent pollutant is nitrogen-rich wastewater containing high concentrations of sulfur-containing compounds such as nitrate and sulfide ions. Sources of these pollutants include fertilizer runoff, industrial discharges, and domestic sewage, and they pose significant risks through eutrophication, toxicity to aquatic organisms, and potential carcinogenicity to humans. Electrochemical methods offer a promising approach to convert nitrate and sulfide pollutants into useful chemicals under mild conditions. Electrocatalytic nitrate reduction has emerged as a sustainable pathway for ammonia production, while the sulfide oxidation reaction (SOR) offers an energetically favorable alternative to the oxygen evolution reaction (OER), significantly reducing the potential for the formation of elemental sulfur or polysulfides. These dual electrochemical processes not only mitigate environmental pollution but also yield value-added chemicals. However, despite recent progress, the NO3RR involves a complex eight-electron, nine-proton transfer mechanism, resulting in sluggish kinetics and intense competition with the hydrogen evolution reaction (HER), leading to low selectivity and efficiency. In the generation of by-products (such as NO, N2H4), catalysts with special activity and selectivity are required. In addition, the anodic oxygen evolution reaction (OER, 1.23V vs. RHE) in traditional electrolyzers imposes a significant energy barrier, which has promoted the development of alternative anodic reactions. At the same time, the sulfide oxidation reaction (SOR, S 2- →S,E 0 =-0.48 V vs. RHE) provides an energetically favorable alternative to OER, allowing the generation of elemental sulfur or polysulfides at significantly lower potentials. Coupling SOR with NO3RR can simultaneously remove NO3, a toxic pollutant from groundwater. - and S 2- , simultaneously producing NH3 (cathode) and elemental sulfur (anode), thereby establishing a closed-loop system for pollutant proliferation. However, despite recent progress, the practical implementation of these reactions is hampered by the lack of efficient, stable and multifunctional catalysts that can simultaneously drive NO3RR and SOR. High-entropy perovskite oxides (HEPOs) have attracted widespread attention as a new generation of electrocatalysts, characterized by the occupation of multiple metal ions at both the A and B sites to form a homogeneous solid solution. This unique composition gives HEPOs two key advantages: 1) the high entropy effect can precisely tune the spin state of transition metal ions; 2) the lattice distortion caused by the coordination of multiple metal ions produces abundant oxygen vacancies and surface active sites. Summary of the Invention

[0003] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a high-entropy perovskite oxide with easily available raw materials, simple preparation method and high catalytic efficiency, as well as its preparation method and application.

[0004] To achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is: a high-entropy perovskite oxide, wherein the high-entropy perovskite oxide is LaBxO3, wherein B=Fe, Co, Cu, Cr, Ni, one or a combination of two or more.

[0005] Preferably, B=Fe, and the high entropy perovskite oxide is LaB1O3.

[0006] Preferably, B=Fe, Cu, and the high entropy perovskite oxide is LaB2O3.

[0007] Preferably, B=Fe, Co, Cu, and the high entropy perovskite oxide is LaB3O3.

[0008] Preferably, B=Fe, Co, Cu, Cr, and the high entropy perovskite oxide is LaB4O3.

[0009] Preferably, B=Fe, Co, Cu, Cr, Ni, and the high entropy perovskite oxide is LaB5O3.

[0010] A method for preparing a high-entropy perovskite oxide comprises the following steps:

[0011] 1) dissolving a plurality of metal nitrates and lanthanum nitrate (La(NO3)3·6H2O) in water and ethylene glycol, adding ammonium citrate as a complexing agent, and heating at 115°C-125°C for 10-12 hours to obtain a gel precursor; the plurality of metal nitrates are selected from one or a combination of two or more metal nitrates of Fe, Co, Cu, Cr, and Ni;

[0012] 2) heating the gel precursor in a muffle furnace at a heating rate of 8°C-10°C / min to 550°C-650°C and maintaining the temperature for 2h-3h, and then cooling to obtain a high entropy perovskite oxide.

[0013] Furthermore, in step 1), the plurality of metal nitrates are added in an equal molar ratio; the total molar number of each metal nitrate in the plurality of metal nitrates: the molar number of lanthanum nitrate = 1:1.

[0014] The present invention provides an application of a high-entropy perovskite oxide as an electrocatalyst in electrocatalytic nitrate reduction.

[0015] Furthermore, the method is as follows: high entropy perovskite oxide LaBxO3 is loaded on carbon cloth as a working electrode, the reference electrode is Ag / AgCl, the counter electrode is a platinum sheet, the electrolyte is 1.0M KOH solution and 0.1M potassium nitrate solution, and catalyzes the reduction of nitrate to synthesize NH3.

[0016] The present invention provides a high-entropy perovskite oxide for use as an electrocatalyst in electrocatalytic sulfur ion oxidation.

[0017] Furthermore, the method is as follows: high entropy perovskite oxide LaBxO3 is loaded on carbon cloth as a working electrode, the reference electrode is Ag / AgCl, the counter electrode is a platinum sheet, the electrolyte is 1.0M KOH solution and 1.0M sodium sulfide solution, catalyzing the oxidation of sulfur ions to elemental sulfur.

[0018] The present invention provides an application of a high-entropy perovskite oxide as an electrocatalyst in the simultaneous electrocatalytic reduction of nitrate and oxidation of sulfide ions.

[0019] Furthermore, the method is as follows: the high entropy perovskite oxide LaBxO3 is loaded on carbon cloth and serves as the working electrodes of the cathode and anode at the same time, the cathode electrolyte is 1.0M KOH solution and 0.1M potassium nitrate solution, and the anode electrolyte is 1.0M KOH solution and 1.0M sodium sulfide solution, and simultaneously catalyzes the reduction of nitrate to synthesize NH3 and catalyzes the oxidation of sulfur ions to elemental sulfur.

[0020] The beneficial effects of the present invention are:

[0021] 1. The high entropy perovskite oxide provided by the present invention has high catalytic efficiency. Among them, the FE of NH3 reaches 95.83% at -0.7 (V vs. RHE), which is 5.6% higher than that of LaB1O3, and the side reaction (NO2 - FE<2%).

[0022] 2. The high entropy perovskite oxide provided by the present invention, wherein LaB5O3 exhibits excellent SOR activity, at 10 mA cm -2 An ultra-low overpotential of 0.484 V relative to RHE was achieved, which is significantly lower than the overpotential required for the oxygen evolution reaction (OER).

[0023] 3. The high entropy perovskite oxide provided by the present invention, when in a paired NO3RR||SOR electrolytic cell, the system -2 Only 1.079V voltage is required to drive NO3 - Converted to NH3 and S 2- Converted into elemental sulfur.

[0024] 4. The high-entropy perovskite oxide prepared by the method of the present invention lays the foundation for the preparation of electrocatalysts for achieving sustainable nitrogen fixation and sulfur recovery in practical water treatment applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the XRD spectrum of LaB1O3-LaB5O3 prepared in Example 1.

[0026] Figure 2 This is the SEM image of LaB1O3-LaB5O3 prepared in Example 1.

[0027] Figure 3 This is a high-angle annular dark field image of LaB5O3 prepared in Example 1 and an EDS surface scan of each element.

[0028] Figure 4 This is a comparison chart of the Faraday efficiency of LaB5O3 in Example 2.

[0029] Figure 5 This is a comparison of the LSV curves of OER and SOR of the LaB5O3 electrocatalyst in Example 3.

[0030] Figure 6 This is the XRD pattern of the product after SOR test in Example 3.

[0031] Figure 7 This is a comparison of the LSV curves of NO3RR||OER and NO3RR||SOR of the LaB5O3 electrocatalyst in Example 4.

[0032] Figure 8 This is a schematic diagram of the principle of the high entropy perovskite oxide of the present invention simultaneously catalyzing the reduction of nitrate to synthesize NH3 and catalyzing the oxidation of sulfide ions to elemental sulfur. DETAILED DESCRIPTION

[0033] Example 1 High Entropy Perovskite Oxide

[0034] 1. High-entropy perovskite oxide (LaB5O3)

[0035] The preparation method is as follows:

[0036] 1. Preparation of gel precursor:

[0037] Using the sol-gel method, 1.1mmol of iron nitrate (Fe(NO3)3·9H2O), 1.1mmol of cobalt nitrate (Co(NO3)2·6H2O), 1.1mmol of copper nitrate (Cu(NO3)2·3H2O), 1.1mmol of chromium nitrate (Cr(NO3)3·9H2O), 1.1mmol of nickel nitrate (Ni(NO3)2·6H2O) and 5.5mmol of lanthanum nitrate (La(NO3)3·6H2O) were dissolved in 25mL of water and 24mL of ethylene glycol, and 37.5mmol of ammonium citrate complexing agent was added, and then heated at 120℃ for 10h to obtain a gel precursor.

[0038] 2. Preparation of high entropy perovskite oxides:

[0039] The gel precursor was heated to 600°C in a muffle furnace at a heating rate of 10°C / min and maintained for 2 h. After cooling, a high-entropy perovskite oxide was obtained, which was labeled as LaB5O3 (B = Fe, Co, Cu, Cr, Ni).

[0040] 2. High Entropy Perovskite Oxide (LaB4O3)

[0041] The preparation method is as follows:

[0042] 1. Preparation of gel precursor:

[0043] Using the sol-gel method, 1.375mmol of iron nitrate (Fe(NO3)3·9H2O), 1.375mmol of cobalt nitrate (Co(NO3)2·6H2O), 1.375mmol of copper nitrate (Cu(NO3)2·3H2O), 1.375mmol of chromium nitrate (Cr(NO3)3·9H2O) and 5.5mmol of lanthanum nitrate (La(NO3)3·6H2O) were dissolved in 25mL of water and 24mL of ethylene glycol, and 37.5mmol of ammonium citrate complexing agent was added, and then heated at 120℃ for 10h to obtain a gel precursor.

[0044] 2. Preparation of high entropy perovskite oxides:

[0045] The gel precursor was heated to 600°C in a muffle furnace at a heating rate of 10°C / min and maintained for 2 h. After cooling, a high-entropy perovskite oxide was obtained, which was labeled as LaB4O3 (B=Fe, Co, Cu, Cr).

[0046] 3. High Entropy Perovskite Oxide (LaB3O3)

[0047] The preparation method is as follows:

[0048] 1. Preparation of gel precursor:

[0049] Using the sol-gel method, 1.833 mmol of iron nitrate (Fe(NO3)3·9H2O), 1.833 mmol of cobalt nitrate (Co(NO3)2·6H2O), 1.833 mmol of copper nitrate (Cu(NO3)2·3H2O) and 5.5 mmol of lanthanum nitrate (La(NO3)3·6H2O) were dissolved in 25 mL of water and 24 mL of ethylene glycol, and 37.5 mmol of ammonium citrate complexing agent was added, and then heated at 120°C for 10 h to obtain a gel precursor.

[0050] 2. Preparation of high entropy perovskite oxides:

[0051] The gel precursor was heated to 600°C in a muffle furnace at a heating rate of 10°C / min and maintained for 2 hours. After cooling, a high-entropy perovskite oxide was obtained, which was labeled as LaB3O3 (B=Fe, Co, Cu).

[0052] 4. High Entropy Perovskite Oxide (LaB2O3)

[0053] The preparation method is as follows:

[0054] 1. Preparation of gel precursor:

[0055] Using the sol-gel method, 2.75 mmol of iron nitrate (Fe(NO3)3·9H2O), 2.75 mmol of copper nitrate (Cu(NO3)2·3H2O) and 5.5 mmol of lanthanum nitrate (La(NO3)3·6H2O) were dissolved in 25 mL of water and 24 mL of ethylene glycol, and 37.5 mmol of ammonium citrate complexing agent was added, and then heated at 120°C for 10 h to obtain a gel precursor.

[0056] 2. Preparation of high entropy perovskite oxides:

[0057] The gel precursor was heated to 600°C in a muffle furnace at a heating rate of 10°C / min and maintained for 2 hours. After cooling, a high-entropy perovskite oxide was obtained, which was labeled as LaB2O3 (B=Fe, Cu).

[0058] 5. High-entropy perovskite oxide (LaB1O3)

[0059] The preparation method is as follows:

[0060] 1. Preparation of gel precursor:

[0061] Using the sol-gel method, 5.5 mmol of ferric nitrate (Fe(NO3)3·9H2O) and 5.5 mmol of lanthanum nitrate (La(NO3)3·6H2O) were dissolved in 25 mL of water and 24 mL of ethylene glycol, and 37.5 mmol of ammonium citrate complexing agent was added, and then heated at 120°C for 10 h to obtain a gel precursor.

[0062] 2. Preparation of high entropy perovskite oxides:

[0063] The gel precursor was heated to 600°C in a muffle furnace at a heating rate of 10°C / min and maintained for 2 hours. After cooling, a high-entropy perovskite oxide was obtained, which was labeled as LaB1O3 (B=Fe).

[0064] 6. Test Results

[0065] Figure 1 This is the XRD spectrum of LaB1O3-LaB5O3 prepared in this example. Powder X-ray diffraction (XRD) analysis confirmed that LaB1O3 and LaB2O3 are orthorhombic perovskite structures with a spacer of Pnma (LaFeO3 PDF#88-0641), while LaB3O3, LaB4O3 and LaB5O3 crystallize into cubic perovskite structures with a spacer of Pm-3m (LaFeO3 PDF#75-0439). The Rietveld refinement of the simulated XRD spectrum of LaB5O3 is in good agreement with the experimental data, especially at the peaks corresponding to the (100), (100), (111), (200), (200) and (211) crystal planes of the cubic perovskite oxide. With the addition of metal elements, the main diffraction peaks gradually broadened, and LaB5O3 showed a splitting phenomenon (such as Figure 1 (marked in red), further confirming the lattice distortion caused by the multi-component cations of the high entropy material.

[0066] Figure 2 This is a scanning electron micrograph of the LaB1O3-LaB5O3 prepared in this example. After annealing the gel precursor in air, an irregular, blocky nanostructure composed of nanoparticles with an average size of approximately 37 nm was formed. The morphologies of the LaB1O3-LaB5O3 samples are similar.

[0067] Figure 3 Figure 2 shows a high-angle annular dark field image and EDS scan of LaB5O3 prepared in this example. High-angle annular dark field scanning TEM (HAADF-STEM) combined with energy dispersive X-ray spectroscopy (EDS) confirms the uniform distribution of La, Fe, Cu, Co, Cr, Ni, and O across the probe area.

[0068] Example 2 Application of LaB5O3 as an electrocatalyst in electrocatalytic nitrate reduction

[0069] Method: The high entropy perovskite oxide LaB5O3 prepared in Example 1 was loaded on carbon cloth as an electrocatalyst as a working electrode, the reference electrode was Ag / AgCl, the counter electrode was a platinum sheet, and the electrolyte was a 1.0 M KOH solution and a 0.1 M potassium nitrate solution.

[0070] Evaluation of electrochemical reduction of NO3 by chronoamperometry - The performance of LaB5O3 is shown in Figure 2. The NH3 production rate reaches a maximum of 5.053 mg h at -0.9 V (V vs. RHE). -1 cm -2 .like Figure 4 As shown in Figure 2, the Faradaic efficiency (FE) first increases and then decreases slightly, reaching a peak of 95.83% at -0.7 V (V vs. RHE). Analysis of nitrogen-containing byproducts shows that NO2 - The FE was kept below 2% and no detectable hydrazine was formed.

[0071] Example 3 Application of LaB5O3 as an electrocatalyst in electrocatalytic sulfur ion oxidation

[0072] Method: The high entropy perovskite oxide LaB5O3 prepared in Example 1 was loaded on carbon cloth as an electrocatalyst as a working electrode, the reference electrode was Ag / AgCl, the counter electrode was a platinum sheet, and the electrolyte was a 1.0 M KOH solution and a 1.0 M sodium sulfide solution.

[0073] like Figure 5 As shown, linear sweep voltammetry (LSV) was used to test the LaB5O3 in 1.0 M KOH with or without 1.0 M sodium sulfide solution. The results show that LaB5O3 requires a potential of 1.358 V (V vs. RHE) and 1.776 V (V vs. RHE) to achieve 1 mA cm -2 and 10mAcm -2 In comparison, the corresponding potentials for SOR are only 0.102 V and 0.484 V, indicating that SOR has a significantly lower oxidation potential and faster kinetics than OER.

[0074] The yellow precipitate formed during the reaction was analyzed by XRD. Figure 6 As shown, the characteristic peak was found to correspond to elemental sulfur (PDF#08-0247), indicating that sulfur was successfully recovered from the sulfide-containing wastewater.

[0075] These findings highlight the practical applicability of LaB5O3 for sustainable sulfur recovery and environmental remediation.

[0076] Example 4 Application of LaB5O3 as an electrocatalyst in simultaneous electrocatalytic nitrate reduction and sulfide oxidation

[0077] Method: The high entropy perovskite oxide LaB5O3 prepared in Example 1 was loaded on carbon cloth as an electrocatalyst and simultaneously served as the working electrodes for the cathode and anode. The cathode electrolyte was 1.0 M KOH solution and 0.1 M potassium nitrate solution, and the anode electrolyte was 1.0 M KOH solution and 1.0 M sodium sulfide solution.

[0078] Given the excellent catalytic performance of LaB5O3 in SOR and NO3RR, a two-electrode system was constructed using LaB5O3 as the electrode material. In this structure, the cathode electrolyte consists of a mixture of 0.1M KNO3 and 1.0M KOH, while the anode electrolyte is a solution containing 1.0M Na2S and 1.0M KOH. In order to evaluate the electrochemical behavior of LaB5O3 under different reaction conditions, LSV measurements were performed on the NO3RR||SOR and NO3RR||OER systems. Figure 7 The results clearly show that the NO3RR||SOR system significantly outperforms the conventional NO3RR||OER system. -2 At a current density of 1.5 Å, the cell voltage required for SOR-assisted NO3RR is only 1.079 V, which is significantly lower than the 2.932 V required for OER-assisted NO3RR, highlighting the energy-saving potential of replacing OER with SOR.

Claims

1. A high entropy perovskite oxide, characterized in that The high entropy perovskite oxide is LaBxO3, wherein B=Fe, Co, Cu, Cr, Ni, or a combination of two or more.

2. A high entropy perovskite oxide according to claim 1, characterized in that The high entropy perovskite oxide is LaB1O3 with B=Fe, or the high entropy perovskite oxide is LaB2O3 with B=Fe, Cu, or the high entropy perovskite oxide is LaB3O3 with B=Fe, Co, Cu, or the high entropy perovskite oxide is LaB4O3 with B=Fe, Co, Cu, Cr, or the high entropy perovskite oxide is LaB5O3 with B=Fe, Co, Cu, Cr, Ni.

3. A method for preparing a high entropy perovskite oxide, characterized in that: The method for preparing a high-entropy perovskite oxide according to claim 1 or 2 comprises the following steps: 1) dissolving a plurality of metal nitrates and lanthanum nitrate in water and ethylene glycol, adding ammonium citrate as a complexing agent, and heating at 115° C. to 125° C. for 10 to 12 hours to obtain a gel precursor; the plurality of metal nitrates being selected from one or a combination of two or more metal nitrates of Fe, Co, Cu, Cr, and Ni; 2) heating the gel precursor in a muffle furnace at a heating rate of 8°C-10°C / min to 550°C-650°C and maintaining the temperature for 2h-3h, and then cooling to obtain a high entropy perovskite oxide.

4. The method for preparing a high entropy perovskite oxide according to claim 3, wherein: In step 1), the plurality of metal nitrates are added in an equal molar ratio; the total molar number of each metal nitrate in the plurality of metal nitrates: the molar number of lanthanum nitrate = 1:

1.

5. Use of a high entropy perovskite oxide according to claim 1 or 2 as an electrocatalyst in electrocatalytic nitrate reduction.

6. The use according to claim 5, characterized in that The method is as follows: high entropy perovskite oxide LaBxO3 is loaded on carbon cloth as a working electrode, the reference electrode is Ag / AgCl, the counter electrode is a platinum sheet, the electrolyte is 1.0M KOH solution and 0.1M potassium nitrate solution, and catalyzes the reduction of nitrate to synthesize NH3.

7. Use of a high entropy perovskite oxide according to claim 1 or 2 as an electrocatalyst in electrocatalytic sulfur ion oxidation.

8. The use according to claim 7, characterized in that The method is as follows: high entropy perovskite oxide LaBxO3 is loaded on carbon cloth as a working electrode, the reference electrode is Ag / AgCl, the counter electrode is a platinum sheet, the electrolyte is 1.0M KOH solution and 1.0M sodium sulfide solution, catalyzing the oxidation of sulfur ions to elemental sulfur.

9. Use of a high entropy perovskite oxide according to claim 1 or 2 as an electrocatalyst in the simultaneous electrocatalytic reduction of nitrate and oxidation of sulfide.

10. The use according to claim 9, characterized in that The method is as follows: high entropy perovskite oxide LaBxO3 is loaded on carbon cloth and used as the working electrodes of cathode and anode at the same time. The cathode electrolyte is 1.0M KOH solution and 0.1M potassium nitrate solution, and the anode electrolyte is 1.0M KOH solution and 1.0M sodium sulfide solution. It simultaneously catalyzes the reduction of nitrate to synthesize NH3 and catalyzes the oxidation of sulfur ions to elemental sulfur.

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