High-catalytic-activity fe-te urea oxidation electrode and preparation method thereof

Abstract

The application discloses a high-catalytic-activity Fe-Te urea oxidation electrode, which comprises a conductive base and a Fe-Te plating layer deposited on the surface of the conductive base by an electrodeposition method. The application further discloses a preparation method of the high-catalytic-activity Fe-Te urea oxidation electrode. The Fe-Te urea oxidation electrode has a low urea oxidation overpotential and can be used as an alkaline water electrolysis urea oxidation electrode material. The application selects three-dimensional structure foam nickel with good conductive performance and stable structure as a base material, and adopts an electrodeposition method to synthesize the Fe-Te urea oxidation electrode in one step. The constant current electrodeposition method has the advantages of short preparation time, mild reaction condition and simple steps, and the obtained Fe-Te plating layer is uniform in composition, small in grain size and uniform in thickness. Meanwhile, the electrodeposition method makes the Fe-Te plating layer firmly combined with the base material, reduces the falling phenomenon of the electrode material in the urea oxidation reaction process, and greatly improves the electrochemical stability of the electrode.

Description

Technical Field

[0001] This invention relates to a Fe-Te urea oxidation electrode with high catalytic activity, and also to a method for preparing the above-mentioned Fe-Te urea oxidation electrode. Background Technology

[0002] Water electrolysis is one of the most promising methods for hydrogen production. It consists of the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. However, the theoretical potential of the OER at the anode is too high, resulting in slow kinetics and affecting the overall efficiency of water electrolysis. In recent years, the use of urea oxidation to assist water electrolysis for hydrogen production has gained favor in the electrocatalysis field. The theoretical potential of the urea oxidation reaction (UOR) at the anode is only 0.37V, which can replace the energy-intensive OER (1.23V), achieving the goal of reducing energy consumption. Furthermore, using urea oxidation to assist hydrogen production can also degrade urea, mitigating the environmental pollution caused by urea wastewater.

[0003] In recent years, a large amount of research has focused on developing low-cost non-precious metal electrocatalysts to improve the efficiency of urea oxidation. Among numerous catalyst materials, transition metal tellurides have excellent electrical conductivity, making them promising non-precious metal urea oxidation catalysts. Patent CN109985642A discloses a Ni-Te-S composite carbon material, its preparation method, and its applications. The material synthesized using this method exhibits good catalytic activity, stability, and good acid-base adaptability; however, the synthesis steps are relatively cumbersome.

[0004] Currently, the main methods for synthesizing transition metal tellurides are exfoliation (including physical and chemical exfoliation) and chemical vapor deposition. Patent CN115274883A discloses a bismuth selenide (Bi₂Se₃) electrode, its preparation method, and its applications. This method involves a long reaction time and high energy consumption, with cumbersome preparation steps. Furthermore, the synthesized catalyst material is a powder, requiring an organic binder to be loaded onto the substrate, which reduces the charge transfer rate during the reaction. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a Fe-Te urea oxidation electrode with high catalytic activity. Another purpose of this invention is to provide a method for preparing the above-mentioned Fe-Te urea oxidation electrode by electrodeposition.

[0006] Technical solution: The highly catalytically active Fe-Te urea oxidation electrode of the present invention includes a conductive substrate and a Fe-Te coating deposited on the surface of the conductive substrate by electrodeposition.

[0007] In the Fe-Te coating, the mass percentage of Fe is 20-70%, and the remainder is Te.

[0008] The thickness of the Fe-Te coating is 1 to 2 micrometers. If the Fe-Te coating is too thin, the coverage will be insufficient; if the Fe-Te coating is too thick, the resistance will be relatively high and it will be prone to cracking.

[0009] The conductive substrate is nickel foam.

[0010] The preparation method of the above-mentioned highly catalytically active Fe-Te urea oxidation electrode includes the following steps:

[0011] (1) Preparation of electroplating aqueous solution: Dissolve iron source, tellurium source, buffer and conductive agent in water to obtain electroplating aqueous solution;

[0012] (2) Electrodeposition preparation of Fe-Te electrode: Using a pretreated conductive substrate as the working electrode, a graphite sheet as the auxiliary electrode, and a saturated calomel electrode as the reference electrode, an electroplating aqueous solution is electroplated to obtain a Fe-Te urea oxide electrode.

[0013] In step (1), the iron source is one or a mixture of several water-soluble iron salts; the tellurium source is one or a mixture of several tellurium dioxide, sodium tellurite, or sodium tellurate.

[0014] In step (1), the buffer is one of boric acid, citric acid or ammonium chloride; the conductive agent is one of NaCl, LiCl or KCl.

[0015] In step (1), the iron source in the electroplating aqueous solution has a mass concentration of 20-40 g / L; the tellurium source has a mass concentration of 1-3 g / L; the buffer has a mass concentration of 20-30 g / L; and the conductive agent has a mass concentration of 2-5 g / L.

[0016] In step (2), the pretreatment of the conductive substrate refers to: cutting the conductive substrate into rectangular pieces, placing the cut conductive substrate in anhydrous ethanol for ultrasonic vibration, and then rinsing it clean with deionized water; then ultrasonically vibrating it in dilute hydrochloric acid, and rinsing it with deionized water until the pH of the rinsing solution is neutral, and storing it in a vacuum drying oven to obtain the conductive substrate.

[0017] In step (2), the electrodeposition method is constant current electrodeposition, and the current magnitude during the constant current electrodeposition process is 20-30 mA·cm. -2 The temperature of the plating solution during the constant current electrodeposition process is 20–60℃, and the electroplating time during the constant current electrodeposition process is 30–60 min.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The Fe-Te urea oxidation electrode of the present invention has a low urea oxidation overpotential and can be used as an alkaline water electrolysis urea oxidation electrode material; (2) The present invention selects three-dimensional foam nickel with good conductivity and stable structure as the substrate material, and uses the electrodeposition method to synthesize the Fe-Te urea oxidation electrode in one step. The constant current electrodeposition method has the advantages of short preparation time and simple steps, and the Fe-Te coating obtained has uniform composition, small grain size and uniform thickness. This morphology coating can increase the specific surface area of ​​the electrode and increase the number of active sites, thereby improving the catalytic performance of the Fe-Te electrode. At the same time, the electrodeposition method makes the Fe-Te coating firmly bonded to the substrate material, reducing the phenomenon of electrode material falling off during the urea oxidation reaction, and greatly improving the electrochemical stability of the electrode. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the Fe-Te urea oxidation electrode in Example 1;

[0020] Figure 2 Linear voltammetry (LSV) plots of the Fe-Te urea oxidation electrode in Examples 1-3;

[0021] Figure 3 Linear voltammetry (LSV) plots of the urea oxidation electrodes in Example 1 and Comparative Examples 1-3 are shown. Detailed Implementation

[0022] Example 1

[0023] The preparation method of the highly catalytically active Fe-Te urea oxidation electrode of the present invention includes the following steps:

[0024] (1) Pretreatment of nickel foam: The cut nickel foam material is ultrasonically vibrated in anhydrous ethanol for 20 minutes to remove chemical oil, and then rinsed with deionized water; then ultrasonically vibrated in 10% hydrochloric acid for 20 minutes to remove oxides on the surface of the material, rinsed with deionized water until the pH of the rinsing solution is neutral, and finally placed in a vacuum drying oven for storage.

[0025] (2) Electrodeposition preparation of Fe-Te electrodes

[0026] Fe-Te urea oxide electrode was prepared by electrodeposition on a DC power supply using a two-electrode system. The foamed nickel treated in step (1) was used as the working electrode, the graphite sheet as the auxiliary electrode, and the saturated calomele electrode (SCE) as the reference electrode. The mass concentrations of each substance in the electroplating aqueous solution were 30 g / L FeSO4, 1 g / L TeO2, 26 g / L NH4Cl, and 4 g / L LiCl, and the pH value of the electroplating aqueous solution was 2.4. During the constant current electrodeposition process, the temperature of the electroplating aqueous solution was 40℃, and the current density was 30 mA·cm. -2 The electroplating temperature is 40℃ and the electroplating time is 30min;

[0027] (3) After the electroplating deposition is completed, the foamed nickel is taken out, rinsed with distilled water until the pH of the residual liquid is neutral, and dried at 70°C in a vacuum environment for 12 hours to obtain the Fe-Te urea oxidation electrode.

[0028] The morphology of the Fe-Te urea oxidation electrode prepared in Example 1 was analyzed using scanning electron microscopy, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the electrode surface exhibits a cauliflower-like structure, with relatively tight bonding and small nanoparticles attached to the structure, which greatly increases the specific surface area of ​​the electrode and the number of active sites, thus improving the urea oxidation performance of the electrode. Scanning electron microscopy observation of the Fe-Te cross-section revealed that the coating thickness is approximately 1 μm. Energy dispersive spectroscopy (EDS) of the Fe-Te urea oxidation electrode showed that the mass percentage of Fe was 40%, with the remainder being Te.

[0029] Example 2

[0030] The preparation method of the highly catalytically active Fe-Te urea oxidation electrode of the present invention includes the following steps:

[0031] (1) Pretreatment of nickel foam: The cut nickel foam material is ultrasonically vibrated in anhydrous ethanol for 20 minutes to remove chemical oil, and then rinsed with deionized water; then ultrasonically vibrated in 10% hydrochloric acid for 20 minutes to remove oxides on the surface of the material, rinsed with deionized water until the pH of the rinsing solution is neutral, and finally placed in a vacuum drying oven for storage.

[0032] (2) Electrodeposition preparation of Fe-Te electrodes

[0033] Fe-Te urea oxide electrode was prepared by electrodeposition on a DC power supply using a two-electrode system. The foamed nickel treated in step (1) was used as the working electrode, the graphite sheet as the auxiliary electrode, and the saturated calomele electrode (SCE) as the reference electrode. The mass concentrations of each substance in the electroplating aqueous solution were 30 g / L FeSO4, 2 g / L TeO2, 26 g / L NH4Cl, and 4 g / L LiCl, and the pH value of the electroplating aqueous solution was 2.4. During the constant current electrodeposition process, the temperature of the electroplating aqueous solution was 40℃, and the current density was 30 mA·cm. -2 The electroplating temperature is 40℃ and the electroplating time is 30min;

[0034] (3) After the electroplating deposition is completed, the foamed nickel is taken out, rinsed with distilled water until the pH of the residual liquid is neutral, and dried at 70°C in a vacuum environment for 12 hours to obtain the Fe-Te urea oxidation electrode.

[0035] Scanning electron microscopy (SEM) was used to observe and measure the cross-section of the Fe-Te coating, revealing a thickness of approximately 1.5 μm. Energy dispersive spectroscopy (EDS) analysis of the Fe-Te urea oxide electrode showed a Fe mass percentage of 48%, with the remainder being Te.

[0036] Example 3

[0037] The preparation method of the highly catalytically active Fe-Te urea oxidation electrode of the present invention includes the following steps:

[0038] (1) Pretreatment of nickel foam: The cut nickel foam material is ultrasonically vibrated in anhydrous ethanol for 20 minutes to remove chemical oil, and then rinsed with deionized water; then ultrasonically vibrated in 10% hydrochloric acid for 20 minutes to remove oxides on the surface of the material, rinsed with deionized water until the pH of the rinsing solution is neutral, and finally placed in a vacuum drying oven for storage.

[0039] (2) Electrodeposition preparation of Fe-Te electrodes

[0040] Fe-Te urea oxide electrode was prepared by electrodeposition on a DC power supply using a two-electrode system. The foamed nickel treated in step (1) was used as the working electrode, the graphite sheet as the auxiliary electrode, and the saturated calomele electrode (SCE) as the reference electrode. The mass concentrations of each substance in the electroplating aqueous solution were 30 g / L FeSO4, 3 g / L TeO2, 26 g / L NH4Cl, and 4 g / L LiCl, and the pH value of the electroplating aqueous solution was 2.4. During the constant current electrodeposition process, the temperature of the electroplating aqueous solution was 40℃, and the current density was 30 mA·cm. -2The electroplating temperature is 40℃ and the electroplating time is 30min;

[0041] (3) After the electroplating deposition is completed, the foamed nickel is taken out, rinsed with distilled water until the pH of the residual liquid is neutral, and dried at 70°C in a vacuum environment for 12 hours to obtain the Fe-Te urea oxidation electrode.

[0042] The Fe-Te cross-section was observed and measured using a scanning electron microscope, revealing a coating thickness of approximately 2 μm. Energy dispersive spectroscopy (EDS) analysis of the Fe-Te urea oxide electrode showed a Fe mass percentage of 53%, with the remainder being Te.

[0043] Comparative Example 1

[0044] The preparation method of the urea oxidation electrode in Comparative Example 1 is basically the same as that in Example 1, except that no iron source was added to the electroplating aqueous solution.

[0045] Comparative Example 2

[0046] The preparation method of the urea oxidation electrode in Comparative Example 2 is basically the same as that in Example 1, except that a tellurium source was not added to the electroplating aqueous solution.

[0047] Comparative Example 3

[0048] The preparation method of the highly catalytically active Fe-Te urea oxidation electrode of the present invention includes the following steps:

[0049] (1) Pretreatment of nickel foam: First, NF samples with dimensions of 1cm×1cm were washed and ultrasonically cleaned for 5 minutes each in acetone, ethanol, and deionized water. After ultrasonic cleaning, the samples were dried at 70℃ in an Eyela-NDO-420 constant temperature dryer;

[0050] (2) Microwave-assisted preparation of Fe-Te electrodes

[0051] Under continuous magnetic stirring, 0.25 g TeCl4 and 15 g FeSO4 powder were dissolved in 10 mL of 1-butyl-3-methylimidazolium tetrafluoroborate (C8H4O3) at 65 °C. 15 In an organic electrolyte (BF4N2), after magnetic stirring for 3 hours, the solution turned yellow. To eliminate dissolved oxygen in the solution, argon gas was introduced into the reaction flask for 10 minutes. The yellow solution was the Fe-Te precursor solution. NF was soaked in it before synthesis. The glass vial containing NF and the precursor solution was positioned in the center of a 700W microwave oven with adjustable power options, and then heated under three different power conditions of 90W, 130W and 180W respectively. The glass vial and the solution inside cooled naturally.

[0052] (3) After the process is completed, the sample is taken out and washed with acetone, water and ethanol aqueous solution for 2 to 3 minutes each. After drying, the Fe-Te urea oxidation electrode is obtained.

[0053] Scanning electron microscopy (SEM) analysis of the Fe-Te cross-section revealed a catalyst layer thickness of approximately 15 μm. Energy dispersive spectroscopy (EDS) analysis of the Fe-Te urea oxidation electrode showed a Fe mass percentage of 46%, with the remainder being Te.

[0054] Fe-Te electrode urea oxidation performance test

[0055] Electrochemical performance tests were performed on the Fe-Te urea oxidation electrode materials prepared in Examples 1-3 using an electrochemical workstation (CHI600E, Beijing World Trade Center Far East Scientific Instruments Co., Ltd.) in a three-electrode system. The Fe-Te urea oxidation electrode material was used as the working electrode, the graphite sheet as the auxiliary electrode, and the SCE as the reference electrode. The linear scan curves of urea oxidation were measured in a mixed solution of 1 mol / L KOH and 0.33 mol / L urea at a temperature of 25 °C and a scan rate of 5 mV / s. Impedance compensation correction was applied to the electrode potentials. All potentials were obtained according to the following Nernst equation: E RHE =E SCE +0.242+0.059pH-iR (where i is the test current and R is the solution impedance). The urea oxidation performance test of Comparative Examples 1-3 is roughly the same as the above method.

[0056] Figure 2 Linear voltammetry (LSV) plots of the Fe-Te urea oxidation electrode in Examples 1-3; Figure 3 Linear voltammetry (LSV) plots of the urea oxidation electrodes in Example 1 and Comparative Examples 1-3 are shown.

[0057] The electrodes prepared in Examples 1-3 and Comparative Examples 1-3 were used to test the urea oxidation performance. The urea oxidation overpotential (V) obtained from the tests are shown in Table 1.

[0058] Table 1 Overpotential Test Table for Electrocatalytic Urea Oxidation Materials

[0059]

[0060] As can be seen from Table 1, the urea oxidation overpotential of the Fe-Te urea oxidation electrode prepared by the present invention is much lower than that of the urea oxidation overpotential of Comparative Examples 1 to 3, indicating that the Fe-Te urea oxidation electrode of the present invention has excellent urea oxidation performance.

[0061] from Figure 2As can be seen, Example 1 has the best performance. The reason for this phenomenon is that as the mass of TeO2 increases, the number of small nanoparticles on the coating surface gradually increases, the specific surface area increases, and the catalytic performance is improved. However, after a certain amount, the Fe-Te compound grows rapidly, the number of small nanoparticles on the coating surface decreases, the specific surface area decreases, and the catalytic performance will also decrease.

Claims

1. A method for preparing a high catalytic activity Fe-Te urea oxidation electrode, characterized in that, The method comprises the following steps: (1) preparing an aqueous plating solution: dissolving a ferrous source, a tellurium source, a buffer and a conductive agent in water to obtain an aqueous plating solution; the ferrous source is ferrous sulfate; the tellurium source is tellurium dioxide; the buffer is ammonium chloride; in the aqueous plating solution, the mass concentration of the ferrous source is 20-40 g / L; the mass concentration of the tellurium source is 1-3 g / L; the mass concentration of the buffer is 20-30 g / L; and the mass concentration of the conductive agent is 2-5 g / L; (2) preparing a Fe-Te electrode by electrodeposition: taking a pretreated conductive substrate as a working electrode, taking a graphite sheet as an auxiliary electrode, and taking a saturated calomel electrode as a reference electrode, the aqueous plating solution is subjected to electrodeposition plating to obtain a Fe-Te urea oxidation electrode. The electrodepositing mode is constant current electrodepositing, and the current size is 20-30 mA·cm -2 during the electrodepositing process, and the electrodepositing time is 30-60 min.

2. The method of claim 1, wherein: In step (1), the conductive agent is one of NaCl, LiCl or KCl.

3. The method of claim 1, wherein: In step (2), the pretreatment of the conductive substrate refers to: cutting the conductive substrate into a rectangular sheet, ultrasonically oscillating the cut conductive substrate in anhydrous ethanol, and then washing it with deionized water; then ultrasonically oscillating it in dilute hydrochloric acid, and then washing it with deionized water until the washing liquid has a neutral pH, and then storing it in a vacuum drying box to obtain the conductive substrate.

4. The method of claim 1, wherein: In step (2), the temperature of the plating solution during the constant-current electrodeposition process is 20-60 DEG C.

5. The Fe-Te urea oxidation electrode prepared by the method of claim 1, characterized in that: The Fe-Te electrode comprises a conductive substrate and a Fe-Te plating layer deposited on the surface of the conductive substrate by electrodeposition.

6. The Fe-Te urea oxidation electrode of claim 5, wherein: The thickness of the Fe-Te plating layer is 1-2 microns.

7. The Fe-Te urea oxidation electrode of claim 5, wherein: The conductive substrate is foamed nickel.

Images