Preparation of low-load palladium-based electrode and application of low-load palladium-based electrode in hydrogen production by electrooxidation of formaldehyde wastewater

Abstract

The invention discloses preparation of a low-load palladium-based electrode and application of the low-load palladium-based electrode in hydrogen production through electrooxidation of formaldehyde wastewater, and relates to the technical field of formaldehyde wastewater purification and clean energy. The palladium-based electrode is composed of a metal foam substrate and a palladium active component loaded on the substrate. According to the invention, the palladium-based electrode is prepared under mild conditions by adopting a one-step atom self-replacement method, and accurate regulation and control of the palladium loading capacity are realized by regulating and controlling the components and proportion of the palladium-based composite solution. When the electrode is used for electrochemical oxidation treatment of formaldehyde-containing wastewater, in a mixed electrolyte of 0.5 M of HCHO and 1.0 M of KOH, the optimal current density can reach the industrial-grade current density of 1400 mA cm <-2 >, and the electrode shows outstanding catalytic activity. The problem of palladium particle agglomeration is effectively solved, controllable design of the electrode palladium loading capacity is achieved, and the method has wide practical application prospects in the fields of formaldehyde wastewater purification and clean energy production.

Description

Technical Field

[0001] This invention belongs to the field of formaldehyde wastewater purification and clean energy technology, specifically relating to the preparation of a low-load palladium-based electrode and its application in the electro-oxidation of formaldehyde wastewater to produce hydrogen. Background Technology

[0002] Formaldehyde (HCHO) is a common volatile organic compound widely present in industrial production processes, especially in wastewater generated by industries such as wood processing, furniture manufacturing, and chemicals. Formaldehyde release seriously threatens the ecological environment and human health. Currently, common methods for treating formaldehyde in wastewater include chemical oxidation and biological oxidation. Chemical oxidation involves adding oxidants such as hydrogen peroxide (H2O2) or ozone (O3) to oxidize and decompose formaldehyde into harmless substances. However, this method requires large amounts of oxidants, increasing treatment costs and potentially causing secondary pollution. Biological oxidation is limited by the sensitivity of microbial activity to temperature and pH, resulting in large fluctuations in treatment efficiency and a limited range of applicability.

[0003] Electrocatalytic oxidation technology, as an emerging method for treating formaldehyde wastewater, boasts advantages such as high treatment efficiency, mild operating conditions, no secondary pollution, and high-value conversion products, making it considered the most promising alternative. Especially under industrial conditions, the electrocatalytic oxidation process, driven by "green" electricity, can rapidly eliminate formaldehyde in wastewater with extremely low energy input, converting it into high-value formate products and green hydrogen. This method not only achieves high-value conversion of pollutants but also brings considerable economic benefits.

[0004] The material and structure of the catalytic electrode directly determine the activity and selectivity of the electrocatalytic reaction in formaldehyde wastewater. In recent years, although copper-based electrodes have exhibited excellent initial catalytic activity in the electrooxidation of formaldehyde, their activity is limited by the low intrinsic oxidation potential of copper-based electrodes (Cu). 0 →Cu + / 2+ The inherent oxidation potential (0.52 V vs. RHE) and weak resistance to poisoning limit the performance of palladium (Pd) electrodes at wider potential windows and higher current densities, making it difficult to meet the current density and stability requirements of industrial processing. In contrast, Pd-based electrodes possess a higher intrinsic oxidation potential (approximately 0.85 V vs. RHE), a favorable electronic structure, and stronger resistance to poisoning and oxidation, giving them a significant advantage in formaldehyde electro-oxidation and related energy conversion reactions. Therefore, achieving high dispersion, high utilization, and long-term stable operation of palladium while reducing the amount of precious metals used is a key issue in current research and engineering applications.

[0005] Currently, the mainstream methods for preparing supported palladium-based electrodes mainly include deposition-precipitation, template methods, and impregnation methods. While deposition-precipitation can control the palladium loading, high-temperature treatment often leads to palladium particle migration and aggregation, thus reducing catalytic activity. Template methods have advantages in morphology control and size uniformity, but the process is complex, costly, and the template removal step is cumbersome, limiting its large-scale application. Patent CN102872860A uses a lyotropic liquid crystal template-assisted in-situ photoreduction method, which can control the morphology but relies on precise illumination conditions (incandescent lamp illumination intensity and time control), making it complex and costly. Furthermore, while impregnation is convenient, it often fails to achieve uniform palladium particle distribution, resulting in poor particle size and dispersion control. Patent CN109052586A uses a nickel foam impregnation method, which is simple but suffers from high palladium loading and uncontrollable nanoparticle aggregation, making it difficult to meet the needs of industrial-scale production.

[0006] In summary, the key technological challenge in the current field of supported palladium-based electrode preparation lies in how to reduce the palladium loading while avoiding high-temperature treatment, and achieving highly uniform dispersion and controllable synthesis of palladium nanoparticles on a support. Against this backdrop, developing a method for synthesizing low-loading palladium-based electrodes under mild conditions without high-temperature treatment, and applying it to the electro-oxidation of formaldehyde wastewater for hydrogen production, is of paramount importance for developing an economically and environmentally beneficial electrocatalytic treatment technology for formaldehyde wastewater and promoting its practical industrial application. Summary of the Invention

[0007] To address the problem that high-temperature calcination methods for preparing palladium-based electrodes in existing technologies easily lead to palladium particle aggregation and reduced activity, this invention provides a method for preparing a low-loading palladium-based electrode and its application in the electro-oxidation of formaldehyde wastewater to produce hydrogen. This invention employs a one-step atom self-substitution method to prepare the palladium-based electrode under mild conditions, simplifying the synthesis process of supported low-loading palladium-based electrodes and avoiding high-temperature treatment and uneven dispersion of palladium nanoparticles on the support. By controlling the composition and ratio of the palladium-based composite solution, precise control of the palladium loading is achieved. This invention also provides a method for electrochemical oxidation of formaldehyde wastewater to produce hydrogen, further applying the prepared electrode to the electrocatalytic oxidation treatment of formaldehyde-containing wastewater. Within the electrocatalytic system, formaldehyde in the wastewater is efficiently upgraded into high-value-added formate products and green hydrogen.

[0008] This invention is achieved through the following technical solution:

[0009] This invention provides a method for preparing a low-loading palladium-based electrode, comprising the following steps:

[0010] (1) Preparation of palladium-based composite solution: Dissolve palladium salt, complexing agent, reaction promoter and surfactant in water, mix evenly, and then adjust the pH to 1-3 with acid to form a composite solution; introduce an inert gas (such as nitrogen or argon) into the composite solution to fully remove dissolved oxygen and obtain an oxygen-free composite solution.

[0011] (2) Synthesis of palladium-based electrode: The metal foam carrier is immersed in the palladium-based composite solution obtained in step (1) and kept at a certain temperature range (e.g., 25°C to 80°C) for a certain time (e.g., 1.0h to 20h) to allow the palladium component in the composite solution to fully react with the surface of the metal foam carrier, thereby achieving in-situ deposition of palladium nanoparticles; after the reaction is completed, the sample is taken out, rinsed thoroughly with deionized water to remove residual reactants and byproducts, and then dried to obtain the palladium-based electrode.

[0012] Preferably, in step (1), the palladium-based composite solution has a palladium salt molar concentration of 0.28–11.28 mM, preferably 0.56–2.26 mM; a complexing agent molar concentration of 10–200 mM, preferably 100–150 mM; a reaction promoter molar concentration of 1.0–50 mM, preferably 20–40 mM; and a surfactant molar concentration of 0.1–1.0 mM, preferably 0.5–1.0 mM.

[0013] Preferably, in step (1), the molar ratio of the palladium salt, complexing agent, reaction promoter, and surfactant is 0.28–11.28: 10–200: 1.0–50: 0.1–1.0. More preferably, the concentration ratio of the palladium salt, complexing agent, reaction promoter, and surfactant is 0.56–2.26: 100–150: 20–40: 0.5–1.0.

[0014] Preferably, in step (1), the palladium salt includes at least one of PdCl2, Pd(NO3)2, and Pd(C2H3O2)2, with PdCl2 being the most preferred.

[0015] Preferably, in step (1), the complexing agent includes at least one of KBr and NaBr, preferably KBr.

[0016] Preferably, in step (1), the reaction promoter includes at least one of NaCl and KCl, with NaCl being the most preferred.

[0017] Preferably, in step (1), the surfactant includes at least one of poloxamer 407 (F127) and poloxamer 188 (F68), with poloxamer 407 (F127) being the most preferred.

[0018] Preferably, in step (1), the acid is at least one of HCl, H2SO4, and HNO3, with HCl being the most preferred.

[0019] Preferably, in step (1), the flow rate of the inert gas is approximately 10–40 mL / min. -1 The time is 10-30 minutes.

[0020] Preferably, in step (2), the theoretical oxidation potential of the metal foam carrier must be lower than that of palladium. The metal foam carrier includes copper foam, nickel foam, iron foam, or cobalt foam, preferably nickel foam. The metal foam carrier is a commercially available metal foam carrier.

[0021] Preferably, in step (2), the metal foam carrier is a pretreated metal foam carrier. The pretreatment method is to ultrasonically clean the metal foam carrier with ethanol, acetone and hydrochloric acid for 10-20 minutes respectively to obtain the pretreated metal foam carrier.

[0022] Preferably, in step (2), the temperature is controlled by a water bath or an oil bath, with a water bath being preferred.

[0023] Preferably, in step (2), the reaction temperature is 25-80℃, more preferably 30-70℃, such as 30℃, 40℃, 50℃, 60℃, 70℃, etc., and more preferably 30±2℃.

[0024] Preferably, in step (2), the reaction time is 1.0-20h, preferably 3-15h, such as 3h, 6h, 9h, 12h, 15h, etc., and more preferably 12h.

[0025] Preferably, in step (2), the drying conditions are: drying in a vacuum drying oven at 25-60℃ for 2-10 hours.

[0026] This invention also protects a low-loading palladium-based electrode prepared by the above method, which consists of a metal foam substrate and a palladium active component loaded on the substrate, wherein the palladium loading in the palladium-based electrode is 0.06–1.92 mg / cm³. -2 .

[0027] This invention also protects the application of the above-mentioned low-loading palladium-based electrode in the electrocatalytic oxidation of formaldehyde wastewater to produce hydrogen.

[0028] Preferably, the reaction is tested in an H-type reaction cell at room temperature: the anolyte is an alkaline solution containing HCHO, with a formaldehyde concentration of 0.05–1.0 M, preferably 0.5 ± 0.02 M; the alkaline solution includes at least one solution of KOH and NaOH, preferably KOH; the concentration of the alkaline solution is 0.01–10.0 M, preferably 1.0 ± 0.2 M. The catholyte is an alkaline solution, including at least one solution of KOH and NaOH, preferably KOH; the concentration of the alkaline solution is 0.01–10.0 M, preferably 1.0 ± 0.2 M. The working electrode (anode) is a palladium-based electrode, and the counter electrode (cathode) includes at least one of graphite rod, platinum sheet, and platinum-plated titanium felt, preferably a graphite rod; the reference electrode is Hg / HgO. Activity is tested using linear sweep voltammetry (LSV) at a scan rate of 5–100 mV / s. -1 The preferred value is: 20±0.1mV s -1 The test range is 0-1.5V vs. RHE.

[0029] Preferably, the low-load palladium-based electrode is used for 500mA cm -2 The above industrial-grade current density is used for the electro-oxidation of formaldehyde wastewater to produce hydrogen.

[0030] Compared with the prior art, the technical advantages and beneficial effects of the present invention are as follows:

[0031] 1. Simple and efficient preparation method, avoiding high-temperature agglomeration: This invention uses a one-step atomic self-displacement method to prepare palladium-based electrodes under mild conditions without the need for high-temperature calcination. This method fundamentally avoids the severe agglomeration problem of palladium nanoparticles caused by traditional high-temperature processes, and significantly improves the dispersion of palladium nanoparticles on the carrier surface.

[0032] 2. Significantly reduced precious metal usage, resulting in outstanding economic cost advantages: This invention successfully prepared a palladium-based electrode with high formaldehyde electro-oxidation activity, while optimizing the palladium loading to approximately 0.06 mg / cm³. -2 The low level of palladium significantly reduced the amount of precious metal used and the production cost.

[0033] 3. Industrial-grade formaldehyde wastewater degradation system: The electrode of this invention is used for the electrochemical oxidation treatment of formaldehyde-containing wastewater. When tested in a mixed electrolyte composed of 0.5M HCHO and 1.0M KOH, it achieves a high current-to-temperature (ΔA) of approximately 1400 mA·cm⁻¹ at 1.5V vs. RHE potential. -2 The industrial-grade current density exhibits outstanding catalytic activity. This performance far surpasses traditional chemical oxidation and biodegradation methods, fully demonstrating its enormous application potential and technological advantages in treating industrial-scale formaldehyde wastewater, and providing a feasible solution for efficient, economical, and environmentally friendly formaldehyde wastewater treatment.

[0034] In summary, this invention effectively solves the problem of palladium particle agglomeration and realizes the controllable design of palladium loading on the electrode, which has broad practical application prospects in the fields of formaldehyde wastewater purification and clean energy production. Attached Figure Description

[0035] To further understand the present invention, detailed descriptions are provided below with examples, and the palladium-based electrode obtained by the present invention is illustrated with accompanying drawings. Wherein:

[0036] Figure 1 Scanning electron microscope (SEM) image and elemental distribution map (EDS) of the palladium-based electrode prepared in Example 1 of the present invention.

[0037] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the palladium-based electrode prepared in Example 1 of the present invention.

[0038] Figure 3 The linear sweep voltammetry curve is shown for the palladium-based electrode prepared in Example 1 of the present invention.

[0039] Figure 4 The linear sweep voltammetry curve of the palladium-based electrode prepared in Comparative Example 1 of the present invention is shown.

[0040] Figure 5 Scanning electron microscope (SEM) images of the surface (left) and cross-section (right) of the palladium-based electrode prepared in Example 2 of the present invention.

[0041] Figure 6 The X-ray diffraction (XRD) pattern of the palladium-based electrode prepared in Example 2 of the present invention.

[0042] Figure 7 The linear sweep voltammetry curve of the palladium-based electrode prepared in Example 2 of the present invention is shown.

[0043] Figure 8 A scanning electron microscope (SEM) image of the palladium-based electrode prepared in Example 3 of the present invention.

[0044] Figure 9 The image shows the X-ray diffraction (XRD) pattern of the palladium-based electrode prepared in Example 3 of this invention.

[0045] Figure 10 The linear sweep voltammetry curve is shown for the palladium-based electrode prepared in Example 3 of the present invention.

[0046] Figure 11 The linear sweep voltammetry curve of the palladium-based electrode prepared in Example 6 of the present invention is shown.

[0047] Figure 12 The linear sweep voltammetry curve of the palladium-based electrode prepared in Example 7 of the present invention is shown. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0049] Example 1

[0050] This embodiment provides a low-loading palladium-based electrode, which is prepared by the following method:

[0051] (1) Preparation of palladium-based composite solution: PdCl2 (1.13 mM), KBr (130 mM), NaCl (36 mM), and F127 (0.79 mM) were dissolved in water and mixed thoroughly. The pH was then adjusted to 1 with HCl to form a composite solution. The composite solution was then diluted with approximately 20 mL of water. -1 Nitrogen gas was introduced at a flow rate of approximately 20 minutes to fully remove dissolved oxygen, resulting in an oxygen-free composite solution.

[0052] (2) Synthesis of palladium-based electrode: A nickel foam support (1.0cm × 2.0cm × 0.3mm) was ultrasonically cleaned with ethanol, acetone, and hydrochloric acid for 15 min each, then immersed in the composite solution obtained in step (1) and reacted in a water bath at 30℃ for 12 h to allow the palladium component in the composite solution to fully react with the surface of the nickel foam support. After the reaction, the sample was removed, rinsed thoroughly with deionized water to remove residual reactants and byproducts, and then dried in a vacuum drying oven at 60℃ for 10 h to obtain the palladium-based electrode, as shown below. Figure 1 As shown, the palladium-based electrode has a nanoporous morphology, and the palladium is uniformly dispersed and loaded on the nickel foam support. Figure 2 The XRD pattern of the palladium-based electrode shows that only Ni characteristic peaks belonging to the nickel foam substrate are present, with no palladium characteristic peaks. This indicates that the palladium loading is extremely low. ICP quantification shows that the palladium content in the nickel foam per square centimeter of the palladium-based electrode is 0.29 mg / cm². -2 .

[0053] Performance testing: The anolyte was an aqueous solution of 0.5M HCHO and 1.0M KOH, and the catholyte was an aqueous solution of 1.0M KOH. A three-electrode system was used (working electrode: palladium-based electrode; counter electrode: graphite rod; reference electrode: Hg / HgO); the test scan rate was 20 mV / s. -1 The test range is 0-1.5V vs. RHE. For example... Figure 3As shown, at potentials of 1.0V vs. RHE and 1.5V vs. RHE, a current of 800mA cm can be achieved respectively. -2 and 1400mA cm -2 Industrial-grade current density.

[0054] Comparative Example 1

[0055] The palladium-based electrode prepared in this comparative example is basically prepared using the same method as in Example 1. The difference is that no complexing agent, reaction promoter, or surfactant is added to the composite solution. The pretreated nickel foam carrier is immersed in the solution and reacted at 30°C for 12 hours. The sample is then removed, thoroughly rinsed with deionized water, and subsequently dried in a vacuum drying oven at 60°C for 10 hours to obtain the palladium-based electrode. Figure 4 The linear sweep voltammetry (LSV) activity curve of the palladium-based electrode prepared in Comparative Example 1 in the electrocatalytic oxidation of formaldehyde shows a value of 290 mA cm⁻¹ at 1.0 V vs. RHE potential. -2 The current density is much lower than that of Example 1, and its electrocatalytic activity is much lower.

[0056] Example 2

[0057] This embodiment provides a low-loading palladium-based electrode, which is prepared by the following method:

[0058] (1) Preparation of the palladium-based composite solution: PdCl2 (9.02 mM), KBr (130 mM), NaCl (36 mM), and F127 (0.79 mM) were dissolved in water and mixed thoroughly. The pH was then adjusted to 1 with HCl to form the composite solution. The composite solution was then diluted with approximately 20 mL of water. -1 Nitrogen gas was introduced at a flow rate of approximately 20 minutes to fully remove dissolved oxygen, resulting in an oxygen-free composite solution.

[0059] (2) Synthesis of palladium-based electrode: A nickel foam support (1.0cm × 2.0cm × 0.3mm) was ultrasonically cleaned with ethanol, acetone, and hydrochloric acid for 15 min each, then immersed in the composite solution obtained in step (1) and reacted in a water bath at 30℃ for 12 h to allow the palladium component in the composite solution to fully react with the surface of the nickel foam support. After the reaction, the sample was removed, rinsed thoroughly with deionized water to remove residual reactants and byproducts, and then dried in a vacuum drying oven at 60℃ for 10 h to obtain the palladium-based electrode, as shown below. Figure 5 As shown, the palladium-based electrode has a nanorod morphology and is distributed very uniformly on the surface of the nickel foam substrate. Figure 6The XRD pattern of the palladium-based electrode shows the presence of characteristic Ni peaks attributable to the nickel foam substrate and characteristic peaks attributable to palladium. ICP quantification indicates that the palladium content in the nickel foam per square centimeter of the palladium-based electrode is 1.92 mg / cm². -2 .

[0060] Performance testing: The anolyte was an aqueous solution of 0.5M HCHO and 1.0M KOH, and the catholyte was an aqueous solution of 1.0M KOH. A three-electrode system was used (working electrode: palladium-based electrode; counter electrode: graphite rod; reference electrode: Hg / HgO); the test scan rate was 20 mV / s. -1 The test range is 0-1.5V vs. RHE. For example... Figure 7 As shown, at a potential of 1.0V vs. RHE, a current of 540mA cm⁻¹ can be achieved. -2 It achieves industrial-grade current density and performs well.

[0061] Example 3

[0062] This embodiment provides a low-loading palladium-based electrode, which is prepared by the following method:

[0063] (1) Preparation of palladium-based composite solution: PdCl2 (0.28 mM), KBr (130 mM), NaCl (36 mM), and F127 (0.79 mM) were dissolved in water and mixed thoroughly. The pH was then adjusted to 1 with HCl to form a composite solution. The composite solution was then diluted with approximately 20 mL of water. -1 Nitrogen gas was introduced at a flow rate of approximately 20 minutes to fully remove dissolved oxygen, resulting in an oxygen-free composite solution.

[0064] (2) Synthesis of palladium-based electrode: A nickel foam support (1.0cm × 2.0cm × 0.3mm) was ultrasonically cleaned with ethanol, acetone, and hydrochloric acid for 15 min each, then immersed in the composite solution obtained in step (1) and reacted in a water bath at 30℃ for 12 h to allow the palladium component in the composite solution to fully react with the surface of the nickel foam support. After the reaction, the sample was removed, rinsed thoroughly with deionized water to remove residual reactants and byproducts, and then dried in a vacuum drying oven at 60℃ for 10 h to obtain the palladium-based electrode, as shown below. Figure 8 As shown, the palladium-based electrode has a nanoparticle morphology with a particle size of approximately 100 nm. Figure 9 The XRD pattern of the palladium-based electrode shows that only Ni characteristic peaks, belonging to the nickel foam substrate, are present, with no Pd characteristic peaks. ICP quantification indicates that the palladium content in the nickel foam per square centimeter of the palladium-based electrode is 0.06 mg / cm². -2 .

[0065] Performance testing: The anolyte was an aqueous solution of 0.5M HCHO and 1.0M KOH, and the catholyte was an aqueous solution of 1.0M KOH. A three-electrode system was used (working electrode: palladium-based electrode; counter electrode: graphite rod; reference electrode: Hg / HgO); the test scan rate was 20 mV / s. -1 The test range is 0-1.5V vs. RHE. For example... Figure 10 As shown, at a potential of 1.0V vs. RHE, a current of 550mA cm⁻¹ can be achieved. -2 It achieves industrial-grade current density and performs well.

[0066] Example 4

[0067] This embodiment provides a low-loading palladium-based electrode, which is prepared by the following method:

[0068] (1) Preparation of the palladium-based composite solution: PdCl2 (2.26 mM), KBr (100 mM), NaCl (36 mM), and F127 (0.79 mM) were dissolved in water and mixed thoroughly. The pH was then adjusted to 1 with HCl to form the composite solution. The composite solution was then diluted with approximately 20 mL of water. -1 Nitrogen gas was introduced at a flow rate of approximately 20 minutes to fully remove dissolved oxygen, resulting in an oxygen-free composite solution.

[0069] (2) Synthesis of palladium-based electrode: A nickel foam support (1.0 cm × 2.0 cm × 0.3 mm) was ultrasonically cleaned with ethanol, acetone, and hydrochloric acid for 15 min each, and then immersed in the composite solution obtained in step (1). The mixture was then kept in a water bath at 30 °C for 12 h to allow the palladium component in the composite solution to fully react with the surface of the nickel foam support. After the reaction was completed, the sample was removed and thoroughly rinsed with deionized water to remove residual reactants and byproducts. The sample was then dried in a vacuum drying oven at 60 °C for 10 h to obtain the palladium-based electrode.

[0070] Performance testing: The anolyte was an aqueous solution of 0.5M HCHO and 1.0M KOH, and the catholyte was an aqueous solution of 1.0M KOH. A three-electrode system was used (working electrode: palladium-based electrode; counter electrode: graphite rod; reference electrode: Hg / HgO); the test scan rate was 20 mV / s. -1 The test range is 0–1.5V vs. RHE. At a potential of 1.0V vs. RHE, a current of 720mA can be achieved. -2 It has an industrial-grade current density and good catalytic effect.

[0071] Example 5

[0072] This embodiment provides a low-loading palladium-based electrode, which is prepared by the following method:

[0073] (1) Preparation of the palladium-based composite solution: PdCl2 (1.13 mM), KBr (130 mM), NaCl (30 mM), and F127 (0.79 mM) were dissolved in water and mixed thoroughly. The pH was then adjusted to 1 with HCl to form the composite solution. The composite solution was then diluted with approximately 20 mL of water at a time. -1 Nitrogen gas was introduced at a flow rate of approximately 20 minutes to fully remove dissolved oxygen, resulting in an oxygen-free composite solution.

[0074] (2) Synthesis of palladium-based electrode: A nickel foam support (1.0 cm × 2.0 cm × 0.3 mm) was ultrasonically cleaned for 15 min each with ethanol, acetone, and hydrochloric acid, respectively. Then, it was immersed in the composite solution obtained in step (1) and reacted at 80 °C for 3 h to allow the palladium component in the composite solution to fully react with the surface of the nickel foam support. After the reaction, the sample was removed, thoroughly rinsed with deionized water to remove residual reactants and byproducts, and then dried in a vacuum drying oven at 60 °C for 10 h to obtain the palladium-based electrode.

[0075] Example 6

[0076] This embodiment provides a low-loading palladium-based electrode, which is prepared by the following method:

[0077] (1) Preparation of palladium-based composite solution: Pd(NO3)2 (1.20 mM), KBr (100 mM), KCl (36 mM), and F127 (0.79 mM) were dissolved in water and mixed thoroughly. The pH was then adjusted to 1 with HNO3 to form a composite solution. The composite solution was then diluted with approximately 20 mL of water. -1 Nitrogen gas was introduced at a flow rate of approximately 30 minutes to fully remove dissolved oxygen, resulting in an oxygen-free composite solution.

[0078] (2) Synthesis of palladium-based electrode: A nickel foam support (1.0 cm × 2.0 cm × 0.3 mm) was ultrasonically cleaned with ethanol, acetone, and hydrochloric acid for 15 min each, and then immersed in the composite solution obtained in step (1). The reaction was carried out in a water bath at 40 °C for 6 h to allow the palladium component in the composite solution to fully react with the surface of the nickel foam support. After the reaction was completed, the sample was taken out and thoroughly rinsed with deionized water to remove residual reactants and byproducts. Then it was dried in a vacuum drying oven at 60 °C for 10 h to obtain the palladium-based electrode.

[0079] Performance testing: The anolyte was an aqueous solution of 0.5M HCHO and 1.0M KOH, and the catholyte was an aqueous solution of 1.0M KOH. A three-electrode system was used (working electrode: palladium-based electrode; counter electrode: graphite rod; reference electrode: Hg / HgO); the test scan rate was 20 mV / s. -1The test range is 0–1.5V vs. RHE. At a potential of 1.0V vs. RHE, a current of 640mA cm⁻¹ can be achieved. -2 It has an industrial-grade current density and good catalytic effect.

[0080] Example 7

[0081] This embodiment provides a low-loading palladium-based electrode, which is prepared by the following method:

[0082] (1) Preparation of palladium-based composite solution: Pd(C2H3O2)2 (1.50 mM), KBr (100 mM), KCl (36 mM), and F127 (0.79 mM) were dissolved in water and mixed thoroughly. The pH was then adjusted to 1 with HNO3 to form a composite solution. The composite solution was then diluted with approximately 20 mL of water. -1 Nitrogen gas was introduced at a flow rate of approximately 30 minutes to fully remove dissolved oxygen, resulting in an oxygen-free composite solution.

[0083] (2) Synthesis of palladium-based electrode: A nickel foam support (1.0 cm × 2.0 cm × 0.3 mm) was ultrasonically cleaned with ethanol, acetone, and hydrochloric acid for 15 min each, and then immersed in the composite solution obtained in step (1). The mixture was then kept in a water bath at 50 °C for 6 h to allow the palladium component in the composite solution to fully react with the surface of the nickel foam support. After the reaction was completed, the sample was removed and thoroughly rinsed with deionized water to remove residual reactants and byproducts. The sample was then dried in a vacuum drying oven at 60 °C for 10 h to obtain the palladium-based electrode.

[0084] Performance testing: The anolyte was an aqueous solution of 0.5M HCHO and 1.0M KOH, and the catholyte was an aqueous solution of 1.0M KOH. A three-electrode system was used (working electrode: palladium-based electrode; counter electrode: graphite rod; reference electrode: Hg / HgO); the test scan rate was 20 mV / s. -1 The test range is 0–1.5V vs. RHE. At a potential of 1.0V vs. RHE, a current of 790 mA cm⁻¹ can be achieved. -2 It has an industrial-grade current density and good catalytic effect.

[0085] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a low-loading palladium-based electrode, characterized in that, Includes the following steps: (1) Preparation of palladium-based composite solution: Dissolve palladium salt, complexing agent, reaction promoter and surfactant in water, mix evenly, and then adjust the pH to 1-3 with acid to form composite solution; An inert gas is introduced into the composite solution to remove dissolved oxygen, resulting in an oxygen-deoxygenated composite solution. (2) Synthesis of palladium-based electrode: The metal foam carrier is immersed in the palladium-based composite solution obtained in step (1) and kept at a temperature range of 25-80℃ for 1.0-20h. After the reaction is completed, the sample is taken out, rinsed with deionized water to remove residual reactants and by-products, and then dried to obtain the palladium-based electrode.

2. The preparation method according to claim 1, characterized in that, In step (1), the palladium salt is at least one of PdCl2, Pd(NO3)2, and Pd(C2H3O2)2; the complexing agent is at least one of KBr and NaBr; the reaction promoter is at least one of NaCl and KCl; the surfactant is at least one of F127 and F68; and the acid is at least one of HCl, H2SO4, and HNO3.

3. The preparation method according to claim 1, characterized in that, In step (1), the flow rate of the inert gas is 10-40 mL / min. -1 The time is 10-30 minutes; the inert gas is nitrogen or argon.

4. The preparation method according to claim 1, characterized in that, In step (1), the palladium-based composite solution has a molar concentration of 0.28-11.28 mM for the palladium salt, a molar concentration of 10-200 mM for the complexing agent, a molar concentration of 1.0-50 mM for the reaction promoter, and a molar concentration of 0.1-1.0 mM for the surfactant.

5. The preparation method according to claim 1, characterized in that, In step (2), the metal foam carrier is nickel foam, copper foam, iron foam, or cobalt foam.

6. The preparation method according to claim 1, characterized in that, In step (2), the temperature is controlled by a water bath or an oil bath; the drying conditions are: drying in a vacuum drying oven at 25-60℃ for 2-10 hours.

7. The low-load palladium-based electrode prepared by the preparation method according to any one of claims 1-6.

8. The low-loading palladium-based electrode according to claim 7, characterized in that, The palladium loading in the palladium-based electrode is 0.06–1.92 mg / cm³. -2 .

9. The application of the low-load palladium-based electrode according to claim 7 or 8 in the electrocatalytic oxidation of formaldehyde wastewater to produce hydrogen.

10. The application method according to claim 9, characterized in that, The low-load palladium-based electrode is used for 500mA cm -2 The above industrial-grade current density is used for the electro-oxidation of formaldehyde wastewater to produce hydrogen.

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