Titanium-based ruthenium monatomic catalytic membrane electrode and preparation method and application thereof

Abstract

The invention relates to a titanium-based ruthenium monatomic catalytic membrane electrode and a preparation method and application thereof.The preparation method comprises the following steps that a titanium filter element is sequentially subjected to cleaning, first dipping and calcination, and the pretreated titanium filter element is obtained; and mixing a ruthenium source, an organic ligand and the pretreated titanium filter element, and sequentially carrying out second dipping, freeze-drying and annealing treatment to obtain the titanium-based ruthenium monatomic catalytic membrane electrode. The catalytic membrane electrode disclosed by the invention has high specific surface area and uniformly distributed monatomic active sites, the electro-catalytic performance of the membrane electrode is enhanced, and the service life of the membrane electrode is prolonged. According to the preparation method, the dispersity of a ruthenium source is improved by utilizing an organic ligand, the generation of ruthenium single atoms is promoted, structural fixation is realized through freeze-drying, and ruthenium is ensured to exist in a membrane electrode in the form of single atoms after being annealed. On the basis of keeping efficient removal of pollutants, the energy consumption can be reduced, the generation of intermediate byproducts is reduced, resource recovery is also facilitated, and the economic benefit is improved.

Description

Technical Field

[0001] The present invention relates to the field of electrocatalysis technology, and relates to a catalytic membrane electrode and a preparation method and application thereof, and in particular to a titanium-based ruthenium single-atom catalytic membrane electrode and a preparation method and application thereof. Background Art

[0002] Chlorophenol pollutants are widely present in multiple industries such as coal chemical industry, petroleum refining and pharmacy. Due to its high toxicity, it is impossible to adopt biological treatment method to degrade. In the prior art, for the wastewater treatment containing extremely high concentration phenols (such as> 1000mg / L), solvent extraction is the mainstream method, and the method can realize water purification and phenols recovery simultaneously. However, due to the ionization of phenols, the extraction efficiency is lower under alkaline or neutral conditions, while bringing high energy consumption, the consumption of organic solvents can also be improved. In addition, extraction is only applicable to the phenol wastewater with higher concentration.

[0003] Electrocatalytic hydrogenation is an emerging processing technology that can reduce phenolic compounds under mild conditions by cathode reduction. The hydrogenated products (such as cyclohexanol) prepared can be used as fuel and chemical fuel, and the boiling point of the hydrogenated products is significantly reduced, and they can be separated by simple distillation and extraction. This method can not only reduce production costs, but also prepare products with high application value and great application potential.

[0004] CN117430209A discloses a method for preparing a Cu-ZnO membrane electrode with a titanium filter as a substrate and its application in the in-situ electro-Fenton degradation of pollutants in water. The Cu-ZnO catalytic layer is uniformly grown on the titanium filter substrate by a template control strategy to obtain a penetrating membrane electrode. The membrane electrode can reduce dissolved oxygen molecules in water to hydroxyl radicals as a cathode and is applied to the rapid removal of pollutants in water. However, the membrane electrode needs to be pre-exposed to oxygen in the wastewater before use, which increases energy consumption, and the organic matter in the water is oxidized and removed, which cannot be recycled and has low economic benefits. CN112774668A discloses a method for preparing a single-atom noble metal / graphene catalyst for hydrodechlorination of para-chlorophenol. The noble metal salt is loaded on graphene by electrochemical intercalation and ultrasonic stripping of graphite, and then reduced by microwave radiation to obtain a single-atom noble metal / graphene catalyst for hydrodechlorination of para-chlorophenol. However, the graphene substrate is difficult to mass produce, and the catalyst needs to use a hydrogen balloon, the reaction conditions are relatively harsh, and the catalyst dispersed in water is difficult to recover after use.

[0005] Ruthenium (Ru)-based catalysts show high activity in electrocatalytic hydrogenation, but traditional electrodes are mostly made by attaching catalyst particles to a conductive substrate using polymers, resulting in fewer catalyst active sites, low specific surface area and poor stability. In contrast, single-atom catalysts exist in the form of single metal atoms dispersed on a carrier, which can maximize the exposure of active sites and significantly improve catalytic efficiency. In addition, due to their unique atomic-level distribution, single-atom catalysts usually show special catalytic selectivity and excellent stability, and can maintain efficient catalytic performance under a variety of reaction conditions.

[0006] The titanium filter element is a new type of penetrating membrane electrode substrate with high chemical stability and a unique porous structure. It can significantly increase the specific surface area of ​​the electrode and provide more reactive sites. At the same time, operating in penetration mode can increase the mass transfer rate and further improve the efficiency of the electrocatalytic hydrogenation reaction.

[0007] Therefore, it has become an urgent problem to provide a titanium-based ruthenium single-atom catalytic membrane electrode by combining ruthenium single atoms with a titanium filter element substrate, which provides a potential solution for the treatment of chlorophenol wastewater. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a titanium-based ruthenium single-atom catalytic membrane electrode and its preparation method and application. The catalytic membrane electrode has a high specific surface area and uniformly distributed single-atom active sites, which enhances the electrocatalytic performance and service life of the membrane electrode. The present invention uses organic ligands to improve the dispersibility of the ruthenium source, promote the generation of ruthenium single atoms, and achieves structural fixation through freeze-drying to ensure that ruthenium exists in the membrane electrode in the form of single atoms after annealing. On the basis of maintaining efficient removal of pollutants, the present invention can not only reduce energy consumption and reduce the generation of intermediate by-products, but also facilitate resource recovery and improve economic benefits.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In the first aspect, the present invention provides a method for preparing a titanium-based ruthenium single-atom catalytic membrane electrode, the preparation method comprising the following steps: washing, first impregnating and calcining a titanium filter element in sequence to obtain a pretreated titanium filter element; mixing a ruthenium source, an organic ligand and the pretreated titanium filter element, and sequentially performing a second impregnation, freeze-drying and annealing treatment to obtain the titanium-based ruthenium single-atom catalytic membrane electrode, wherein the organic ligand comprises polyvinyl pyrrolidone and / or polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol diacrylate.

[0011] The catalytic membrane electrode of the present invention has a high specific surface area and uniformly distributed single-atom active sites, which enhances the electrocatalytic performance and service life of the membrane electrode. The present invention uses organic ligands to improve the dispersibility of the ruthenium source, promotes the generation of ruthenium single atoms, and achieves structural fixation through freeze-drying to ensure that ruthenium exists in the membrane electrode in the form of single atoms after annealing. On the basis of maintaining efficient removal of pollutants, the present invention can not only reduce energy consumption and reduce the generation of intermediate by-products, but also facilitate resource recovery and improve economic benefits.

[0012] Preferably, the cleaning in step (1) includes a first cleaning, an acid etching and a second cleaning performed sequentially.

[0013] Preferably, the one-time washing comprises alkali washing, alcohol washing and water washing performed in sequence.

[0014] Preferably, the detergent for alkali washing includes any one of sodium hydroxide solution, potassium hydroxide solution or calcium hydroxide solution, or a combination of at least two of them. Typical but non-limiting combinations include a combination of sodium hydroxide solution and potassium hydroxide solution, or a combination of sodium hydroxide solution, potassium hydroxide solution and calcium hydroxide solution.

[0015] Preferably, the mass concentration of the alkaline washing detergent is 3% to 6%, for example, 3%, 3.5%, 4%, 5% or 6%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] Preferably, the detergent for the alcohol wash comprises ethanol.

[0017] Preferably, the etchant of the acid etching comprises oxalic acid.

[0018] Preferably, the mass concentration of oxalic acid is 8% to 12%, for example, 8%, 9%, 10%, 11% or 12%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the etching temperature of the acid etching is 80° C. to 120° C., for example, 80° C., 90° C., 100° C., 110° C. or 120° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the etching time of the acid etching is 0.5 h to 1.5 h, for example, 0.5 h, 0.8 h, 1 h, 1.2 h or 1.5 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] Preferably, the detergent for the secondary cleaning comprises deionized water.

[0022] Preferably, the first impregnation includes an alkali impregnation, a first acid impregnation and a second acid impregnation performed sequentially.

[0023] Preferably, the alkaline impregnation solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0024] Preferably, the mass concentration of the alkali impregnation solution is 10% to 20%, for example, 10%, 12%, 14%, 16%, 18% or 20%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the alkali impregnation time is 2 h to 8 h, for example, 2 h, 3 h, 4 h, 5 h, 7 h or 8 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the alkali impregnation temperature is 150°C to 200°C, for example, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the first acid-impregnating solution comprises hydrochloric acid and / or nitric acid.

[0028] Preferably, the mass concentration of the first acid impregnation solution is 1% to 5%, for example, 1%, 2%, 3%, 4% or 5%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the immersion time of the first acid immersion is 1 h to 2 h, for example, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h or 2 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the immersion temperature of the first acid immersion is 20°C to 30°C, for example, 20°C, 22°C, 24°C, 26°C, 28°C or 30°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, a third cleaning is performed after the first acid dipping and before the second acid dipping.

[0032] Preferably, the detergent for the third wash comprises deionized water.

[0033] Preferably, the endpoint of the third cleaning is to make the pH value of the washing liquid 6.5-7.5, for example, it can be 6.5, 6.8, 7, 7.2 or 7.5, but it is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0034] Preferably, the impregnation solution of the second acid impregnation comprises a mixture of ammonium fluorotitanate and boric acid.

[0035] The present invention can further optimize the titanium dioxide structure formed on the surface of the titanium filter element by alkali impregnation and the first acid impregnation by further regulating the type of the impregnation solution of the second acid impregnation, thereby increasing the specific surface area of ​​the membrane electrode, which is beneficial to the loading of ruthenium single atoms.

[0036] Preferably, in the impregnation solution of the second acid impregnation, the concentration of ammonium fluorotitanate is 4 mmol / L to 6 mmol / L, for example, 4 mmol / L, 4.5 mmol / L, 5 mmol / L, 5.5 mmol / L or 6 mmol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, in the impregnation solution of the second acid impregnation, the concentration of boric acid is 40 mmol / L to 60 mmol / L, for example, 40 mmol / L, 45 mmol / L, 50 mmol / L, 55 mmol / L or 60 mmol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the immersion time of the second acid immersion is 20 h to 30 h, for example, 20 h, 22 h, 24 h, 26 h, 28 h or 30 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the immersion temperature of the second acid immersion is 20°C to 30°C, for example, 20°C, 22°C, 24°C, 26°C, 28°C or 30°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the calcination in step (1) comprises a first stage calcination and a second stage calcination performed sequentially.

[0041] Preferably, the atmosphere of the primary calcination comprises an oxygen-containing atmosphere.

[0042] Preferably, the oxygen-containing atmosphere includes an air atmosphere and / or an oxygen atmosphere.

[0043] Preferably, the holding temperature of the first stage calcination is 350°C to 450°C, for example, 350°C, 380°C, 400°C, 420°C or 450°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] Preferably, the holding time of the calcination stage is 1 h to 3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] The present invention can stabilize the titanium dioxide structure formed by the first acid impregnation and the second acid impregnation on the surface of the titanium filter element through a one-stage calcination. Furthermore, the stability of the membrane electrode can be further improved by regulating the insulation temperature and insulation time of the one-stage calcination.

[0046] Preferably, the atmosphere of the second-stage calcination includes a nitrogen-containing atmosphere.

[0047] Preferably, the nitrogen-containing atmosphere comprises a mixture of ammonia and nitrogen.

[0048] Preferably, in the mixed gas, the volume ratio of ammonia to nitrogen is 1:(8-12), for example, it can be 1:8, 1:9, 1:10, 1:11 or 1:12, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the holding temperature of the second-stage calcination is 450°C to 550°C, for example, 450°C, 480°C, 500°C, 520°C or 550°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] Preferably, the holding time of the second-stage calcination is 3 h to 5 h, for example, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] The present invention can achieve nitrogen doping of the titanium filter element and increase the oxygen vacancy concentration in the membrane electrode through two-stage calcination. Further, by regulating the insulation temperature and insulation time of the two-stage calcination, the adsorption of the ruthenium source on the vacancies can be promoted, the dispersibility of the ruthenium source can be improved, the generation of ruthenium in a single atomic state can be promoted, and the electrical performance of the membrane electrode can be improved.

[0052] Preferably, the ruthenium source in step (2) comprises any one of ruthenium chloride, ruthenium acetate or ruthenium bromide, or a combination of at least two of them. Typical but non-limiting combinations include a combination of ruthenium chloride and ruthenium acetate, or a combination of ruthenium chloride, ruthenium acetate and ruthenium bromide.

[0053] Preferably, the molar concentration of the ruthenium source is 80mmol / L to 100mmol / L, for example, 80mmol / L, 85mmol / L, 90mmol / L, 95mmol / L or 100mmol / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] The present invention can further improve the dispersibility of the ruthenium source and promote the generation of ruthenium single atoms by further regulating the molar concentration of the ruthenium source, thereby improving the selectivity of the membrane electrode. Within the preferred molar concentration range of the ruthenium source, the dispersibility of the ruthenium source is high and the selectivity of the membrane electrode is high.

[0055] Preferably, the mass concentration of the organic ligand is 40 g / L to 60 g / L, for example, 40 g / L, 45 g / L, 50 g / L, 55 g / L or 60 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] The organic ligand can coordinate with the ruthenium source to avoid the aggregation of the ruthenium source and promote the generation of ruthenium single atoms. Furthermore, the present invention can further improve the dispersibility of the ruthenium source and promote the generation of ruthenium single atoms by regulating the mass concentration of the organic ligand, thereby improving the selectivity of the membrane electrode. Within the preferred mass concentration range of the organic ligand, the dispersibility of the ruthenium source is high and the selectivity of the membrane electrode is high.

[0057] Preferably, the immersion temperature of the second immersion in step (2) is 40°C to 60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] Preferably, the second impregnation time is 18 h to 24 h, for example, 18 h, 20 h, 21 h, 22 h, 23 h or 24 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] Preferably, in step (2), pre-lyophilization is performed after the second impregnation and before lyophilization.

[0060] Preferably, the pre-freeze-drying method comprises pre-freeze-drying using liquid nitrogen.

[0061] Preferably, the freeze-drying cold trap temperature is -60°C to -40°C, for example, it can be -60°C, -55°C, -50°C, -45°C or -40°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0062] Preferably, the duration of the freeze-drying is 24 h to 48 h, for example, 24 h, 28 h, 32 h, 36 h, 42 h or 48 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0063] The present invention achieves structural fixation through freeze drying, ensures that the ruthenium source is fixed in the membrane electrode in a highly dispersed form, and can also promote the formation of ruthenium single atoms. Furthermore, the present invention can further improve the dispersion of the ruthenium source on the membrane electrode surface by regulating the freeze-drying cold trap temperature and duration, promote the formation of ruthenium single atoms, and improve the selectivity of the membrane electrode.

[0064] Preferably, the ambient atmosphere of the annealing treatment in step (2) includes a reducing atmosphere.

[0065] Preferably, the reducing atmosphere comprises a hydrogen atmosphere.

[0066] Preferably, the holding temperature of the annealing treatment is 150°C to 250°C, for example, 150°C, 175°C, 200°C, 225°C or 250°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0067] Preferably, the holding time of the annealing treatment is 1 h to 3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0068] The present invention can further regulate the dispersion of ruthenium in the membrane electrode and promote the formation of ruthenium single atoms by further regulating the insulation temperature and insulation time of the annealing treatment. Within the preferred insulation temperature and insulation time of the annealing treatment, the reduction degree of the ruthenium source is high, the dispersion is good, the purity of the ruthenium single atoms is high, and the selectivity of the membrane electrode is further improved.

[0069] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0070] (1) After the titanium filter element is first cleaned, it is acid-etched with an oxalic acid solution, and then secondly cleaned with deionized water to obtain a pretreated titanium filter element.

[0071] (2) The pretreated titanium filter element is sequentially subjected to alkali impregnation, first acid impregnation, third cleaning, and second acid impregnation, and then calcined to obtain a titanium filter element containing nitrogen-doped titanium dioxide.

[0072] (3) Mixing a ruthenium source and an organic ligand to obtain a mixed solution, placing the nitrogen-doped titanium dioxide titanium filter element described in step (2) in the mixed solution, and immersing it at 40° C. to 60° C. for 18 h to 24 h to obtain the nitrogen-doped titanium dioxide titanium filter element after ruthenium adsorption.

[0073] (4) The titanium filter element containing nitrogen-doped titanium dioxide after ruthenium adsorption is pre-freeze-dried in liquid nitrogen, and after freeze-drying in a freeze dryer, annealed at 150° C. to 250° C. for 1 h to 3 h in a reducing atmosphere to obtain the titanium-based ruthenium single-atom catalytic membrane electrode.

[0074] In a second aspect, the present invention provides a titanium-based ruthenium single-atom catalytic membrane electrode prepared by the preparation method described in the first aspect, and the titanium-based ruthenium single-atom catalytic membrane electrode is applied to the process of chlorophenol wastewater treatment and resource utilization.

[0075] In a third aspect, the present invention provides an electrochemical reactor, which includes a treated water outlet, an anode tank, an anode, a silicone gasket, the titanium-based ruthenium single-atom catalytic membrane electrode described in the second aspect, a cathode tank and a cathode water inlet, which are arranged in sequence.

[0076] Preferably, the operating current of the electrochemical reactor is 10 mA / cm 2 ~80mA / cm 2 , for example, it can be 10mA / cm 2 , 20mA / cm 2 , 40mA / cm 2 、60mA / cm 2 or 80mA / cm 2 , but not limited to the listed values, other unlisted values ​​within the numerical range are also applicable.

[0077] Preferably, the operating voltage of the electrochemical reactor is -1.3V to -0.4V compared to the reversible hydrogen reference electrode, for example, it can be -1.3V, -1.1V, -0.8V, -0.6V or -0.4V, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0078] Preferably, the chlorophenol content of the inlet water of the electrochemical reactor is 1 mg / L to 10000 mg / L, for example, it can be 1 mg / L, 10 mg / L, 100 mg / L, 1000 mg / L or 10000 mg / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0079] Preferably, in the electrochemical reactor, the residence time of the pollutants is 7s to 1800s, for example, 7s, 50s, 150s, 300s, 600s or 1800s, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0080] Preferably, the pH of the inlet water of the electrochemical reactor is 3-11, for example, 3, 5, 7, 9 or 11, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0081] Preferably, 2.8 g / L to 71 g / L of sodium sulfate is also added to the electrochemical reactor, for example, it can be 2.8 g / L, 5 g / L, 10 g / L, 20 g / L, 50 g / L, 70 g / L or 71 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0082] Compared with the prior art, the present invention has at least the following beneficial effects:

[0083] (1) The catalytic membrane electrode of the present invention has a high specific surface area and uniformly distributed single-atom active sites, which enhances the electrocatalytic performance and service life of the membrane electrode.

[0084] (2) The present invention utilizes organic ligands to improve the dispersibility of the ruthenium source, promotes the generation of ruthenium single atoms, and achieves structural fixation through freeze-drying, thereby ensuring that ruthenium exists in the membrane electrode in the form of single atoms after annealing.

[0085] (3) The present invention can not only reduce energy consumption and the generation of intermediate by-products while maintaining high efficiency in removing pollutants, but also achieve a reaction selectivity of up to 87%, thereby facilitating resource recovery and improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 is a TEM image of the titanium-based ruthenium single-atom catalytic film electrode described in Example 1 of the present invention;

[0087] Figure 2 It is a schematic diagram of an electrochemical reactor corresponding to the titanium-based ruthenium single-atom catalytic film electrode of the present invention;

[0088] Figure 3 It is the chlorophenol wastewater treatment process flow chart of the present invention;

[0089] Figure 4 This is a rendering of the organic product obtained by treating chlorophenol wastewater as described in Application Example 1-1 of the present invention;

[0090] Figure 5 It is a chlorophenol removal effect diagram of the chlorophenol wastewater treatment process described in Application Example 1-1 and Application Example 12-Application Example 13 of the present invention under the condition of pH value of 3, 7 or 11;

[0091] Figure 6 This is a rendering of the chlorophenol wastewater treatment process described in Application Example 1-1 of the present invention running continuously for 96 hours;

[0092] Among them, 1-treated water outlet, 2-anode tank, 3-anode, 4-silica gel spacer, 5-titanium-based ruthenium single-atom catalytic membrane electrode, 6-cathode tank and 7-cathode water inlet. DETAILED DESCRIPTION

[0093] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0094] Example 1

[0095] This embodiment provides a method for preparing a titanium-based ruthenium single-atom catalytic membrane electrode, the preparation method comprising the following steps:

[0096] (1) After the titanium filter element is first cleaned, it is etched with a 10% oxalic acid solution at 100° C. for 1 hour, and then secondly cleaned with deionized water to obtain a pretreated titanium filter element; the first cleaning includes cleaning with a 5% sodium hydroxide solution, ethanol and deionized water for 30 minutes each;

[0097] (2) The pretreated titanium filter element is sequentially subjected to alkali impregnation, first acid impregnation, third cleaning and second acid impregnation, and then calcined to obtain a titanium filter element doped with nitrogen-containing titanium dioxide; the alkali impregnation solution is 15% sodium hydroxide solution, the alkali impregnation time is 2 hours, and the impregnation temperature is 180°C; the first acid impregnation solution is 4% hydrochloric acid, the first acid impregnation time is 1 hour, and the impregnation temperature is 25°C; the third cleaning detergent is deionized water, and the washing is performed until the pH value of the washing solution is 7; the second acid impregnation solution is 5mmol / L ammonium fluorotitanate and 50mmol / L boric acid solution, the second acid impregnation time is 24 hours, and the impregnation temperature is 25°C; the first calcination is calcined at 400°C for 2 hours in an air atmosphere; the second calcination is calcined at 500°C for 4 hours in an atmosphere with a volume ratio of ammonia to nitrogen of 1:10;

[0098] (3) preparing a solution containing 90 mmol / L ruthenium chloride and 50 g / L polyvinyl pyrrolidone, placing the nitrogen-doped titanium dioxide titanium filter element described in step (2) in the mixed solution, and immersing it at 50° C. for 20 h to obtain the nitrogen-doped titanium dioxide titanium filter element after ruthenium adsorption;

[0099] (4) The titanium filter element containing nitrogen-doped titanium dioxide after ruthenium adsorption is pre-freeze-dried in liquid nitrogen, and freeze-dried in a freeze dryer at -50°C for 36 hours, and then annealed at 200°C for 2 hours in a hydrogen atmosphere to obtain the titanium-based ruthenium single-atom catalytic membrane electrode.

[0100] Figure 1 This is a TEM image of the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 1 of the present invention. It can be seen from the image that the catalytic membrane electrode contains single ruthenium atoms.

[0101] Example 2

[0102] This embodiment provides a method for preparing a titanium-based ruthenium single-atom catalytic membrane electrode, the preparation method comprising the following steps:

[0103] (1) After the titanium filter element is first cleaned, it is acid-etched with 8% oxalic acid solution at 80° C. for 1.5 hours, and then secondly cleaned with deionized water to obtain a pretreated titanium filter element; the first cleaning includes cleaning with 3% sodium hydroxide solution, ethanol and deionized water for 40 minutes each;

[0104] (2) The pretreated titanium filter element is sequentially subjected to alkali impregnation, first acid impregnation, third cleaning and second acid impregnation, and then calcined to obtain a titanium filter element doped with nitrogen-containing titanium dioxide; the alkali impregnation solution is a 10% potassium hydroxide solution, the alkali impregnation time is 8 hours, and the impregnation temperature is 150°C; the first acid impregnation solution is 1% nitric acid, the first acid impregnation time is 2 hours, and the impregnation temperature is 30°C; the third cleaning detergent is deionized water, and the washing is performed until the pH value of the washing solution is 6.5; the second acid impregnation solution is 4mmol / L ammonium fluorotitanate and 40mmol / L boric acid solution, the second acid impregnation time is 20 hours, and the impregnation temperature is 30°C; the first calcination is calcined at 350°C for 3 hours in an oxygen atmosphere; the second calcination is calcined at 550°C for 3 hours in an atmosphere with a volume ratio of ammonia to nitrogen of 1:12;

[0105] (3) preparing a solution containing 80 mmol / L ruthenium acetate and 40 g / L polyvinyl pyrrolidone, placing the nitrogen-doped titanium dioxide titanium filter element described in step (2) in the mixed solution, and immersing it at 40° C. for 24 h to obtain the nitrogen-doped titanium dioxide titanium filter element after ruthenium adsorption;

[0106] (4) The titanium filter element containing nitrogen-doped titanium dioxide after ruthenium adsorption is pre-freeze-dried in liquid nitrogen, and freeze-dried in a freeze dryer at -40°C for 48 hours, and then annealed at 150°C for 3 hours in a hydrogen atmosphere to obtain the titanium-based ruthenium single-atom catalytic membrane electrode.

[0107] Example 3

[0108] This embodiment provides a method for preparing a titanium-based ruthenium single-atom catalytic membrane electrode, the preparation method comprising the following steps:

[0109] (1) After the titanium filter element is first cleaned, it is acid-etched with a 12% mass concentration oxalic acid solution at 120° C. for 0.5 h, and then secondly cleaned with deionized water to obtain a pretreated titanium filter element; the first cleaning includes cleaning with a 6% potassium hydroxide solution, ethanol and deionized water for 20 min each;

[0110] (2) The pretreated titanium filter element is sequentially subjected to alkali impregnation, first acid impregnation, third cleaning and second acid impregnation, and then calcined to obtain a titanium filter element doped with nitrogen-containing titanium dioxide; the alkali impregnation solution is a 20% calcium hydroxide solution, the alkali impregnation time is 2 hours, and the impregnation temperature is 200°C; the first acid impregnation solution is 5% hydrochloric acid, the first acid impregnation time is 1 hour, and the impregnation temperature is 20°C; the third cleaning detergent is deionized water, and the washing is performed until the pH value of the washing solution is 7.5; the second acid impregnation solution is 6mmol / L ammonium fluorotitanate and 60mmol / L boric acid solution, the second acid impregnation time is 30 hours, and the impregnation temperature is 20°C; the first calcination is calcined at 450°C for 1 hour in an air atmosphere; the second calcination is calcined at 450°C for 5 hours in an atmosphere with a volume ratio of ammonia to nitrogen of 1:8;

[0111] (3) preparing a solution containing 100 mmol / L ruthenium bromide and 60 g / L polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol diacrylate, placing the nitrogen-doped titanium dioxide titanium filter element described in step (2) in the mixed solution, and immersing at 60° C. for 18 h to obtain a nitrogen-doped titanium dioxide titanium filter element after ruthenium adsorption;

[0112] (4) The titanium filter element containing nitrogen-doped titanium dioxide after ruthenium adsorption is pre-freeze-dried in liquid nitrogen, and freeze-dried in a freeze dryer at -60°C for 24 hours, and then annealed at 250°C for 1 hour in a hydrogen atmosphere to obtain the titanium-based ruthenium single-atom catalytic membrane electrode.

[0113] Example 4

[0114] The only difference between this embodiment and embodiment 1 is that, except that the concentration of ruthenium chloride in step (3) is 60 mmol / L, the rest is the same as embodiment 1.

[0115] Example 5

[0116] The only difference between this embodiment and embodiment 1 is that, except that the concentration of ruthenium chloride in step (3) is 130 mmol / L, the rest is the same as embodiment 1.

[0117] Example 6

[0118] The only difference between this embodiment and embodiment 1 is that, except that the concentration of polyvinyl pyrrolidone in step (3) is 35 g / L, the rest is the same as embodiment 1.

[0119] Example 7

[0120] The only difference between this embodiment and embodiment 1 is that, except that the concentration of polyvinyl pyrrolidone in step (3) is 65 g / L, the rest is the same as embodiment 1.

[0121] Example 8

[0122] The only difference between this embodiment and embodiment 1 is that, except for the freeze-drying temperature in step (4) being -70°C, the rest is the same as embodiment 1.

[0123] Example 9

[0124] The only difference between this embodiment and embodiment 1 is that, except for the freeze-drying temperature in step (4) being -30°C, the rest is the same as embodiment 1.

[0125] Example 10

[0126] The only difference between this embodiment and embodiment 1 is that, except that a calcination step is not performed in step (2), the rest is the same as embodiment 1.

[0127] Embodiment 11

[0128] The only difference between this embodiment and embodiment 1 is that, except that the second-stage calcination is not performed in step (2), the rest is the same as embodiment 1.

[0129] Comparative Example 1

[0130] The difference between this comparative example and Example 1 is that, except that polyvinyl pyrrolidone is not added in step (3), the rest is the same as Example 1.

[0131] Comparative Example 2

[0132] The difference between this comparative example and Example 1 is that except that freeze-drying is not performed in step (4), the rest is the same as Example 1.

[0133] Comparative Example 3

[0134] The difference between this comparative example and Example 1 is that, except for the use of a copper filter element in step (1), the rest is the same as Example 1.

[0135] Application Example 1-1

[0136] This application example provides a process for treating chlorophenol wastewater using an electrochemical reactor, and the process parameters are as follows:

[0137] The anode is a titanium mesh with a pore size of 1 mm loaded with RuO2, and the membrane cathode is a titanium-based ruthenium single-atom catalytic membrane electrode described in Example 1. The 4-chlorophenol content of the influent is 128 mg / L, the pH value is 7, and the working current is 20 mA / cm 2 , the operating voltage was -1.0 V compared to the reversible hydrogen reference electrode, the salt concentration was 14 g / L sodium sulfate, and the residence time was 180 s.

[0138] Figure 2Schematic diagram of the electrochemical reactor corresponding to the titanium-based ruthenium single-atom catalytic membrane electrode of the present invention, wherein the positive and negative electrodes are separated by a 1 mm silicone pad. Figure 3 It is a schematic diagram of the process of applying the present invention to the resource recovery of chlorophenol wastewater, Figure 4 This is a rendering of the organic products obtained by treating chlorophenol wastewater as described in Application Example 1-1 of the present invention. It can be seen from the figure that at a residence time of 180s, the removal rate of 4-chlorophenol is 99%, the main product is cyclohexanol, and the selectivity is 94%. Figure 6 This is the effect of the chlorophenol wastewater treatment process described in Application Example 1-1 of the present invention running continuously for 96 hours. It can be seen from the figure that after 96 hours, the 4-chlorophenol removal rate is 96%, the main product is cyclohexanol, and the selectivity is 94%.

[0139] Application Example 1-2

[0140] This application example provides a process for treating chlorophenol wastewater using an electrochemical reactor, and the process parameters are as follows:

[0141] The anode is a titanium mesh with a pore size of 1 mm loaded with RuO2, and the membrane cathode is a titanium-based ruthenium single-atom catalytic membrane electrode described in Example 1. The 4-chlorophenol content of the influent is 1 mg / L, the pH value is 11, and the working current is 10 mA / cm 2 , the operating voltage was -0.7 V compared to the reversible hydrogen reference electrode, the salt concentration was 2.8 g / L sodium sulfate, and the residence time was 10 s.

[0142] Application Examples 1-3

[0143] This application example provides a process for treating chlorophenol wastewater using an electrochemical reactor, and the process parameters are as follows:

[0144] The anode is a titanium mesh with a pore size of 1 mm loaded with RuO2, and the membrane cathode is a titanium-based ruthenium single-atom catalytic membrane electrode described in Example 1. The 4-chlorophenol content of the influent is 10000 mg / L, the pH value is 3, and the working current is 80 mA / cm 2 The operating voltage was -1.3 V compared to the reversible hydrogen reference electrode, the salt concentration was 71 g / L sodium sulfate, and the residence time was 1800 s.

[0145] Application Example 2

[0146] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 2, the rest is the same as application example 1-1.

[0147] Application Example 3

[0148] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 3, the rest is the same as application example 1-1.

[0149] Application Example 4

[0150] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 4, the rest is the same as application example 1-1.

[0151] Application Example 5

[0152] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 5, the rest is the same as application example 1-1.

[0153] Application Example 6

[0154] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 6, the rest is the same as application example 1-1.

[0155] Application Example 7

[0156] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 7, the rest is the same as application example 1-1.

[0157] Application Example 8

[0158] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 8, the rest is the same as application example 1-1.

[0159] Application Example 9

[0160] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 9, the rest is the same as application example 1-1.

[0161] Application Example 10

[0162] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 10, the rest is the same as application example 1-1.

[0163] Application Example 11

[0164] The only difference between this application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in Example 11, the rest is the same as application example 1-1.

[0165] Application Example 12

[0166] The difference between this application example and application example 1-1 is that, except for the pH value of 3 in the process parameters, the rest are the same as those in application example 1-1.

[0167] Application Example 13

[0168] The difference between this application example and application example 1-1 is that, except for the pH value of 11 in the process parameters, the rest are the same as those in application example 1-1.

[0169] Figure 5 This is the chlorophenol removal effect of the chlorophenol wastewater treatment process described in Application Example 1-1 and Application Example 12-Application Example 13 of the present invention under the condition of pH value of 3, 7 or 11. It can be seen from the figure that at a residence time of 180s, the 4-chlorophenol removal rates are 97%, 99% and 98% respectively.

[0170] Comparative application example 1

[0171] The only difference between this comparative application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in comparative example 1, the rest is the same as application example 1-1.

[0172] Comparative Application Example 2

[0173] The only difference between this comparative application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in comparative example 2, the rest is the same as application example 1-1.

[0174] Comparative Application Example 3

[0175] The only difference between this comparative application example and application example 1-1 is that, except for using the titanium-based ruthenium single-atom catalytic membrane electrode described in comparative example 3, the rest is the same as application example 1-1.

[0176] Test Method

[0177] The products recovered in the corresponding application examples 1-1-application example 13 and comparative application example 1-3 were subjected to gas chromatography analysis. The gas chromatography-mass spectrometry analyzer used was Agilent 7890A-7000C. The column temperature was maintained at 40°C for 5 minutes, and then increased to 200°C at a rate of 10°C / min. The ion signals with m / z of 40 to 140 were detected, and the analysis results were recorded in Table 1.

[0178] Table 1

[0179]

[0180]

[0181] The test results show that:

[0182] (1) It can be seen from Application Example 1-1 to Application Example 13 and Comparative Application Example 1 to Comparative Application Example 3 that the catalytic membrane electrode of the present invention has a high specific surface area and uniformly distributed single-atom active sites, which enhances the electrocatalytic performance and service life of the membrane electrode. The present invention uses organic ligands to improve the dispersibility of the ruthenium source, promote the generation of ruthenium single atoms, and achieves structural fixation through freeze-drying to ensure that ruthenium exists in the membrane electrode in the form of single atoms after annealing. On the basis of maintaining efficient removal of pollutants, the present invention can not only reduce energy consumption and reduce the generation of intermediate by-products, but also facilitate resource recovery and improve economic benefits.

[0183] (2) It can be seen from Application Example 1-1 and Application Example 4-Application Example 5 that the present invention can further improve the removal rate of chlorophenol and the selectivity of the product by further regulating the concentration of the ruthenium source.

[0184] (3) It can be seen from Application Example 1-1 and Application Example 6-Application Example 7 that the present invention can further improve the removal rate of chlorophenol and the selectivity of the product by further regulating the concentration of the organic ligand.

[0185] (4) It can be seen from Application Example 1-1 and Application Example 8-Application Example 9 that the present invention can not only save electric energy but also further improve the removal rate of chlorophenols and the selectivity of the product by further regulating the freeze-drying temperature.

[0186] (5) It can be seen from Application Example 1-1 and Application Example 10-Application Example 11 that the present invention can further improve the removal rate of chlorophenols and the selectivity of the product by regulating the titanium dioxide structure grown on the surface of the titanium filter element and doping nitrogen elements.

[0187] (6) It can be seen from Application Example 1-1 and Application Example 12-Application Example 13 that the present invention can maintain a high removal rate of chlorophenols and a high selectivity of the product within a wide range of wastewater pH values.

[0188] In summary, the catalytic membrane electrode of the present invention has a high specific surface area and uniformly distributed single-atom active sites, which enhances the electrocatalytic performance and service life of the membrane electrode. The present invention uses organic ligands to improve the dispersibility of the ruthenium source, promotes the generation of ruthenium single atoms, and achieves structural fixation through freeze-drying to ensure that ruthenium exists in the membrane electrode in the form of single atoms after annealing. On the basis of maintaining efficient removal of pollutants, the present invention can not only reduce energy consumption and reduce the generation of intermediate by-products, but also facilitate resource recovery and improve economic benefits.

[0189] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a titanium-based ruthenium single-atom catalytic membrane electrode, characterized in that: The preparation method comprises the following steps: (1) sequentially cleaning, first impregnating and calcining the titanium filter element to obtain a pretreated titanium filter element; (2) mixing a ruthenium source, an organic ligand and the pretreated titanium filter element, and sequentially performing a second impregnation, freeze drying and annealing treatment to obtain the titanium-based ruthenium single-atom catalytic membrane electrode; The organic ligand includes polyvinyl pyrrolidone and / or polyethylene glycol-block-polypropylene glycol-block-polyethylene glycol diacrylate.

2. The preparation method according to claim 1, characterized in that: The cleaning in step (1) includes a first cleaning, an acid etching and a second cleaning performed sequentially; Preferably, the first impregnation comprises an alkali impregnation, a first acid impregnation and a second acid impregnation performed sequentially; Preferably, the impregnation solution of the second acid impregnation comprises a mixture of ammonium fluorotitanate and boric acid.

3. The preparation method according to claim 1 or 2, characterized in that: The calcination in step (1) includes a first stage calcination and a second stage calcination performed sequentially; Preferably, the atmosphere of the first stage calcination comprises an oxygen-containing atmosphere; Preferably, the holding temperature of the first stage calcination is 350°C to 450°C; Preferably, the atmosphere of the second-stage calcination includes a nitrogen-containing atmosphere; Preferably, the insulation temperature of the second-stage calcination is 450°C to 550°C.

4. The preparation method according to any one of claims 1 to 3, characterized in that The ruthenium source in step (2) includes any one of ruthenium chloride, ruthenium acetate or ruthenium bromide, or a combination of at least two thereof; Preferably, the molar concentration of the ruthenium source is 80 mmol / L to 100 mmol / L; Preferably, the mass concentration of the organic ligand is 40 g / L to 60 g / L.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The second dipping step (2) has a dipping temperature of 40° C. to 60° C.; Preferably, the second impregnation time is 18 h to 24 h.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Step (2) after the second impregnation and before freeze-drying, pre-freeze-drying is also performed; Preferably, the pre-freeze-drying method comprises pre-freeze-drying using liquid nitrogen; Preferably, the freeze-drying cold trap temperature is -60°C to -40°C; Preferably, the freeze-drying duration is 24 h to 48 h.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The ambient atmosphere of the annealing treatment in step (2) includes a reducing atmosphere; Preferably, the annealing treatment is carried out at a holding temperature of 150°C to 250°C; Preferably, the holding time of the annealing treatment is 1 h to 3 h.

8. A titanium-based ruthenium single-atom catalytic membrane electrode prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The titanium-based ruthenium single-atom catalytic membrane electrode is applied to the process of chlorophenol wastewater treatment and resource utilization.

9. An electrochemical reactor, characterized in that: The electrochemical reactor comprises a treated water outlet, an anode tank, an anode, a silicone gasket, the titanium-based ruthenium single-atom catalytic membrane electrode according to claim 8, a cathode tank and a cathode water inlet which are arranged in sequence.

10. The electrochemical reactor according to claim 9, characterized in that: The working current of the electrochemical reactor is 10 mA / cm 2 ~80mA / cm 2 ; Preferably, the operating voltage of the electrochemical reactor is -1.3V to -0.4V compared to the reversible hydrogen reference electrode.

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