CN113846342B

CN113846342B - Inorganic-organic core-shell skeleton loaded low-dose noble metal palladium material, preparation thereof and application thereof in electrocatalytic dechlorination hydrogenation reaction

Info

Publication number: CN113846342B
Application number: CN202111191179.XA
Authority: CN
Inventors: 赵浙菲; 俞丽; 郑华均
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Zhejiang University of Technology ZJUT
Priority date: 2021-10-13
Filing date: 2021-10-13
Publication date: 2023-09-05
Anticipated expiration: 2041-10-13
Also published as: CN113846342A

Abstract

The invention discloses a low-dose noble metal palladium material loaded on an inorganic-organic core-shell framework, a preparation method thereof and application thereof in electrocatalytic dechlorination hydrogenation reaction; the invention utilizes the in-situ self-polymerization of dopamine to polymerize the dopamine on TiO with array structure vertically grown on the surface of FTO ₂ Around the one-dimensional nano rod, tiO wrapped by polydopamine is formed ₂ An inorganic-organic core-shell structure of the nanorods; uniformly dispersing and loading extremely low amount of palladium nano particles on a core-shell framework by adopting a chemical impregnation method to obtain an electrode material; the loading of noble metal palladium in the electrode material is only 0.29%, and the electrode material is used as a cathode for the dechlorination reaction of the electrocatalytic chlorinated organic compound, and the mass activity is up to 44.39min ^‑1 g ^‑1 The highest conversion rate of the chloro-organic compound can reach 94%, and the catalyst shows high electrocatalytic reaction activity and has a great application prospect in electrocatalytic hydrodechlorination.

Description

Inorganic-organic core-shell skeleton loaded low-dose noble metal palladium material, preparation thereof and application thereof in electrocatalytic dechlorination hydrogenation reaction

Technical Field

The invention relates to a low-dose noble metal electrode material loaded by an inorganic-organic core-shell framework, a preparation method and application thereof, in particular to a material loaded by TiO ₂ PDA is a carrier loaded low-dose metal palladium electrode material, a preparation method thereof and application thereof in electrocatalytic dechlorination hydrogenation reaction.

Background

Chlorinated organic compounds (chlorophenol, polychlorinated pyridine acid, polychlorinated biphenyl and the like) are widely applied to the fields of chemical industry, medicines, pesticides and the like, and the chlorinated organic compounds have the characteristics of high toxicity, durability, biological enrichment and the like, are extremely difficult to convert in nature in a biodegradation mode, and are easy to cause pollution of water, soil and groundwater systems due to improper disposal. Therefore, how to effectively treat chlorinated organic pollutants is a problem to be solved in long-term development of related human beings.

In the prior art, the electrocatalytic reduction method has the advantages of good dechlorination effect, mild conditions and the like. Noble metal-based (including platinum, rhodium, palladium, etc.) materials are commonly used as catalysts in catalytic dechlorination, where palladium-based catalysts can intercalate hydrogen atoms in the palladium lattice, producing sufficient adsorbed hydrogen to facilitate cleavage of the c—cl bond, and are therefore the most efficient dechlorination catalysts. Therefore, noble metal palladium-based composites are often used as catalysts in electrocatalytic dechlorination reactions. For example, the invention patent CN112657507a discloses a wrapped bimetallic catalyst with a core-shell structure, wherein the core is active metal (palladium, platinum, iridium and nickel) nano particles, the shell layer uses copper, tin, silver and zinc as a second metal carrier, and the catalyst is used for hydrodechlorination reaction and has high activity, stability and reaction selectivity. However, the active metal particles are generally 50-60 nm in size, so that the active metal particles are easy to agglomerate, the dispersibility is poor, the exposed catalytic area per unit mass of the active metal is small, and the mass activity of the active metal is low. The invention patent CN108097249A also discloses a preparation method of the hydrodechlorination catalyst, which takes diatomite and citric acid mixed roasting material as a carrier, and the carrier is soaked in palladium-containing salt solution and then dried and roasted again, so that the catalyst can be used for hydrodechlorination of chloroacetic acid. Because the preparation process of the catalyst involves multiple roasting, the temperature is up to 400-500 ℃, palladium metal particles are coarse, the unit load metal palladium amount is large, and the cost of the catalyst is high.

Because noble metal resources are scarce, the price is high, and the high-dosage noble metal catalyst has high cost and cannot be applied to mass production. An effective solution to this dilemma is to prepare low dose precious metal nanoparticles highly dispersed on a support with a nanoarray structure. However, because noble metal nano particles are unstable in thermodynamics, the noble metal nano particles are easy to agglomerate into large particles in the preparation process, so that effective reactive sites are reduced, the reaction efficiency is reduced, the activity per unit mass is low, and the highest mass activity of the existing catalyst is 8.5min ^-1 g ^-1 Therefore, the invention of the high-dispersion low-dosage noble metal catalyst is a key for realizing dechlorination industrialization by an electrocatalytic reduction method.

Disclosure of Invention

The high-dispersivity and low-dosage noble metal palladium nanoparticle is loaded, and a material with high specific surface area is required to be used as a carrier. The invention adopts more common TiO for growing one-dimensional nano rod array structure on FTO conductive glass ₂ The catalyst has the advantages of large surface area, low synthesis cost, good chemical stability and the like.

As a load type electrocatalytic electrode material, the active substances and the carrier have stronger binding force so as to ensure the stability of the electrode material in the electrolysis process; at the same time, conductivity is also an important factor in examining the performance of electrode materials. According to the invention, polydopamine is selected as a binder, and dopamine is polymerized around the titanium dioxide one-dimensional nanorod to form an inorganic-organic core-shell skeleton as a carrier for loading noble metal palladium nanoparticles. On the one hand, the polydopamine has a reducing effect, can reduce noble metal palladium from ionic state to metal palladium particles without adding other reducing agents, and on the other hand, the polydopamine is a high-conductivity organic polymer and can be combined with TiO ₂ Forming strong binding force.

Therefore, the invention provides a Pd nanoparticle material with high dispersibility and low dosage loaded by an inorganic-organic core-shell framework and a preparation method thereof, and the Pd nanoparticle material is used as an electrode for electrocatalytic dechlorination hydrogenation reaction, and has higher electrocatalytic dechlorination capacity and stability.

The technical scheme of the invention is as follows:

the preparation method of the low-dose noble metal palladium material loaded by taking the inorganic-organic core-shell framework as the carrier comprises the following steps:

(1) Growth of TiO on FTO conductive substrate by hydrothermal method ₂ Nanorod array

Immersing an FTO conductive matrix in a tetrabutyl titanate hydrochloric acid aqueous solution, performing hydrothermal reaction, and calcining to obtain the TiO with the nano rod array structure ₂ Material (designated FTO/TiO) ₂ )；

In the hydrochloric acid aqueous solution of tetrabutyl titanate, the mass fraction of the tetrabutyl titanate is 2-3wt% and the solvent is 15-37wt% hydrochloric acid aqueous solution;

TiO with nano rod array structure ₂ Vertically growing on an FTO conductive substrate to serve as a carrier material;

(2) Coating polydopamine on TiO by in-situ self-polymerization ₂ Around the nanorods

Immersing the material obtained in the step (1) in a dopamine solution at 10-80 ℃ (preferably 15 ℃) for 1-30 h (preferably 12h, allowing dopamine to self-polymerize in TiO with an array structure) ₂ Surrounding nanorods), followed by washing and drying to form a polydopamine-coated TiO ₂ Inorganic-organic core-shell framework material of nanorods (denoted as FTO/TiO ₂ @PDA)；

The concentration of the dopamine solution is 0.1-1.5 g/L, preferably 1g/L; the solvent of the dopamine solution is Tris-HCl buffer solution, methanol or ethanol;

(3) Uniformly dispersing and loading metal palladium nano particles on polydopamine shell layer by adopting in-situ reduction method

The material obtained in the step (2) is placed in palladium salt solution, immersed for 5 to 20 hours (preferably 12 hours) at a temperature of between 0 and 30 ℃ (preferably 15 ℃), then washed and dried, and the low-dose noble metal palladium material (marked as FTO/TiO) loaded by taking the inorganic-organic core-shell framework as a carrier is obtained ₂ @PDA/Pd)；

The concentration of metal Pd in the palladium salt solution is 0.01-1 g/L, preferably 0.05g/L; the solvent of the palladium salt solution is 0.1 to 0.2 weight percent hydrochloric acid aqueous solution or 0.1 to 0.3 weight percent NaCl aqueous solution; the palladium salt may be palladium chloride or the like.

The low-dose noble metal palladium material loaded by taking the inorganic-organic core-shell skeleton as the carrier can be used as a cathode material for the electrocatalytic hydrogenation dechlorination reaction of chlorinated organic compounds. The specific application method comprises the following steps:

an H-type electrode reaction tank is used as a reaction device, and an N117 cation membrane is used between the cathode reaction tank and the anode reaction tank to separate electrolyte (only cations are allowed to pass through a diaphragm, see figure 1); the anode is made of graphite rod material, and the cathode is made of the inventionFTO/TiO ₂ PDA/Pd material; the electrolyte in the anode reaction tank is inorganic acid or inorganic alkali aqueous solution, and the electrolyte in the cathode reaction tank is chlorinated organic compound aqueous solution; carrying out electrocatalytic reaction by adopting a constant current electrolysis mode under stirring;

the conditions of the electrocatalytic reaction are as follows: constant temperature of 15-40 ℃ and constant current density of 1-10 mA cm ^-2 The electrolysis time is 2-8 h.

Compared with the prior art, the invention has the advantages that:

TiO used in the invention ₂ The PDA inorganic-organic core-shell skeleton is used as a carrier, can provide a larger surface area, controls the particle size of the metal palladium nano particles to be in the range of 1.2-2.0 nm, is highly dispersed on the carrier and does not agglomerate, and can provide more active sites participating in electrocatalytic reaction. Meanwhile, the size of the noble metal palladium nano-particles can be regulated by controlling the thickness of the dopamine polymerized layer.

The preparation method greatly reduces the use amount of noble metal palladium, and has the advantages of simple process, green and environment-friendly performance and atom economy. The catalyst shows higher activity per unit mass in the electrocatalytic hydrodechlorination of chlorinated organic compounds such as p-chlorophenol, 3, 6-dichloropicolinic acid and the like, and the highest mass activity can reach 44.39min ^-1 g ^-1 。

Drawings

FIG. 1 is a schematic view of an electrolyzer unit in an embodiment of the invention.

FIG. 2 shows an FTO/TiO according to an embodiment of the present invention ₂ SEM image of vertical nanorods.

FIG. 3 shows an FTO/TiO according to an embodiment of the present invention ₂ SEM image of PDA.

FIG. 4 shows an FTO/TiO according to an embodiment of the present invention ₂ TEM image of PDA/Pd.

FIG. 5 is a graph showing the electrocatalytic dechlorination performance of parachlorophenol in accordance with example I of the present invention.

FIG. 6 is a liquid phase diagram of parachlorophenol after electrocatalytic dechlorination in accordance with example I of the present invention.

FIG. 7 is a liquid phase diagram of the third embodiment of the invention after electrocatalytic dechlorination of 3, 6-dichloropicolinic acid.

Detailed Description

In order that the invention may be readily understood, a particular description of the invention will be rendered by reference to specific embodiments that are merely illustrative of the invention and are not intended to limit the scope of the invention. The terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of the scope of the invention. The preparation method of the present invention will be described in detail with reference to the accompanying drawings and examples.

Example 1

1. Preparation of TiO with nanoarray Structure ₂ Vertical nanorods. Immersing FTO conductive glass into tetrabutyl titanate hydrochloric acid aqueous solution (tetrabutyl titanate content 2.8%, solvent is 37wt% hydrochloric acid aqueous solution), carrying out hydrothermal reaction for 5 hours at constant temperature of 150 ℃, washing, and calcining in air at constant temperature of 450 ℃ for 3 hours to obtain FTO/TiO ₂ A material. FIG. 2 is an FTO/TiO ₂ As can be seen from SEM image of (C) ₂ The nano-rod has a one-dimensional nano-rod array structure and is vertically grown on the surface of the FTO, and the average diameter of the nano-rod is about 160nm.

2.FTO/TiO ₂ Preparation of @ PDA. The FTO/TiO is prepared ₂ Is vertically arranged at 1.21 and 1.21g L ^-1 Tris-HCl and 0.5. 0.5g L ^-1 Stirring for 12 hours at a constant temperature of 15 ℃ in the dopamine solution, then washing with deionized water, and drying to obtain FTO/TiO ₂ @ PDA. FIG. 3 is an SEM image of the resulting material, and it can be seen that dopamine has been present in each TiO ₂ Self-polymerizing to form thin layer on the surface of nano rod to obtain FTO/TiO ₂ The diameter of each nanorod remained around 165nm, indicating that the PDA thin layer was in the range of 5-10 nm.

3.FTO/TiO ₂ Preparation of PDA/Pd. The FTO/TiO is prepared ₂ The @ PDA was placed vertically in a container containing 0.05g L ^-1 PdCl ₂ Stirring at 15 ℃ for 12 hours, washing with deionized water, and drying to obtain FTO/TiO ₂ @ PDA/Pd. FIG. 4 is a TEM image of the resulting material, showing self-polymerization in TiO ₂ The average thickness of the PDA thin layer perpendicular to the surface of the nanorods was 5.23nm, and the particle size of the pd nanoparticles was about 1.5nm, uniformly dispersed in the PDA thin film layer. Pd nano-particles on PDA thinThe content in the layer was very low, calculated as Pd loading was 0.29%.

4. In FTO/TiO ₂ The @ PDA/Pd material is used as a cathode, and the parachlorophenol is subjected to electrocatalytic dechlorination hydrogenation. Adopting an H-type electrode reaction tank, adopting an N117 cationic membrane to separate cathode and anode electrolyte, adopting a graphite rod electrode as an anode, and adopting the prepared FTO/TiO as a cathode ₂ PDA/Pd material. The electrolyte in the anode reaction tank is phosphoric acid buffer solution (ph=3); the catholyte was then 1mmol L ^-1 P-chlorophenol solution, the pH of which is regulated to 3.0 by adopting phosphate buffer solution. The electrolyte is in water bath and is kept at 30 ℃ and the electrolytic current is controlled at 6mA cm ^-2 Electrolysis was carried out for 4 hours with constant stirring.

High performance liquid chromatography is adopted for detection, and the conversion rate of parachlorophenol is 94.04 percent, and FTO/TiO is determined as a result ₂ The dechlorination mass activity of the @ PDA/Pd electrode can reach 44.39min ^-1 g ^-1 The electrode material was demonstrated to have excellent atomic economy.

FIG. 5 shows the results of the electrolytic dechlorination performance of parachlorophenol.

FIG. 6 shows the results of liquid chromatography detection of p-chlorophenol and phenol after electrolysis.

Example two

1.FTO/TiO ₂ Preparation of vertical nanorods. The preparation method and the process are the same as those of the embodiment, and TiO with an array structure is vertically grown on the surface of the FTO ₂ A one-dimensional nanorod.

2.FTO/TiO ₂ Preparation of @ PDA. The preparation method and procedure were as in example one, except that the dopamine concentration was 1.0. 1.0g L ^-1 FTO/TiO thus obtained ₂ The thickness of the polydopamine thin layer of the one-dimensional nanorods is 12.15nm, which is higher than 5.23nm in the first embodiment.

3.FTO/TiO ₂ Preparation of PDA/Pd. The preparation method and process are the same as in example one, except that the carrier adopts FTO/TiO with a polydopamine layer thickness of 12.15nm ₂ PDA, FTO/TiO thus obtained ₂ The particle size of the palladium nanoparticle on PDA/Pd was about 2.0nm, calculated to be 0.60% Pd loading.

4. In FTO/TiO ₂ The @ PDA/Pd material is used for electro-catalytic dechlorination hydrogenation of p-chlorophenol at the cathode. In the same way as in example one, the difference is that the cathode uses FTO/TiO with a polydopamine layer thickness of 12.15nm and Pd loading of 0.60% ₂ PDA/Pd material. The conversion rate of the parachlorophenol is 74.49 percent, and the dechlorination mass activity can reach 9.17min after being measured and calculated ^-1 g ^-1 。

Example III

1. And (5) preparing a cathode material. The preparation method and the process are the same as in example one, and the obtained result is the same as in example one.

2. In FTO/TiO ₂ The @ PDA/Pd material is used as a cathode to perform electrocatalytic dechlorination hydrogenation on 3, 6-dichloropicolinic acid. An H-type electrode reaction tank is adopted, an N117 cationic membrane is adopted to separate cathode and anode electrolyte, a graphite rod material is adopted as an anode, and the prepared FTO/TiO is adopted as a cathode ₂ PDA/Pd material. The electrolyte in the anode reaction tank is sodium hydroxide buffer solution (ph=10); the catholyte was then 1mmol L ^-1 3, 6-dichloropicolinic acid solution, the pH of which is adjusted to 10.0 by sodium hydroxide buffer. The electrolyte is in water bath at constant 30 ℃ and the electrolysis current is controlled at 5.0mA cm ^-2 Electrolysis was carried out for 4 hours with constant stirring.

The high performance liquid chromatography is adopted for detection, and the conversion rate of the 3, 6-dichloropicolinic acid is 72.85 percent through measurement and calculation.

FIG. 7 shows the results of liquid chromatography detection of dechlorination of 3, 6-dichloropicolinic acid after electrolysis.

Claims

1. The preparation method of the noble metal palladium-loaded material with the inorganic-organic core-shell framework as the carrier is characterized by comprising the following steps:

(1) Immersing an FTO conductive matrix in a tetrabutyl titanate hydrochloric acid aqueous solution, performing hydrothermal reaction, and calcining to obtain the TiO with the nano rod array structure ₂ A material;

(2) Placing the material obtained in the step (1) into a dopamine solution, soaking for 1-30 h at 10-80 ℃, washing, drying, and performing in-situ self-polymerization to form the polydopamine-coated TiO ₂ An inorganic-organic core-shell scaffold material of the nanorods;

the concentration of the dopamine solution is 0.1-1.5 g/L;

(3) Placing the material obtained in the step (2) into palladium salt solution, soaking for 5-20 h at 0-30 ℃, washing and drying to obtain the noble metal palladium material loaded by taking the inorganic-organic core-shell framework as a carrier;

the concentration of metal Pd in the palladium salt solution is 0.01-1 g/L.

2. The method for preparing the noble metal palladium-loaded material by taking the inorganic-organic core-shell framework as a carrier according to claim 1, wherein in the step (2), the concentration of the dopamine solution is 0.1-1.5 g/L, and the solvent of the dopamine solution is Tris-HCl buffer solution, methanol or ethanol.

3. The method for preparing a noble metal-supported palladium material by using an inorganic-organic core-shell framework as a carrier according to claim 1, wherein in the step (3), the concentration of metal Pd in the palladium salt solution is 0.01-1 g/L, and the solvent of the palladium salt solution is 0.1-0.2 wt% of aqueous hydrochloric acid or 0.1-0.3 wt% of aqueous NaCl.

4. The method for preparing a noble metal-supported palladium material with an inorganic-organic core-shell skeleton as a carrier according to claim 1, wherein in the step (3), the palladium salt is palladium chloride.

5. The method of claim 1, wherein the noble metal palladium material is supported on an inorganic-organic core-shell framework.

6. The use of an inorganic-organic core-shell framework as a carrier for supporting noble metal palladium materials as a cathode material in the electrocatalytic hydrodechlorination of chlorinated organic compounds as claimed in claim 5.

7. The application according to claim 6, wherein the method of application is:

an H-type electrode reaction tank is used as a reaction device, and an N117 cation membrane is used between the cathode reaction tank and the anode reaction tank to separate electrolyte; the anode is made of graphite rod materials, and the cathode is made of noble metal palladium materials loaded by taking the inorganic-organic core-shell framework as a carrier; the electrolyte in the anode reaction tank is inorganic acid or inorganic alkali aqueous solution, and the electrolyte in the cathode reaction tank is chlorinated organic compound aqueous solution; carrying out electrocatalytic reaction by adopting a constant current electrolysis mode under stirring;