Pd / P-MoS2 / NF electrode and preparation method and application thereof

Abstract

The invention provides a Pd / P-MoS2 / NF electrode as well as a preparation method and application thereof. The preparation method of the Pd / P-MoS2 / NF electrode comprises the following steps: preparing a nanoflower-shaped MoS2 / NF electrode by adopting a hydrothermal method; doping a phosphorus source and the nanoflower-shaped MoS2 / NF electrode by adopting a calcination method to obtain a defect-rich P-MoS2 / NF electrode; and loading a palladium element into the defect-rich P-MoS2 / NF electrode by adopting an electro-deposition method to obtain the defect-rich P-MoS2 / NF palladium-loaded electrode. According to the invention, by utilizing the synergistic effect of heteroatom doping and defect engineering, P-MoS2 with a nanoflower-shaped structure and rich active sites is introduced as a Pd NPs attachment site, so that a better electrode cathode material is obtained, and the effect is improved while the cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic hydrodechlorination, and particularly relates to a Pd / P-MoS2 / NF electrode, a preparation method thereof, and an application thereof. Background Art

[0002] The electrocatalytic hydrodechlorination technology has been favored by many researchers due to its characteristics such as greenness and no secondary pollution, and thus has been widely applied in the removal of chlorinated organic compounds. It should be noted that the electrocatalytic hydrodechlorination technology is often limited by its cathode materials. How to effectively solve problems such as high-cost noble metals, low atomic H* generation rate, and easy poisoning of catalysts is the focus of current researchers' exploration. The patent with the publication number CN105879891A discloses a preparation method of a nickel-phosphorus / molybdenum disulfide hydrogen evolution composite material. First, layered molybdenum disulfide microparticles are prepared and subjected to exfoliation treatment. Then, the exfoliated molybdenum disulfide is sensitized and activated, and then a nickel-phosphorus coating is deposited on its surface by electroless plating technology. Finally, heat treatment is carried out under a nitrogen protection atmosphere to obtain the nickel-phosphorus / molybdenum disulfide composite material. However, its removal effect on chlorinated organic compounds is poor. The patent with the publication number CN102849798A discloses two preparation methods of molybdenum disulfide nanosheet thin film materials. One is to place a conductive substrate in a sulfur-containing solution of molybdate for hydrothermal reaction to grow a dense, uniform, and ordered MoS2 nanosheet thin film on the substrate. Another method is to directly place a molybdenum sheet in a solution containing a sulfur source and carry out a sulfidation reaction under hydrothermal conditions to form a dense and uniform MoS2 nanosheet ordered thin film on the molybdenum substrate. However, the electrocatalytic activity of the materials prepared by this technology is not high.

[0003] Therefore, preparing an electrode material with high activity and less noble metal consumption is the key to solving the problem. Summary of the Invention

[0004] In view of this, the present invention aims to overcome the defects in the prior art and proposes a Pd / P-MoS2 / NF electrode, a preparation method thereof, and an application thereof. The present invention utilizes the synergistic effect of heteroatom doping and defect engineering to introduce P-MoS2 with a nanoflower-like structure having abundant active sites as the attachment site for Pd NPs, so as to obtain a better cathode material for the electrode, and achieve the improvement of the effect while reducing the cost.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows: In the first aspect, the present invention provides a preparation method of a Pd / P-MoS2 / NF electrode, including the following steps: Step S1: Prepare a nanoflower-like MoS2 / NF electrode by a hydrothermal method; Step S2: The phosphorus source and the nanoflower-like MoS2 / NF electrode are doped by a calcination method to obtain a defective P-MoS2 / NF electrode; Step S3: Palladium element is loaded into the defective P-MoS2 / NF electrode by an electrodeposition method to obtain a defective P-MoS2 / NF palladium-loaded electrode, denoted as Pd / P-MoS2 / NF.

[0006] In some embodiments of the present invention, the molar ratio of the phosphorus source to the nanoflower-like MoS2 / NF electrode is (1-2.3):3.3.

[0007] In some embodiments of the present invention, Step S2 includes the following steps: The phosphorus source and the nanoflower-like MoS2 / NF electrode are loaded into a ceramic boat and placed in a tube furnace, and annealed under a nitrogen atmosphere to obtain a defective P-MoS2 / NF electrode.

[0008] In some embodiments of the present invention, the phosphorus source is sodium hypophosphite and / or sodium phosphate.

[0009] In some embodiments of the present invention, the process of the annealing treatment is as follows: The calcination temperature is 200°C - 450°C, and the heating rate is 3°C·min -1 -8°C·min -1 , and the calcination time is 1-3 h.

[0010] In some embodiments of the present invention, Step S1 includes the following steps: Step S11: (NH4)6Mo7O 24 •4H2O and CH4N2S are dissolved in deionized water, and after being mixed evenly, a precursor solution is obtained; Step S12: The precursor solution is poured into a reaction kettle, and the Ni-foam substrate is immersed in the precursor solution for a hydrothermal reaction to obtain a nanoflower-like MoS2 / NF electrode; Step S13: The nanoflower-like MoS2 / NF electrode is washed until the solution is clear, and then dried for standby.

[0011] In some embodiments of the present invention, the temperature of the hydrothermal reaction in Step S12 is 150-200°C, and the reaction time is 8-16 h.

[0012] In some embodiments of the present invention, Step S3 includes the following steps: The defective P-MoS2 / NF electrode is placed in a deposition solution containing Pd element for electrodeposition and then dried to prepare a defective P-MoS2 / NF palladium-loaded electrode.

[0013] In some embodiments of the present invention, the deposition solution is a mixed solution of one or two of PdCl2 solution and chloropalladic acid solution.

[0014] In some embodiments of the present invention, the concentration of the deposition solution is 0.2 - 0.5 mmol·L -1 .

[0015] In some embodiments of the present invention, the parameters of the electrodeposition are: electrodeposition for 1.5 - 2.5 h under a constant current condition of 6 - 10 mA.

[0016] In a second aspect, the present invention provides a Pd / P-MoS2 / NF electrode prepared by the above preparation method.

[0017] In a third aspect, the present invention provides the application of the above Pd / P-MoS2 / NF electrode as a catalytic electrode in the electrocatalytic hydrodechlorination reaction of chlorinated organic compounds.

[0018] Compared with the prior art, the present invention has the following advantages: (1) The MoS2 prepared by the hydrothermal method in the present invention is a nanoflower structure stacked by flaky structures, and through the doping of P element under high temperature conditions, a stable structure is still maintained. This provides more attachment sites for the deposition of Pd NPs, which is beneficial to the electron transfer between various structures. At the same time, the Pd NPs reduced by the electrodeposition method have smaller nano-sizes, which provides an advantage for increasing the active sites of the catalyst.

[0019] (2) The present invention confirms the existence of catalyst defects through XRD analysis of the Pd-rich defective electrode and MoS2-related powder catalysts. The calculation of the ratio of the two characteristic peaks, the in-plane vibration peak E12g and the out-of-plane vibration peak A1g in the Raman spectrum, confirms the activation of the edge active sites of inert MoS2; the electron paramagnetic resonance spectrum confirms that the doping of P element can induce the generation of S vacancies, which strongly illustrates the influence of the synergistic effect of heteroatom doping and defect engineering on the Pd-rich defective electrode. Electrochemical impedance spectroscopy analysis shows that Pd / P-MoS2 / NF can provide more active sites of the catalyst, accelerate the electron transfer between the electrode and the pollutants, and thus obtain a more efficient pollutant removal effect.

[0020] (3)The present invention finds that the Pd-loaded defective P-MoS2 / NF electrode achieves the best effect and the best removal rate for lamotrigine, and the complete removal of pollutants can be realized within 120 min. At the same time, the Pd-loaded defective P-MoS2 / NF electrode also exhibits excellent catalytic activity for various chlorinated PPCPs. The Pd / P-MoS2 / NF electrode basically achieves complete removal of three pollutants, bezafibrate, florfenicol, and chlorpheniramine maleate, within 150 min. The removal effects of lornoxicam and losartan potassium both reach more than 90%. It shows that the Pd / P-MoS2 / NF electrode has good general applicability. Description of the Drawings

[0021] Figure 1 SEM images of Pd / P-MoS2 / NF at different magnifications: (a) 1000×; (b) 5000×; (c) 10000×; (d) 20000×; (e) 30000×; (f) 50000×; Figure 2 HRTEM images of the defective P-MoS2 / NF electrode (a-c) and Pd / P-MoS2 / NF (d-f): The scale bar in (a) is 100 nm; the scale bar in (b) is 10 nm; the scale bar in (c) is 1 nm; the scale bar in (d) is 100 nm; the scale bar in (e) is 5 nm; the scale bar in (f) is 10 nm; (g) Particle size distribution diagram of Pd / P-MoS2 / NF; Figure 3 X-ray diffraction patterns of the Pd-loaded defective P-MoS2 electrode and Pd / MoS2 / NF electrode; Figure 4 Raman spectra of MoS2 and P-MoS2; Figure 5 Electron paramagnetic resonance spectra of MoS2, MoS2(def), and P-MoS2; Figure 6 Electrochemical impedance diagram of the Pd / P-MoS2 / NF electrode (counter electrode: carbon black; reference electrode: Ag / AgCl); Figure 7 Removal efficiency diagrams of four electrodes, Pd / P-MoS2 / NF, Pd / MoS2(def) / NF, Pd / MoS2 / NF, and P-MoS2 / NF, for lamotrigine: (a) Removal effect; (b) Reaction kinetics; (c) Removal rate of lamotrigine at different times; Figure 8 Removal efficiency diagram of the Pd / P-MoS2 / NF electrode for various chlorinated PPCPs; Figure 9 Long-term stability results of the Pd-loaded defective P-MoS2 electrode. Detailed Embodiments

[0022] The embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0023] In this document, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs.

[0024] In this document, when a value is described as a range, it should be understood that such disclosure includes the disclosure of all possible sub-ranges within that range, as well as specific numerical values falling within that range, regardless of whether the specific numerical values or specific sub-ranges are explicitly indicated.

[0025] In this document, when referring to "multiple", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0026] In this document, when referring to "preferred", "more preferred", it is only to describe embodiments or examples with better effects, and it should be understood that it does not constitute a limitation on the protection scope of the present invention.

[0027] In this document, when referring to "further", etc., for descriptive purposes, it indicates a difference in content, but should not be construed as a limitation on the protection scope of the present invention.

[0028] In this document, the term "and / or" is a description of the association relationship of an object, indicating that three relationships can exist. For example, A and / or B means: A or B, or the three relationships of A and B.

[0029] In this document, the term "about" means + / - 10% of the specified value, preferably + / - 5%, more preferably + / - 1%.

[0030] In this document, the terms "comprising", "including", "having", "containing", etc. are all open-ended terms, that is, they are intended to include but not be limited to.

[0031] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0032] The present invention will be described in detail below in conjunction with the embodiments.

[0033] Example 1

[0034] (1) Preparation of MoS2 nanoflower electrode First, 0.22 mmol of (NH4)6Mo7O 24 ·4H2O and 6.6 mmol of CH4N2S were dissolved in 50 mL of deionized water, and magnetically stirred for 30 min to form a homogeneous precursor mixed solution. Secondly, the well-mixed precursor solution was poured into a 100 mL polytetrafluoroethylene-lined autoclave, and the pre-treated Ni-foam was immersed in the precursor solution to allow the growth of MoS2 nanoflowers on the Ni-foam substrate. The hydrothermal reaction was carried out at 180 °C for 12 h and then naturally cooled to room temperature. Finally, the prepared nanoflower-like MoS2 / NF electrode was thoroughly washed with deionized water until the solution was clear, and dried at 60 °C for standby.

[0035] (2) Preparation of defective P-MoS2 / NF electrode 1.5 mmol of sodium hypophosphite anhydrous (NaH2PO2) and the prepared MoS2 / NF electrode were placed in two porcelain boats respectively. The boat containing NaH2PO2 was placed at the inlet end, and the boat with the MoS2 electrode was placed at the outlet end, with a 2 cm interval between them. Under N2 atmosphere, it was heated to 300 °C at a rate of 5 °C·min -1 and maintained for 2 h.

[0036] (3) Preparation of defective P-MoS2 supported palladium electrode The preparation of the defective P-MoS2 / NF supported Pd electrode adopted a simple electrodeposition method. The prepared defective P-MoS2 / NF electrode was placed in a PdCl2 deposition solution containing 0.4 mmol·L -1 , and electrodeposited for 2 h under a constant current of 7 mA. At this time, the PdCl2 solution was clear and transparent, and the defective P-MoS2 / NF supported palladium electrode was prepared and dried in an oven at 60 °C for standby, denoted as Pd / P-MoS2 / NF.

[0037] Example 2

[0038] (1) Preparation of MoS2 nanoflower electrode First, 0.22 mmol of (NH4)6Mo7O 240.22 mmol of (NH4)6Mo7O·4H2O and 6.6 mmol of CH4N2S were dissolved in 50 mL of deionized water, and magnetically stirred for 30 min to form a homogeneous precursor mixed solution. Secondly, the uniformly mixed precursor solution was poured into a 100 mL polytetrafluoroethylene-lined autoclave, and the pre-treated Ni-foam was immersed in the precursor solution to allow MoS2 nanoflowers to grow on the Ni-foam substrate. The hydrothermal reaction was carried out at 150 °C for 16 h, and then naturally cooled to room temperature. Finally, the prepared MoS2 / NF electrode with nanoflower shape was thoroughly washed with deionized water until the solution was clear, and dried at 60 °C for standby.

[0039] (2) Preparation of Defect-Rich P-MoS2 / NF Electrode 2.3 mmol of sodium hypophosphite anhydrous (NaH2PO2) and the prepared MoS2 / NF electrode were placed in two porcelain boats respectively. The boat containing NaH2PO2 was placed at the inlet end, and the boat with the MoS2 electrode was placed at the outlet end, with a 2 cm interval between them. Under N2 atmosphere, it was heated to 200 °C at a rate of 3 °C·min -1 and maintained for 3 h.

[0040] (3) Preparation of Defect-Rich P-MoS2 Palladium-Loaded Electrode The preparation of the defect-rich P-MoS2 / NF Pd-loaded electrode adopted a simple electrodeposition method. The prepared defect-rich P-MoS2 / NF electrode was placed in a PdCl2 deposition solution containing 0.2 mmol·L -1 , and electrodeposited for 1.5 h under a constant current of 6 mA. At this time, the PdCl2 solution was clear and transparent, and the defect-rich P-MoS2 / NF Pd-loaded electrode was prepared and dried in an oven at 60 °C for standby, denoted as Pd / P-MoS2 / NF.

[0041] Example 3

[0042] (1) Preparation of MoS2 Nanoflower Electrode First, 0.22 mmol of (NH4)6Mo7O 24 ·4H2O and 6.6 mmol of CH4N2S were dissolved in 50 mL of deionized water, and magnetically stirred for 30 min to form a homogeneous precursor mixed solution. Secondly, the uniformly mixed precursor solution was poured into a 100 mL polytetrafluoroethylene-lined autoclave, and the pre-treated Ni-foam was immersed in the precursor solution to allow MoS2 nanoflowers to grow on the Ni-foam substrate. The hydrothermal reaction was carried out at 200 °C for 8 h, and then naturally cooled to room temperature. Finally, the prepared MoS2 / NF electrode with nanoflower shape was thoroughly washed with deionized water until the solution was clear, and dried at 60 °C for standby.

[0043] (2) Preparation of Defect-Rich P-MoS2 / NF Electrode Put 1 mmol of sodium hypophosphite anhydrous (NaH2PO2) and the prepared MoS2 / NF electrode into two porcelain boats respectively. Place the boat containing NaH2PO2 at the inlet end and the boat with the MoS2 electrode at the outlet end, with a 2 cm gap between them. Under N2 atmosphere, heat it to 450 °C at a rate of 8 °C·min -1 and maintain for 1 h.

[0044] (3) Preparation of Defect-Rich P-MoS2 Palladium-Loaded Electrode The preparation of the defect-rich P-MoS2 / NF Pd-loaded electrode adopted a simple electrodeposition method. Put the prepared defect-rich P-MoS2 / NF electrode into a PdCl2 deposition solution containing 0.5 mmol·L -1 and perform electrodeposition for 2.5 h under a constant current of 10 mA. At this time, the PdCl2 solution is clear and transparent, and the defect-rich P-MoS2 / NF palladium-loaded electrode is prepared. Put it in an oven at 60 °C to dry for later use, denoted as Pd / P-MoS2 / NF.

[0045] Example 4

[0046] Put 1.5 mmol of sodium hypophosphite anhydrous (NaH2PO2) and the prepared MoS2 electrode into two porcelain boats respectively. Place the boat containing NaH2PO2 at the inlet end and the boat with the MoS2 electrode at the outlet end, with a 2 cm gap between them. Under N2 atmosphere, heat it to 300 °C at a rate of 8 °C·min -1 and maintain for 2 h. A defect-rich MoS2 electrode was prepared using the same heating program.

[0047] Example 5

[0048] When the phosphorus source is sodium phosphate and the addition amount of sodium phosphate is 1.5 mmol, other steps and conditions for electrode preparation are the same as those in Example 1.

[0049] Comparative Example 1 When the addition amount of sodium hypophosphite anhydrous is 2.5 mmol, other steps and conditions for electrode preparation are the same as those in Example 1.

[0050] Comparative Example 2 When the addition amount of sodium hypophosphite anhydrous is 0.5 mmol, other steps and conditions for electrode preparation are the same as those in Example 1.

[0051] Comparative Example 3 When the addition amount of sodium hypophosphite anhydrous is 3.0 mmol, other steps and conditions for electrode preparation are the same as those in Example 1.

[0052] Comparative Example 4 1.5mmol black phosphorus and 3.3mmol MoS2 were mixed and subjected to a spheroidal graphite procedure with the preparation conditions of 1200 r / min, temperature of 25°C and time of 2h to obtain phosphorus-doped molybdenum sulfide powder. The phosphorus-doped molybdenum sulfide powder was added to a nafion solution and drop-coated on a nickel foam electrode substrate to prepare a phosphorus-doped molybdenum sulfide / nickel foam electrode.

[0053] Comparative Example 5 The difference between this comparative example and Example 1 is that the prepared nanoflower-shaped MoS2 / NF electrode is directly placed in a liquid containing 0.4 mmol·L -1 The electrodeposition was carried out for 2 h in a PdCl2 deposition solution at a constant current of 7 mA. At this time, the PdCl2 solution was clear and transparent, and the MoS2 / NF palladium-supported electrode was prepared. It was placed in an oven at 60°C for drying and was denoted as Pd / MoS2 / NF.

[0054] Comparative Example 6 The difference between this comparative example and Example 1 is that the MoS2 palladium electrode (Pd / MoS2(def) / NF) contains only S vacancy defects. The specific preparation method is: The prepared nanoflower-like MoS2 / NF electrode was placed in a ark and placed in a tube furnace under N2 atmosphere at 5℃·min -1 The temperature was raised to 300℃ at a rate of 1.50 and maintained for 2 h to obtain MoS2(def) / NF. The MoS2(def) / NF electrode was placed in a solution containing 0.4 mmol·L -1 The electrodeposition was carried out for 2 h in a PdCl2 deposition solution at a constant current of 7 mA. At this time, the PdCl2 solution was clear and transparent, and the MoS2(def) / NF palladium-supported electrode was prepared. It was placed in an oven at 60°C for drying and was denoted as Pd / MoS2(def) / NF.

[0055] Electrochemical hydrogenation dechlorination experiments were conducted on the electrodes prepared in Examples 1 to 5 and Comparative Examples 1 to 6, and the specific steps were as follows: The electrochemical hydrogenation dechlorination experiment was carried out in an H-type electrolytic cell made of polytetrafluoroethylene. In order to prevent the detached chlorine atoms from being freed to the anode and emitting harmful chlorine gas, a cation exchange membrane was used between the two cells. The dechlorination experiment was carried out under the conditions of a constant current of 7 mA and a water bath temperature of 40°C, with the platinum sheet as the counter electrode (anode) and the electrodes (cathode) prepared in Examples 1 to 5 and Comparative Examples 1 to 7 as the working electrodes. The working electrode was immersed in a solution containing 15 mg·L -1Lamotrigine (abbreviated as LTG hereinafter) and 50 mmol·L -1 in Na2SO4 solution. The counter electrode was immersed in a solution containing 50 mmol·L -1 Na2SO4 solution. The distance between the two electrodes was 2 cm. When the electrocatalytic hydrodechlorination time was 150 min, the removal rates are shown in the following table: Table 1 Removal efficiency of lamotrigine

[0056] The SEM images of Pd / P-MoS2 / NF prepared in Example 1 at different magnifications are as Figure 1 shown. It can be seen that obvious spherical particle clusters appear on the surface of the Ni-foam electrode, indicating that the catalyst is successfully loaded. At the same time, with the continuous increase of the magnification, the Pd-loaded catalyst with rich defects P-MoS2 grows on the Ni-foam substrate, presenting a flower-like structure.

[0057] The HRTEM images of the rich-defect P-MoS2 / NF electrode and the prepared Pd / P-MoS2 / NF electrode in Example 1 are as Figure 2 shown. It can be seen that the rich-defect P-MoS2 / NF electrode ( Figure 2 a) and the Pd / P-MoS2 / NF electrode ( Figure 2 d) are composed of sheet structures, fully confirming that Pd nanoparticles are attached to the surface of the sheet-like P-MoS2 / NF electrode, making the sheet-like flower structure less obvious. Preparing rich-defect MoS2 through P doping and vacancy engineering is beneficial to the activation of more inert sites. Obviously, the lattice of the P-MoS2 / NF electrode is not complete ( Figure 2 b), with dislocations and deficiencies existing, which fully demonstrates the existence of catalyst defects and confirms the successful preparation of the rich-defect material. Figure 2 The inset regarding Site 1 in b shows that the lattice spacing in P-MoS2 / NF is 0.673 nm, corresponding to the (002) crystal plane of 2H-MoS2. The enlarged view of Site 2 ( Figure 2 c) shows that there are vacancies in the lattice, confirming the existence of catalyst defect sites. Similarly, the lattice spacing of Pd was analyzed ( Figure 2 e). The lattice spacing of 0.219 nm perfectly corresponds to the (111) crystal plane of Pd. The size of Pd particles has an important influence on the catalytic performance of the catalyst. Therefore, the particle size of Pd particles in the HRTEM image was analyzed. Figure 2g shows that the particle size of Pd particles is about 1.82 nm. The existence of smaller Pd nanoparticles is conducive to the exposure of more catalytic active sites of the catalyst. Indirectly, it shows that the unique flaky nanoflower structure of defect-rich P-MoS2 / NF is conducive to the uniform dispersion of Pd and reduces particle agglomeration.

[0058] The X-ray diffraction patterns of Pd / P-MoS2 / NF prepared in Example 1 and Pd / MoS2 / NF prepared in Comparative Example 4 are as Figure 3 shown. It can be seen that the same crystal plane structures are detected for the Pd / P-MoS2 / NF electrode and the Pd / MoS2 / NF electrode. The diffraction peaks at 2θ of 40.148°, 46.696°, and 68.147° correspond to the (111), (200), and (220) crystal planes of Pd (PDF#46-1043), respectively. The appearance of these three characteristic peaks confirms that Pd elements on the catalyst surface exist in the form of particles.

[0059] The Raman spectra of the nanoflower-like MoS2 / NF electrode and the defect-rich P-MoS2 / NF electrode in Example 1 are as Figure 4 shown, Figure 4 in which the peaks at 375.15 cm -1 and 403.60 cm -1 correspond to the two characteristic peaks of E 1 2g and A 1g respectively. The frequency difference (△f) between the two peaks is 28.45 cm -1 , which is much greater than 20 cm -1 , indicating that 2H-MoS2 has a multi-layer nanoflower structure. The magnitude of the ratio of E 1 2g to A 1g illustrates the degree of defect of the catalyst material. By integrating the peak values of the two curves, the peak areas of each peak of MoS2 and P-MoS2 are shown in Table 2.

[0060] Table 2 Integral areas of the E 1 2g and A 1g characteristic peaks of MoS2 and P-MoS2

[0061] As can be seen from the table, the ratio of the two peaks of the defect-rich P-MoS2 / NF electrode is 0.32, which is less than the peak ratio (0.45) of the nanoflower-like MoS2 / NF electrode. The smaller the ratio of the two characteristic peaks, the more edge exposure and the higher the catalyst activity. At the same time, it also means that more defect sites are generated on 2H-MoS2 after P doping, enhancing the ability of Pd / P-MoS2 / NF to generate atomic H*, and improving the electrocatalytic hydrodechlorination efficiency of the catalyst.

[0062] Figure 5 EPR curves of three molybdenum sulfide catalysts, namely the nanoflower-like MoS2 / NF electrode prepared in Example 1, MoS2(def) prepared in Comparative Example 6, and the defect-rich P-MoS2 / NF electrode prepared in Example 1, are presented. The vacancy content of the catalysts is represented by the signal (g = 2.004) of the Mo-S dangling bond. It can be seen from the figure that there is no S vacancy in the MoS2 catalyst prepared by the hydrothermal method, and the signal peak of the Mo-S dangling bond is significantly enhanced after high-temperature calcination. The doped P atoms occupy the available S vacancies and act as a bridge, balancing the charge distribution between Mo and S atoms, which also explains the reason for the reduction of S vacancies after P doping.

[0063] Figure 6 Electrochemical impedance diagrams of the nanoflower-like MoS2 / NF electrode prepared in Example 1, Pd / P-MoS2 / NF electrode, Pd / MoS2 / NF electrode prepared in Comparative Example 5, and Pd / MoS2(def) / NF electrode prepared in Comparative Example 6 are shown. It can be seen that the electrochemical impedance values of MoS2 / NF, Pd / MoS 2 / NF, Pd / MoS2(def) / NF, and Pd / P-MoS2 / NF are 5.637 Ω, 3.336 Ω, 4.316 Ω, and 0.644 Ω, respectively. The electrochemical impedance value of the activated Pd / P-MoS2 / NF electrode is significantly lower than that of the other electrodes, and the impedance value is reduced by up to 8.75 times. This phenomenon indicates that by exposing the edge active sites of inert 2H-MoS2, more catalyst active sites can be provided, accelerating the electron transfer between the electrode and the pollutants, thereby achieving a more efficient pollutant removal effect.

[0064] Figure 7Removal efficiency of the nanoflower-like MoS2 / NF electrode prepared in Example 1, Pd / P-MoS2 / NF electrode, Pd / MoS2 / NF electrode prepared in Comparative Example 5, and Pd / MoS2(def) / NF electrode prepared in Comparative Example 6 for lamotrigine. It can be seen that the Pd / P-MoS2 / NF electrode can achieve complete removal of lamotrigine within 120 min. Under the same electrocatalytic conditions, the removal effects of the three electrodes of Pd / MoS2(def) / NF, Pd / MoS2 / NF, and P-MoS2 / NF only reached 98.65%, 65.22%, and 27.81% within 150 min. The removal effect of the Pd / P-MoS2 / NF electrode on LTG was significantly improved. The reason for this phenomenon can be attributed to the fact that P doping created more edge active sites on MoS2, accelerated the rate of electrolyzing water by the catalyst to generate atomic H*, and thus improved the electrocatalytic hydrodechlorination effect of the Pd / P-MoS2 / NF electrode.

[0065] Pseudo-first-order kinetic analysis was performed on different electrode materials, and the results are as Figure 7 shown in b. After taking the negative logarithm of the lamotrigine concentration at different times and fitting, it was found that the removal kinetics of the palladium-loaded defective P-MoS2 electrode for lamotrigine followed the pseudo-first-order rate law (R 2 = 0.98), and there was a good linear relationship between the removal of LTG by the catalyst and the removal time. The R 2 values of the three electrodes of Pd / MoS2(def) / NF, Pd / MoS2 / NF, and P-MoS2 / NF also reached 0.99, 0.80, and 0.98, respectively, which also confirmed that there was a good linear relationship between the removal effect and time. The palladium-loaded defective P-doped MoS2 electrode of the present invention obtained the fastest reaction rate for lamotrigine, and its reaction rate constant was 0.06 min -1 , which was 1.95 times (0.03 min -1 ), 10.61 times (0.006 min -1 ), and 20.48 times (0.003 min -1 ) of the three electrodes of Pd / MoS2(def) / NF, Pd / MoS2 / NF, and P-MoS2 / NF, respectively, and the reaction rate was greatly improved. The acquisition of the largest k obs value fully confirmed that the introduction of defective materials could optimize the electrocatalytic hydrodechlorination performance of the catalyst for chlorinated PPCPs. The defective materials promoted by P doping had better removal effects than the S vacancy defective materials prepared by the pure calcination method, indicating that P doping played an important role in stabilizing the material defects and maintaining the catalyst activity.

[0066] To evaluate the excellent performance of a catalyst, in addition to looking at the final removal effect of the catalyst on pollutants, the removal rate is also an important indicator to describe the quality of the catalyst performance. Figure 7 c shows the removal rates of electrocatalytic hydrodechlorination of LTG by four electrode materials at different time periods. Within 0 - 60 min, the removal rates of the four electrodes are significantly different. The Pd / P-MoS2 / NF electrode has the fastest removal rate, which is 0.24 mg·L -1 ·min -1 , significantly better than the Pd / MoS2(def) / NF, Pd / MoS2 / NF, and P-MoS2 / NF electrodes. After 60 min, the removal rate decreases significantly, which is mainly attributed to the fact that the low LTG concentration in the system cannot achieve effective binding with H ads on the catalyst surface, resulting in a large amount of H* overflowing in the form of H2. Looking at the entire reaction process, there is no obvious difference in the overall removal rate between the Pd / P-MoS2 / NF electrode and the Pd / MoS2(def) / NF electrode, with only a 1.02-fold increase. However, within the first 60 min, the removal rate of the Pd / P-MoS2 / NF electrode increases significantly. The removal rate of the Pd / P-MoS2 / NF electrode is 1.26 times that of the Pd / MoS2(def) / NF electrode, and the removal rate has reached 99.77% at 90 min of dechlorination time.

[0067] Figure 8 The removal effects of the Pd / P-MoS2 / NF electrode prepared in Example 1 on five chlorinated PPCPs, namely bezafibrate, lornoxicam, losartan, florfenicol, and chlorphenamine, as target pollutants are shown. It can be seen that the Pd / P-MoS2 / NF electrode has basically achieved complete removal of bezafibrate, florfenicol, and chlorphenamine within 150 min. The removal effects on lornoxicam and losartan both reach more than 90%. This indicates that the Pd / P-MoS2 / NF electrode has good general applicability.

[0068] Figure 9 To test the stability of the electrode under long-term use, the electrocatalytic hydrodechlorination experiment of LTG was carried out continuously ten times at a constant current of 7 mA, as Figure 9As shown. The experimental conditions for each cycle are the same as those in the single-cycle exploration. It can be seen that at the end of each cycle, the removal effect of the Pd / P-MoS2 / NF electrode prepared in Example 1 on LTG decreases. In the first six cycles carried out, the Pd / P-MoS2 / NF electrode showed good stability. At the end of the sixth cycle, the removal effect of LTG was maintained at 91.60%. The results prove the strong stability of the Pd / P-MoS2 / NF electrode of the present invention.

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a Pd / P-MoS2 / NF electrode, characterized in that: It includes the following steps: Step S1: Prepare a nanoflower-like MoS2 / NF electrode by a hydrothermal method; Step S2: Dope a phosphorus source and the nanoflower-like MoS2 / NF electrode by a calcination method to obtain a defect-rich P-MoS2 / NF electrode; Step S3: Load palladium element into the defect-rich P-MoS2 / NF electrode by an electrodeposition method to obtain a defect-rich P-MoS2 / NF palladium-loaded electrode; The molar ratio of the phosphorus source to the nanoflower-like MoS2 / NF electrode is (1 - 2.3):3.

3.

2. The preparation method of the Pd / P-MoS2 / NF electrode according to claim 1, wherein: The said Step S2 includes the following steps: Load the phosphorus source and the nanoflower-like MoS2 / NF electrode into a ceramic boat and place it in a tubular furnace, and perform annealing treatment under a nitrogen atmosphere to obtain a defect-rich P-MoS2 / NF electrode; and / or The said phosphorus source is sodium hypophosphite and / or sodium phosphate.

3. The preparation method of the Pd / P-MoS2 / NF electrode according to claim 2, characterized in that: The process of the said annealing treatment is as follows: The calcination temperature is 200℃-450℃, and the heating rate is 3℃·min -1 -8℃·min -1 , the calcination time is 1-3h.

4. The preparation method of the Pd / P-MoS2 / NF electrode according to claim 1, characterized in that: The said Step S1 includes the following steps: Step S11: Dissolve (NH4)6Mo7O 24 •4H2O and CH4N2S in deionized water, and after mixing evenly, obtain a precursor solution; Step S12: Pour the precursor solution into a reaction kettle, and immerse the Ni-foam substrate into the precursor solution to carry out a hydrothermal reaction to obtain a nanoflower-like MoS2 / NF electrode; Step S13: Wash the nanoflower-like MoS2 / NF electrode until the solution is clear, and dry it for standby.

5. The preparation method of the Pd / P-MoS2 / NF electrode according to claim 4, wherein: The temperature of the hydrothermal reaction in the said Step S12 is 150 - 200 °C, and the reaction time is 8 - 16 h.

6. The preparation method of the Pd / P-MoS2 / NF electrode according to claim 1, wherein: The said Step S3 includes the following steps: Put the defect-rich P-MoS2 / NF electrode into a deposition solution containing Pd element for electrodeposition and then dry it to prepare a defect-rich P-MoS2 / NF palladium-loaded electrode.

7. The preparation method of the Pd / P-MoS2 / NF electrode according to claim 6, wherein: The said deposition solution is a mixed solution of one or two of PdCl2 solution and chloropalladic acid solution; and / or The concentration of the deposition solution is 0.2 - 0.5 mmol·L -1 .

8. The preparation method of the Pd / P-MoS2 / NF electrode according to claim 1, characterized in that: The parameters of the said electrodeposition are: electrodeposit for 1.5 - 2.5 h under the condition of a constant current of 6 - 10 mA.

9. The Pd / P-MoS2 / NF electrode prepared by the preparation method according to any one of claims 1 - 8.

10. The application of the Pd / P-MoS2 / NF electrode according to claim 9 as a catalytic electrode in the electrocatalytic hydrodechlorination reaction of chlorinated organic compounds.

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