High-activity nanocrystal transition metal chalcogenide, preparation method thereof and application of high-activity nanocrystal transition metal chalcogenide in electrochemical production of hydrogen peroxide

Abstract

The invention discloses a high-activity nanocrystal transition metal chalcogenide, a preparation method thereof and application of the high-activity nanocrystal transition metal chalcogenide in electrochemical production of hydrogen peroxide. The transition metal chalcogenide catalyst has a nanocrystal form and is in a small particle shape, the particle size of a single particle is 5-20 nm, and elements in the particle are uniformly distributed. According to the method disclosed by the invention, the high-activity nanocrystal transition metal chalcogenide catalyst can be rapidly, simply and conveniently prepared on a large scale, and the prepared nanocatalyst has more obvious active sites, and shows excellent catalytic activity, two-electron oxygen reduction selectivity and relatively high stability in electro-catalytic H2O2 production; the problems of high cost, low efficiency and the like of preparation of H2O2 through oxygen reduction of an electrocatalyst in an existing acidic electrolyte can be effectively solved, and various refractory organic pollutants can be effectively degraded.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysis, and in particular relates to a high-activity nanocrystalline transition metal sulfide, a preparation method thereof, and an application of electrochemically generating hydrogen peroxide. Background Art

[0002] Hydrogen peroxide, commonly known as hydrogen peroxide, is an important green chemical. It is widely used in sewage treatment, pulp bleaching, disinfection and sterilization, chemical synthesis and other fields. At present, the global demand for H 2 O 2 The demand for H 2 O 2 The production of H relies on a complex and energy-intensive anthraquinone oxidation process, which results in a large amount of chemical waste and organic waste. Two-electron oxygen reduction technology in acidic electrolyte is a green and low-cost method for generating H 2 O 2 The technology has broad practical application value and great future potential.

[0003] Among the numerous electrocatalysts, transition metal sulfide has become one of the hot topics in the current research of two-electron oxygen reduction in acidic electrolytes due to its advantages such as low cost, abundant reserves, good environmental compatibility and adjustable structure. However, the preparation process of transition metal sulfide is cumbersome, the yield is low, and most sulfide catalysts have problems such as low activity and poor stability in application, which cannot meet the needs of practical applications. For example, Liang et al. prepared NiS by hydrothermal method and high temperature calcination method. 2 Electrocatalysts have high selectivity for two-electron oxygen reduction in acidic electrolytes, but the presence of H 2 O 2 The problems of low activity and poor stability (J. Mater. Chem. A, 2021, 9, 6117-6122). Sheng et al. prepared CoSe by double hydrothermal method and high temperature calcination method. 2 Electrocatalyst to solve H in acidic electrolyte 2 O 2 The problem of poor activity, but also has the problems of poor selectivity and low stability (Energy Environ. Sci., 2020, 13, 4189-4203). Zhang et al. prepared CoSe rich in Se defects by hydrothermal method. 2 , its maximum ring current density in acidic electrolyte is only 0.6 mA cm -2 , there exists H 2 O 2 Low activity and poor selectivity (CN116081579A). Sheng et al. prepared NiSe by two hydrothermal methods. 2Electrocatalysts with high selectivity and stability in acidic electrolytes, but low activity and H 2 O 2 The problem of low yield (Nat. Catal. 2022, 5, 716-725). In general, there is an urgent need to develop a transition metal sulfide catalyst with high catalytic performance for electrocatalytic oxidation of native hydrogen peroxide in acidic electrolyte. Summary of the invention

[0004] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a highly active nanocrystalline transition metal sulfide catalyst. The method of the present invention can quickly and easily prepare a highly active nanocrystalline transition metal sulfide catalyst on a large scale. The prepared nanocatalyst has significantly more active sites, which can effectively solve the current problem of preparing H by electrocatalyst oxygen reduction in acidic electrolyte. 2 O 2 Problems such as high cost and low efficiency.

[0005] The invention also provides a preparation method of the high-activity nano-crystalline transition metal sulfide catalyst and its application.

[0006] Technical solution: In order to achieve the above-mentioned purpose, the present invention provides a nanocrystalline transition metal sulfide catalyst, wherein the nanocrystalline transition metal sulfide catalyst is a nano-nature MX 2 , where M represents a transition metal and X represents a chalcogen.

[0007] Wherein, the nanocrystalline transition metal chalcogenide catalyst is nano-MX 2 , with obvious nano properties, M represents transition metal, and X represents chalcogen.

[0008] The nano-crystalline transition metal sulfide catalyst has nano characteristics and is in the form of small particles, with a single particle size of 5 to 20 nm.

[0009] Furthermore, the catalyst has not only small particles but also many active sites. The small particles have significantly more active sites. A single particle is 5 to 20 nm in size and exhibits high activity during the catalytic process.

[0010] The method for preparing the nanocrystalline transition metal chalcogenide catalyst of the present invention comprises the following steps:

[0011] (1) ultrasonically dispersing a transition metal salt in a specific surfactant solvent to obtain a highly dispersed first suspension;

[0012] (2) mixing the first suspension with a chalcogen precursor, and subjecting the mixture to ultrasonic reaction to obtain a second suspension;

[0013] (3) refluxing the second suspension mixed solution to obtain a third suspension after sufficient reaction;

[0014] (4) Cooling the third suspension, centrifuging and drying it to obtain a nanocrystalline transition metal sulfide catalyst.

[0015] The transition metal salt in step (1) is one or more of cobalt acetate, cobalt nitrate, cobalt chloride, nickel acetate, nickel nitrate and nickel chloride; the surfactant solvent in step (1) is a high boiling point and reducing solvent; the molar ratio of the surfactant to the transition metal salt is 10:1 to 100:1; the ultrasonic time in step (1) is 30 min to 60 min, the ultrasonic frequency is 30 KHz to 90 KHz, and the ultrasonic power is 200 W to 500 W.

[0016] Preferably, the surfactant solvent is a mixture of ferrocene and oleylamine in a mixing ratio of 1:1000 to 1:100.

[0017] Wherein, the sulfide precursor in step (2) is thioacetamide, S powder, thiourea, Se powder, Na 2 SeO 3 or one of dibenzyl diselenide; the molar ratio of the transition metal salt to the precursor is 1:1 to 1:3; the ultrasonic time in step (2) is 10 min to 60 min, the ultrasonic frequency is 10 KHz to 90 KHz, and the ultrasonic power is 50 W to 500 W.

[0018] Wherein, the reflux reaction in step (3) is an oil bath reflux reaction, the oil bath temperature is 160 to 280° C., and the oil bath reaction time is 0.5 to 3 h.

[0019] Furthermore, in step (4), the centrifugal separation speed is 5000-10000 rpm, and the time is 1-5 min; the washing reagent is one or two of acetone, anhydrous ethanol or water, and the washing times are 3-6 times; the vacuum drying temperature is 40-80° C., and the time is 12-24 h.

[0020] The nanocrystalline transition metal sulfide catalyst of the present invention is used to electrocatalyze the preparation of H in an acidic electrolyte. 2 O 2 Application in.

[0021] The acidic electrolyte includes sulfuric acid or perchloric acid with a concentration of 0.05 to 0.5 mol / L. The electrocatalysis adopts an H-Cell double-chamber electrolytic cell or a single-chamber electrolytic cell and a three-electrode working mode. The transition metal sulfide catalyst is coated on a rotating ring disk electrode as a working electrode or the transition metal sulfide catalyst is coated on a hydrophobic carbon paper as a working electrode. A potential range of -0.15 to 0.1 V vs RHE is applied to the working electrode of the H-Cell electrolytic cell to electrocatalyze H 2 O 2 experiment.

[0022] Preferably, an electrochemical workstation is used as the electrochemical generating device, a three-electrode measurement system is adopted, the catalyst is coated on a rotating ring disk electrode as the working electrode, a graphite rod is used as the counter electrode, saturated mercurous sulfate is used as the reference electrode, and H 2 SO 4 solution as the electrolyte, where H 2 SO 4 The concentration of the aqueous solution is 0.05 to 0.5 mol / L, preferably 0.05 mol / L.

[0023] Furthermore, the catalyst is coated on the rotating ring disk electrode by adding the catalyst to a mixed solution of isopropanol and Nafion solution and ultrasonically dispersing the obtained dispersion. The obtained dispersion is dripped onto the rotating ring disk electrode by spin coating at a speed of 300 to 800 r, and the number of repetitions is 1 to 3, so that Nano-MX 2 The catalyst is attached to the electrode and the preparation is complete.

[0024] Furthermore, the H-Cell (dual-chamber electrolytic cell) was used as the reaction device, and a three-electrode measurement system was used to measure the Nano-MX 2 The catalyst was coated on hydrophobic carbon paper as the working electrode, a graphite rod as the counter electrode, saturated mercuric sulfate as the reference electrode, and H 2 SO 4 solution as the electrolyte, where H 2 SO 4 The concentration of the aqueous solution is 0.05-0.5 mol / L, preferably 0.05 mol / L, and the working electrode is applied with a potential range of -0.15-0.1 V vs RHE to conduct an electrocatalytic test experiment.

[0025] The nanocrystalline transition metal sulfide catalyst of the present invention electrocatalyzes the generation of H 2 O 2 Application of electro-Fenton degradation of refractory organic pollutants.

[0026] The electrocatalysis adopts a single-chamber electrolytic cell and a three-electrode working mode, and the transition metal sulfide catalyst is coated on a hydrophobic carbon paper as a working electrode for electro-Fenton degradation of different pollutants.

[0027] Furthermore, a single-chamber electrolytic cell was used as a reaction device, and a three-electrode measurement system was used to measure the Nano-MX 2 The catalyst was coated on hydrophobic carbon paper as the working electrode, and the electro-Fenton degradation of refractory organic pollutants was carried out. 0.5 mMFeSO 4 7H 2 O, pollutant concentration (100 mg L -1 ).

[0028] Further, the contaminants are bisphenol A (BPA), parachlorophenol (4-CP), ciprofloxacin (CAP), acetaminophen (ACT) and sulfamethoxazole (SMX).

[0029] The present invention provides a method for preparing a highly active nanocrystalline transition metal sulfide catalyst for effectively electrocatalytically reducing oxygen to hydrogen peroxide in an acidic electrolyte. The prepared catalyst has good electrocatalytic performance in the production of hydrogen peroxide. 2 O 2 It exhibits excellent catalytic activity, two-electron oxygen reduction selectivity and high stability, achieving efficient H 2 O 2 Electrochemical synthesis and effective electro-Fenton degradation of refractory organic pollutants.

[0030] The nanocrystalline transition metal chalcogenide catalyst of the present invention has good two-electron oxygen reduction activity in the RRDE test. 2 O 2 The highest selectivity can reach 96%, producing H 2 O 2 The ring current density can reach up to 3.02 mg cm -2 After 20,000 cycles, the stability was almost unchanged. The average yield per hour at -0.1 V vs. RHE using an H-type electrolyzer was 2355 mmol g cat -1 h -1 The Faraday efficiency is as high as 91%, and a variety of difficult-to-degrade organic pollutants can be completely degraded within 2 hours.

[0031] The present invention prepares for the first time nanocrystalline transition metal chalcogenide catalysts with obvious nano properties, which are collectively referred to as nano-MX 2, M represents transition metal, and X represents chalcogen. The catalyst prepared by the present invention not only has small particles but also has many active sites, a larger specific surface area, and an increased number of active sites per unit mass of the catalyst, and the catalytic activity in the catalytic process is significantly improved. The present invention finally obtains a highly active nanocrystalline transition metal sulfide through a specific preparation method, which exhibits electrocatalytic H 2 O 2 The invention discloses a method for preparing a catalyst having a high activity, wherein a specific surfactant and ultrasonic conditions are used to ensure the high activity nano-crystalline transition metal sulfide. In the present invention, a mixture of ferrocene and oleylamine in a specific ratio is used as a surfactant solvent to achieve the generation of high activity nano-crystalline transition metal sulfide, while the use of a single traditional surfactant, such as oleic acid, oleylamine, ethylenediamine or octadecene, cannot generate the material with the catalytic effect of the present invention. In addition, the use of an ultrasonic step in the preparation process of the present invention is also very important. If it is replaced by conventional stirring, the prepared material has a high yield. 2 O 2 The activity will be significantly reduced.

[0032] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0033] 1. The high-activity nano-crystalline transition metal sulfide catalyst prepared by the present invention has a simple preparation process and is easy to produce industrially. The obtained nano-particles are uniform and highly active.

[0034] 2. The electrochemical test in RRDE of the present invention shows that the prepared catalyst has excellent comprehensive performance in acidic electrolyte, and the catalytic activity, selectivity and stability are significantly improved.

[0035] 3. The catalyst prepared by the present invention also exhibits high H in the simulated practical application in H-Cell. 2 O 2 The yield and Faraday efficiency are high, which is conducive to further practical applications.

[0036] 4. The catalyst prepared by the present invention can effectively degrade a variety of difficult-to-degrade organic pollutants in a single-chamber electrolytic cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a topographical diagram of the present invention;

[0038] Figure 2 It is a structural analysis diagram of the present invention;

[0039] Figure 3 is the electrocatalytic performance diagram of the present invention;

[0040] Figure 4 Electrocatalytic performance diagram optimized for the conditions of the present invention

[0041] Figure 5This is a stability test experiment of the present invention;

[0042] Figure 6 For the present invention 2 O 2 Actual production test;

[0043] Figure 7 This is the pollutant degradation experiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0045] The experimental methods described in the examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0046] Example 1

[0047] 1. Preparation process of transition metal chalcogenide catalyst:

[0048] 1. Weigh 0.119g NiCl 2 6H 2 O was transferred into a two-necked flask, 10 mL of oleylamine (containing 0.006 g of ferrocene) was drawn with a pipette and injected into the two-necked flask, the flask was covered with a stopper, and the flask was placed in a 60°C water bath and ultrasonically treated at 200 W and 90 KHz for 30 min to cause NiCl 2 6H 2 O was completely dissolved; 0.0790g Se powder was added and ultrasonicated at 200W and 90KHz in a 60℃ water bath for 30min to make Se powder and NiCl 2 6H 2 O is fully soluble in oleylamine;

[0049] 2. Place the mixture in an oil bath set at 180°C and reflux at 600 rpm for 1 hour; stop the reaction and allow the solution to cool naturally to room temperature;

[0050] 3. Centrifugal washing: The centrifuge was set to 6000 rpm, and the oleylamine and the sample were separated by centrifugation for 5 minutes. The precipitate was washed five times by centrifugation with anhydrous ethanol and deionized water; the precipitate was placed in a vacuum drying oven and dried at 60°C for 24 hours. The catalyst (named o-NiSe 2 ).

[0051] 2. Electrocatalytic performance test:

[0052] The material obtained in this example was ground into powder, and the ORR performance of the obtained material was tested using a rotating ring disk electrode.

[0053] 1. The electrochemical tests were all conducted on a CHI 760e electrochemical workstation. The standard three-electrode system was used in this test, with a rotating ring disk electrode (RRDE) with a Pt ring as the working electrode (disk electrode area: 0.126 cm 2 ), saturated mercurous sulfate as the reference electrode, graphite rod as the counter electrode, and the electrolyte is 0.05MH 2 SO 4 (pH 1.25).

[0054] 2. Preparation of working electrode: Weigh 10 mg of the above-prepared catalyst, add 400 μL isopropanol, 600 μL deionized water and 30 μL 5wt% Nafion, and ultrasonically disperse for 20 min. Pipette the above dispersion and spin coat it onto the rotating ring disk electrode. The spin coating speed is 300-800 rpm, and the number of times is 1-3. Spin the catalyst to dry. The catalyst loading on the rotating ring disk electrode is about 0.0925 mg cm -2 .

[0055] 3. During the measurement process, O 2 Continuous coverage at 0.05MH 2 SO 4 Electrolyte surface.

[0056] (1) In O 2 Under saturation conditions, o-NiSe is loaded 2 The disk electrode was first subjected to cyclic voltammetry in the range of -0.025 to 0.75 V vs. RHE at a scan rate of 100 mV / s and 1600 rpm for 10 cycles, while the Pt ring was kept at 1.3 V vs. RHE;

[0057] (2) The Pt ring was then subjected to 10 cycles of CV adjustment in the range of 0.05 to 1.20 V vs. RHE at a scan rate of 100 mV / s and 1600 rpm. 2 The disk electrode was held at 0.75 V vs. RHE.

[0058] (3) After cyclic voltammetry test, LSV test was performed from 0.75 to -0.025 V vs. RHE at a scan rate of 10 mV / s, RRDE rotation speed of 1600 rpm, while the Pt ring was kept at 1.3 V vs. RHE.

[0059] 4. The catalyst was used to perform actual electrocatalytic synthesis of H using an H-type dual-chamber electrolytic cell (H-Cell). 2 O 2test.

[0060] The test was carried out on a CHI 760e electrochemical workstation. A three-electrode system was used to test the o-NiSe 2 Hydrophobic carbon paper (slurry configuration is the same as the above electrosynthesis test, unit area 1*1cm 2 Loading capacity is about 0.25mgcm -2 catalyst) as the working electrode and graphite rod as the counter electrode, with saturated Hg / Hg 2 SO 4 As a reference electrode, the electrolyte was 30 mL O 2 Saturated 0.05MH 2 SO 4 Solution (pH 1.25), stirring rate 600 r min -1 The working electrode was subjected to constant potentials of -0.15, -0.1, -0.05, 0, and 0.1 V vs RHE for electrocatalytic testing experiments.

[0061] 5. Concentration measurement using UV spectrophotometer

[0062] During each electrolysis, samples were taken from the working electrode chamber and diluted with Ce(SO 4 ) 2 The solution was titrated at 318 nm to quantitatively detect the accumulated H 2 O 2 Concentration, yield and Faradaic efficiency.

[0063] 6. Experiments on degradation of different pollutants

[0064] Five typical refractory organic pollutants were selected as probes to further verify the 2 O 2 The production conditions of bisphenol A (BPA), parachlorophenol (4-CP), ciprofloxacin (CAP), acetaminophen (ACT) and sulfamethoxazole (SMX) were respectively prepared in a single-chamber electrolytic cell with 1 mM FeSO 4 7H 2 O, pollutant concentration (100 mg L -1 ), the three-electrode system was carried out (as in step 4 above), and the electro-Fenton degradation experiment was carried out at -0.1 V vs. RHE.

[0065] Example 2

[0066] Catalyst c-NiSe 2 Preparation

[0067] The c-NiSe was prepared in the same manner as in Example 1. 2The oxygen reduction catalyst is different in that the 180°C in step 2 is replaced by 260°C for oil bath heating, i.e. c-NiSe 2 ; The electrochemical test conditions are the same as those in Example 1.

[0068] Example 3

[0069] Catalyst o-CoSe 2 Preparation

[0070] o-CoSe was prepared in the same manner as in Example 1. 2 Oxygen reduction catalyst, the difference is that NiCl in step 1 2 6H 2 O replaced by CoCl 2 6H 2 O; The electrochemical test conditions are the same as those in Example 1.

[0071] Example 4

[0072] Catalyst c-CoSe 2 Preparation

[0073] c-CoSe was prepared in the same manner as in Example 1. 2 Oxygen reduction catalyst, the difference is that NiCl in step 1 2 6H 2 O replaced by CoCl 2 6H 2 O, the 180℃ in step 2 was replaced with 260℃ for oil bath heating, i.e. c-CoSe 2 ; The electrochemical test conditions are the same as those in Example 1.

[0074] Example 5

[0075] Catalyst NiS 2 Preparation

[0076] NiS was prepared in the same manner as in Example 1. 2 Oxygen reduction catalyst, except that 0.0790g Se powder in step 1 is replaced with 0.032g S powder; the electrochemical test conditions are the same as those in Example 1.

[0077] Example 6

[0078] Catalyst CoS 2 Preparation

[0079] NiS was prepared in the same manner as in Example 1. 2 Oxygen reduction catalyst, except that 0.0790g Se powder in step 1 was replaced with 0.032g S powder; NiCl 2 6H 2O replaced by CoCl 2 6H 2 O, electrochemical test conditions are the same as those in Example 1.

[0080] Comparative Example 1

[0081] o-NiSe was prepared in the same manner as in Example 1. 2 The oxygen reduction catalyst is different in that oleylamine alone is used in step 1 without the addition of ferrocene activator.

[0082] Comparative Example 2

[0083] o-NiSe was prepared in the same manner as in Example 1. 2 The oxygen reduction catalyst is different in that the ultrasonic wave in step 1 is replaced by stirring (600 rpm).

[0084] Test Example 1

[0085] 1. o-NiSe prepared in Example 1 2 Scanning electron microscopy, such as Figure 1 As shown, from Figure 1 It can be seen that the small particles are evenly dispersed, with a single particle of 5 to 20 nm, and the elements within the particles are evenly distributed, which greatly increases the specific surface area of ​​the catalyst.

[0086] 2. o-NiSe prepared in Example 1 2 The X-ray diffraction pattern of Figure 2 As shown, all diffraction peaks can be well indexed to the orthorhombic structure of NiSe 2 (ICSD#5071), indicating the synthesis of pure phase o-NiSe 2 .

[0087] 3. The catalyst prepared in Examples 1-6 was used for electrocatalytic oxygen reduction in RRDE to prepare H 2 O 2 The specific results are shown in Table 1. Among them, the maximum ring current density represents the H production 2 O 2 Activity and selectivity calculations involve the ratio of ring current density to disk current density. At the same time, in the field of ORR electrocatalysis, in order to accurately characterize the H production per unit mass of the catalyst, 2 O 2 Performance (referred to as MA h ), the present invention defines the quality activity parameter where j ring is the maximum ring current density (mA / cm 2 ), m is the catalyst loading mass (mg). Table 1 shows that: o-NiSe synthesized according to this method Example 1 2The electrocatalytic performance is the best, with the highest ring current density reaching 3.02 mA cm -2 , H 2 O 2 Selectivity up to 96%. Highest mass activity (Ag -1 ) can reach 32.65, significantly exceeding other embodiments.

[0088] Table 1 Different catalysts at 0.05 MH 2 SO 4 Maximum ring current density and H at 1600 rpm in (pH 1.25) electrolyte 2 O 2 Selective comparison

[0089]

[0090] The oxygen reduction curves of different sulfur catalysts prepared in Examples 1-6 of the present invention are as follows Figure 3 As shown. Different catalysts at 0.05MH 2 SO 4 (pH 1.25) have different electrocatalytic properties. 2 The catalyst has the highest ring current density of 3.02 mA cm -2 The selectivity is as high as 96%, which is much higher than other transition metal-based catalysts. 2 The catalyst has good oxygen reduction activity and H 2 O 2 Highly selective.

[0091] 4. o-NiSe prepared under different synthesis conditions of the present invention 2 The catalyst oxygen reduction curve is as follows Figure 4 The black line represents the synthesis method of Example 1, and the highest ring current density can reach 3.02 mA cm -2 ; Red line: the synthesis method of comparative example 1, without the addition of ferrocene in the surfactant, and other synthesis steps remain unchanged, the maximum ring current density can only be 1.83 mA cm -2 ; Blue line: The synthesis method of comparative example 2 uses stirring instead of the ultrasonic step of the present invention, and the other synthesis steps remain unchanged. The maximum ring current density can only be 1.21 mA cm -2 The addition of the surfactant ferrocene and the ultrasonic conditions in the synthesis method of the present invention are very important. If ferrocene is not added or the ultrasonic condition is replaced by stirring, the H 2 O 2 The activity was significantly reduced.

[0092] 5. o-NiSe prepared in Example 1 of the present invention 2Catalyst accelerated durability test Figure 5 Specific test method: According to the method in Example 1, 2 Saturated 0.05MH 2 SO 4 The CV cycle test was carried out for 20,000 times in the electrolyte solution (pH 1.25), and then the rotating ring disk electrode was used in the oxygen-saturated 0.05 MH 2 SO 4 The ORR polarization curve was measured in the electrolyte solution (pH 1.25). The scan rate was 100 mV s when measuring the CV curve. -1 When measuring the polarization curve, the rotation speed of the rotating disk electrode was 1600 rpm and the curve scanning rate was 10 mV s -1 Comparing the two curves, it can be seen that o-NiSe 2 The catalyst has good long-term durability, and the current density has almost no significant change after 20000 CV cycles. These results show that o-NiSe 2 Has excellent durability.

[0093] 6. o-NiSe prepared in Example 1 of the present invention 2 Catalyst produces H in H-Cell 2 O 2 like Figure 6 According to the method in Example 1, (a) H generated under different voltages 2 O 2 (a) The relationship between the concentration and time; (b) The corresponding Faraday efficiency under different voltages. When the voltage is -0.1 V vs. RHE, H 2 O 2 The concentration was as high as 157 mM, with an average yield of 2355 mmol g cat per hour -1 h -1 , the maximum Faraday efficiency reaches 91%.

[0094] 7. o-NiSe prepared in Example 1 of the present invention 2 Experimental study on electro-Fenton degradation of different pollutants by catalyst in a single-chamber electrolytic cell Figure 7 As shown. According to the method in Example 1, (a) the change of different pollutants over time; (b) the degradation efficiency. 2 The catalyst can effectively degrade a variety of organic pollutants, further verifying that o-NiSe 2 The catalyst has high electrocatalytic H production in acidic electrolyte. 2 O 2 Activity, corresponding to the above experiment.

[0095] 8. o-NiSe prepared in Example 1 of the present invention 2 Electrocatalytic oxygen reduction to H in RRDE catalyst 2 O 2 The comparison with existing materials is shown in Table 2.

[0096] Table 2 Existing catalyst MA h

[0097]

[0098]

[0099] In the field of ORR electrocatalysis, in order to accurately characterize the H production per unit mass of the catalyst 2 O 2 Performance (referred to as MA h ), the present invention defines the quality activity parameter where j ring is the maximum ring current density (mA / cm 2 ), m is the catalyst loading mass (mg). This parameter overcomes the applicability limitations of traditional mass activity indicators in hydrogen peroxide synthesis scenarios and can more truly reflect the catalytic performance under industrial electrolysis. 2 Electrocatalytic oxygen reduction to H in RRDE catalyst 2 O 2 The performance is significantly superior to related materials in the prior art.

Claims

1. A nanocrystalline transition metal chalcogenide catalyst, characterized in that: The nanocrystalline transition metal chalcogenide catalyst is nano-sized MX2, wherein M represents a transition metal and X represents a chalcogen element.

2. The nanocrystalline transition metal chalcogenide catalyst according to claim 1, characterized in that: The nano-crystalline transition metal sulfide catalyst has nano characteristics and is in the form of small particles, with a single particle size of 5 to 20 nm.

3. A method for preparing the nanocrystalline transition metal chalcogenide catalyst according to claim 1, characterized in that: The steps include: (1) ultrasonically dispersing a transition metal salt in a specific surfactant solvent to obtain a first suspension; (2) mixing the first suspension with a chalcogen precursor, and subjecting the mixture to ultrasonic reaction to obtain a second suspension; (3) refluxing the second suspension to obtain a third suspension after sufficient reaction; (4) Cooling the third suspension, centrifuging and drying it to obtain a nanocrystalline transition metal sulfide catalyst.

4. The preparation method according to claim 3, characterized in that: The transition metal salt in step (1) is one or more of cobalt acetate, cobalt nitrate, cobalt chloride, nickel acetate, nickel nitrate and nickel chloride; the surfactant solvent in step (1) is preferably a solvent with a high boiling point and reducing properties; the molar ratio of the surfactant to the transition metal salt is 10:1 to 100:1; the ultrasonic time in step (1) is 30 min to 60 min, the ultrasonic frequency is 30 KHz to 90 KHz, and the ultrasonic power is 200 W to 500 W.

5. The preparation method according to claim 3, characterized in that: The sulfide precursor in step (2) is one of thioacetamide, S powder, thiourea, Se powder, Na2SeO3 or dibenzyl diselenide; the molar ratio of the transition metal salt to the precursor is 1:1 to 1:3; the ultrasonic time in step (2) is 10 min to 60 min, the ultrasonic frequency is 10 KHz to 90 KHz, and the ultrasonic power is 50 W to 500 W.

6. The preparation method according to claim 3, characterized in that: The reflux reaction in step (3) is an oil bath reflux reaction, the oil bath temperature is 160 to 280° C., and the oil bath reaction time is 0.5 to 3 h.

7. Use of the nanocrystalline transition metal sulfide catalyst according to claim 1 in the electrocatalytic preparation of H2O2 in an acidic electrolyte.

8. The use according to claim 7, characterized in that: The acidic electrolyte includes sulfuric acid or perchloric acid with a concentration of 0.05 to 0.5 mol / L. The electrocatalysis adopts an H-Cell double-chamber electrolytic cell or a single-chamber electrolytic cell and a three-electrode working mode. The transition metal sulfide catalyst is coated on a rotating ring disk electrode as a working electrode or the transition metal sulfide catalyst is coated on a hydrophobic carbon paper as a working electrode. A potential range of -0.15 to 0.1 V vs RHE is applied to the working electrode of the H-Cell electrolytic cell to carry out an electrocatalytic H2O2 production experiment.

9. Use of the nanocrystalline transition metal sulfide catalyst according to claim 1 in electro-catalytically producing H2O2 in an acidic electrolyte for electro-Fenton degradation of refractory organic pollutants.

10. The use according to claim 9, characterized in that: The electrocatalysis adopts a single-chamber electrolytic cell and a three-electrode working mode, and the transition metal sulfide catalyst is coated on a hydrophobic carbon paper as a working electrode to electro-Fenton degrade different pollutants.

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