Method for preparing plasma nanoparticle Ag / Ag2S photocatalyst

Abstract

The present invention discloses a method for preparing a plasmonic nanoparticle Ag / Ag2S photocatalyst, comprising the following steps: S1. adding thioglycolic acid to water and vigorously stirring for 2 hours to obtain a mixed solution; S2. adding AgNO3 to the mixed solution and stirring for 2 hours to obtain a uniform mixture, followed by adding Na2S·9H2O and stirring for 1 hour to obtain a gray suspension; S3. centrifuging the suspension to obtain a precipitate a, which is then washed several times with ultrapure water and ethanol to obtain Ag2S; S4. dissolving the Ag2S in water, followed by in-situ reduction of silver sulfide with a sodium borohydride solution to obtain a precipitate b; S5. washing the precipitate b several times with ultrapure water and ethanol, and then drying at 60°C overnight to obtain the Ag / Ag2S photocatalyst. The present invention improves the photocatalytic activity of nanorod-shaped Ag2S by synthesizing Ag nanoparticles on the surface of Ag2S. Plasmonic nanoparticle Ag / Ag2S photocatalysts can be prepared at room temperature using a simple in-situ growth method.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic materials, and in particular to a method for preparing plasma nanoparticle Ag / Ag2S photocatalyst. Background Art

[0002] Over the past few decades, polycyclic aromatic hydrocarbons (PAHs), characterized by their high toxicity and persistence, have been identified as an emerging threat to monitoring in industrial wastewater. Of particular note, naphthols, important fine chemical intermediates, are ubiquitous in the environment, both naturally and through anthropogenic activities, and have garnered widespread attention. Their hazards have been confirmed by the U.S. Environmental Protection Agency (EPA), leading to numerous initiatives to remediate aquatic environments contaminated by PAHs.

[0003] Semiconductor photocatalysis is considered one of the most promising green technologies for splitting water into oxygen and hydrogen and completely degrading various pollutants. Conventional semiconductor photocatalysts, such as TiO2 and ZnO, have proven to be highly effective photocatalytic materials for splitting water and decomposing organic pollutants. However, their wide band gaps limit their practical applications, as the ultraviolet light required for their reactions only accounts for 3%-5% of total sunlight. Therefore, the synthesis of novel narrow-bandgap semiconductor photocatalysts that can be excited by visible light has attracted widespread attention.

[0004] Ag2S is a semiconductor with a narrow bandgap (0.9-1.76 eV) and has a wide range of applications in optics and electronics, including electronic conductors, photovoltaics, and light-emitting devices. Furthermore, Ag2S is reported to have low toxicity and poses no acute risk to freshwater benthic organisms. However, due to its poor electron-hole pair separation, the photocatalytic performance of Ag2S remains to be improved.

[0005] Constructing and controlling novel nanostructures of different sizes (zero, one, two, and three dimensions) is considered an effective way to improve the performance of photocatalysts, as their size and shape play a key role in the performance of nanocrystals. Therefore, the development of Ag2S photocatalysts with novel nanostructures is of great significance. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing plasma nanoparticle Ag / Ag2S photocatalyst.

[0007] The technical solution of the present invention is: a method for preparing plasma nanoparticle Ag / Ag2S photocatalyst, comprising the following steps:

[0008] S1. Add thioglycolic acid to water and stir vigorously for 2 h to obtain a mixed solution;

[0009] S2. Add AgNO3 to the mixed solution and stir for 2 h to obtain a uniform mixture, then add Na2S·9H2O and stir for 1 h to obtain a gray suspension;

[0010] S3, centrifuging the suspension to obtain precipitate a, and then washing it with ultrapure water and ethanol several times to obtain Ag2S;

[0011] S4, adding water to dissolve the Ag2S, and then adding sodium borohydride solution to in situ reduce silver sulfide to obtain a precipitate b;

[0012] S5. The precipitate b was washed with ultrapure water and ethanol several times, and then dried at 60°C overnight to obtain the photocatalyst Ag / Ag2S.

[0013] Furthermore, the amount of thioglycolic acid added is: based on 1 L of water, add 480 to 530 μL of thioglycolic acid.

[0014] Description: The core Ag is formed by adding thioglycolic acid (MAA) to water under vigorous stirring and then introducing a silver ion source through AgNO3. + / MAA, so that during the entire reaction process, MAA acts as a structure-directing agent to control the preferential growth of nanorods Ag2S and regulate the material morphology, thereby preparing uniform rod-shaped Ag2S.

[0015] Furthermore, the amount of AgNO3 added is: based on 1L of water, add 0.4 to 0.6g of AgNO3.

[0016] Note: AgNO3 is used to add a silver ion source to the reaction system. AgNO3 is easy to purchase and obtain.

[0017] Furthermore, the amount of Na2S·9H2O added is: based on 1L of water, add 0.6-0.7g Na2S·9H2O.

[0018] Description: By using Na2S·9H2O to add a silver ion source to the reaction system, Na2S·9H2O is easy to purchase and obtain.

[0019] Furthermore, the amount of water and sodium borohydride solution added in step S4 is: taking 1L of water as the base amount of Ag2S, adding it to 403mL of water to dissolve it, and using 403mL of sodium borohydride solution to in situ reduce silver sulfide; wherein, the concentration of the sodium borohydride solution is: 0.025mM to 0.2mM.

[0020] Description: By introducing NaBH4 aqueous solution, it can +It is reduced to Ag nanoparticles anchored on the surface of Ag2S, thereby ultimately achieving the Ag / Ag2S photocatalyst obtained at room temperature using a simple in situ growth method; the sodium borohydride solution at the dosage concentration within the above range makes the prepared Ag / Ag2S photocatalyst have the relatively optimal use effect.

[0021] Furthermore, the vigorous stirring in step S1 is 400-600 rpm; and the stirring in step S2 is 200-300 rpm.

[0022] Note: The above-mentioned vigorous stirring and stirring parameters can make the silver ion source introduced by MAA and AgNO3 form nucleated Ag + / MAA, and under the action of MAA, the preferential growth of nanorods Ag2S is controlled to prepare uniform rod-shaped Ag2S.

[0023] Furthermore, the sodium borohydride solution is added gradually and is assisted by plasma treatment during the addition.

[0024] Note: By introducing NaBH4 into the reaction system in a gradual manner and supplemented with plasma treatment, the Ag in the reaction system can be further promoted. + The Ag2S photocatalyst is reduced to Ag nanoparticles anchored on the Ag2S surface, thereby further enhancing the performance of the obtained Ag / Ag2S photocatalyst.

[0025] Furthermore, the method of adding gradually comprises the following steps:

[0026] 1) Setting the parameters of the plasma discharge device to: a discharge voltage of 15 to 30 kV, a frequency of 5 to 15 kHz, and an initial flow rate of the working gas of 8 to 10 L / min; adding the sodium borohydride solution in multiple portions at a rate of 5 to 10% per minute;

[0027] 2) When the amount of sodium borohydride solution added increases to 20% to 30%, the initial flow rate begins to decrease at a rate of 0.5 L / min until it reaches a constant flow rate after the amount of sodium borohydride solution added increases to 70% to 80%, and then maintains a constant flow rate until the addition of the sodium borohydride solution is completed, and then stops the plasma treatment.

[0028] Description: Using the parameter settings of the above plasma discharge device, the flow rate of the working gas is regulated according to the addition amount of NaBH4 aqueous solution, and the dynamic adjustment of the working gas is used to effectively promote the removal of Ag in the reaction system. + The reduction effect is to anchor the Ag nanoparticles on the Ag2S surface, thereby further enhancing the performance of the obtained Ag / Ag2S photocatalyst.

[0029] Furthermore, the working gas is nitrogen.

[0030] Note: Nitrogen is selected as the working gas, which can well meet the use requirements of working gas. At the same time, it is easy to obtain and low in cost.

[0031] The beneficial effects of the present invention are:

[0032] (1) The method of the present invention can improve the photocatalytic activity of nanorod-shaped Ag2S to a certain extent by synthesizing Ag nanoparticles on the surface of Ag2S. Since Ag has perfect electrical conductivity, its nanostructure can induce LSPR on the surface of nanorod-shaped Ag2S. At the same time, the electron transfer between Ag and Ag2S may have a positive effect on the separation of electrons and holes.

[0033] (2) The present invention innovatively adopts a simple in-situ growth method to prepare plasma nanoparticles Ag / Ag2S photocatalyst at room temperature. By introducing thioglycolic acid (MAA), it acts as a structure-directing agent to control the preferential growth of nanorods Ag2S and regulate the material morphology, thereby preparing a uniform rod-like morphology. By introducing NaBH4 aqueous solution, it can make Ag + It is reduced to Ag nanoparticles anchored on the Ag2S surface, thus finally achieving the Ag / Ag2S photocatalyst using a simple in situ growth method at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram of the synthesis steps of Ag / Ag2S photocatalyst.

[0035] Figure 2 is the XRD spectrum of Ag / Ag2S samples with different Ag doping amounts.

[0036] Figure 3 is the TEM image, among which, (a) Ag2S; (b) 0.025-Ag / Ag2S; (c) 0.050-Ag / Ag2S; (d) 0.075-Ag / Ag2S; (e) 0.100-Ag / Ag2S; (f) 0.200-Ag / Ag2S.

[0037] Figure 4 This is the EDS-surface scan spectrum of 0.075-Ag / Ag2S.

[0038] Figure 5 This is the XPS spectrum of 0.075-Ag / Ag2S.

[0039] Figure 6 It is the specific surface area map of the sample.

[0040] Figure 7 (a) Solid UV spectrum of the sample, (b) direct transition (αhv) of Ag2S2 Relationship between band gap energy (hv) and (c) direct transition (αhv) of 0.075-Ag / Ag2S 2 and band gap energy (hv).

[0041] Figure 8 (a) PL spectrum and (b) fluorescence lifetime spectrum of the sample.

[0042] Figure 9 (a) Photocurrent spectrum and (b) electrochemical impedance spectroscopy of the sample.

[0043] Figure 10 (a) Graph showing the adsorption efficiency of 2-naphthol on the sample, (b) graph showing the degradation efficiency of 2-naphthol by the sample, and (c) graph showing the kinetic curve fitting.

[0044] Figure 11 This is the cyclic degradation experiment diagram of the sample.

[0045] Figure 12 (a) The effect of different quenchers on the degradation activity of 2-naphthol in the sample, and the ERP spectra of the sample captured by DMPO under visible light conditions when dispersed in (b) methanol and (c) water.

[0046] Figure 13 Calculation of the work functions of (a) Ag and (b) Ag2S; and (c) diagram of the photocatalytic degradation mechanism of two-phase Ag / Ag2S. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below in conjunction with specific implementation methods to better demonstrate the advantages of the present invention.

[0048] In certain embodiments, a method for preparing a plasma nanoparticle Ag / Ag2S photocatalyst comprises the following steps: adding 480 to 530 μL of thioglycolic acid to 1 L of water, for example, 480 μL, 500 μL, 530 μL, etc., and vigorously stirring at 400 to 600 rpm for 2 h, for example, 400 rpm, 500 rpm, 600 rpm, etc., to obtain a mixed solution; adding 0.4 to 0.6 g of AgNO3 to the mixed solution and stirring at 200 to 300 rpm for 2 h, for example, 0.4 g, 0.5 g, 0.6 g, etc.; 200 rpm, 250 rpm, 300 rpm, etc., to obtain a uniform mixture, and then adding 0.6 to 0.7 g of Na2S·9H2O was stirred at 200-300 rpm for 1 hour (e.g., 0.6 g, 0.625 g, 0.7 g, etc.); 200 rpm, 250 rpm, 300 rpm, etc., to obtain a gray suspension. The suspension was centrifuged to obtain precipitate a, which was then washed several times with ultrapure water and ethanol to obtain Ag2S. The Ag2S was dissolved in 403 mL of water, followed by in situ reduction of silver sulfide with 403 mL of sodium borohydride solution to obtain precipitate b. Precipitate b was washed several times with ultrapure water and ethanol, and then dried at 60°C overnight to obtain the photocatalyst Ag / Ag2S. This method enables the preparation of plasmonic nanoparticle Ag / Ag2S photocatalysts using a simple in situ growth method at room temperature.

[0049] In some embodiments, the concentration of the sodium borohydride solution is 0.025 mM to 0.2 mM, for example, 0.2 mM, 0.1 mM, 0.075 mM, 0.05 mM, 0.025 mM, etc. The sodium borohydride solution in this range of concentration can achieve the best effect of the prepared Ag / Ag2S photocatalyst.

[0050] In some embodiments, the sodium borohydride solution is added gradually and plasma treatment is performed during the addition, including the following steps: setting the parameters of the plasma discharge device to: a discharge voltage of 15 to 30 kV, for example, 15 kV, 25 kV, 30 kV, etc., a frequency of 5 to 15 kHz, for example, 5 kHz, 10 kHz, 15 kHz, etc., an initial flow rate of the working gas of 8 to 10 L / min, for example, 8 L / min, 9 L / min, 10 L / min, etc.; adding the sodium borohydride solution; The solution is added in multiple times at a rate of 5% to 10% per minute, for example: 5% per minute, 10% per minute, etc.; 2) when the amount of sodium borohydride solution added is increased to 20% to 30%, for example: 20%, 25%, 30%, etc., the initial flow rate begins to decrease at a rate of 0.5L / min until it reaches a constant flow rate after the amount of sodium borohydride solution added is increased to 70% to 80%, for example: 70%, 75%, 80%, etc., and then the constant flow rate is maintained until the addition of sodium borohydride solution is completed, and the plasma treatment is stopped. Using the parameter setting of the above-mentioned plasma discharge device, by introducing NaBH4 into the reaction system in a gradual addition manner, it can further promote the removal of Ag in the reaction system. + The Ag2S photocatalyst is reduced to Ag nanoparticles anchored on the Ag2S surface, thereby further enhancing the performance of the obtained Ag / Ag2S photocatalyst.

[0051] Example 1

[0052] The method for preparing plasma nanoparticle Ag / Ag2S photocatalyst comprises the following steps:

[0053] S1. Add 100 μL of thioglycolic acid to 200 mL of water and vigorously stir at 600 rpm for 2 h to obtain a mixed solution;

[0054] S2. Add 0.1 g of AgNO3 to the mixed solution and stir at 300 rpm for 2 h to obtain a uniform mixture, then add 0.125 g of Na2S·9H2O and stir at 300 rpm for 1 h to obtain a gray suspension;

[0055] S3, centrifuging the suspension to obtain precipitate a, and then washing it with ultrapure water and ethanol five times respectively to obtain Ag2S;

[0056] S4, adding the Ag2S to 80.6 mL of water to dissolve it, and then adding 80.6 mL of 0.075 mM sodium borohydride solution to in situ reduce the silver sulfide to obtain a precipitate b;

[0057] S5. The precipitate b was washed 5 times with ultrapure water and ethanol respectively, and then dried at 60° C. overnight to obtain the photocatalyst Ag / Ag2S.

[0058] Example 2

[0059] This example differs from Example 1 in that 80.6 mL of a 0.2 mM sodium borohydride solution is used for in-situ reduction of silver sulfide.

[0060] Example 3

[0061] This example differs from Example 1 in that 80.6 mL of a 0.1 mM sodium borohydride solution is used to in situ reduce silver sulfide.

[0062] Example 4

[0063] This example differs from Example 1 in that 80.6 mL of a 0.05 mM sodium borohydride solution is used for in-situ reduction of silver sulfide.

[0064] Example 5

[0065] This example differs from Example 1 in that 80.6 mL of a 0.025 mM sodium borohydride solution is used to in situ reduce silver sulfide.

[0066] The Ag / Ag2S photocatalyst prepared by the method of Examples 1-5 was subjected to photodegradation of refractory 2-naphthol to evaluate its photocatalytic performance.

[0067] Sodium sulfide (Na2S·9H2O) and ethanol (CH3ch2OH) were purchased from Nanjing Chemical Reagent Co., Ltd. (Nanjing, China); silver nitrate (AgNO3) and sodium borohydride (NaBH4) were provided by Sinopharm Chemical Co., Ltd. (Shanghai, China); thioglycolic acid (C2H4O2S) was provided by TCI Co., Ltd. (Shanghai, China); 2-naphthol (C 10 HO) was provided by Chengdu Kelong Chemical Co., Ltd. All reagents were of analytical grade and were not further purified. Ultrapure water was used throughout the experiments.

[0068] 1) HPLC analysis

[0069] The concentration of the target compound was accurately determined using an Agilent 1200 high-performance liquid chromatography (HPLC) with a DAD detector and a C18 reversed-phase column (5 μm, 4.6 × 150 mm). The activity of the photocatalyst can be directly reflected in the degradation efficiency of the target compound. The photocatalytic degradation efficiency is calculated as follows:

[0070]

[0071] Where η represents the photocatalytic efficiency; C0 and C tThe concentrations of the pollutant solutions before and after the reaction are shown in Table 1. The degradation products of 2-naphthol were analyzed by gas chromatography using a TG-5 SILMS column (30 m×0.25 mm, 0.25 μm).

[0072] For 2-naphthol, methanol-water (3:2, v / v) was used as the mobile phase, the detection wavelength was 230 nm, and the injection volume of each sample was 20 μL.

[0073] 2) GC-MS analysis

[0074] Prior to gas chromatography-mass spectrometry analysis, water samples (50 mL) were centrifuged and filtered through a 0.22 μm microporous filter to remove suspended particles. The resulting solution was then extracted three times with a certain ratio of dichloromethane (2:1, v:v). The extract was concentrated to approximately 1 mL by rotary evaporation, dried with nitrogen purge, and then dissolved in 1 mL of n-hexane. For GC-MS analysis, the following method was used: the GC temperature was initially 70°C for 1 min, then increased to 160°C at 10°C / min, and then increased to 290°C at 4°C / min for 5 min. The injection line, transfer line, and ion source temperatures were 260°C, 290°C, and 280°C, respectively. Helium was used as the carrier gas at 1.0 mL / min. EI mode was used, and the energy was set to 70 eV.

[0075] 3) Evaluation of photocatalytic activity

[0076] The photocatalytic activity of the prepared samples was systematically evaluated by degradation of 2-naphthol under visible light irradiation. The simulated illumination system (XPA-7, Nanjing, China) consisted of a 1000W xenon lamp, a 420nm cutoff filter, a 50mL quartz reaction tube, and a cooling water circulation system (to prevent thermal catalytic effects). During the experiment, 25mg of each catalyst was dispersed into 50mL of the target pollutant solution. The initial concentration of 2-naphthol was 10mg / L. Acetonitrile was used as the solubilizer (acetonitrile:water volume ratio of 1:1000). Before irradiation, the suspension was magnetically stirred in the dark for 1 hour to ensure adsorption-desorption equilibrium of the pollutant on the photocatalyst surface. Under visible light irradiation, approximately 3mL of the suspension was sampled from the reaction tube at specified time intervals, centrifuged, and filtered through a 0.22μm microporous filter to remove suspended particles. To verify the stability and reproducibility of the photocatalytic reaction, the photocatalysts were collected and repeated multiple cycles were performed under the same conditions.

[0077] 4) Characterization and calculation

[0078] The crystallinity of the samples was determined by X-ray diffraction at room temperature using an XRD-6000 X-ray powder diffractometer (Shimadzu) at 40 kV and 30 mA. Field emission scanning electron microscopy (FESEM) images were acquired on a FEI-quanta 250 scanning electron microscope at an accelerating voltage of 10 kV. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were performed on a JEM-200CX instrument. The surface chemical composition and chemical state of the photocatalysts were analyzed using X-ray photoelectron spectroscopy (XPS) on a PHI5000 Versa Probe electron spectrometer (ULVAC-PHI, Japan). The specific surface area and pore size were analyzed using the Brunauer-Emmett-Teller (BET) method and the Barrett-Joyner-Halenda (BJH) method (ASAP 2020, Micromeritics, USA) under a nitrogen adsorption-desorption isotherm at 77 K. UV-visible absorption spectroscopy was performed on a Lambda 750 (PerkinElmer) spectrophotometer in the wavelength range of 200–800 nm. Fluorescence emission spectra were recorded from 200 to 800 nm using a fluorescence spectrophotometer and a time-resolved fluorescence spectrophotometer with an excitation wavelength of 365 nm. Photoelectrochemical characterization was performed on an electrochemical workstation (CHI760E, Shanghai, China) using a standard three-electrode system. The prepared samples were uniformly coated on an ITO electrode as the working electrode. A Pt electrode and an Ag / AgCl electrode were used as the counter electrode and reference electrode, respectively. The electrolyte was 0.2 M NaSO. A 1000 W xenon lamp provided the light source.

[0079] The molecular orbital calculations of 2-naphthol were performed using the Gaussian 09W program, using the B3LYP / 6-311+G* energy level. Based on the Gaussian calculation results, the FEDs (frontier electron density) of the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) of each atom were carefully analyzed. In addition, (FED 2 HOMO +FED 2 LUMO )and 2FED 2 LUMO The calculations were performed to predict possible attack sites within the contaminant molecules. The generalized gradient approximation (GGA) in the Perdue-Burke-Enzer (PBE) functional form and hypercomplex pseudopotentials were applied. Density functional theory (DFT) calculations were performed using the plane wave pseudopotential method within the CASTEP program. The work function was estimated using the PBE-corrected GGA within the CASTEP code.

[0080] 5) Morphology and microstructure

[0081] XRD can provide detailed information about the crystal structure and phase purity. The XRD patterns of Ag / Ag2S with different Ag doping amounts are shown in Figure 2. Figure 2 As shown, the XRD pattern of the single-phase photocatalyst (Ag2S) was analyzed. The diffraction peaks of Ag2S at 22.43°, 24.91°, 26.32°, 28.96°, 33.61°, 36.81°, 43.40°, 44.20° and 50.73° correspond to the characteristic peaks of the standard card (JCPDS No.14-0072) (-101), (110), (012), (111), (120), (121), (200), (103) and (-221) of orthorhombic Ag2S, respectively. For the Ag / Ag2S sample, in addition to the diffraction peak of Ag2S, a diffraction peak corresponding to face-centered cubic Ag (200) appeared at 44.28°. As the concentration of NaBH4 increased during the preparation process, the intensity of the Ag diffraction peak became stronger. However, the peaks may be less sharp and less distinct due to the overlap of the (103) planes of Ag2S (JCPDS No. 04-0783, 2θ = 44.20). Compared with the diffraction peaks of the single Ag2S photocatalyst, the diffraction peaks of the composite sample are slightly broadened. In addition, no obvious diffraction peaks of other phases were detected in the composite material, indicating that the introduction of Ag does not affect the crystal structure of the Ag2S photocatalyst.

[0082] TEM images of Ag2S and Ag / Ag2S are shown in Figure 2. Figure 3 As shown. SEM of nanorod-shaped Ag2S catalyst is shown Figure 3 As shown in (a), it is formed by irregular stacking of nanorods. Figure 3 In (a), it can be observed that the surface of a single nanorod-shaped Ag2S sample is smooth and the width is about 80-110nm. Figure 3 (b)-(f) are TEM images of Ag / Ag2S with varying amounts of Ag. Ag nanoparticles are uniformly dispersed on the surface of Ag2S, and the microstructure of Ag2S remains virtually unchanged after Ag deposition. Furthermore, the number of Ag nanoparticles formed on the Ag2S surface increases quantitatively with increasing NaBH4 content. The structure of Ag2S remains unchanged after Ag nanoparticle deposition. A close interface exists between the Ag2S and Ag2S, forming a heterojunction.

[0083] In order to further confirm the elemental composition of 0.075-Ag / Ag2S, the EDS-mapping results are as follows Figure 4 As shown. EDS mapping of single Ag2S ( Figure 4 ) clearly and unambiguously defines the spatial distribution of Ag and S elements in the nanorods.

[0084] 6) Surface structure and properties

[0085] X-ray photoelectron spectroscopy (XPS) is an effective tool for elucidating the surface chemical state and composition of heterostructures. The XPS data of Ag2S and 0.075-Ag / Ag2S further demonstrate the successful preparation of 0.075-Ag / Ag2S. Figure 5 (a) is the total XPS spectrum of single Ag2S and composite 0.075-Ag / Ag2S. For single Ag2S sample and composite 0.075-Ag / Ag2S, both samples show characteristic peaks of Ag 3d and S 2p, which are attributed to the deposition of Ag2S and Ag nanoparticles on the surface of the composite material. In order to further observe the chemical information of various elements in the sample, we Figure 5 Their corresponding high-resolution XPS spectra are analyzed in (bc). Figure 5 In (b), 0.075-Ag / Ag2S has two characteristic peaks S 2p3 / 2 and S2 p1 / 2, whose binding energies are 159.9 eV and 161.7 eV, respectively. These peaks are obviously shifted to lower binding energies than those of single Ag2S. Figure 5 (c) shows the high-resolution XPS spectra of Ag 3d of samples Ag2S and 0.075-Ag / Ag2S. There are two independent peaks at 366.8eV and 372.7eV of Ag2S, corresponding to Ag 3d, respectively. + The characteristic peaks of Ag 3d5 / 2 and Ag3d3 / 2 can be seen from the XPS spectrum of 0.075-Ag / Ag2S. These two peaks can be deconvoluted into four bands, indicating the existence of different Ag valence states. The two strong peaks in the spectrum of 0.075-Ag / Ag2S correspond to Ag + 3d 5 / 2 and 3D 3 / 2 , whose binding energies are 366.2eV and 372.2eV respectively, and the other two relatively weak peaks are closely related to metallic Ag. 0 Well matched 3d 5 / 2 and 3D 3 / 2 , the binding energies are 367.0eV and 373.1eV. In 0.075-Ag / Ag2S, the Ag3d binding energy in the XPS spectrum also shifts by 0.6eV toward the low binding energy direction. 0.075-Ag / Ag2S is compared with single Ag2S. The shift of the Ag 3d peak indicates that Ag2S acts as an electron acceptor and electrons are transferred from Ag to the Ag2S surface. These results confirm the presence of metallic Ag in the two-phase plasma photocatalyst Ag / Ag2S. On the other hand, the metallic Ag of the sample Ag / Ag2S is 0 The surface molar ratio of Ag to total Ag species was semi-quantitatively estimated to be ca. 0.14, respectively. The detailed data are shown in Table 1(a). The calculation results further show that Ag 0 It was successfully formed on the Ag2S surface.

[0086] Table 1 Ag3d XPS peak area analysis of sample 0.075-Ag / Ag2S

[0087]

[0088] The specific surface area of a photocatalyst, determined by the porosity and geometry of the material, plays a crucial role in its photocatalytic activity. It is well known that photocatalytic reactions in nanocomposites are generally interface-mediated processes. The larger surface area of a nanocomposite provides more active sites for reactions with reactant molecules. Furthermore, higher adsorption capacity facilitates and accelerates the photocatalytic degradation process. Figure 5 Nitrogen adsorption-desorption isotherms and Barrett-Hoyner-Hallendar (BJH) pore size distribution curves of Ag2S and 0.075-Ag / Ag2S. The adsorption isotherms can be classified as type IV H3 hysteresis loops, indicating that the samples aggregate to form slit-like pores. Figure 6 The pore sizes of single Ag2S and 0.075-Ag / Ag2S were compared. Most of the pores in the samples were mainly distributed in the size range of 1nm-8nm. The 0.075-Ag / Ag2S composite material showed a wider pore size distribution, which was due to the presence of aggregated pore structure between Ag / Ag2S nanorods and the uneven surface structure of nanocrystals. The specific surface areas of the pore sizes of single Ag2S and 0.075-Ag / Ag2S were calculated (Table 2) to be 26.727 and 31.711, respectively. Compared with the single sample, the specific surface area and pore volume of the 0.075-Ag / Ag2S composite material were significantly increased, which is beneficial to the adsorption of reactants and the diffusion of reaction products, thereby improving the photocatalytic performance.

[0089] Table 2 Porosity and specific surface area characteristics of samples

[0090]

[0091] 7) Optical and electrochemical properties

[0092] The photocatalytic performance of semiconductors is significantly correlated with their optical properties. To verify the changes in optical properties caused by doping with nanoparticles of Ag, samples Ag2S and Ag / Ag2S were studied using UV-visible diffuse reflectance spectroscopy, fluorescence emission, and photocurrent measurements. Figure 7(a) shows the UV-visible absorption spectra of single Ag2S and Ag / Ag2S doped with different amounts of Ag in the range of 200-700nm. The figure clearly shows the absorption of Ag2S and Ag / Ag2S from the ultraviolet to the visible light region. In addition, the UV-visible spectra of all Ag / Ag2S composites clearly show a red shift between 200 and 700nm. This may be due to the plasma resonance caused by the in-situ deposition of Ag nanoparticles on the surface of Ag2S nanorods. It is worth noting that the absorption of 0.075-Ag / Ag2S plasma photocatalyst is higher than that of other doped Ag / Ag2S, and the absorption of the photocatalyst does not increase with further increase of Ag content. This is because the Ag covering the surface of Ag2S nanorods 0 The content is relatively large. It is obvious that Ag nanoparticles significantly improve the light absorption capacity, which may increase the formation rate of electron-hole pairs at the interface of Ag and Ag2S, thereby improving the photocatalytic performance. In addition, the band gap energy of the semiconductor can be used to estimate the light response ability of the photocatalyst using the Kubelka-Munk equation:

[0093] αhν=A(hν-Eg) n

[0094] Here, α, hν, A, and Eg represent the absorption coefficient, light energy, proportionality constant, and band gap, respectively. The exponent n depends on the semiconductor's electronic transitions, with n = 1 / 2 for directional-gap semiconductors and n = 2 for indirect-gap semiconductors. It is reported that Ag2S is a direct-gap semiconductor with an n value of 1 / 2.

[0095] like Figure 7 As shown in (b, c), the band gap of Ag2S is approximately 1.68 eV, consistent with previous reports. The band gap of 0.075-Ag / Ag2S is 1.61 eV. The band gap of the 0.075-Ag / Ag2S composite is significantly lower than that of its single-material Ag2S counterpart. These results indicate that a smaller band gap leads to higher utilization of visible light.

[0096] During the photocatalytic reaction, the recombination of electrons and holes greatly affects the photocatalytic performance of the photocatalyst. Therefore, fluorescence spectroscopy and photocurrent measurement were used to study the charge separation and transfer characteristics of the samples.

[0097] Photoluminescence (PL) emission spectroscopy reveals the migration, separation, and recombination of photogenerated electrons and holes. Photocatalysts with lower PL intensities have slower recombination rates. Since photocatalysts generate electrons and holes upon photoactivation, some of these electrons and holes recombine, releasing energy in the form of fluorescence emission. Figure 8(a) shows the PL spectra of single Ag2S and composites of Ag / Ag2S with different Ag contents excited at 365nm. All samples showed similar spectral shapes. Single Ag2S showed the highest intensity among these samples. Compared with single Ag2S, the release intensity of the composite material was significantly reduced, indicating that the PL intensity of the Ag / Ag2S nanocomposite material varies with the amount of Ag. Due to the LSPR effect and dipole characteristics of Ag, electron-hole pairs can be effectively generated. It should be noted that 0.075-Ag / Ag2S has the lowest PL intensity among all two-phase composites, indicating that the recombination rate of photoexcited electron-hole pairs is the lowest. In order to further understand the lifetime of photogenerated electron-hole pairs in photocatalysts, the lifetime decay of photogenerated electron-hole pairs of single Ag2S and 0.075-Ag / Ag2S was analyzed by fitting their kinetic curves. Average lifetime (τ avg ) is determined by the following equation:

[0098] f(t)=B+A1×exp(-t / τ1)+A2×exp(-t / τ2)

[0099] Where A1, A2 are amplitudes, τ1, τ are radiation lifetimes. The kinetic parameters are summarized in Table 3. Figure 8 As shown in (b), the Ag2S sample with Ag nanoparticles deposited on the surface has a longer carrier life than the single Ag2S sample. In addition, the decay time of the two-phase composite material 0.075-Ag / Ag2S is relatively longer than that of the single Ag2S sample. Specific calculations show that the average decay life (τ avg ) are 0.011 and 0.046 ns, respectively. The improvement of carrier expected lifetime indicates that the electron transfer process exists on the surface of Ag2S nanorods.

[0100] Table 3 Summary of fluorescence transient lifetime data of samples

[0101] Sample <![CDATA[τ1(ns)]]> <![CDATA[A1]]> <![CDATA[τ2(ns)]]> <![CDATA[A2]]> <![CDATA[τ avg (ns)]]> <![CDATA[Ag2S]]> 0.0109 2966.91 0.166 0.00287 0.011 <![CDATA[0.075-Ag / Ag2S]]> 0.0315 -600.97 0.0456 573.61 0.046

[0102] Transient photocurrent analysis provides additional evidence supporting the efficiency of photoinduced electron-hole separation. Generally speaking, photocurrent is related to the lifetime of photogenerated carriers, which are generated by electrons transferring from the valence band to the conduction band of the sample. Higher photocurrent intensities indicate longer lifetimes of photocatalyst electron-hole pairs. Figure 9(a) shows the I-T curves of single Ag2S and Ag / Ag2S composites with different Ag contents. Under visible light, the photocurrent intensity of single Ag2S is very low, with almost no obvious photocurrent response. In contrast, the photocurrent intensity of the 0.075-Ag / Ag2S sample is higher than that of single Ag2S and other Ag / Ag2S composites with different molar ratios. With increasing Ag mass ratio, the photocurrent intensity of Ag / Ag2S increases due to the LSPR effect of Ag, but when the Ag content reaches the ideal concentration, its photocurrent intensity subsequently decreases. Electrochemical impedance spectroscopy (EIS) response experiments were used to examine the charge transfer resistance and interfacial reaction behavior of photoinduced carriers in the samples. Figure 9 (b) Electrochemical impedance spectroscopy (EIS) plots of single Ag2S and 0.075-Ag / Ag2S. A smaller arc radius on the EIS plot indicates lower charge transfer resistance and higher separation efficiency of photogenerated electrons and holes; a larger arc radius indicates lower separation efficiency. Therefore, depositing Ag on Ag2S improves charge mobility and enhances electron-hole pair separation efficiency. The PL, photocurrent, and EIS results are generally consistent.

[0103] 8) Photocatalytic performance evaluation

[0104] In order to characterize the photocatalytic performance of the prepared samples, the photocatalytic degradation effects of Ag2S and Ag / Ag2S samples on 2-naphthol in aqueous solution were determined ( Figure 10 In the blank experiment, in the absence of catalyst, 2-naphthol showed no obvious photodegradation ( Figure 10 (a)), indicating that the self-photolysis of 2-naphthol can be ignored. At the same time, a 60-min dark experiment was carried out before illumination, and the adsorption-desorption equilibrium was reached between the photocatalyst and the pollutant. In order to verify the optimal mass ratio of Ag in the composite material Ag / Ag2S, the photocatalytic activity of Ag / Ag2S composite materials doped with different amounts of Ag for the degradation of 2-naphthol was studied ( Figure 10 (b) and (c)). It is obvious that the photodegradation efficiency of 0.075-Ag / Ag2S under 120 min illumination is higher than that of single Ag2S and other molar ratios of Ag / Ag2S ( Figure 9 (b)). The pseudo-first-order kinetic rate constants (k) of various composite materials Ag / Ag2S are as follows Figure 10(c) As shown. The k value of 0.075-Ag / Ag2S is about 3.6 times that of single Ag2S. In addition, the removal concentration of 2-naphthol initially increases with the increase of the amount of Ag in the composite Ag / Ag2S during 120 min, and then decreases after the amount of reduced Ag reaches the optimal level (the concentration of sodium borohydride during the preparation process is 0.075 mM). The decrease in the photodegradation activity of the composite material with excessive Ag deposition may be due to the excessive Ag nanoparticles covering some active sites on the surface of nanorod Ag2S. The above results indicate that the introduction of Ag plays a key role in the photodegradation process. The appropriate amount of Ag deposited on the surface of Ag2S will help to improve the photocatalytic performance.

[0105] The stability and reusability of the 0.075-Ag / Ag2S two-phase photocatalyst for the photodegradation of 2-naphthol were studied repeatedly. Obviously, after 4 cycles, the photocatalytic efficiency of the 0.075-Ag / Ag2S plasma photocatalyst decreased slightly. Figure 11 The results showed that the 0.075-Ag / Ag2S sample had good photocatalytic stability and recyclability for 2-naphthol during the photodegradation process.

[0106] 9) Photocatalytic mechanism

[0107] Through sample characterization and pollutant degradation results, it was found that the 0.075-Ag / Ag2S photocatalyst can successfully degrade 2-naphthol under visible light. However, in order to better understand the significant improvement in photocatalytic performance, the underlying degradation mechanism needs to be discussed.

[0108] 10) Role of active species

[0109] Conducting active species capture experiments is crucial and necessary to capture the active species produced during photodegradation. In the photocatalytic degradation process, the main active species involved in the reaction are ·OH, ·O2 - and h + In the degradation process, one or more active substances may play a role in the photocatalytic oxidation process. In this study, the hydroxyl radical (·OH) inhibitor isopropyl alcohol (IPA), superoxide radical (·O2 - ) inhibitors of nitroxide free radicals piperidinol (TEMPOL) and holes (h + ) inhibitor ammonium oxalate (AO). Figure 12 As shown in (a), the degradation efficiency of 2-naphthol did not change significantly after adding TEMPOL and AO; similarly, the photodegradation effect of 2-naphthol was also partially inhibited after adding IPA. The effects of quenchers on photocatalytic activity are arranged in the following order: TEMPOL (·O2 - )>AO(h +)>IPA(·OH). In the quenching experiment, the worse the photocatalytic performance of the photocatalyst is after adding the scavenger, the more significant the role of the corresponding free radicals in the photodegradation process. Therefore, the conclusion is that all ·O2 - ,h + and ·OH radicals are involved in the photodegradation process, especially ·O2 - and h + The effect on the degradation effect is greater. In order to further observe the role of active species intuitively, we conducted EPR experiments on free radicals captured by DMPO on the photocatalyst samples. Under dark conditions and without catalyst, all samples had no characteristic peaks ( Figure 12 (b) and (c)). It can be seen that O2 was detected in the 0.075-Ag / Ag2S sample. - and ·OH characteristic peaks. In the photocatalytic Ag2S degradation system, ·O2 - The characteristic peaks of ·O2 and ·OH are weak, which shows that adding Ag to single Ag2S is beneficial to improving the photocatalytic activity. - ,h + and ·OH are the main active species in the photodegradation process. The EPR experimental results are basically consistent with the EPR capture experimental results of free radical active species.

[0110] 11) Potential photodegradation mechanism

[0111] By studying the energy band structure and work function of the prepared samples, the possible mechanism of the improved photocatalytic performance of 0.075-Ag / Ag2S was elucidated. The work function analysis can also reveal the interfacial electron transfer process. Figure 13 From (a) and (b), we can see that the work function sequences of Ag and Ag2S are 4.378 and 4.988 eV respectively, which means that the electrons in the Ag nanoparticles will tend to transfer to Ag2S. In addition, the position of the conduction band of Ag2S (E CB ) and valence band position (E vb ) can be calculated using the following two equations:

[0112] E CB =XE e -0.5E g

[0113] E VB =E CB +E g

[0114] Where X represents the potential of the semiconductor, E e Equal to 4.5eV, E g is the band gap of the photocatalyst. Figure 13(c) The average value of silver sulfide obtained from UV-visible data is 1.68eV, the conduction band potential of Ag2S is -0.38eV, and its valence band potential is 1.30eV. - Compared with the standard reduction potential of Ag2S (-0.33eV), the conduction band potential of Ag2S is negative enough. The results show that there are a large number of electrons on the conduction band surface of Ag2S that can capture O2 in aqueous solution and reduce it to O2 - Participate in the degradation reaction, and the abundant photogenerated electrons can further react with O2 - The reaction generates ·OH and reacts with pollutants; however, the valence band position of Ag2S is significantly lower than that of ·OH / H2O (2.27 eV) and ·OH / OH - (2.38eV) potential, indicating that most of the h + There is not enough oxidizing power to convert H2O or OH - Oxidized to ·OH. The holes in the valence band can directly react with the target pollutants. ·O2 - , OH and h + Working together, they ultimately degrade 2-naphthol.

[0115] As mentioned above, the two-phase nanoparticle Ag / nanorodal Ag2S can make the Ag / Ag2S bandgap smaller, better utilize visible light, faster carrier formation and transfer, and more efficient separation of electron-hole pairs. These factors all improve the degradation efficiency of the three-phase plasmonic photocatalyst.

[0116] In summary, a simple method was used for the first time to successfully prepare a novel nano-morphology Ag / Ag2S photocatalyst at room temperature. The morphology, structure and photoelectrochemical properties of the prepared photocatalyst were comprehensively characterized by XRD, SEM, TEM, HRTEM, SEM-EDS, XPS, BET, UV-Vis, PL and EIS. Compared with single Ag2S, composite Ag / Ag2S has a higher photocatalytic degradation rate for 2-naphthol. Among them, the Ag / Ag2S photocatalyst prepared by 0.075mM sodium borohydride solution has the best effect, and the degradation efficiency of 2-naphthol reaches 89.5% within 120min. This may be due to the LSPR effect of Ag nanoparticles, which inhibits the recombination of photogenerated carriers. ·OH, ·O2 - and h + It is the key active species in the photodegradation system. Free radical capture experiments have determined that h + and O2 - Free radicals have a greater impact on the photodegradation system. Combining the experimental data of photocatalysts and work function calculations, the photocatalytic mechanism of plasma photocatalysts was analyzed.

[0117] Example 6

[0118] This embodiment differs from embodiment 1 in that 96 μL of thioglycolic acid is added.

[0119] Example 7

[0120] This embodiment differs from embodiment 1 in that 106 μL of thioglycolic acid is added.

[0121] Example 8

[0122] The difference between this embodiment and embodiment 1 is that 0.08 g of AgNO 3 and 0.12 g of Na 2 S·9H 2 O are added.

[0123] Example 9

[0124] The difference between this embodiment and embodiment 1 is that 0.12 g of AgNO 3 and 0.14 g of Na 2 S·9H 2 O are added.

[0125] Example 10

[0126] The difference between this embodiment and embodiment 1 is that the vigorous stirring is 400 rpm; the stirring is 200 rpm.

[0127] Example 11

[0128] The difference between this embodiment and embodiment 1 is that the vigorous stirring is 500 rpm; the stirring is 250 rpm.

[0129] To further verify the effects of the above parameters on the prepared Ag / Ag2S photocatalyst, the following experiment is briefly described to determine the degradation efficiency of 2-naphthol by the Ag / Ag2S photocatalyst prepared in Examples 6-11 within 120 min, as shown in Table 4 below:

[0130] Table 4 Degradation efficiency of 2-naphthol over Ag / Ag2S photocatalyst

[0131] Group Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 2-Naphthol degradation rate 87.7％ 89.5％ 88.4％ 89.6％ 86.7％ 88.9％

[0132] By measuring the degradation efficiency of 2-naphthol by Ag / Ag2S photocatalysts prepared in different embodiments within 120 min, the preparation parameter range of Ag / Ag2S photocatalyst was systematically determined; in comparison with Example 1, the introduction of different proportions of thioglycolic acid had a certain effect on the catalytic activity of the prepared Ag / Ag2S photocatalyst, but as the proportion of thioglycolic acid continued to increase, the Ag / Ag2S photocatalyst had no obvious improvement; in comparison with Example 1, the catalytic activity of the prepared Ag / Ag2S photocatalyst was significantly improved when different proportions of AgNO3 and Na2S·9H2O were added. There is a certain influence, which may be related to the content of Ag2S, but as the content of AgNO3 and Na2S·9H2O continues to increase, the Ag / Ag2S photocatalyst is improved less, and it can be selected as needed according to the actual production cost and other requirements; in comparison with Example 1, using different violent stirring and stirring rates to control the preferential growth of nanorods Ag2S under the action of MAA has a certain influence, and by observing the improvement effect of the 2-naphthol degradation rate in each interval, it can be found that the improvement rate in the interval of Example 10-Example 11 is greater than the improvement rate in the interval of Example 11-Example 1, and it can be selected as needed according to the actual production cost and other requirements.

[0133] Example 12

[0134] This embodiment differs from embodiment 1 in that the sodium borohydride solution is added gradually and plasma treatment is performed during the addition. Specifically, the following steps are included:

[0135] 1) The parameters of the plasma discharge apparatus were set as follows: discharge voltage of 25 kV, frequency of 10 kHz, and initial nitrogen flow rate of 9 L / min; sodium borohydride solution was added in 10 portions at a rate of 10% per minute;

[0136] 2) When the amount of sodium borohydride solution added increased to 30%, the initial flow rate began to decrease at a rate of 0.5 L / min until it reached a constant flow rate of 7 L / min after the amount of sodium borohydride solution added increased to 70%. The constant flow rate was then maintained until the addition of the sodium borohydride solution was completed, and the plasma treatment was stopped.

[0137] Example 13

[0138] The difference between this embodiment and embodiment 1 is that the discharge voltage is 15 kV and the frequency is 5 kHz.

[0139] Example 14

[0140] The difference between this embodiment and embodiment 1 is that the discharge voltage is 30 kV and the frequency is 15 kHz.

[0141] Example 15

[0142] This embodiment differs from embodiment 1 in that the initial flow rate of nitrogen is 8 L / min.

[0143] Example 16

[0144] This embodiment differs from embodiment 1 in that the initial flow rate of nitrogen is 10 L / min.

[0145] Example 17

[0146] This embodiment differs from embodiment 1 in that the sodium borohydride solution is added in multiple portions at a rate of 10% per minute. When the amount of sodium borohydride solution added increases to 20%, the initial flow rate begins to decrease at a rate of 0.5 L / min until it reaches a constant flow rate of 6 L / min after the amount of sodium borohydride solution added increases to 80%. The constant flow rate is then maintained until the addition of the sodium borohydride solution is completed, and the plasma treatment is stopped.

[0147] Example 18

[0148] This embodiment differs from embodiment 1 in that the sodium borohydride solution is added in multiple portions at a rate of 5% per minute. When the amount of sodium borohydride solution added increases to 30%, the initial flow rate begins to decrease at a rate of 0.5 L / min until it reaches a constant flow rate of 5 L / min after the amount of sodium borohydride solution added increases to 70%. The constant flow rate is then maintained until the addition of the sodium borohydride solution is completed, and the plasma treatment is terminated.

[0149] To further verify the effects of the above methods and parameters on the prepared Ag / Ag2S photocatalyst, the following experiment is briefly described to determine the degradation efficiency of 2-naphthol by the Ag / Ag2S photocatalysts prepared in Examples 12-18 within 120 min. At the same time, based on Example 12, a group of control example 1 without plasma treatment and a group of control example 2 with a constant initial nitrogen flow rate were set, as shown in Table 5 below:

[0150] Table 5 Degradation efficiency of 2-naphthol over Ag / Ag2S photocatalyst

[0151] Group Example 12 Example 13 Example 14 Example 15 Example 16 2-Naphthol degradation rate 95.7％ 94.9％ 95.2％ 93.5％ 94.3％ Group Example 17 Example 18 Comparative Example 1 Comparative Example 2 / 2-Naphthol degradation rate 93.7％ 95.8％ 90.1％ 91.7％ /

[0152] By measuring the degradation efficiency of 2-naphthol by Ag / Ag2S photocatalysts prepared in different embodiments within 120 min, the effects of different process methods and related parameter settings of Ag / Ag2S photocatalysts were systematically determined.

[0153] In comparison with Example 1, the performance of the prepared Ag / Ag2S photocatalyst was further improved by gradually adding sodium borohydride solution and plasma treatment. In comparison with Example 12, under different plasma discharge device parameters, the catalytic activity of the prepared Ag / Ag2S photocatalyst was affected to a certain extent, among which the discharge voltage and frequency had relatively little effect on the prepared Ag / Ag2S photocatalyst, and the initial flow rate of nitrogen had a relatively large effect on the prepared Ag / Ag2S photocatalyst. In comparison with Example 17 and 18, the performance of the prepared Ag / Ag2S photocatalyst was further improved by gradually adding sodium borohydride solution and plasma treatment. In comparison with Example 12, under different plasma discharge device parameters, the catalytic activity of the prepared Ag / Ag2S photocatalyst was affected to a certain extent, among which the discharge voltage and frequency had relatively little effect on the prepared Ag / Ag2S photocatalyst, and the initial flow rate of nitrogen had a relatively large effect on the prepared Ag / Ag2S photocatalyst. 2. By comparison, when using different amounts of sodium borohydride solution, the catalytic activity of the prepared Ag / Ag2S photocatalyst is affected to a certain extent. Among them, the catalytic performance of Examples 12 and 18 is relatively better, but the addition time of Example 12 is 10 minutes, and the addition time of Example 18 is 20 minutes. Therefore, from the perspective of production efficiency, Example 12 is relatively better overall. By comparing the two groups of control examples 1 and 2 with Example 12, when not supplemented with plasma treatment, nitrogen flow rate adjustment, etc., the performance of the Ag / Ag2S photocatalyst is reduced to a certain extent.

[0154] Therefore, by further improving the introduction method of sodium borohydride solution, the dynamic adjustment of working gas is used to effectively promote the Ag in the reaction system. + The reduction effect is to anchor the Ag nanoparticles on the Ag2S surface, thereby further effectively enhancing the performance of the obtained Ag / Ag2S photocatalyst.

Claims

1. A method for preparing plasma nanoparticle Ag / Ag2S photocatalyst, characterized in that: The following steps are involved: S1. Add thioglycolic acid to water and stir vigorously for 2 h to obtain a mixed solution; S2. Add AgNO3 to the mixed solution and stir for 2 h to obtain a uniform mixture, then add Na2S·9H2O and stir for 1 h to obtain a gray suspension; S3, centrifuging the suspension to obtain precipitate a, and then washing it with ultrapure water and ethanol several times to obtain Ag2S; S4, adding water to dissolve the Ag2S, and then adding sodium borohydride solution to in situ reduce silver sulfide to obtain a precipitate b; S5. The precipitate b was washed with ultrapure water and ethanol several times, and then dried at 60°C overnight to obtain the photocatalyst Ag / Ag2S; The sodium borohydride solution is added gradually and plasma treatment is performed during the addition. The gradual addition method includes the following steps: 1) Setting the parameters of the plasma discharge device to: a discharge voltage of 15 to 30 kV, a frequency of 5 to 15 kHz, and an initial flow rate of the working gas of 8 to 10 L / min; adding the sodium borohydride solution in multiple portions at a rate of 5 to 10% per minute; 2) When the amount of sodium borohydride solution added increases to 20% to 30%, the initial flow rate begins to decrease at a rate of 0.5 L / min until it reaches a constant flow rate after the amount of sodium borohydride solution added increases to 70% to 80%, and then maintains a constant flow rate until the addition of the sodium borohydride solution is completed, and then stops the plasma treatment.

2. The method for preparing plasma nanoparticle Ag / Ag2S photocatalyst according to claim 1, characterized in that: The amount of thioglycolic acid added is: based on 1 L of water, add 480 to 530 μL of thioglycolic acid.

3. The method for preparing plasma nanoparticle Ag / Ag2S photocatalyst according to claim 1, characterized in that: The amount of AgNO3 added is: based on 1L of water, add 0.4-0.6g AgNO3.

4. The method for preparing plasma nanoparticle Ag / Ag2S photocatalyst according to claim 1, characterized in that: The amount of Na2S·9H2O added is: based on 1L of water, add 0.6-0.7g Na2S·9H2O.

5. The method for preparing plasma nanoparticle Ag / Ag2S photocatalyst according to claim 1, characterized in that: In step S4, the amount of water and sodium borohydride solution added is as follows: taking 1 L of water as the base amount of Ag2S, adding it to 403 mL of water to dissolve it, and using 403 mL of sodium borohydride solution to in situ reduce the silver sulfide; wherein the concentration of the sodium borohydride solution is: 0.025 mM to 0.2 mM.

6. The method for preparing plasma nanoparticle Ag / Ag2S photocatalyst according to claim 1, characterized in that: The vigorous stirring in step S1 is 400-600 rpm; the stirring in step S2 is 200-300 rpm.

7. The method for preparing plasma nanoparticle Ag / Ag2S photocatalyst according to claim 1, characterized in that: The working gas is nitrogen, and the initial flow rate of the working gas is 8-10 L / min.

Images