A lead-free halide Cs(Ag 1-x Cu x )2I3 and applications thereof

Abstract

The application discloses a kind of lead-free halide Cs (Ag 1‑ x Cu x )2I3 Preparation and application, belong to the field of luminescent material.The application has prepared a kind of Cu + And Ag + Doped Cs (Ag 1‑x Cu x )2I3 Lead-free halide, preparation method is: first, CsI, AgI and CuI are dissolved in N, N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) mixed solvent;It is heated and stirred for 6 hours under 20~90 ℃, makes it completely dissolved;Then, titration is carried out with methanol, when white powder appears, stop titration;Then filter with filter head, the transparent solution after filtering is injected into beaker, and tin paper and paraffin film with small holes are sealed to the mouth of beaker;Finally, growth device is placed into sealed large beaker with methanol, keeps 2~7 days under 40~80 ℃, can obtain Cs (Ag 1‑x Cu x )2I3 Crystal;The Cs (Ag 1‑x Cu x )2I3 Crystal prepared can be applied to the degradation of organic pollutants.

Description

Technical Field

[0001] This invention relates to a lead-free halide Cs(Ag) 1-x Cu x The preparation and application of 2I3 belong to the field of photocatalytic organic degradation. Background Technology

[0002] With the rapid development of global industrialization, environmental pollution has become increasingly prominent, especially posing a serious threat to human health. Therefore, advanced treatment technologies capable of effectively removing organic pollutants from water and air are particularly important. In recent years, research on the degradation of organic pollutants using green and pollution-free solar energy has received widespread attention. It has been reported that some metal oxides and sulfides possess good photocatalytic performance, but the high recombination rate of electron-hole pairs limits their practical application.

[0003] Lead halides (APbX3; A=CH3NH3) + CH(NH2)2 + Cs + X = Cl - , Br - I - Due to its excellent optical properties, lead halides have been widely used in solar cells, photocatalytic synthesis, photocatalytic degradation, photocatalytic CO2 reduction, and photocatalytic hydrogen evolution. In these applications, lead halides exhibit excellent organic degradation characteristics. However, lead's high environmental and biological toxicity and poor stability limit the use of these materials. Therefore, using environmentally friendly metal ions to replace toxic lead is of great significance.

[0004] Silver-based compounds, due to their excellent optical properties, have been used as alternatives to lead-free compounds and are applied in the field of ultraviolet light detectors. In photocatalysis, not only is it necessary to ensure material stability to guarantee photocatalytic efficiency, but it is also necessary to adjust the band gap to improve the utilization of sunlight. Researchers have found that the atomic orbitals of the B-site element in doped compounds directly affect their valence and conduction bands; therefore, metal ion doping is considered a method to adjust the band gap and photoelectric properties. As a transition metal with a small ionic radius, copper has potential applications in doping. Summary of the Invention

[0005] To address the problems associated with existing lead halides, this invention provides a lead-free Cs(Ag) halide. 1-x Cu x The preparation method of 2I3 is described in detail below:

[0006] (1) Dissolve CsI, AgI, and CuI in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and stir at 20-90°C until the solutes are completely dissolved to obtain a mixed solution.

[0007] (2) Titrate the mixed solution obtained in step (1) with methanol, and stop titrating when a white powder appears.

[0008] (3) Filter the mixed solution obtained in step (2) with a filter head to obtain filtrate.

[0009] (4) Seal the filtrate obtained in step (3) to obtain the growth device.

[0010] (5) Place the growth apparatus obtained in step (4) into a sealed container filled with methanol and maintain it at 40–80°C for 3 days to obtain Cs(Ag) 1-x Cu x )2I3 crystal.

[0011] Preferably, in step (1), the amounts of CsI, AgI, and CuI added to the mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide are CsI 1 mmol / mL, AgI 2(1-x) mmol / mL, and CuI 2x mmol / mL, respectively. <x<1。

[0012] Preferably, x = 0.2, 0.4, 0.6 or 0.8.

[0013] Preferably, the volume ratio of DMF to DMSO in step (1) is 1:10 to 10:1.

[0014] Preferably, the filter diameter of the filter head in step (3) is 0.22 μm.

[0015] Preferably, the sealing method of the filtrate in step (4) is as follows: the filtrate is injected into a beaker, sealed with tin foil and paraffin film, and several small holes are punched in the tin foil so that the antisolvent diffuses into the solution through the small holes.

[0016] The present invention also provides a lead-free halide Cs(Ag) 1-x Cu x Application of 2I3 in photocatalytic degradation of organic pollutants.

[0017] The principle of this invention:

[0018] Under illumination, Cs(Ag) 1-x Cu x Electrons from 2I₃ transition from the valence band (VB) to the conduction band (CB) to produce electrons. - and h + And according to the formation of O2- The standard redox potential of -0.33 eV is located at Cs(Ag) 1-x Cu x The band gap of 2I3 leads to the formation of ·O by dissolved oxygen on the catalyst surface capturing electrons from CB. 2- Groups. Based on the above analysis, the possible photocatalytic processes are as follows:

[0019] Cs(Ag 1-x Cu x )2I3+hv→e - +h + (1)

[0020] e - +O2→·O 2- (2)

[0021] ·O 2- +MB→degradedproducts (3)

[0022] Beneficial effects of the present invention

[0023] (1) The lead-free halide Cs(Ag) prepared by this invention 1-x Cu x )2I3 crystals can be used for photocatalytic degradation of organic pollutants.

[0024] (2) Cu in this invention + Partially replaces Ag + It can narrow the band gap, thereby making better use of sunlight, and also facilitates the transport of electrons and holes.

[0025] (3) The Cs(Ag) prepared in this invention 1-x Cu x Cu2I3 is a direct bandgap semiconductor. + and Ag + It helps to improve photocatalytic performance.

[0026] (4) Cs(Ag) prepared by this invention 0.8 Cu 0.2 )2I3 can degrade 99.0% of methylene blue contaminants within 4 hours and has good reusability and stability. Attached Figure Description

[0027] Figure 1 The XRD patterns of the crystals obtained in all examples and comparative examples are shown.

[0028] Figure 2 for Figure 2 Enlarged view of the (221) diffraction peaks corresponding to each sample.

[0029] Figure 3 Optical absorption spectra of the crystals obtained in all embodiments and comparative examples.

[0030] Figure 4 This is a bandgap diagram of the crystals obtained in all embodiments and comparative examples.

[0031] Figure 5 The graph shows the band gap of the crystals obtained in all embodiments and comparative examples as a function of the Ag / Cu molar ratio.

[0032] Figure 6 The concentration of crystal-degraded methylene blue obtained in all examples and comparative examples (C) t The curve showing the relationship between / C0) and illumination time.

[0033] Figure 7 The corresponding reaction kinetic curves for the crystals obtained in all examples and comparative examples are shown. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The reagents used in the examples are as follows:

[0036] Cesium iodide (CsI, 99.9%), cuprous iodide (CuI, 98%), silver iodide (I) (AgI, 99%), N,N-dimethylformamide (DMF, 99.9%), dimethyl sulfoxide (DMSO, 99%), methanol (CH3OH, 99.5%), anhydrous ethanol (C2H5OH, 99.8%), methylene blue (C 16 H 18 ClN3S·3H2O), all raw materials were used directly without further purification, and all raw materials came from Aladdin Company.

[0037] Example 1

[0038] The lead-free halide prepared in this embodiment is Cs(Ag) 0.8 Cu 0.2 The specific preparation steps for 2I3 are as follows:

[0039] (1) Dissolve 5 mmol CsI, 8 mmol AgI, and 2 mmol CuI in a mixed solvent of 2.5 mL LDMF and 2.5 mL DMSO. Stir at 60 °C until the solutes are completely dissolved to obtain a mixed solution.

[0040] (2) Titrate the mixed solution obtained in step (1) with methanol, and stop titrating when a white powder appears.

[0041] (3) Filter the mixed solution obtained in step (2) with a 0.22 μm filter head to obtain filtrate.

[0042] (4) Pour the filtrate obtained in step (3) into a beaker and seal the mouth of the beaker with tin foil and paraffin film with small holes to obtain the growth device.

[0043] (5) Place the growth apparatus obtained in step (4) into a sealed beaker containing methanol and maintain it at 60°C for 3 days to obtain Cs(Ag) 0.8 Cu 0.2 )2I3 crystal.

[0044] Example 2

[0045] The lead-free halide prepared in this embodiment is Cs(Ag) 0.6 Cu 0.4 The specific preparation steps for 2I3 are as follows:

[0046] (1) Dissolve 5 mmol CsI, 6 mmol AgI, and 4 mmol CuI in a mixed solvent of 2.5 mL LDMF and 2.5 mL DMSO. Stir at 80 °C until the solutes are completely dissolved to obtain a mixed solution.

[0047] (2) Titrate the mixed solution obtained in step (1) with methanol, and stop titrating when a white powder appears.

[0048] (3) Filter the mixed solution obtained in step (2) with a 0.22 μm filter head to obtain filtrate.

[0049] (4) Pour the filtrate obtained in step (3) into a beaker and seal the mouth of the beaker with tin foil and paraffin film with small holes to obtain the growth device.

[0050] (5) Place the growth apparatus obtained in step (4) into a sealed beaker containing methanol and maintain it at 80°C for 3 days to obtain Cs(Ag) 0.6 Cu 0.4 )2I3 crystal.

[0051] Example 3

[0052] The lead-free halide prepared in this embodiment is Cs(Ag) 0.4 Cu 0.6 The specific preparation steps for 2I3 are as follows:

[0053] (1) Dissolve 5 mmol CsI, 4 mmol AgI, and 6 mmol CuI in a mixed solvent of 2.5 mL LDMF and 2.5 mL DMSO. Stir at 70 °C until the solutes are completely dissolved to obtain a mixed solution.

[0054] (2) Titrate the mixed solution obtained in step (1) with methanol, and stop titrating when a white powder appears.

[0055] (3) Filter the mixed solution obtained in step (2) with a 0.22 μm filter head to obtain filtrate.

[0056] (4) Pour the filtrate obtained in step (3) into a beaker and seal the mouth of the beaker with tin foil and paraffin film with small holes to obtain the growth device.

[0057] (5) Place the growth apparatus obtained in step (4) into a sealed large beaker containing methanol and maintain it at 70°C for 3 days to obtain Cs(Ag) 0.4 Cu 0.6 )2I3 crystal.

[0058] Example 4

[0059] The lead-free halide prepared in this embodiment is Cs(Ag) 0.2 Cu 0.8 The specific preparation steps for 2I3 are as follows:

[0060] (1) Dissolve 5 mmol CsI, 2 mmol AgI, and 8 mmol CuI in a mixed solvent of 2.5 mL LDMF and 2.5 mL DMSO. Stir at 50 °C until the solutes are completely dissolved to obtain a mixed solution.

[0061] (2) Titrate the mixed solution obtained in step (1) with methanol, and stop titrating when a white powder appears.

[0062] (3) Filter the mixed solution obtained in step (2) with a 0.22 μm filter head to obtain filtrate.

[0063] (4) Pour the filtrate obtained in step (3) into a beaker and seal the mouth of the beaker with tin foil and paraffin film with small holes to obtain the growth device.

[0064] (5) Place the growth apparatus obtained in step (4) into a sealed large beaker containing methanol and maintain it at 50°C for 3 days to obtain Cs(Ag)0.2 Cu 0.8 )2I3 crystal.

[0065] Comparative Example 1

[0066] In comparison, the lead-free halide prepared in this embodiment is CsAg2I3, and the specific preparation steps are as follows:

[0067] (1) Dissolve 5 mmol CsI and 10 mmol AgI in a mixed solvent of 2.5 mL DMF and 2.5 mL DMSO, and stir at 40 °C until the solutes are completely dissolved to obtain a mixed solution.

[0068] (2) Titrate the mixed solution obtained in step (1) with methanol, and stop titrating when a white powder appears.

[0069] (3) Filter the mixed solution obtained in step (2) with a 0.22 μm filter head to obtain filtrate.

[0070] (4) Pour the filtrate obtained in step (3) into a beaker and seal the mouth of the beaker with tin foil and paraffin film with small holes to obtain the growth device.

[0071] (5) Place the growth apparatus obtained in step (4) into a sealed large beaker containing methanol and keep it at 40°C for 3 days to obtain CsAg2I3 crystals.

[0072] Comparative Example 2

[0073] In comparison, the lead-free halide prepared in this embodiment is CsCu2I3, and the specific preparation steps are as follows:

[0074] (1) Dissolve 5 mmol CsI and 10 mmol CuI in a mixed solvent of 2.5 mL DMF and 2.5 mL DMSO, and stir at 50 °C until the solutes are completely dissolved to obtain a mixed solution.

[0075] (2) Titrate the mixed solution obtained in step (1) with methanol, and stop titrating when a white powder appears.

[0076] (3) Filter the mixed solution obtained in step (2) with a 0.22 μm filter head to obtain filtrate.

[0077] (4) Pour the filtrate obtained in step (3) into a beaker and seal the mouth of the beaker with tin foil and paraffin film with small holes to obtain the growth device.

[0078] (5) Place the growth apparatus obtained in step (4) into a sealed large beaker containing methanol and keep it at 50°C for 3 days to obtain CsCu2I3 crystals.

[0079] The crystals obtained in Examples 1–4 and Comparative Examples 1–2 were characterized using an X-ray diffractometer (DX-2700BH diffractometer, with the X-ray source being the Kα1 line of a copper target), with measurements ranging from 10° to 75°. The results are as follows: Figure 1 As shown, six diffraction peaks were observed on the X-ray diffraction of CsAg₂I₃, located at 2θ = 10.25°, 20.97°, 25.09°, 25.42°, 31.08°, and 40.90°, corresponding to the (110), (130), (221), (131), (330), and (350) crystal planes, respectively. Compared to CsAg₂I₃, no additional peaks were observed after the Ag portion was substituted with Cu, indicating that no second phase was formed. Figure 1 The magnification of the (221) diffraction peaks corresponding to each sample was obtained. Figure 2 ,from Figure 2 As can be seen from the results, the diffraction peaks of the sample shift to higher angles as the Cu / Ag molar ratio (x) increases. This may be due to the lattice shrinkage caused by the smaller radius of copper ions compared to silver ions.

[0080] To describe the optical properties of the crystals obtained in Examples 1-4 and Comparative Examples 1-2, steady-state absorption spectroscopy was performed. The light absorption spectra of the samples were measured using a UV-Vis spectrophotometer (TU-1901, PERSEE, China), with a wavelength range of 200-800 nm. The results are as follows: Figure 3 As shown, the samples in all embodiments exhibit a steep absorption edge at 365 nm, a characteristic of direct band gaps. The band gaps of different samples were calculated using the Dow equation, as follows: Figure 4 As shown. The band gap of the samples obtained in all examples and comparative examples is a function of the Ag / Cu molar ratio, as shown in the figure. Figure 5 As shown, the band gap of CsAg₂I₃ is 3.43 eV. When Cu replaces Ag, the band gap of Cs(Ag)₂I₃ increases. 1-x Cu x The band gap of Cu2I3 is significantly lower than that of CsAg2I3. This is because the Cu3d orbitals overlap with the Ag4d orbitals, causing the Ag4d diffraction valence band (VB) to shift to a higher energy level. However, as the Cu substitution amount increases, this effect gradually weakens, and therefore the band gap gradually increases again. Compared to the ternary crystals in Comparative Examples 1 and 2, the quaternary crystals in Examples 1-4 have smaller band gaps, which can increase the absorption of sunlight and thus improve the photocatalytic efficiency of the crystals.

[0081] To evaluate the photocatalytic performance of the crystals obtained in all examples, the methylene blue solution was degraded under simulated sunlight (400W halogen lamp). The distance between the sample and the light source was fixed at 20 cm. 30 mg of the crystal sample and 20 mL of methylene blue solution (10 mg / L) were dispersed in a 25 mL glass bottle and magnetically stirred for 30 min in the dark to ensure adsorption-desorption equilibrium. The photocatalytic performance was determined by measuring the methylene blue concentration at A... max The absorbance at 654 nm was used to determine the concentration of methylene blue during the degradation process. The formula for calculating the photodegradation rate of the catalyst is (1-C). t / C0)×100%, where the initial intensity of the absorption peak at position C0 is C t The absorption intensity is given after a degradation time of t min. The results are as follows: Figure 6 As shown, the photocatalytic degradation efficiency of the crystals obtained in Examples 1-4 is much higher than that in Comparative Examples 1-2. Among them, the Cs(Ag) crystals obtained in Example 1 have significantly higher photocatalytic degradation efficiency. 0.8 Cu 0.2 The photocatalytic degradation effect of 2I3 was the best, with a degradation efficiency of 99.0% after 4 hours. Figure 7 It shows ln(C0 / C) t The kinetic relationship between Cs(Ag) and illumination time (t) also shows that the photocatalytic degradation reaction constant K of the crystals obtained in Examples 1-4 is much higher than that in Comparative Examples 1-2, where Cs(Ag) 0.8 Cu 0.2 The reaction constant of 2I3 is the highest, approximately 1.1576 h⁻¹. -1 These results show that, compared with Comparative Examples 1-2, the crystals obtained in Examples 1-4 of this invention exhibit significantly increased photocatalytic performance, thus demonstrating the application advantages of this invention in the photocatalytic degradation of organic pollutants.

Claims

1. A lead-free halide Cs(Ag) 1-x Cu x The application of 2I3 in the photocatalytic degradation of organic pollutants is characterized by: The lead-free halide Cs(Ag) 1-x Cu x The specific preparation steps of 2I3 are as follows: (1) Dissolve CsI, AgI, and CuI in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide, and stir at 20~90 °C until the solutes are completely dissolved to obtain a mixed solution; (2) Titrate the mixed solution obtained in step (1) with methanol, and stop titrating when a white powder appears; (3) Filter the mixed solution obtained in step (2) using a filter head to obtain the filtrate; (4) Seal the filtrate obtained in step (3) to obtain the growth device; (5) Place the growth apparatus obtained in step (4) into a sealed container filled with methanol and maintain it at 40~80℃ for 3 days to obtain Cs(Ag) 1-x Cu x )2I3 crystal; In step (1), the amounts of CsI, AgI, and CuI added to the mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide are CsI 1 mmol / mL, AgI 2(1-x) mmol / mL, and CuI 2x mmol / mL, respectively. <x≤0.8。 2. The application according to claim 1, characterized in that: In step (1), the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 1:

1.

3. The application according to claim 1, characterized in that: In step (3), the filter head has a filter diameter of 0.22 μm.

4. The application according to claim 1, characterized in that: The sealing method for the filtrate in step (4) is as follows: inject the filtrate into a beaker, seal it with tin foil and paraffin film, and punch several small holes in the tin foil so that the antisolvent can diffuse into the solution through the small holes.

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