Application of water-soluble AIGS modified by thiohydracrylic acid ligand in photocatalytic CO2 reduction reaction

Abstract

The invention relates to application of thiohydracrylic acid ligand modified water-soluble AIGS in photocatalytic CO2 reduction reaction, the photocatalytic CO2 reduction reaction is carried out based on the thiohydracrylic acid ligand modified water-soluble AIGS, the water-soluble AIGS adopts a Ga < 3 + > doping strategy, and through selective substitution of Ga < 3 + > to In < 3 + > sites, lattice defect repair and passivation are synchronously realized, non-radiative recombination is reduced, and the photocatalytic CO2 reduction reaction is carried out on the basis of the thiohydracrylic acid ligand modified water-soluble AIGS. The AIS quantum dot prepared by the method disclosed by the invention has the advantages that an electron structure is regulated and controlled, the position of a conduction band is moved to a higher position (-0.65 Vvs.NHE), the thermodynamic driving force of CO2 reduction is enhanced, and meanwhile, surface catalytic sites are optimized, so that the photocatalytic CO2 reduction activity and CH4 selectivity of the AIS quantum dot are remarkably improved, and the overall yield is improved.

Description

Technical Field

[0001] This invention relates to the application of mercaptopropionic acid ligand-modified water-soluble AIGS in photocatalytic CO2 reduction reactions, and belongs to the field of quantum dot technology. Background Technology

[0002] The efficient conversion of carbon dioxide into hydrocarbon fuels such as methane through semiconductor photocatalysis is considered one of the most promising technological pathways to achieving carbon neutrality. Traditional Cd-based quantum dots, such as CdSe and CdS, are limited in application due to their high toxicity. AgInS2 (AIS) quantum dots, as typical group I-III-VI semiconductor materials, demonstrate significant application value in the field of photocatalysis due to their unique advantages, including non-toxicity and a wide visible light response range.

[0003] However, existing research indicates that current AIS quantum dots still face the following technical bottlenecks in practical applications: (1) The prevalent cation vacancy defects in the crystal structure lead to severe nonradiative recombination, resulting in a short carrier lifetime. Quantum dot lattice defects also cause rapid recombination of photogenerated carriers, limiting photocatalytic efficiency; (2) The low conduction band potential of AIS results in insufficient thermodynamic driving force, making it difficult to achieve efficient CO2 reduction; (3) Insufficient surface active sites lead to weak adsorption-activation ability of reaction intermediates, with CO being the main product and low selectivity for methane (CH4). Therefore, current AIS quantum dots suffer from numerous surface defects, high carrier recombination rates, and low catalytic activity and selectivity.

[0004] To address the aforementioned issues, existing modification strategies primarily focus on surface ligand engineering or heterostructure construction. However, these methods often have significant limitations: on the one hand, while simple surface modification can improve the dispersion of quantum dots, it cannot effectively control the band structure of AIS; on the other hand, while heterostructure construction can promote charge separation, it often fails to simultaneously address the problem of weak conduction band electron reduction capability of AIS.

[0005] Therefore, developing an AIS quantum dot with a long carrier lifetime, multiple surface active sites, and the ability to meet the thermodynamic requirements for deep reduction of CO2 to CH4 is of great significance for the efficient conversion of CO2 into hydrocarbon fuels such as CH4 by AIS quantum dot photocatalysis. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides the application of water-soluble AIGS modified with mercaptopropionic acid ligands in photocatalytic CO2 reduction reactions.

[0007] The photocatalytic CO2 reduction reaction of this invention is based on water-soluble AIGS modified with mercaptopropionic acid ligands, and the water-soluble AIGS uses Ga 3+ Doping strategy, through Ga 3+ For In3+ Precise selective substitution of catalytic sites simultaneously achieves lattice defect passivation and electronic structure modulation; gallium doping-induced lattice contraction effectively suppresses nonradiative recombination, extending carrier lifetime to 372.5 ns, while negatively shifting the conduction band position to -0.65 V (vs. NHE), significantly enhancing the thermodynamic driving force of CO2 reduction; optimized surface catalytic sites promote the adsorption and conversion of key intermediates COOH / CHO, guiding the reaction pathway towards methanation via 8-electron transfer. The synergistic effect of these two aspects significantly improves the activity, selectivity, and stability of AgInS2 quantum dot photocatalytic CO2 reduction, enhances the thermodynamic driving force of CO2 reduction, and significantly improves photocatalytic CO2 reduction activity and CH4 selectivity, thereby increasing the overall yield.

[0008] Terminology Explanation: AIGS: This invention AgIn 1-x Ga x S2 is an abbreviation for S2.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: The application of water-soluble AIGS modified with mercaptopropionic acid ligands in photocatalytic CO2 reduction reaction, and the application method includes the following steps: (1) Disperse water-soluble AIGS quantum dots modified with mercaptopropionic acid ligands in n-hexane to obtain a stable suspension. Load the suspension uniformly onto glass and then place it in a photoreactor and add deionized water. (2) A sealed photoreactor is used to continuously introduce CO2 into deionized water to remove air under dark conditions; (3) The photoreactor is irradiated with sunlight to photocatalytically reduce CO2 to produce CH4.

[0010] According to a preferred embodiment of the present invention, in step (1), the mass-to-volume ratio of the mercaptopropionic acid ligand-modified water-soluble AIGS quantum dots to n-hexane is (4-10):(0.1-1), unit, mg / mL.

[0011] According to a preferred embodiment of the present invention, in step (2), the CO2 introduction time is 20-50 min.

[0012] According to a preferred embodiment of the present invention, in step (3), irradiating the photoreactor with sunlight specifically involves using a 200-400W xenon lamp to simulate sunlight, at a concentration of 100-300mW / cm². 2 A high-intensity light source shines vertically onto the photoreactor.

[0013] According to a preferred embodiment of the present invention, in step (3), the irradiation time is 4-12 hours.

[0014] According to a preferred embodiment of the present invention, the general chemical formula of the water-soluble AIGS quantum dots modified with mercaptopropionic acid ligand is AgIn. 1- x Ga x S2, 0≤x≤0.8.

[0015] According to a preferred embodiment of the present invention, the general chemical formula of the water-soluble AIGS quantum dots modified with mercaptopropionic acid ligand is AgIn. 1- x Ga x S2, x=0.5.

[0016] According to a preferred embodiment of the present invention, the water-soluble AIGS quantum dots modified with mercaptopropionic acid ligands are prepared by the following method: S1. Sodium diethyldithiocarbamate (NaDDTC) aqueous solution was added dropwise to an aqueous solution of gallium source compound (Ga(NO3)3) under stirring. After the reaction, the precipitate was collected, washed, and dried under vacuum overnight at room temperature to obtain gallium diethyldithiocarbamate (Ga[DDTC]3). S2. Add the silver source compound, the indium source compound and the gallium diethyldithiocarbamate (Ga[DDTC]3) obtained in S1 to oleylamine (OLA), heat up and evacuate, and continue to heat up to the reaction temperature under an argon atmosphere to obtain a mixed solution A; S3. Under an inert atmosphere, the mixed solution A obtained in S2 was cooled to room temperature, centrifuged to remove large particles, methanol was added to wash the precipitate, and centrifuged again to obtain oleylamine ligand-modified AIGS quantum dots. S4. Disperse the AIGS quantum dots obtained in S3 in chloroform to obtain mixed solution B; S5. Mix 3-mercaptopropionic acid (MPA) with methanol and adjust the pH to 10-11 to obtain mixed solution C. S6. Under an inert atmosphere, the mixed solution C obtained in S5 is added to the mixed solution B obtained in S4. The mixture is stirred vigorously. After stirring is stopped, water is added to separate the layers, and the aqueous phase is the mixed solution D. S7. Add anhydrous ethanol to the mixed solution D to precipitate, centrifuge, and vacuum dry the product to obtain water-soluble AIGS quantum dots modified with mercaptopropionic acid ligands.

[0017] According to a preferred embodiment of the present invention, in step S1, the concentration of the sodium diethyldithiocarbamate aqueous solution is 0.1~0.5M.

[0018] According to a preferred embodiment of the present invention, in step S1, the concentration of the aqueous solution of the gallium source compound is 0.05-0.3M.

[0019] According to a preferred embodiment of the present invention, in step S1, the volume ratio of sodium diethyldithiocarbamate aqueous solution to gallium source compound aqueous solution is (1~2):(1~2).

[0020] According to a preferred embodiment of the present invention, in step S1, the reaction is carried out at 25°C for 1 to 4 hours.

[0021] According to a preferred embodiment of the present invention, in step S2, the silver source compound is silver acetate (AgOAc), silver nitrate (AgNO3), silver acetylacetone (Ag(acac)), or silver oleate (AgOA).

[0022] According to a preferred embodiment of the present invention, in step S2, the silver source compound is silver acetate (AgOAc). Silver acetate (AgOAc) has a suitable dissociation temperature and good solubility.

[0023] The silver source compound of the present invention should have good oil solubility or be effectively dispersed in oleylamine.

[0024] According to a preferred embodiment of the present invention, in step S2, the indium source compound is indium acetate (In(OAc)3), indium nitrate (In(NO3)3), indium chloride (InCl3), or indium acetylacetone (In(acac)3).

[0025] More preferably, in step S2, the indium source compound is indium acetate (In(OAc)3). Indium acetate (In(OAc)3) has good compatibility with oleylamine and a moderate decomposition temperature.

[0026] The indium source compound of the present invention should have good thermal decomposition characteristics and be able to effectively release indium ions at the reaction temperature.

[0027] According to a preferred embodiment of the present invention, in step S2, the molar ratio of the silver source compound, the indium source compound and the gallium diethyldithiocarbamate obtained in S1 is 1:(0.2~0.67):(0.33~0.8).

[0028] Most preferably, in step S2, the molar ratio of the silver source compound, the indium source compound, and the gallium diethyldithiocarbamate obtained in S1 is 1:0.5:0.5.

[0029] According to a preferred embodiment of the present invention, in step S2, the molar ratio of the silver source compound to the volume ratio of oleylamine is (0.2~0.67):(10~25), in mmol / mL.

[0030] According to a preferred embodiment of the present invention, in step S2, the heating and vacuuming is performed by heating to 100°C.

[0031] According to a preferred embodiment of the present invention, in step S2, the reaction is further heated in an argon atmosphere by raising the temperature to 140~200°C and holding it for 20~60 minutes.

[0032] According to a preferred embodiment of the present invention, in step S3, the volume ratio of methanol to mixed solution A is (1~5):1.

[0033] According to a preferred embodiment of the present invention, in step S4, the mass-to-volume ratio of AIGS quantum dots to chloroform is 1:(5~20), in mg / mL.

[0034] Mixed solution C is a 3-mercaptopropionic acid (MPA) precursor solution.

[0035] According to a preferred embodiment of the present invention, in step S5, the volume ratio of 3-mercaptopropionic acid (MPA) to methanol is (0.1~0.5):1.

[0036] According to a preferred embodiment of the present invention, in step S5, the pH is adjusted to 10-11 using a 30% (w / w) NaOH solution.

[0037] According to a preferred embodiment of the present invention, in step S6, the volume ratio of mixed solution C to mixed solution B is 1:(5~10).

[0038] According to a preferred embodiment of the present invention, in step S7, the volume ratio of the mixed solution D to anhydrous ethanol is 1:(3~6).

[0039] The technical effect of the application method described in this invention is that the selectivity of CH4 in CO2 reduction is significantly higher than that of CO, and the cycle stability is ≥4 times.

[0040] Technical features and advantages of the present invention: 1. The photocatalytic CO2 reduction reaction of this invention is based on water-soluble AIGS modified with mercaptopropionic acid ligands, which enhances the thermodynamic driving force of CO2 reduction, significantly improves the photocatalytic CO2 reduction activity and CH4 selectivity, and increases the overall yield, with a CH4 yield as high as 9.65 μmol·g. -1 ·h -1 It exhibits a 4.7-fold increase in catalytic activity compared to undoped AIS, demonstrating high catalytic activity.

[0041] 2. The photocatalytic CO2 reduction reaction of this invention is based on water-soluble AIGS modified with mercaptopropionic acid ligands, especially with an In / Ga molar ratio of 1:1 and the quantum dots being AgIn. 0.5 Ga 0.5 S2 can simultaneously achieve high CH4 yield and high selectivity.

[0042] 3. The AIGS quantum dots provided by this invention promote the 8-electron reduction pathway, with methane selectivity significantly higher than CO, resulting in high selectivity.

[0043] 4. The AIGS quantum dots provided by this invention retain 80% of their activity after 4 cycles, and XRD shows no structural degradation, demonstrating excellent stability.

[0044] 5. The AIGS quantum dots provided by this invention are environmentally friendly and non-toxic, avoiding the environmental risks of Cd-based materials and meeting the requirements of green chemistry. Attached Figure Description

[0045] Figure 1 The elemental map of the AIGS quantum dots in Embodiment 1 of the present invention is based on EDX analysis (X-ray energy spectroscopy). Figure 2 High-resolution transmission electron microscope (HRTEM) images of the structures of AIGS quantum dots in Example 1 and AIS quantum dots in Comparative Example 1 of the present invention are shown. The insets are magnified views of the AIGS quantum dots and AIS quantum dots. Figure 3 The X-ray diffraction patterns of AIGS quantum dots in Example 1 and AIS quantum dots in Comparative Example 1 are shown below. Figure 4 The transient fluorescence spectra of the AIGS quantum dot of Example 1 and the AIS quantum dot of Comparative Example 1 are shown below. Figure 5 The results show the photocatalytic CO2 reduction performance of AIGS quantum dots and AIS quantum dots with different In / Ga ratios in Example 2 and Comparative Examples 2, 3, 4, and 5 of this invention. Figure 6 The results are from the photocatalytic stability test conducted using AIGS quantum dots as a catalyst in Example 3 of this invention.

[0046] Figure 7 The X-ray diffraction pattern of AIGS quantum dots after photocatalytic reaction in Example 2 of this invention is shown. Specific Implementation

[0047] The technical solution of the present invention will be further described in detail with reference to the following specific examples.

[0048] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials and reagents used can be purchased from biological or chemical reagent companies.

[0049] In this embodiment, the photoreactor is a Pyrex photoreactor, and the Pyrex photoreactor and xenon lamp are commercially available products.

[0050] Example 1 Preparation of water-soluble AIGS quantum dots modified with mercaptopropionic acid ligands (AIGS, In / Ga molar ratio = 1:1): (1) Preparation of precursor: 50 mL of 0.3 M sodium diethyldithiocarbamate (NaDDTC) aqueous solution was slowly added dropwise to 50 mL of 0.1 M gallium nitrate (Ga(NO3)3) aqueous solution under stirring, and the reaction was carried out at 25 °C for 2 hours. After the reaction, the white precipitate was collected, washed with deionized water, and dried under vacuum overnight at room temperature to obtain gallium diethyldithiocarbamate (Ga[DDTC]3) precursor; (2) Quantum dot synthesis: Silver acetate (AgOAc, 0.4 mmol, 66.8 mg), indium acetate (In(OAc)3, 0.2 mmol, 58.2 mg) and gallium diethyldithiocarbamate (Ga[DDTC]3, 0.2 mmol, 81.8 mg) obtained in step (1) were added to 10 mL of oleylamine (OLA), heated to 100 °C and vacuumed for 30 minutes. Then, the temperature was raised to 150 °C under an argon atmosphere and the reaction was continued for 30 minutes to obtain mixed solution A. Under an inert atmosphere, mixed solution A was cooled to room temperature and centrifuged at 11000 rpm for 10 minutes to remove large particles. 20 mL of methanol was added to the supernatant for precipitation, and centrifuged again at 11000 rpm for 10 minutes to obtain oleylamine ligand-modified AIGS quantum dots.

[0051] (3) Ligand exchange: The oleylamine ligand-modified AIGS quantum dots obtained in step (2) were dispersed in 10 mL of chloroform to obtain mixed solution B; 200 μL of 3-mercaptopropionic acid (MPA) was mixed with 1 mL of methanol, and the pH was adjusted to 10-11 with 300 μL of 30% NaOH solution (3 g NaOH dissolved in 7 mL H2O) to obtain mixed solution C; under an inert atmosphere, mixed solution C was added to mixed solution B and stirred vigorously at 8500~1000 rpm for 30 minutes. After stopping the stirring, 6 mL of deionized water was added to separate the layers, and the upper aqueous phase was collected to obtain mixed solution D; mixed solution D was added to 30 mL of anhydrous ethanol to precipitate, centrifuged at 11000 rpm for 10 minutes, the precipitate was collected and dried under vacuum at 45 °C to obtain the final product, MPA ligand-modified water-soluble AIGS quantum dots.

[0052] Comparative Example 1 Preparation of MPA-modified AIS quantum dots: The method described in the same way as in Example 1 differs in that: Step (1) is omitted. In step (2), the gallium diethyldithiocarbamate (Ga[DDTC]3) precursor is replaced with sodium diethylamine benzoate (NaDDTC, 1.2 mmol, about 108 mg), and other conditions and parameters are as in Example 1.

[0053] Experimental Example 1: 1. The elemental distribution and composition of the AIGS quantum dots prepared in Example 1 were characterized using energy-dispersive X-ray spectroscopy (EDX), and the results are as follows: Figure 1 As shown. From Figure 1 The graph shows that elements such as Ga and S are distributed quite evenly, proving the successful doping of Ga into quantum dots.

[0054] 2. The AIGS quantum dots prepared in Example 1 and the MPA-modified AIS quantum dots prepared in Comparative Example 1 were characterized using high-resolution transmission electron microscopy (HRTEM). The results are as follows: Figure 2 As shown. From Figure 2 The HRTEM images show that the lattice spacing of AIGS quantum dots is 0.32 nm. The HRTEM images of AIS quantum dots show a lattice spacing of 0.34 nm. These high-resolution TEM images clearly demonstrate that the lattice spacing of AIGS decreases after doping.

[0055] 3. The AIGS quantum dots prepared in Example 1 were subjected to X-ray diffraction (XRD) analysis and compared with the AIS quantum dots in Comparative Example 1. The results are as follows: Figure 3 As shown, both undoped quantum dots (AIS) and gallium-doped quantum dots (AIGS) maintain a tetragonal crystal phase. However, AIGS quantum dots exhibit broadened diffraction peaks at 2θ = 26.7°, 44.6°, and 51.8°, located between the (112), (204), and (312) crystal planes of AgInS2 (PDF#00-025-1330) and AgGaS2 (PDF#00-027-0615). With increasing gallium content, the peaks gradually shift to higher angles, due to the presence of some In atoms with larger radii. 3+ Ions (ionic radius: 0.80 Å) are affected by Ga atoms with smaller ionic radii. 3+ The lattice distortion caused by ion (0.62 Å) substitution demonstrates the successful synthesis of gallium-doped AgInS2 quantum dots in this invention.

[0056] 4. The time-resolved fluorescence spectra of the AIGS quantum dots prepared in Example 1 and the AIS quantum dots prepared in Comparative Example 1 were characterized and analyzed using transient fluorescence spectroscopy. The results are as follows: Figure 4 As shown. Compared to AIS (218.4 ns), Ga 3+ Doping extended the average carrier lifetime of the AIGS QD (372.5 ns). This extended lifetime is consistent with the reduction in defect-mediated recombination, further demonstrating the defect reduction and carrier lifetime extension of the doped sample.

[0057] Example 2 The application of mercaptopropionic acid ligand-modified water-soluble AIGS in photocatalytic CO2 reduction reaction, the steps are as follows: (1) Disperse 5 mg of AIGS quantum dots prepared in Example 1 in 0.5 mL of n-hexane to obtain a stable suspension, and load the mixture uniformly onto glass; (2) Add the glass to a 30 mL Pyrex photoreactor and add 100 μL of deionized water; (3) Before starting the photocatalytic experiment, seal the photoreactor with a rubber diaphragm and continuously bubble CO2 into the solution in the dark for 20 min to remove as much air as possible; (4) A 300W xenon lamp was used as the light source to simulate sunlight, and the light intensity was controlled at 150mW / cm². 2 The photoreactor is continuously irradiated to carry out photocatalytic reduction of CO2; (5) After 6 hours of irradiation, the yields of CO, CH4 and H2 were determined by gas chromatography.

[0058] Comparative Example 2 The method described in the same way as in Example 2 differs in that: Step (1): Replace the MPA-modified AIGS quantum dots with the MPA-modified AIS quantum dots of Comparative Example 1, and perform other conditions and parameters as in Example 2.

[0059] Comparative Example 3 The preparation of water-soluble AIGS quantum dots modified with mercaptopropionic acid ligands (AIGS, In / Ga molar ratio = 2:1) was carried out according to the method of Example 1, with the following difference: In step (2), the original dosage was replaced with 0.26 mmol In(OAc)3 and 0.13 mmol Ga[DDTC]3 respectively, and other conditions and parameters were performed as in Example 1.

[0060] The application of water-soluble AIGS modified with mercaptopropionic acid ligands in the photocatalytic CO2 reduction reaction was carried out according to Example 2, with the following differences. Gallium-doped AgInS2 quantum dots (In / Ga=1:1) were replaced with gallium-doped AgInS2 quantum dots (In / Ga=2:1) ​​as in Comparative Example 3, and other conditions and parameters were performed as in Example 2.

[0061] Comparative Example 4 The preparation of water-soluble AIGS quantum dots modified with mercaptopropionic acid ligands (AIGS, In / Ga molar ratio = 1:2) was carried out according to the method of Example 1, with the following difference: In step (2), the original dosage was replaced with 0.13 mmol In(OAc)3 and 0.26 mmol Ga[DDTC]3 respectively, and other conditions and parameters were performed as in Example 1.

[0062] The application of water-soluble AIGS modified with mercaptopropionic acid ligands in the photocatalytic CO2 reduction reaction was carried out according to Example 2, with the following differences. Gallium-doped AgInS2 quantum dots (In / Ga=1:1) were replaced with gallium-doped AgInS2 quantum dots (In / Ga=1:2) as in Comparative Example 4, and other conditions and parameters were performed as in Example 2.

[0063] Comparative Example 5 The preparation of water-soluble AIGS quantum dots modified with mercaptopropionic acid ligands (AIGS, In / Ga molar ratio = 1:4) was carried out according to the method of Example 1, with the following difference: In step (2), the original dosage was replaced with 0.08 mmol In(OAc)3 and 0.32 mmol Ga[DDTC]3 respectively, and other conditions and parameters were performed as in Example 1.

[0064] The application of water-soluble AIGS modified with mercaptopropionic acid ligands in the photocatalytic CO2 reduction reaction was carried out according to Example 2, with the following differences. Gallium-doped AgInS2 quantum dots (In / Ga=1:1) were replaced with gallium-doped AgInS2 quantum dots (In / Ga=1:4) from Comparative Example 5, and other conditions and parameters were performed as in Example 2.

[0065] Experimental Example 2: 1. Figure 5 The results show the photocatalytic CO2 reduction performance of AIGS quantum dots and AIS quantum dots with different In / Ga ratios in Example 2 and Comparative Examples 2, 3, 4, and 5 of this invention. Figure 5 The effect of Ga doping level on the photocatalytic CO2 reduction performance of AIGS quantum dots can be observed. By adjusting the In / Ga ratio, when the In / Ga ratio increases from 0.5 to 1.0, the CH4 yield increases from 5.35 μmol·g⁻¹. -1 ·h -1 Increased to 9.65 μmol·g -1 ·h -1 This indicates that appropriate Ga doping can significantly improve photocatalytic activity. However, when the In / Ga ratio continues to increase (>1.0), the catalytic activity shows a decreasing trend. This phenomenon is attributed to the fact that excessive Ga doping significantly widens the photogap, reducing the overlap between the photon energy of the light source and the absorption threshold of the material, thereby reducing the carrier density and decreasing the CO2 reduction capacity. When the In / Ga ratio is 1.0 (AgIn... 0.5 Ga 0.5 At S2), the yield of CH4 was 9.65 μmol·g. -1 ·h -1The yield was 4.7 times higher than that of undoped AgInS2 (AIS) (2.07 μmol·g). -1 ·h -1 This result highlights the crucial role of controllable Ga doping in promoting charge separation and enhancing catalytic efficiency.

[0066] 2. From Figure 5 The results also show that AIGS quantum dots exhibit significantly higher CH4 selectivity than CO in CO2 reduction, directly demonstrating that Ga doping effectively redirects the reaction pathway from 2-electron CO formation to 8-electron CH4 formation, significantly improving the selectivity for CH4 products. Simultaneously, the Ga doping ratio modulates the selectivity. When the Ga doping amount is too low (In / Ga = 2:1), the improvement in CH4 selectivity is limited. When the Ga doping amount is too high (In / Ga = 0.5:1), the excessively wide bandgap leads to a decrease in light absorption, resulting in a decline in both overall yield and selectivity. Only at the optimal In / Ga ratio of 1:1 can both high CH4 yield and high selectivity be achieved simultaneously.

[0067] Example 3 Photocatalytic cycling tests were performed on the water-soluble AIGS quantum dots modified with mercaptopropionic acid ligands from Example 1: (1) First test: Same as steps (1) to (5) in Example 2.

[0068] (2) Second test: Take the solution after the above test and add 100 μL of deionized water to the photoreactor as a new sacrificial agent. Then repeat steps (3) to (5) in Example 2.

[0069] (3) Third test: Repeat step (2) above.

[0070] (4) Fourth test: Repeat step (2) above.

[0071] Experimental Example 3: 1. Figure 6 Stability tests were conducted using the AIGS quantum dots from Example 1 as a photocatalyst. From... Figure 6 As can be seen, the photocatalytic activity of AIGS quantum dots did not decrease significantly during four 6-hour cycles, retaining 80% of its original activity, indicating that the AIGS quantum dot photocatalyst has good stability, with a cycle stability of ≥4 cycles.

[0072] 2. The AIGS quantum dots after the photocatalytic reaction in Example 2 were analyzed by X-ray diffraction (XRD). The results are as follows: Figure 7 As shown. From Figure 7As can be seen, the characteristic diffraction peaks of AIGS quantum dots maintained their original positions and intensities after the photocatalytic reaction. These results provide conclusive evidence that AIGS quantum dots possess excellent structural stability during photocatalysis.

Claims

1. Application of mercaptopropionic acid ligand modified water-soluble AIGS in photocatalytic CO2 reduction reaction, the application method comprising the following steps: (1) dispersing mercaptopropionic acid ligand modified water-soluble AIGS quantum dots in n-hexane to obtain a stable suspension, uniformly loading the suspension on glass, and then placing the glass in a photoreactor and adding deionized water; (2) sealing the photoreactor, continuously introducing CO2 into the deionized water under dark conditions to remove air; (3) irradiating the photoreactor with sunlight to photocatalytically reduce CO2 to produce CH4.

2. Use according to claim 1, characterized in that, In step (1), the mass-volume ratio of mercaptopropionic acid ligand modified water-soluble AIGS quantum dots to n-hexane is (4-10):(0.1-1), unit, mg / mL.

3. Use according to claim 1, characterized in that, In step (2), the CO2 introduction time is 20-50 min.

4. Use according to claim 1, characterized in that, In step (3), the solar light irradiation on the photoreactor is specifically as follows: using a 200-400 W xenon lamp to simulate the sunlight, a light source with an intensity of 100-300 mW / cm 2 2 is vertically irradiated on the photoreactor, and the irradiation time is 4-12 hours.

5. The use according to claim 1, characterized in that, Water-soluble AIGS quantum dots modified by mercaptopropionic acid ligand have a chemical formula of AgIn 1-x Ga x S2, x = 0.

5.

6. Use according to claim 1, characterized in that, The mercaptopropionic acid ligand modified water-soluble AIGS quantum dots are prepared by the following method: S1, adding a sodium diethyl dithiocarbamate (NaDDTC) aqueous solution dropwise into a gallium source compound (Ga(NO3)3) aqueous solution under stirring to react, collecting the precipitate after the reaction, washing, and vacuum drying at room temperature overnight to obtain gallium diethyl dithiocarbamate (Ga[DDTC]3); S2, adding a silver source compound, an indium source compound, and the gallium diethyl dithiocarbamate (Ga[DDTC]3) obtained in S1 into oleylamine (OLA), vacuumizing under heating, and continuing to heat to a reaction temperature under an argon atmosphere to obtain a mixed solution A; S3, under an inert atmosphere, centrifuging the mixed solution A obtained in S2 after cooling to room temperature, removing large particles, adding methanol to wash the precipitate, centrifuging again to obtain oleylamine ligand modified AIGS quantum dots; S4, dispersing the AIGS quantum dots obtained in S3 in chloroform to obtain a mixed solution B; S5, mixing 3-mercaptopropionic acid MPA with methanol, adjusting the pH to 10-11 to obtain a mixed solution C S6, under an inert atmosphere, adding the mixed solution C obtained in S5 to the mixed solution B obtained in S4, stirring vigorously, after stopping the stirring, adding water to separate the layers to obtain a mixed solution D; S7, adding anhydrous ethanol to the mixed solution D to precipitate, centrifuging, and vacuum drying the product to obtain mercaptopropionic acid ligand modified water-soluble AIGS quantum dots.

7. Use according to claim 6, characterized in that, In step S1, the concentration of the sodium diethyl dithiocarbamate aqueous solution is 0.1-0.5 M, the concentration of the gallium source compound aqueous solution is 0.05-0.3 M, and the volume ratio of the sodium diethyl dithiocarbamate aqueous solution to the gallium source compound aqueous solution is (1-2):(1-2), and the reaction is carried out at 25°C for 1-4 hours.

8. The application according to claim 6, characterized in that, in step S2, the silver source compound is silver acetate (AgOAc), silver nitrate (AgNO3), silver acetylacetone (Ag(acac)), or silver oleate (AgOA), and the indium source compound is indium acetate In(OAc)3, indium nitrate (In(NO3)3), indium chloride (InCl3), or indium acetylacetone (In(acac)3). The molar ratio of the silver source compound, the indium source compound, and gallium diethyldithiocarbamate obtained in S1 is 1:(0.2~0.67):(0.33~0.8), and the molar amount of the silver source compound to the volume ratio of oleylamine is (0.2~0.67):(10~25). The unit is mmol / mL. Heating and vacuuming means heating to 100°C and then vacuuming. Continuing to heat the reaction under an argon atmosphere means raising the temperature to 140~200°C under an argon atmosphere and holding for 20~60 min.

9. Use according to claim 6, characterized in that, In step S3, the volume ratio of methanol to mixed solution A is (1~5):

1. In step S4, the mass-volume ratio of AIGS quantum dots to chloroform is 1:(5~20). Unit: mg / mL.

10. Use according to claim 6, characterized in that, In step S5, the volume ratio of 3-mercaptopropionic acid (MPA) to methanol is (0.1~0.5):

1. In step S5, the pH is adjusted to 10~11 with a 30% NaOH solution. In step S6, the volume ratio of mixed solution C to mixed solution B is 1:(5~10). In step S7, the volume ratio of mixed solution D to anhydrous ethanol is 1:(3~6).

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