Preparation method and application of functionalized mesoporous material SBA-15

Abstract

The invention discloses a preparation method and application of a functionalized mesoporous material SBA-15, and relates to the field of chemical synthesis and photoelectrocatalysis materials.Organic functionalization is conducted on SBA-15 through a grafting method, and an amino-functionalized mesoporous material NH2-SBA-15 is obtained; and carrying out salicylaldehyde functionalization treatment on the amino functionalized mesoporous material NH2-SBA-15, so as to obtain the salicylaldehyde functionalized mesoporous material S-SBA-15. The functionalized mesoporous material NH2-SBA-15 and the functionalized mesoporous material S-SBA-15 can be used for photoelectrocatalytic reduction of CO2, and have good photoelectrocatalytic activity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical synthesis and photoelectric catalytic materials, and particularly relates to a preparation method of functionalized mesoporous material SBA-15 and application of the functionalized mesoporous material SBA-15 in photoelectric catalytic reduction of carbon dioxide. BACKGROUND

[0002] After Mobil Company invented the ordered mesoporous material M41S series (MCM-41, MCM-48 and MCM-50), Zhao Dongyuan et al. synthesized SBA-15 by using a non-ionic block copolymer as a surfactant and a hydrothermal crystallization method in 1998. Compared with MCM-41, SBA-15 not only extends the pore size to a larger range, but also has better thermal stability, lower toxicity of the template agent, and relatively low price, and provides a wider space for modification and application. In addition, SBA-15 can be prepared in various geometric morphologies according to different synthesis conditions, and different morphological characteristics will inevitably form different pore structures and structural parameters, thereby showing different catalytic properties.

[0003] Although SBA-15 is widely used in various catalytic fields, its research in CO2 reduction is rarely reported, because SBA-15 itself is an insulator, and there are theoretical difficulties and technical obstacles in the application of SBA-15 in photocatalytic or electrocatalytic reduction of CO2. SUMMARY

[0004] The present application provides a preparation method of functionalized mesoporous material SBA-15 and application of the functionalized mesoporous material SBA-15, aiming at the problems of existing SBA-15 in photoelectric catalytic reduction of CO2. The present application obtains the functionalized mesoporous material SBA-15 by using grafting method to organically functionalize SBA-15, and the functionalized mesoporous material SBA-15 is used for photoelectric catalytic reduction of CO2, and has good photoelectric catalytic activity, selectivity and stability.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme: In a first aspect, the present application provides a preparation method of functionalized mesoporous material SBA-15, and the specific steps are as follows: SBA-15 is weighed, placed in a three-necked flask containing anhydrous toluene solvent, heated to 80℃, then APTES is slowly added, refluxed, filtered, and the unreacted APTES is washed with toluene as a solvent, and dried to obtain amino-functionalized mesoporous material NH2-SBA-15; The SBA-15 is any one of rod-like SBA-15 and spherical SBA-15.

[0006] As a preferred, the amount ratio of SBA-15, anhydrous toluene and APTES is 1g: 50mL: 0.1mL.

[0007] Preferably, the refluxing time is 6h.

[0008] In a preferred embodiment of the present application, the synthesis steps of the rod-like SBA-15 are as follows: 2g of template agent EO 20 PO 70 EO 20 (P123) and 4mL of 12mol / L HCl solution and 72mL of deionized water are mixed thoroughly, and after being dissolved thoroughly by stirring at 35℃ for 40min, 4.2mL of TEOS is added dropwise slowly, and stirring is continued for 20h. The reaction solution is transferred to an autoclave, which is sealed and placed in an oven at 110℃ for crystallization for 24h. After cooling, filtration and washing with deionized water until the solution is neutral, the sample is placed in an oven at 80℃ for drying overnight, and finally placed in a muffle furnace, which is raised to 550℃ at a rate of 1℃ / min and calcined for 6h to obtain a white solid powder.

[0009] In a preferred embodiment of the present application, the synthesis steps of the rod-like SBA-15 are as follows: 2g of template agent EO 20 PO 70 EO 20 (P123) and 4mL of 12mol / L HCl solution and 72mL of deionized water are mixed thoroughly, and after being dissolved thoroughly by stirring at 35℃ for 40min, 4.2mL of TEOS is added dropwise slowly, and stirring is continued for 20h. The reaction solution is transferred to an autoclave, which is sealed and placed in an oven at 110℃ for crystallization for 24h. After cooling, filtration and washing with deionized water until the solution is neutral, the sample is placed in an oven at 80℃ for drying overnight, and finally placed in a muffle furnace, which is raised to 550℃ at a rate of 1℃ / min and calcined for 6h to obtain a white solid powder.

[0010] Preferably, the amino-functionalized mesoporous material NH2-SBA-15 is further subjected to salicylaldehyde functionalization treatment to obtain a salicylaldehyde functionalized mesoporous material S-SBA-15, and the specific steps are as follows: 0.5g of NH2-SBA-15 is added to 50mL of anhydrous toluene solution, 1mL of salicylaldehyde is added twice at 80℃, and refluxing is performed for 6h to obtain S-SBA-15.

[0011] In a second aspect, the present application provides the use of NH2-SBA-15 prepared by the preparation method described above in the functional modification of a photoelectric cathode. The preparation steps of the photoelectric cathode modified by NH2-SBA-15 are as follows: (1) In the synthesis process of SBA-15, a clean Cu mesh is placed in the autoclave containing the reaction solution, which is sealed and placed in an oven for crystallization for 24h. After crystallization, the Cu mesh loaded with SBA-15 is dried overnight, and then placed in a muffle furnace, which is raised to 550℃ at a rate of 1℃ / min and maintained for 6h to obtain an electrode sheet loaded with SBA-15. (2) Put the prepared electrode sheet into a three-necked flask containing 50 mL of toluene solution, slowly add 0.1 mL of APTES at 80 DEG C, and reflux for 6 hours to obtain the NH2-SBA-15 / Cu photoelectric cathode.

[0012] In a third aspect, the application provides application of the S-SBA-15 prepared by the preparation method in functional modification of a photoelectric cathode. Put the NH2-SBA-15 / Cu photoelectric cathode into a toluene solution containing salicylaldehyde, and reflux at 80 DEG C for 6 hours to obtain the S-SBA-15 / Cu photoelectric cathode, wherein the volume ratio of salicylaldehyde to anhydrous toluene is 1:50.

[0013] Compared with the prior art, the application has the beneficial technical effects that: The functionalized mesoporous materials NH2-SBA-15 and S-SBA-15 provided by the application have large specific surface areas and rich active sites, good photoelectric catalytic activity and stability, and make CO2 and reactant molecules diffuse and transport more smoothly, thereby effectively promoting the CO2 reduction reaction. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Scanning electron microscope images of different morphology samples prepared in Examples 1 and 2, wherein a is SBA-15(s), b is NH2-SBA-15(s), c is S-SBA-15(s), d is SBA-15(r), e is NH2-SBA-15(r), and f is S-SBA-15(r); Figure 2 TEM images of different scanning directions of different morphology samples prepared in Examples 1 and 2, wherein a-c are TEM images of SBA-15(r), NH2-SBA-15(r) and S-SBA-15(r) samples in parallel to the channel direction, and d-f are TEM images of SBA-15(r), NH2-SBA-15(r) and S-SBA-15(r) samples perpendicular to the channel direction; Figure 3 XRD spectra of different morphology samples prepared in Examples 1 and 2; Figure 4 N2 adsorption-desorption curves and pore size distribution curves of different morphology samples prepared in Examples 1 and 2, wherein a and b are N2 adsorption-desorption isotherm curves of the SBA-15 sample before and after modification, and c and d are pore size distribution diagrams of the SBA-15 sample before and after organic functionalization, which are calculated by the BJH model from the N2 adsorption-desorption curves; Figure 5CO2 adsorption-desorption curves of different morphology samples prepared in Example 1 and 2 at 298 K, wherein a is the CO2 adsorption-desorption curve of SBA-15(r) before and after modification, b is the CO2 adsorption-desorption curve of SBA-15(s) before and after modification; Figure 6 Infrared spectra of different morphology samples prepared in Example 1 and 2, wherein a is the infrared spectrum of SBA-15(s) before and after modification, b is the infrared spectrum of BA-15(r) before and after modification; Figure 7 XPS spectra of SBA-15(r), NH2-SBA-15(r) and S-SBA-15(r) samples prepared in Example 1, wherein a is the XPS full spectrum of sample C1s, N1s, O1s, b is the XPS fine spectrum of sample C1s, c is the XPS fine spectrum of sample N1s, and d is the XPS fine spectrum of sample O1s; Figure 8 Optical performance characterization results of different photoelectrodes prepared in Example 3-6, wherein a is a solid-state ultraviolet absorption spectrum, and b is a photoluminescence (PL) spectrum; Figure 9 Photoelectrochemical performance characterization results of different photoelectrodes prepared in Example 3-6, wherein a is a linear sweep voltammetry (LSV) curve, b is a cyclic voltammetry (CV) curve, c is an electrochemical impedance (Nyquist) curve, and d is a transient photoelectric response curve; Figure 10 Mott-Schottky curves of different photoelectrodes prepared in Example 3-6 at different frequencies, wherein a is NH2-SBA-15(s) / Cu, b is S-SBA-15(s) / Cu, c is NH2-SBA-15(r) / Cu, and d is S-SBA-15(r) / Cu; Figure 11 Photoelectrocatalytic performance results of photoelectrodes prepared in Example 3 and 5 at different voltages, wherein a is the liquid phase product distribution of photoelectrocatalytic reduction of CO2 by different photoelectrodes at -0.6 V vs . SCE bias, b is the selectivity of C1 and C2 products, and c and d are the liquid phase product distribution of photoelectrocatalytic reduction of CO2 by photoelectrodes NH2-SBA-15(r) / Cu and S-SBA-15(r) / Cu at different voltages, respectively; Figure 12 Photoelectrode prepared in Example 3 13 Mass spectrum of C-labeled experimental liquid phase product; Figure 13 TG curve of photoelectrode prepared in Example 3 and 5; Figure 14Current density vs. time curves for the photocathode prepared in Example 5 at -0.6 V vs. SCE; Figure 15 Schematic diagram of the mechanism of photocatalytic reduction of carbon dioxide by the functionalized mesoporous material SBA-15 of the present application. DETAILED DESCRIPTION

[0015] The technical solutions in the present application will be described below in connection with the embodiments, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0016] Example 1 Synthesis of rod-like SBA-15: 2 g of template agent EO 20 PO 70 EO 20 (P123) and 4 mL of 12 mol / L HCl solution were mixed with 72 mL of deionized water, and after being fully dissolved by stirring at 35°C for 40 min, 4.2 mL of tetraethyl orthosilicate (TEOS) was slowly added dropwise, and the stirring was continued for 20 h. The above reaction solution was transferred to a hydrothermal kettle, sealed, and placed in a 110°C oven for crystallization for 24 h. After cooling, it was filtered and washed with deionized water until the solution was neutral. The sample was placed in an 80°C oven for drying overnight, and finally placed in a muffle furnace, and the temperature was increased to 550°C at a rate of 1°C / min, and calcined for 6 h to obtain a white solid powder, marked as SBA-15(r).

[0017] Synthesis of amino-functionalized mesoporous material NH2-SBA-15: 1 g of SBA-15(r) sample was placed in a three-necked flask containing 50 mL of anhydrous toluene solvent, and the temperature of the oil bath was heated to 80°C, then 0.1 mL of APTES was slowly added, and refluxed for 6 h. The unreacted APTES was washed with toluene as a solvent, and the amino-functionalized mesoporous material NH2-SBA-15 was dried to obtain NH2-SBA-15(r).

[0018] Synthesis of salicylaldehyde-functionalized mesoporous material S-SBA-15: 0.5 g of NH2-SBA-15(r) was added to 50 mL of anhydrous toluene solution, and 1 mL of salicylaldehyde was added in two portions at 80°C, and refluxed for 6 h to obtain S-SBA-15(r).

[0019] Example 2 Synthesis of Spherical SBA-15: 2 g of P123 and 0.10 g of CTAB were dispersed into 50 mL of 2 mol / L HCl solution at 35 °C and stirred until they were completely dissolved, then 4.2 mL of tetraethyl orthosilicate (TEOS) was slowly added dropwise, and stirred for 24 h. The reaction solution was transferred to a hydrothermal kettle, which was sealed and placed in a 100 °C oven for crystallization for 24 h. After cooling, it was filtered and washed with deionized water until the solution was neutral. The sample was placed in an 80 °C oven to dry overnight, and finally placed in a muffle furnace, which was raised to 550 °C at a rate of 1 °C / min, and calcined for 6 h to obtain a white solid powder, labeled as SBA-15(s).

[0020] Synthesis of Amino-functionalized Mesoporous Material NH2-SBA-15: 1 g of SBA-15(s) sample was placed in a three-necked flask containing 50 mL of anhydrous toluene solvent, and the temperature of the oil bath was heated to 80 °C. Then 0.1 mL of APTES was slowly added, and refluxed for 6 h. The unreacted APTES was washed with toluene as a solvent, and the amino-functionalized mesoporous material NH2-SBA-15 was dried to obtain NH2-SBA-15(s).

[0021] Synthesis of Salicylaldehyde-functionalized Mesoporous Material S-SBA-15: 0.5 g of NH2-SBA-15(s) was added to 50 mL of anhydrous toluene solution, and 1 mL of salicylaldehyde was added twice at 80 °C, and refluxed for 6 h to obtain S-SBA-15(s).

[0022] Example 3 During the synthesis of SBA-15(r) in Example 1, a clean Cu mesh was placed in the hydrothermal kettle containing the reaction solution, which was sealed and placed in an oven for crystallization for 24 h. After crystallization was completed, the Cu mesh loaded with SBA-15(r) was dried overnight, and then placed in a muffle furnace, which was raised to 550 °C at a rate of 1 °C / min and maintained for 6 h to obtain an electrode sheet loaded with SBA-15(r). The prepared electrode sheet was placed in a three-necked flask containing 50 mL of toluene solution, and 0.1 mL of APTES was slowly added at 80 °C, and refluxed for 6 h to obtain NH2-SBA-15 / Cu(r) photoelectric cathode.

[0023] Example 4 During the synthesis of SBA-15(s) in Example 2, a clean Cu mesh was placed in the hydrothermal kettle containing the reaction solution, which was sealed and placed in an oven for crystallization for 24 h. After crystallization was completed, the Cu mesh loaded with SBA-15(s) was dried overnight, and then placed in a muffle furnace, which was raised to 550 °C at a rate of 1 °C / min and maintained for 6 h to obtain an electrode sheet loaded with SBA-15(r). The prepared electrode sheet was placed in a three-necked flask containing 50 mL of toluene solution, 0.1 mL of APTES was slowly added at 80°C, and the mixture was refluxed for 6 h to obtain NH2-SBA-15 / Cu(s) photoelectric cathode.

[0024] Example 5 The NH2-SBA-15 / Cu(r) photoelectric cathode prepared in Example 3 was placed in a solution of salicylaldehyde in anhydrous toluene, and the mixture was refluxed at 80°C for 6 h to obtain S-SBA-15 / Cu(r) photoelectric cathode, wherein the volume ratio of salicylaldehyde to anhydrous toluene was 1:50.

[0025] Example 6 The NH2-SBA-15 / Cu(s) photoelectric cathode prepared in Example 4 was placed in a solution of salicylaldehyde in anhydrous toluene, and the mixture was refluxed at 80°C for 6 h to obtain S-SBA-15 / Cu(s) photoelectric cathode, wherein the volume ratio of salicylaldehyde to anhydrous toluene was 1:50.

[0026] Experimental Example 1 Chemical characterization of functionalized mesoporous material SBA-15 The samples prepared in Examples 1-2 were subjected to SEM, XRD, N2 adsorption-desorption isotherm, Fourier transform infrared spectroscopy, and XPS analysis, respectively, and the results are shown in Figures 1-9 .

[0027] As can be seen from Figure 1 a, SBA-15(s) exhibits a smooth surface and a uniform microspherical morphology with a diameter of 3-4 microns, Figure 1 b and Figure 1 c are scanning electron micrographs of NH2-SBA-15(s) and S-SBA-15(s) samples, respectively, and it can be seen that the modified samples retain the original microspherical morphology, but the surface becomes rough and is covered with a layer of flocculent material, because the organic functional groups grow on the surface of the microspheres and inside the pore walls of the mesoporous material. Figure 1 d is a scanning electron micrograph of SBA-15(r) sample, and we can see that SBA-15(r) has a rod-like morphology with a length of 6 microns, Figure 1 (e) and Figure 1 (f) are scanning electron micrographs of NH2-SBA-15(r) and S-SBA-15(r) samples, respectively, and it can be seen that the modified samples also retain the original rod-like morphology, with a little flocculent on the surface. All the above indicate that the morphology of the mesoporous molecular sieve after organic functionalization does not change.

[0028] Figure 2(a-c) TEM images of SBA-15(r), NH2-SBA-15(r) and S-SBA-15(r) samples in the direction parallel to the channel, showing long-range ordered, regular channel structure, and two different size of pore channel structure can be observed, Figure 2 (d-f) TEM images of SBA-15(r), NH2-SBA-15(r) and S-SBA-15(r) samples in the direction perpendicular to the channel, showing neat "honeycomb" hexagonal pore structure. For the samples of NH2-SBA-15(r) and S-SBA-15(r) after organic functionalization, the neat honeycomb structure is still observed; due to the introduction of organic groups, the pore size of NH2-SBA-15(r) and S-SBA-15(r) is reduced, and the regularity and order of channel arrangement are reduced to a certain extent. According to the TEM images, the pore size of all samples is 7-9 nm, and the pore wall thickness is 3-5 nm.

[0029] From Figure 3 It can be seen from a that the SBA-15(r) sample has a clear diffraction peak at 2θ = 0.88°, which is the diffraction peak of the (100) crystal plane; two stronger diffraction peaks appear at 2θ = 1.51° and 1.73°, which correspond to the diffraction peaks of the (110) and (200) crystal planes, respectively, and a weaker peak appears at 2θ = 2.26°, which corresponds to the diffraction peak of the (210) crystal plane, indicating that the SBA-15(r) sample prepared by us has a highly ordered two-dimensional hexagonal structure. The (100), (110) and (200) crystal plane diffraction peaks of the organic functionalized NH2-SBA-15(r) and S-SBA-15(r) are still clear, indicating that after organic functionalization, the sample still maintains a highly ordered two-dimensional hexagonal structure, but the intensity of each diffraction peak is weakened, which is due to the assembly of organic groups into the channel of SBA-15, affecting the order of the channel structure. Figure 3 b is the small-angle XRD pattern of SBA-15(s), from which it can be seen that a strong diffraction peak appears at 2θ = 1.19°, which is the diffraction peak of the (100) crystal plane, and two diffraction peaks appear at 2θ = 2.04° and 2.31°, which correspond to the diffraction peaks of the (110) and (200) crystal planes, respectively, indicating that the SBA-15(s) sample also has a highly ordered two-dimensional hexagonal structure, but its order is lower than that of SBA-15(r), and the diffraction peaks as a whole move to high angles, which is consistent with the results of the channel structure parameters of the sample. The samples of NH2-SBA-15(s) and S-SBA-15(s) after organic functionalization still maintain an ordered mesostructure, but the intensity of each diffraction peak is correspondingly weakened, indicating that the introduction of organic groups affects the order of the mesoporous material SBA-15(s). By comparing Figure 3a and Figure 3 It can be found that the diffraction peaks of the spherical sample move to high angle as a whole, which is caused by the shrinkage of the unit cell. Table 1 is the structure parameters of the sample calculated by Bragg equation, and it can be seen that the unit cell parameters of SBA-15(s) series are smaller than those of SBA-15(r) as a whole, which is consistent with the above results.

[0030] Table 1 Structure parameters of the sample

[0031] Figure 4 a and Figure 4 b is the N2 adsorption-desorption isotherm of SBA-15 sample before and after modification, and it can be seen that all the samples show type IV adsorption-desorption isotherm and typical H1 type hysteresis loop. From the adsorption and desorption branches, SBA-15 has sharp adsorption and desorption branches in the relative pressure P / P0 range of 0.50-0.85, which is a clear feature of high-ordered mesoporous material with narrow pore size distribution. It is worth noting that from the adsorption branch, the relative pressure of S-SBA-15(r) is 0.50, which is lower than that of SBA-15(r), and the relative pressure of S-SBA-15(s) is 0.55, which is higher than that of SBA-15(s). This is because the pore size of S-SBA-15(r) is smaller than that of SBA-15(r), and the pore size of S-SBA-15(s) is larger than that of SBA-15(s). Figure 4 a It can be seen that the N2 adsorption-desorption isotherm of S-SBA-15(r) has two inflection points, which is the behavior of different pore structure adsorbing N2, and this is also confirmed in the pore size distribution graph. Compared with SBA-15, the positions of the inflection points and hysteresis loops of the samples of the two morphologies after functionalization move to the low pressure direction, which indicates that the modified samples have capillary condensation phenomenon in the pores in the low relative pressure zone, indicating that the pore size is slightly reduced. Figure 4 c and Figure 4 d is the pore size distribution graph of SBA-15 sample before and after organic functionalization calculated by N2 adsorption-desorption isotherm using BJH model, and it can be seen from Figure 4 c that SBA-15(r) has a bimodal feature at 5.77 and 8.11 nm, respectively, which is consistent with the results of two pore sizes seen in TEM. The pore size distribution of the sample after organic functionalization still shows a bimodal feature, but it moves to the direction of small pore size as a whole, indicating that the functionalized mesoporous material occupies part of the pore space with organic groups, making the pore size smaller as a whole. There are many explanations for the formation of bimodal material, mainly considering that the molecular weight and block size of the triblock copolymer surfactant used are different, and these block copolymers can self-associate to form micelles with branched structure, in which the hydrophobic PPO block first forms the core of the micelle, covering the hydrophilic PEO segment, blocking the hydration process. Then the silica sol is adsorbed on the surface of the PEO segment through hydrogen bonding between ether and silanol groups, because of this interaction, the primary soft particles wrapped in the surfactant aggregate around the micelles as a scaffold, and the soft particles adjacent to the surface hydroxyl group subsequently condense into siloxane bridges, forming a unified micelle, and finally forming a bimodal material. In addition, Figure 4The pore size distribution of the NH2-SBA-15 (s) and S-SBA-15 (s) after organic functionalization in d moves to the direction of low pore size, which also indicates that the introduction of organic groups causes partial blockage of the channels, resulting in slight reduction of the pore size. Subsequently, the results of N2 adsorption-desorption are analyzed, and the pore structure parameters of different samples are shown in Table 2.

[0032] Table 2 Pore structure parameters of different samples

[0033] In Table 2, t w (nm) is the pore wall thickness of the sample, which can be calculated according to the difference between the unit cell parameter a0 (nm) and the average pore size (nm), i.e. t w =a0-average pore size, the average pore size being calculated by the BJH model. Pore volume (cm 3 / g) is the pore volume calculated by the BJH model, i.e. the pore volume, S BET (m 2 / g) is the BET specific surface area. According to Table 2, the specific surface area, average pore size and pore volume of the NH2-SBA-15 and S-SBA-15 after organic functionalization are all reduced compared with those of SBA-15, because the organic groups are assembled into the mesoporous material through silanization and Schiff base, resulting in reduction of the pore size and thickening of the pore wall.

[0034] Figure 5 Fig. 8 is the CO2 adsorption-desorption curves of different samples at 298 K, and Fig. 9 is the CO2 adsorption-desorption curves of different samples at 273 K. Figure 5 It can be seen from Figs. 8 and 9 that the CO2 adsorption amount of the SBA-15 samples with different morphologies increases with the increase of the absolute pressure, the CO2 adsorption and desorption curves of the SBA-15 without organic functionalization are basically coincident, indicating that there is physical adsorption between the sample and the CO2 molecules, and the CO2 adsorption and desorption branches of the NH2-SBA-15 and S-SBA-15 after organic functionalization by APTES and salicylaldehyde are not coincident, indicating that there is chemical adsorption between the sample and the adsorbed CO2 molecules. The CO2 adsorption amount of the rod-like SBA-15 (r) is obviously larger than that of the spherical SBA-15 (s), because the rod-like SBA-15 (r) still has pores larger than 5 nm after organic modification, and there is chemical adsorption, so the adsorption amount increases.

[0035] Figure 6 Fig. 10 is the Fourier transform infrared spectra of the samples with two different morphologies, and it can be seen that there is no obvious difference between the two different morphologies, and the corresponding absorption peaks appear. Figure 6 Taking the sample a as an example, the absorption bands 462 cm -1 , 808 cm -1 and 1082 cm -1corresponding to the bending, symmetric and asymmetric stretching vibrations of Si-O-Si bonds, respectively. The absorption bands are located at 1628 cm -1 and 3435 cm -1 due to the O-H bending vibration and the O-H stretching vibration of the hydrogen-bonded silanol groups. From Figure 6 a we can see that the typical characteristic absorption peaks of SBA-15(s) still exist in the infrared spectra of the functionalized samples. The intensity of the absorption band near 965 cm -1 , which is the stretching vibration of the free silanol groups (Si-OH), decreases, indicating that the silanol groups are grafted with organosilanes. In the infrared spectra of the NH2-SBA-15(s) sample, we can identify the absorption peak near 2933 cm -1 , which is the asymmetric stretching vibration of the C-H bonds in the methylene (CH2-) groups of the aminopropyl groups. In addition, the intensity of the -OH stretching vibration peak at 3435 cm -1 of the sample after amino-functionalization is also significantly smaller than that of the sample before functionalization, indicating that most of the -Si-OH groups are replaced by amino groups. After further salicylaldehyde functionalization, the sample exhibits a stretching vibration peak near 1645 cm -1 , which is the stretching vibration of the imine group (C=N-), and a stretching vibration peak near 1284 cm -1 , which is the stretching vibration of the C-O bonds in the benzene ring, demonstrating that the organic functional groups have been grafted onto the surface of SBA-15(s). Figure 6 In b, the characteristic absorption peaks of the relevant organic groups also appear, demonstrating that SBA-15(r) has also been successfully functionalized.

[0036] Figure 7 The XPS spectra of the samples SBA-15(r), NH2-SBA-15(r) and S-SBA-15(r) are shown in Figure 7 a. From the full spectra, we can see that the C1s signal peak is enhanced and the N1s signal peak appears in the samples after functionalization, and the intensities of the Si2s and Si2p signal peaks are weakened compared with the sample before functionalization. Figure 7 The C1s XPS fine spectra of the samples are shown in b. The C1s fine spectra of NH2-SBA-15(r) and S-SBA-15(r) were fitted by XPS software, and two component peaks were obtained, in which the binding energies of 286.5 eV and 286.05 eV are attributed to the characteristic peaks of C-N. The appearance of the C-N peak demonstrates that salicylaldehyde and APTES have been successfully assembled on the pore walls of the mesoporous material SBA-15(r). From Figure 7c It can be seen that C-N peak and C=N peak appeared in the fine spectrum of N1s of NH2-SBA-15(r) and S-SBA-15(r) respectively. The above results all show that salicylaldehyde and APTES have been successfully assembled into SBA-15(r). Figure 7 d As the O1s fine spectrum of the sample, it can be seen that the O element content of the sample after functionalization is reduced, and moves to the high binding energy direction, indicating that most of the surface silicon hydroxyl groups of SBA-15(r) are replaced by organic groups. The above results show that APTES and salicylaldehyde have been successfully assembled into SBA-15(r) samples.

[0037] Table 3 lists the elemental analysis results of functionalized NH2-SBA-15 and S-SBA-15. As can be seen from Table 3, the N content of S-SBA-15 and NH2-SBA-15 is basically the same, and the C content of S-SBA-15 is significantly increased compared with NH2-SBA-15, which is because salicylaldehyde is further assembled on NH2-SBA-15 to form a Schiff base, greatly increasing the C content in the sample.

[0038] Table 3 Elemental analysis results of organically functionalized SBA-15

[0039] Example 2 Optical and electrical properties of the photoelectric cathode material The optical and electrical properties of the photoelectric cathode material prepared in Examples 3-6 were detected and analyzed, and the results are shown in Figures 8-10 .

[0040] Figure 8 a The solid-state ultraviolet absorption spectra of different samples can be seen. SBA-15 has no absorption in the ultraviolet-visible light region, compared with which the absorption intensity of NH2-SBA-15 after amino functionalization has slightly increased, and the absorption edge band of S-SBA-15 after further functionalization with salicylaldehyde has red shift in the ultraviolet-visible light region, and the intensity has obviously increased. It shows that the absorption and utilization of visible light have been greatly improved after organic functionalization. Figure 8 b The photoluminescence (PL) spectra of different materials reveal their charge separation behavior. Compared with SBA-15, the PL intensity of NH2-SBA-15 and S-SBA-15 is obviously weakened, indicating that fluorescence quenching occurs on the electrode surface, and the electron is quickly transferred from the excited state to the main ground state, which indirectly shows that organic modification is conducive to inhibiting the recombination of carriers.

[0041] As Figure 9As shown in Figure a, under EC conditions, the photocurrent density of the photocathode S-SBA-15(r) is relatively low, while under PEC conditions, its current density increases most rapidly with increasing applied voltage, reaching a maximum current density of 0.034 A cm⁻¹ at an applied voltage of -1.4 V (vs. SCE). -2 This indicates that under illumination, the photocathode S-SBA-15(r) absorbs visible light, generating a photocurrent, which increases the current density of the reaction system. Under Ar saturation conditions, the current density of the photocathode S-SBA-15(r) becomes smaller. Ar, as an inert gas, is inactive in the reaction system and does not participate in the redox reaction, while CO2 undergoes a reduction reaction in the reaction system, consuming electrons. Figure 9 The results of b's CV curve and Figure 9 The LSV curve of a is consistent. Figure 9 In the electrochemical impedance spectroscopy of c, S-SBA-15(r) exhibits the smallest semicircular radius in the low-frequency region, indicating the fastest surface charge transport rate. This is because the channel structure of S-SBA-15(r) allows for greater charge transport and transfer, thereby suppressing the recombination of photogenerated electron-hole pairs. Figure 9 The transient photoelectric response curve of d also shows that, under the condition of an applied voltage of -0.6 V, the photocathode S-SBA-15(r) has the highest current density and the best photoelectric response capability.

[0042] like Figure 10 As shown, we examined the Mott-Schottky curves of the photocathode at different frequencies. All electrodes exhibit pn heterojunction characteristics. From Figure 10 As can be seen, the Efb values ​​obtained by the prepared photocathode at different frequencies are not significantly different, indicating good electrode stability and reliable flat-band potentials. The flat-band potentials of the four electrodes are: -0.35V for NH2-SBA-15(s), -0.38V for S-SBA-15(s), -0.32V for NH2-SBA-15(r), and -0.39V for S-SBA-15(r).

[0043] Example 3 CO2 photoelectrocatalytic reduction performance The performance of the photocathode catalytic reduction of CO2 in Examples 3-6 was tested. The electrolyte was an aqueous solution of 0.1 M KHCO3 containing disodium eosin Y (1 mM) as a sensitizer, and the counter electrode was a bismuth vanadate BiVO4 electrode.

[0044] We examined the applied voltage from -0.4 V to -1.0 V ( vsThe distribution and formation rate of hydrocarbon products under different photocathodes (SCE) were investigated. The results showed that rod-shaped S-SBA-15(r) and NH2-SBA-15(r) exhibited superior performance compared to spherical S-SBA-15(s) and NH2-SBA-15(s) in both hydrocarbon product formation rate and apparent Faraday constant (AFE). This is attributed to the superior CO2 adsorption capacity of the rod-shaped samples. Figure 11 As shown in Figure a, when the applied voltage is -0.6 V ( vs At SCE, the formation rates of hydrocarbon products are in the following order: S-SBA-15(r) > NH2-SBA-15(r) > S-SBA-15(s) > NH2-SBA-15(s), and the apparent Faraday efficiency (AFE) of carbon-based products are in the following order: S-SBA-15(r) > NH2-SBA-15(r) > NH2-SBA-15(s) > S-SBA-15(s).

[0045] Subsequently, we focused on investigating the photoelectrocatalytic performance of the photocathodes S-SBA-15(r) and NH2-SBA-15(r) at different voltages. From... Figure 11 As can be seen from c, at -1.0V ( vs The formation rate of hydrocarbon products at the photocathode NH2-SBA-15(r) can reach up to 106 µM cm⁻¹. -2 h -1 ,from Figure 11 As can be seen from b, at -0.6V ( vs When SCE is used, C2 shows the best selectivity, reaching 86.57%. From Figure 11 As can be seen from d, the photocathode S-SBA-15(r) also operates at -1.0V ( vs The formation rate of hydrocarbon products is highest at SCE, and is highest at -0.6V. vs The AFE at SCE was the highest among all photocathodes, reaching 152.18%. Compared with the two photocathodes, the photocathode NH2-SBA-15(r) showed better selectivity for C2 products. This is because the pores of the amino-modified SBA-15(r) were not blocked, while the pores of the sample after further salicylaldehyde functionalization were partially blocked, thus affecting CC coupling and leading to a decrease in the selectivity of its C2 products.

[0046] Example 4 13 C isotope labeling To provide strong evidence for the origin of carbon in the reduction products, we conducted... 13Carbon isotope labeling experiments verified the carbon source of hydrocarbons in the CO2 photoelectrocatalytic reduction system using an NH2-SBA-15(r) photocathode. The results are as follows: Figure 12 As shown, the product 13 CH3OH ([MH) + = 32.07), 13 CH3 13 CH2OH ([MH) + = 47.04), 13 CH3 13 COOH ([MH)) + = 61.02) was detected by gas chromatography-mass spectrometry (GC-MS). These results indicate that all hydrocarbons are reduction products of CO2. This result proves that all hydrocarbon products originate from CO2.

[0047] Example 5: Stability of the photocathode The thermal stability of catalysts SBA-15(r), NH2-SBA-15(r), and S-SBA-15(r) was investigated using thermogravimetric analysis. Figure 13 As shown, catalysts SBA-15(r), NH2-SBA-15(r), and S-SBA-15(r) all exhibited good thermal stability. Since the photoelectrocatalytic reduction of CO2 occurs at room temperature and pressure, the thermal stability of the samples is sufficient to support the reaction and its reuse. Subsequently, we conducted stability tests on the photocathode S-SBA-15(r). Figure 14 As can be seen, the photocurrent density of the photocathode S-SBA-15(r) remained basically stable after 8 hours of reaction at an applied voltage of -0.6 V (νs. SCE), indicating that the photocathode S-SBA-15(r) has good stability.

[0048] Based on the above experimental results, we explored the mechanism of photoelectrocatalytic reduction of carbon dioxide by the functionalized mesoporous material SBA-15, such as... Figure 15The large specific surface area and rich pore structure of the functionalized mesoporous materials S-SBA-15 and NH2-SBA-15 of the application are conducive to the adsorption of CO2, CO2 molecules are first adsorbed on the -C=N or amino groups, the CO2 molecules are firmly controlled in the pores of the material as a microreactor, under light induction, photoelectrons generated by dye molecules are captured by protons to become active hydrogen atoms, and the electrons on the photoelectrode are in-situ reduced with the CO2 molecules in the pores to promote the formation of C-C bonds, at the same time, under an applied voltage, OH- is transferred to the BiVO4 photoanode to occur oxidation reaction to release oxygen, and the electrons are transferred to the photoelectrode through an external circuit. Due to the synergistic effect of the amino and Schiff base functional groups, the photoelectrode S-SBA-15 and NH2-SBA-15 have high C-C coupling ability and photoelectrocatalytic reduction CO2 activity.

[0049] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application, any modification, equivalent replacement and improvement within the technical scheme and concept of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of functionalized mesoporous material SBA-15, characterized in that, The specific steps are as follows: SBA-15 is weighed, placed in a three-necked flask containing anhydrous toluene solvent, heated to 80℃, then slowly added with APTES, refluxed, filtered, and washed with toluene as a solvent to remove unreacted APTES, and dried to obtain an amino-functionalized mesoporous material NH2-SBA-15. The SBA-15 is any one of rod-like SBA-15 or spherical SBA-15.

2. The method of claim 1, wherein: The amount ratio of SBA-15, anhydrous toluene and APTES is 1g:50mL:0.1mL.

3. The method of claim 1, wherein: The refluxing time is 6h.

4. The method of claim 1, wherein: The synthesis steps of the rod-like SBA-15 are as follows: 2g of template agent EO 20 PO 70 EO 20 (P123) and 4mL of 12mol / L HCl solution are mixed with 72mL of deionized water, and after being fully dissolved by stirring at 35℃ for 40min, 4.2mL of tetraethyl orthosilicate (TEOS) is slowly added dropwise, and stirring is continued for 20h. The above reaction solution is transferred to a hydrothermal kettle, sealed, and placed in a 110℃ oven for crystallization for 24h. After cooling, it is filtered, washed with deionized water until the solution is neutral, and then the sample is placed in an 80℃ oven to dry overnight. Finally, it is placed in a muffle furnace, and the temperature is increased to 550℃ at a rate of 1℃ / min, and calcined for 6h to obtain a white solid powder.

5. The method of claim 1, wherein: The synthesis steps of the spherical SBA-15 are as follows: 2g of P123 and 0.10g of CTAB are dispersed into 50mL of 2mol / L HCl solution at 35℃, stirred to fully dissolve, then 4.2mL of tetraethyl orthosilicate (TEOS) is slowly added dropwise, and stirred for 24h, the reaction solution is transferred to an autoclave, sealed, and placed in a 100℃ oven for crystallization for 24h, then cooled, filtered, and washed with deionized water until the solution is neutral; the sample is placed in an 80℃ oven to dry overnight, finally placed in a muffle furnace, and heated to 550℃ at a rate of 1℃ / min, and calcined for 6h to obtain a white solid powder.

6. The method of claim 1, wherein: The amino-functionalized mesoporous material NH2-SBA-15 is further subjected to salicylaldehyde functionalization treatment to obtain a salicylaldehyde-functionalized mesoporous material S-SBA-15, and the specific steps are as follows: 0.5g of NH2-SBA-15 is weighed and added to 50mL of anhydrous toluene solution, 1mL of salicylaldehyde is added twice at 80℃, refluxed for 6h to obtain S-SBA-15.

7. The application of NH2-SBA-15 prepared by the preparation method of claim 1 in functionalized modification of a photoelectric cathode, and the preparation steps of the NH2-SBA-15 functionalized modification photoelectric cathode are as follows: (1) In the synthesis process of SBA-15, a clean Cu mesh is placed in the autoclave containing the reaction solution, sealed, and placed in an oven for crystallization for 24h, then dried overnight after the crystallization is completed, and finally placed in a muffle furnace, heated to 550℃ at a rate of 1℃ / min, and kept for 6h to obtain an electrode sheet loaded with SBA-15; (2) The prepared electrode sheet is placed in a three-necked flask containing 50mL of toluene solution, 0.1mL of APTES is slowly added at 80℃, refluxed for 6h to obtain an NH2-SBA-15 / Cu photoelectric cathode.

8. The application of S-SBA-15 prepared by the preparation method of claim 7 in functionalized modification of a photoelectric cathode, and the preparation method of the S-SBA-15 functionalized modification photoelectric cathode is as follows: The NH2-SBA-15 / Cu photo-cathode was put into a solution of anhydrous toluene containing salicylaldehyde, and refluxed at 80°C for 6h to obtain a S-SBA-15 / Cu photo-cathode, wherein, The volume ratio of salicylaldehyde to anhydrous toluene is 1:50.

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